23.2: Physical Assessment of the Newborn
By the end of this section, you will be able to:
- Summarize newborn vital signs and implement techniques learned in the clinical setting with minimal disruption to the newborn
- Identify and demonstrate the components of a head-to-toe newborn physical examination
- Distinguish between different newborn skin variations, both normal and abnormal
- Identify newborn neurologic reactions to maternal substance misuse and recognize the appropriate next steps for safe newborn care
The nurse’s assessment of the newborn focuses on knowing and understanding the language of the newborn, their behavioral cues, and normal newborn anatomy and physiology. With that knowledge, the nurse can identify the slightest changes in the condition of the newborn in their care. Neonatal nurses’ expertise in newborn behavior and communication and their ability to assess newborn behavior through vital signs, head-to-toe assessment, and neurologic behavior are imperative to caring for neonates.
Newborn Vital Signs
Obtaining newborn vital sign s is a skill that takes practice. Auscultation may be challenging because of newborns moving and crying during the assessment. Focus on starting with the least invasive assessment item and saving the most invasive for last to decrease the chance of crying. Auscultation is a skill that new nurses will need to practice often, but it is vital to the care and management of a newborn. Newborn vital signs are best obtained in a warm, well-lit place where the newborn is quiet and comfortable. Start with the heart rate and respirations. If the nurse can complete those while the newborn is sleeping or in a calm, relaxed state, that is the best time to obtain them. Heart rate is always counted at the apex, which can best be found at the fourth intercostal space. This will be the same from birth to about 3 years of age.
Listen with a stethoscope for 1 full minute, followed by counting respirations with a stethoscope for 1 full minute. Normal newborn heart rates are 120 to 160 beats per minute (Stanford Medicine, Childrens Health, 2022). If no stethoscope is available in the first few minutes after birth, the base of the umbilicus can be used to assess the heart rate, although the most accurate method is with the use of a stethoscope (Johnson & Schmölzer, 2020). For new nurses, it is sometimes easier to listen for a minute with the stethoscope and put their other hand on the newborn’s abdomen while watching for breaths to correlate with what they are hearing. Normal respirations are 30 to 60 respirations per minute (Stanford Medicine, Childrens Health, 2022) and may increase with crying. Temperatures are obtained by the axillary method, with the thermometer being placed vertically under the arm with the tip in the axilla (Figure 23.2). Expected temperatures are 36.5° C to 37.5° C (97.7° F to 99.4° F) (Stanford Medicine, Childrens Health, 2022). Pain should be assessed as a vital sign, evaluated with a neonatal pain evaluation tool. Blood pressures are not usually assessed on newborns unless they are in the neonatal intensive care unit. Table 23.1 lists expected normal newborn vital signs (Stanford Medicine, Childrens Health, 2022).
| Temperature | Respirations | Heart Rate |
|---|---|---|
36.5° C–37.5° C (97.7° F–99.4° F)
|
|
|
Pain in the newborn cannot be expressed in the way an adult can verbally describe and locate their pain. Pain scales developed specifically for the neonatal or nonverbal population have been created and evaluated to assess this vital sign in the newborn population. The Neonatal/Infant Pain Scale (NIPS) (Sarkaria & Gruszfeld, 2022) and the Face, Legs, Activity, Cry, and Consolability (FLACC) scale are examples of pain scales specifically used in nonverbal patient populations.
The Neonatal/Infant Pain Scales is a pain assessment tool used in children less than 1 year of age. Caregivers and health-care providers can use the child’s body language to determine their degree of pain.
Assessment of General Appearance
The nursing assessment is the part of the nursing process whereby a nurse gathers patient health information using evidence-informed tools to learn more about a patient’s overall health, symptoms, and concerns (Toney-Butler & Unison-Pace, 2022). Newborn assessment begins with an evaluation of the general appearance of the newborn.  Their abdomen will be round and protruding, the chest will appear small and thin, and their arms and legs will be flexed. They will have an umbilical cord in the center of their abdomen that has a cord clamp on it. Newborns will have their hands tightly clenched, and their hands and feet may remain blue for the first 24 to 48 hours , a common finding called acrocyanosis . Their bodies should be a color that is appropriate for their ethnicity, but in general, melanin takes a while to appear after birth.
Weight and Measurements
Full term weights of newborns vary greatly depending on the race of the parents. Newborn infants of Black, Asian, and Hispanic heritage generally are somewhat smaller when born at term than White newborns (Ro et al., 2019). The average weight of a newborn in the United States in the past decade is between 5 pounds, 8 ounces (2,500 grams), and 8 pounds, 13 ounces (3,850 grams) (Desiraju, 2018). Maternal factors that can influence the weight of a newborn are health; nutrition during the pregnancy; intervals between pregnancies; use of substances including tobacco, nicotine, narcotics, and alcohol; gestational diabetes; and the size of both parents. The newborn will initially lose weight—up to 10 percent of their birth weight—in the first 3 days after birth (Figure 23.3). They are expected to regain their birth weight by 2 weeks of life (DiTomasso, 2019).
The U.S. Centers for Disease Control and Prevention ( CDC ) recommends that health-care providers follow World Health Organization (WHO) growth standards for children zero to 2 years of age. The World Health Organization has established breast-fed newborns as the norm for growth and therefore have recommended this as the standard for infant feeding. The chart reflects growth patterns for children who were predominantly breast-fed for at least 4 months and still breast-feeding at 12 months. Clinicians and nurses still use this CDC growth chart as a standard on how children should grow, and this begins in the hospital at the time of birth. Nurses will document the newborn’s weight and length in the chart, and this will be the first measurements plotted on the newborn’s growth chart.
During the initial newborn period of the first week, the newborn will have a physiologic weight loss of approximately 5 to 10 percent due to fluid shifts. This occurs because about 75 percent of the newborn’s body is made of water. Keep in mind that larger babies will have larger weight losses because they have more fluid in proportion to their birth weight. However, a weight loss of more than 10 to 12 percent requires further evaluation (Children's Hospital of Philadephia, 2022). After regaining their birth weight, the infant will double their weight in the first 5 or 6 months. The newborn will increase their weight by approximately 5 to 7 ounces (140 to 200 grams) per week (Children's Hospital of Philadephia, 2022). If the newborn is breast-feeding, the nurse will need to assess feeding effort and coordination, along with collaborating with the care team that includes a lactation consultant and the pediatrician. Typically, birth weight is regained in 14 days (Levinson, 2020).
Health-Care Disparities of the Newborn
Cultural, racial, and ethnic related disparities in newborn medical care is a chronic issue within health care. Newborn infants, particularly preterm infants, who are from Black, Hispanic, Native American, and Puerto Rican populations have been shown to be more likely to experience serious complications or disparities in health outcomes. The long-term possible consequences of disparities in health care include increased risks of morbidity, poor neurodevelopmental outcomes and behavioral deficits that influence health and quality of life over the lifetime (Ravi et al., 2021).
To measure the length of the newborn, the nurse will place the newborn in a supine position with their legs extended as much as possible, remembering that newborns prefer to keep their legs flexed and tense (Figure 23.4). The average length is 50 cm (20 inches), with a range of 46 to 56 cm (18 to 22 inches) determined by a combination of genetics and environmental factors. The newborn will grow approximately one-half inch to one inch (1.5 to 2.5 cm) per month (Stanford Medicine, Children’s Health, 2022). During their lifetime, this is the period of most rapid growth.
Head circumference is measured at birth and regularly during the first 2 years of life. Growth averages 0.5 cm a week during the first 2 months of life and then slows to half that rate. Place the measuring tape at the widest point of the head, from the most prominent point of the forehead around to the back of the head.
Chest circumference is measured at birth or shortly after by using a measuring tape aligned to the nipples (Azevedo et al., 2019). This measurement can help determine if an infant is small for gestational age from intrauterine growth retardation with a small chest-to-head circumference ratio. The infant of a person with gestational diabetes would have a relatively large chest-to-head ratio (Nichols, 1996).
Monitoring Temperature in the Newborn
Newborns are unable to regulate their temperatures. For the first 24 hours of their lives, it is important that the nurse monitor the temperature and assist the parents in maintaining the newborn’s temperature. Keeping newborns in a thermal-neutral environment, between 36.5° C and 37.5° C (97.7° F–99.4° F), is a high priority for nurses. This is a vital function and one that is reflective of physiologic maturity. The earlier the gestational age of the infant, the more difficult it is for them to maintain their temperature (Gardner, 2020).
The nurse’s responsibility in thermoregulation is to monitor the newborn’s temperature and provide an environment that reduces heat loss and avoids cold stress (Gardner, 2020). Thermoregulation by the nurse and caregivers is necessary due to the unique physiologic mechanisms competing within the newborn.
Ideally, placing the newborn skin to skin with one of the parents can aid in thermoregulation. However, if a newborn’s temperature drops too low, the nurse will need to move the infant to a warmer or incubator (Isolette) because skin-to-skin care cannot reverse hypothermia quickly enough.
Excessive heat loss triggers compensatory mechanisms in the newborn, including increased respirations and nonshivering thermogenesis, which are indications of cold stress. These behaviors are the infant’s effort to produce heat and maintain core body temperature. If the newborn is not kept warm, cold stress can lead to hypoglycemia , poor feeding, and even respiratory distress. While inside the uterus, the fetus’s temperature was the same as or slightly higher than that of the pregnant person. When a newborn enters the world, their temperature drops significantly, and the newborn is unable to thermoregulate for themselves. Newborns have very thin skin, their blood vessels are very close to the surface, they have very little brown or subcutaneous fat, and their ratio of body surface to body mass is three times that of adults. Therefore, it is important that the nurse manage the newborn’s environment to help maintain their body temperature.
Take Action: Maintaining Normothermic Temperature in a Newborn
The nurse is preparing to settle a newborn in a bassinet next to their parent in the shared delivery and postpartum room. The nurse knows that the newborn is unable to thermoregulate themselves well and that the environment may decrease their body temperature by evaporation, convection, conduction, and radiation. By both placing a hat on the newborn’s head and swaddling them in a thin blanket, the nurse is modeling behavior for home caregiver behavior and managing the newborn’s environment to maintain their body temperature.
Newborns lose heat in their environments in four ways: evaporation, convection, conduction, and radiation (see Figure 22.11). When heat is lost from liquid on the newborn’s skin, converting to a vapor in the air, it is called evaporation (Gardner, 2020). For example, after the newborn bath when they are wet, they are losing heat in the room by the water evaporating off their skin. That is the reason postpartum nurses will provide sponge baths for newborns around 24 hours of age while keeping most of their bodies covered. When heat is transferred from the body surface to the surrounding air by a current, like a fan in a room, it is called convection. When heat from a newborn is transferred because the newborn is lying naked on something very cold, like a newborn scale that is metal, it is called conduction. And finally, radiation is the transfer of heat to cool, solid objects not in direct contact with the newborn. An example of radiation would be placing a newborn crib too close to a cold hospital wall. It is imperative that a newborn’s temperature be checked often and that nurses manage those temperatures. The nurse can do this by drying the newborn as soon as possible after birth or a bath to prevent evaporation, warming any items that will touch the newborn, keeping the newborn out of drafts and keeping preterm newborns in incubators, and keeping all newborns away from walls and windows.
What Are the Ethical Obligations of the Maternal-Newborn Nurse?
More than four million births occur annually in the United States, making childbirth the most common reason people are hospitalized. The nurse in a maternal-newborn care role will be faced with ethical challenges nearly daily, often in an emotionally charged environment. In these instances, it is important to understand the nurse’s ethical obligations for their patients’ safety and privacy, which are described in the American Nurses Association Code of Ethics for Nurses.
Auscultation
Auscultation is the act of listening, with a stethoscope , to the chest for both heart and lung sounds, and to the abdomen for abdominal activity. When the nurse assesses the heart, auscultating on the left side of the chest while listening is focused on heart rate, rhythm, regularity, and heart sounds. The stethoscope is moved to the front and back of the chest along with moving it left and right laterally to assess breath sounds, listening for equal clear air entry on both sides. The nurse listens for a full minute to count the respirations over a full minute. Abdominal assessment also includes auscultation of the four quadrants, starting with the right lower quadrant. The nurse listens for bowel sounds from each quadrant up to 5 minutes each.
Before conducting a respiratory or cardiovascular assessment of the newborn, the nurse must ensure that the bell of the stethoscope is warmed. A cold stethoscope can startle the newborn, artificially increasing heart and respiratory rates. In addition, the newborn can lose heat due to the cold instrument.
Respiratory Assessment
Normal respirations will be easy, nonlabored, and without the use of accessory muscles, with no evidence of grunting, retractions, or nasal flaring. There should be no adventitious lung sounds auscultated, though fluid may be noted in the lungs of an infant delivered via cesarean section. The normal newborn respiratory rate is 30 to 60 breaths per minute, and newborns are obligate nose breathers. Periodic breathing in newborns is expected (Kondamudi et al., 2023), along with diaphragmatic breathing. This is a good time for the nurse to give anticipatory guidance to new parents about newborn periodic breathing to avoid panic when they notice irregular breathing at home. Newborns have periodic breathing where the rate of breaths changes over time, sometimes faster and sometimes pausing. When breathing has stopped for 20 seconds or longer, it is considered apnea .
Upper airway noises and bowel sounds in a newborn can be heard over the chest wall, making auscultation of newborn breath sounds more difficult. Listening for a full minute with a stethoscope and watching the abdomen rise and fall with the breaths can help the nurse identify what they are hearing. For new nurses performing a newborn respiratory assessment, it is sometimes easier to listen for a minute with the stethoscope while placing the other hand on the newborn’s abdomen to watch for breaths. This will help correlate what they are hearing and seeing.
Newborn Care: Part 2
See Newborn Care: Part 1 for a review of the patient data.
| Flow Chart |
Newborn assessment data at 30 minutes of age
Temp: 97.8° F/36.5° C (ax) Heart rate: 160 bpm Respiration rate: 66 breaths/min Pulse oximetry: 92% Color: acrocyanosis present Respirations: shallow, irregular Nasal flaring Marcus has not been interested in nursing. Capillary glucose: 42 |
Cardiovascular Assessment
Heart rate in a newborn can be as rapid as 180 beats per minute if the newborn is crying or moving. The normal newborn heart rate is 120 to 160 beats per minute (Tveiten et al., 2021). Auscultating a newborn heart rate is done with the stethoscope at the apex of the heart for 1 full minute. The nurse will listen for rate, rhythm, and intensity and will count the beats, preferably when the newborn is quietly awake or sleeping. The heart is relatively large at birth and is located mid to left chest and high in the chest, with the apex somewhere between the fourth and fifth intercostal spaces.
Assessing a Newborn’s Cry
Newborns’ primary way of communication is crying. Cries should be of normal pitch, steady, and consolable by a nurse or the parents. High-pitched cries that are piercing and not consolable can be, and often are, a sign of narcotic withdrawal, birth injury, genetic anomaly, and/or other neurobehavioral insults. A weak cry would indicate the newborn may need resuscitation measures.
Heart Murmurs
Normally, the heart has a “lub dub” sound, but because of the physiologic fetal shunts that close functionally during the newborn’s transition from intrauterine life to extrauterine life, a murmur often remains. All the fetal shunts close functionally at birth but will not close structurally for another 3 to 7 days after delivery. Physiologic murmurs in newborns are an expected finding. When auscultated, they will sound like whooshing in addition to the “lub dub” on S1 and S2. It can be difficult to differentiate heart sounds from lung sounds in a newborn. The nurse must monitor the respiratory pattern to isolate the heart sounds. Ninety percent of murmurs are temporary, lasting only 90 days or so. Many are secondary to closing of the patent ductus arteriosus or the patent foramen ovale. Normally, those will close 1 to 2 days after birth. Rarely, aortic or pulmonary stenosis occurs, or a congenital defect is found. All murmurs must be evaluated by a health-care provider.
Head-to-Toe Physical Assessment
Once auscultation is complete, the head-to-toe physical assessment can begin. This is the first time this person will have ever been examined. A systematic, thoughtful, and thorough approach is the best way to comprehensively examine the entire infant.
Head
For the newborn that moved through the vagina, the head may have some molding and bruising. The evolution of bruising and the return to typical head shape will occur over the first 24 to 48 hours. A newborn delivered via cesarean section may or may not have molding, depending on whether there was a second stage of labor or if the fetus spent time low in the pelvic cavity. The size of the newborn’s head is one-fourth the size of an adult’s head, and the circumference is approximately 32 to 37 cm (12.6 to 14.6 inches). The nurse will measure the newborn’s head by placing the tape over the most prominent part of the occiput, just above the ears, and bring it just above the eyebrows. The circumference of the newborn’s head should be greater than that of the newborn’s chest at birth and will remain that way for the next few months. If the newborn experienced significant trauma during birth, the nurse should reassess the shape of the head and remeasure the head circumference the next day (see Figure 23.4).
Fontanelles
A fontanelle is one of the soft spots located on the newborn’s head where the cranial bones meet and leave openings to allow for molding of the head during birth. Over the first 24 months of life, the anterior and posterior fontanelle will close. Fontanelles should be palpated during this part of the assessment. The anterior fontanelle is the larger of the two that the nurse will assess and can be felt as a diamond shape ranging in size from 0.6 cm to 3.6 cm between the two frontal bones. The posterior fontanelle is a triangle shape approximately 0.5 cm in size and located at the junction of the parietal bones and the occipital bone on the newborn. The average time of closure for the anterior fontanelle ranges from 13 to 24 months. In contrast, the posterior fontanelle will close within approximately 6 to 8 weeks after birth (Lipsett et al, 2022). Both fontanelles should feel soft and flat upon palpation. Bulging or tense fontanelles indicate issues such as hydrocephalus, increased intracranial pressure, meningitis, trauma, or hemorrhage. A sunken or depressed fontanelle indicates dehydration. Pulsatility may be noted later in infancy as an expected variability.
Abnormal Variations Commonly Occurring in Newborns
Abnormal variations that are commonly seen in newborn heads include caput succedaneum and cephalohematoma. The condition in which edema is observed on a newborn’s scalp at birth and is related to the labor and birth process is caput succedaneum . This is a benign condition in which the edema crosses cranial suture lines and feels soft and boggy (spongy). It is often related to extended pushing during vaginal births because the fetal head is subjected to pressure from the uterine contractions and the vaginal walls as it passes through the cervix. This condition has also been associated with forceps-assisted and vacuum-assisted births. Caput succedaneum usually resolves within the first few days following birth with no complications (Lipsett et al, 2022) (Figure 23.5). (For more on the topic of forceps-assisted birth and risk for trauma, see Chapter 25 Care of the Newborn at Risk.)
The condition in which serosanguineous or bloody fluid accumulates below the periosteum of the skull is called cephalohematoma (Figure 23.6). This can result from instrument-assisted births, when the fetus’s head is occiput-posterior or occiput-anterior, or when a scalp electrode has been placed during labor. However, it can also occur spontaneously (Remien & Majmundar, 2022). This is a much deeper injury than caput succedaneum, it does not cross the suture lines, and it requires assessment after birth by the nurse for signs and symptoms of increased or prolonged bleeding, jaundice, and infection. Cephalohematoma should resolve in 2 to 6 weeks after birth (Lipsett et al, 2022; Remien & Majmundar, 2022).
Hair
The nurse assesses the amount of hair, color, hairlines, and any cowlicks in the pattern. There will be very dramatic differences in newborn hair. Some newborns have a lot of hair at birth, and some have almost none. Lanugo is a soft, fine body hair covering a fetus while inside the uterus that may still be present right after birth. It helps to protect the fetus and keeps them warm while they grow. It is more commonly found in newborns born prematurely. The nurse should document what is observed, including hairline, quantity of hair, quality of hair, whether curly or straight, and color.
Face
Newborns’ faces are designed to help them breast-feed, so their chins are recessed, their lips are sensitive to touch, and they demonstrate the rooting reflex when the nurse touches the cheek. Eyes and ears should be symmetrical, as should facial movements. Any facial asymmetry or facial paralysis is not an expected variation. This abnormal finding may appear when the newborn cries and would require follow-up with a pediatrician or other health-care provider.
Eyes
Eye examination should be done when the newborn is in a quiet, awake, alert state. Tipping a newborn backward slightly can result in slight eye opening. Eyes should be equal in size bilaterally and align with the ears. Term newborns can fix and focus on an object that is 8 to 10 inches from their face and can sometimes follow it vertically and horizontally. The nurse will assess the eyes for the ability to fully open, pupil size and shape, and placement on the face. Facial swelling or edema may prevent the newborn from opening their eyes fully in the first few hours after birth. The sclera, the area of the eye around the iris and pupil, should be whitish or white, or have a blue tint; and the iris is often blue, gray, or brown. Pupils should be equal, round, and reactive to light. Permanent eye color may appear in 9 months but can take up to 3 years to be fully permanent (Boyd, 2022).
Nose
Assessment of size, shape, and patency of each nostril is important during the assessment of the newborn’s nose. The nose should be symmetrical and midline on the face. The nurse will use a finger to close one of the newborn’s nostrils and assess patency of the other, then repeat on the opposite side. It is important that the nurse assess this soon after delivery because infants are obligate nose breathers (i.e., they can breathe only through their nose) with an acute sense of smell that assists them in learning to breast-feed. Naris patency is supported by observing continued respiratory effort or by feeling the presence of air movement during breaths. Newborns also use sneezing to clear mucus or to indicate they are overstimulated.
Mouth
All newborns will have their mouth assessed for mobility and anatomy. The mouth should be moist, without drool, pink, and mobile. The nurse places a gloved finger into the newborn’s mouth, assesses the hard and soft palate continuity, and assesses whether the mucous membranes are pink and moist, indicating adequate hydration and oxygenation. The nurse assesses the gums for Epstein pearls , which are small, harmless, firm white cysts that contain keratin and which will resolve spontaneously within 1 to 2 weeks. However, if the Epstein pearls are loose, they should be reported to a provider so that they can be removed to prevent choking.
The frenulum of the tongue is a tiny fold of mucous membrane that runs from the floor of the mouth to the midline of the tongue’s underside. Its purpose is to regulate tongue movements. An abnormally short frenulum or a frenulum that is attached near the bottom of the tongue is a condition known as tongue-tie , or ankyloglossia. This can be a cause for feeding issues (Figure 23.7). The nurse checks the newborn’s frenulum to assess for tongue-tie to avoid issues with breast-feeding. The clinician should be notified early if the nurse notices this during assessment so that an intervention can occur. With intervention, the breast-feeding person can improve the breast-feeding latch and improve the feeding relationship with the newborn. However, intervention is not always necessary at this age.
Nurse:
Jan, MSN, NP
Years in practice:
33
Clinical setting:
Cardiology unit
Geographic location:
Inner city of a medium-sized city in Ohio
We serve a diverse patient population, but many of our patients are middle class, college-educated, and engaged parents who want to advocate for their newborn. In meeting a new birthing parent with a 5-day-old baby boy, we learn that the birthing parent wants to breast-feed but is having difficulties. The new parent has done multiple Google searches and is worried that they do not have enough breast milk supply and that they are doing “something wrong” when attempting to help their newborn latch. A lactation consultation was placed and the trained lactation consultant evaluated both the hold and latch of the newborn during an attempted breast-feeding. Finding a significant tongue-tie led to an ENT consultation and a concrete answer for the parent as to why they were having difficulties with breast-feeding. Ultimately, after working with both ENT and the lactation consultant, the newborn was able to breast-feed successfully.
Ears
Newborn ears should feel firm, flexible, and pliable, and recoil briskly when assessed. The nurse will assess placement of the ear by imagining a line that is parallel to the outer and inner canthus of the eye. If the pinna of the ear is touching the top of the imaginary line, it is correctly placed. If not, the top of the pinna will be below the line, and the ears are deemed low set (Figure 23.8) Ears should be symmetrical, similar in size, and in the same position. Ears can be an indicator of many congenital and chromosomal disorders, like renal agenesis, because kidneys and ears develop at the same time in the womb. Newborns will all have a hearing screen completed before discharge from the hospital, and if they do not pass, they will be rescreened at their pediatrician’s office or referred to a pediatric audiologist after discharge. Nurses are responsible for ensuring that the hearing screen is complete. Knowing that language development begins at birth, it is vital that the nurses assess newborns for hearing loss.
Neck
All newborns have a short neck that should be freely movable in all directions with no webbing present. Asymmetry of the neck is usually due to positioning in utero. The nurse performs range of motion of the neck. The thyroid cannot be palpated.
Chest
The newborn chest should be cylindrical, symmetrical, and have an anterior-posterior diameter of 1:1. Chest circumference should be measured by placing the measuring tape flat on the warmer and laying the newborn supine on top of it with the tape at the scapulae. The tape will then be brought around anteriorly, directly over the nipple line (see Figure 23.4). Average chest circumference in a newborn is 33 cm (13 inches), or 2 cm (1 inch) less than the head circumference. Due to maternal hormones still circulating in the newborn’s body, breast buds will appear enlarged and swollen, and female newborns may experience breast discharge. The nurse should assess the clavicles for crepitus, lumps, or masses, which could indicate an injury during birth.
Assessment of Abdomen
Upon inspection, the newborn’s abdomen is symmetrical, round, cylindrical and protruding. The newborn’s abdomen should move with respiration. Abnormal findings include distention, hernias (Figure 23.9), and visibly engorged vessels. Upon auscultation, the nurse hears bowel sounds present in all four quadrants by 1 to 2 hours of life. On palpation, the abdomen is soft, and the liver can be palpated 1 to 2 cm below the right costal margin.
The umbilical stump contains three vessels: two arteries and one vein (AVA). The cord will begin drying soon after birth. It should remain free of redness and drainage. The nurse will provide education to the family to keep the umbilical stump open to air to facilitate drying. The cord will fall off independently in 7 to 10 days. Along with educating the parents about care of the umbilical stump, the nurse also instructs the parents to call their health-care provider if they notice any redness, persistent bleeding, or bad smell coming from the umbilical stump (Figure 23.10).
Genitourinary Assessment
It is important that the nurse perform a complete and thorough assessment of the genitalia of the newborn. This assessment should be completed at the end of the physical examination, since this is often the most invasive part. If this is the parents’ first child, it is also an appropriate time to teach them how to change a diaper.
Female
The nurse should assess the labia majora, which are slightly swollen from maternal hormones and cover the labia minora and clitoris. Milky discharge and even a reddish discharge, called pseudomenstruation, from the vagina are expected findings for the first 3 to 4 days after birth due to maternal hormones. There may be a vaginal tag, which can be normal and representative of a visible hymenal ring. This will disappear in a few weeks. It is important for the nurse to educate parents about these normal findings in female newborns because they can cause concern if red discharge is found in diapers and parents have not heard this is expected.
Male
Assessment of genitalia in male newborns includes the placement of the urethra, to ensure that it is at the tip of the penis, midline, and patent. Abnormal variations in male genitalia include hypospadias , which occurs when the urethral meatus is located on the ventral side of the penis; alternatively, epispadias is an abnormal condition in which the urethral meatus is located on the dorsal side of the penis. Male newborns with epispadias and hypospadias are not candidates for circumcision until they have a pediatric urology consultation to ensure that there are no additional anatomic abnormalities. Once the newborn is seen by pediatric urology providers after discharge from the hospital, the pediatric urologist will schedule a surgery to correct the meatus and, if the parents choose, may perform a circumcision at the same time. Another abnormal variation in male genitalia the nurse should assess for is phimosis , a condition in which the opening of the foreskin is small and cannot be pulled back over the tip of the penis at all. This can interfere with urination and needs immediate intervention.
Assessment of the scrotum includes noting whether both testes have descended and can be palpated. The abnormal assessment finding in which the testes have not descended is called cryptorchidism . In a newborn, this can be a normal variation that should be followed by the health-care provider to ensure that they do descend in the future. There should be no evidence of hydrocele , which is an abnormal collection of fluid in the scrotal sac.
For newborn boys having a circumcision, that surgical procedure is often performed prior to discharge. The nurse will provide the parents with education regarding care of the surgical site. The nurse will explain to the parents that it is vital not to allow any gauze to adhere to the surgical site and disrupt the clotting that occurs on the tip of the penis. Some circumcision sites may have a device that is left in place until it falls off in 7 to 10 days. Parents will be instructed to use unscented, clear ointment on the tip of the newly circumcised penis and then place a 2-inch × 2-inch gauze pad gently over the surgical site. When it is time to change the dressing, they should remove the gauze and very gently wipe off any meconium or stool waste, using caution not to disrupt the clot. It is not necessary to remove all the ointment. Then, the parents will be told to apply fresh ointment and gauze with every diaper change for the next 7 to 10 days. Newborns would likely have had vitamin K prior to the procedure. If bleeding occurs that will not stop, the parents will be told by the nurse to take the newborn to the emergency department (ED) or for evaluation immediately. (See Chapter 22 Immediate Care of the Newborn.)
Atypical Genitalia
Some newborns are born with enlarged clitoris, labial fusion, and/or urethral openings not ventral to vaginal openings, making it difficult for the nurse to assign their sex. These newborns are among the one in 4,500 births that have atypical genitalia (Cleveland Clinic, 2022). The most common cause of atypical genitalia (sometimes called intersex genitals) in XX chromosome newborns is congenital adrenal hyperplasia (in the United States the overall incidence is 1:13,000 to 1:16,000 live births) (Krone & Arlt, 2009). Genital ambiguity in XY chromosome newborns is rare (de Omena Filho et al., 2022.)
Atypical genitalia in newborns are an uncommon occurrence and are often related to abnormalities in chromosomal formation. Read this article about assessing atypical genitalia for additional information.
Anus
The nurse will inspect the anal area to verify that it is patent and has no fissure. A missing or blocked opening to the anus is abnormal and is termed an imperforate anus . This is ruled out by visual assessment; no digital exam is necessary by the nurse. The passage of meconium can also be noted. When there is no passage of meconium in the first 24 to 48 hours after birth, the newborn is diagnosed with meconium ileus with obstruction, an abnormal finding in the newborn (Cleveland Clinic, 2022).
Nurse’s Response to Parents’ Refusal of Vitamin K Injection for Newborn
Imagine you are the nurse caring for a newborn who is 12 hours old. The parents of that newborn have declined administration of a vitamin K injection, despite education from the labor and delivery nurse and the midwife about the important medical benefits of the injection. As a nurse, you know that vitamin K is given to newborns to remedy their lack of clotting factors and thus prevent potentially fatal bleeding events.
The new parents are asking you when their baby boy can be circumcised. They are adamant that this must be done in the hospital before discharge and that they will not accept the vitamin K injection for their child. You again educate them about the potential for a catastrophic bleed during the procedure. If their newborn does not receive the vitamin K injection beforehand, the newborn is not eligible for this procedure. You explain to them that the American Academy of Pediatrics has recommended this as a routine preventive measure for nearly 60 years. Studies show that newborns are at risk for serious bleeding up to 2 weeks post birth (American Academy of Pediatrics, 2020). Nonetheless, the parents continue to refuse the injection, they ask to move forward with the circumcision, and they demand that the physician performing the procedure come in.
If a health-care provider agrees to perform the circumcisions despite the parents’ refusal of the vitamin K injection, your role as the nurse would require you to witness the parents’ consent for this procedure. However, you have serious concerns about the safety of this newborn under these circumstances.
It is not the nurse’s job to judge. It is the nurse’s job to advocate, provide evidence-based resources, and maintain confidentiality. Nurses respect the autonomy of childbearing people, pregnant people, and those who have given birth to make decisions that they feel are right for themselves and their children. Ethical nursing practice should include beneficence , the obligation to do good and nonmaleficence , the obligation to do no harm. Additionally, the nurse will need confidentiality, justice (treating everyone fairly and equitably), and veracity , demonstrating integrity and truth at all times. Maintaining these ethical principles is especially important when the nurse is in an emotionally charged environment.
Ultimately, in a situation like this, all the nurse can do is document the extensive teaching that was provided to the parents on multiple occasions. It is, by law, the parents’ decision to make, whether the nurse agrees or not. Ethical issues in maternal-health nursing occur frequently; the nurses’ job is to provide evidence-based education, advocate for their patients, and support the families they serve (Callister & Sudia-Robinson, 2011).
Musculoskeletal
In the musculoskeletal assessment , the nurse inspects the newborn’s extremities for gross deformities. The nurse assesses for extra digits, webbing, clubfoot , range of motion, short extremities, flexibility, and symmetrical movement. During the first few weeks of life and specifically in the first 24 hours, the newborn’s preferred position will be one that resembles their position in the uterus. They will remain in the fetal position with arms and legs flexed closely to the front of their body, hands clenched, with elbows and knees bent. This posture will change as the newborn develops more control over their body movements and becomes more comfortable with the outside world. Hypotonia, laxity, or a relaxed overall position may be related to maternal medication or an underlying genetic condition.
Arms and Hands
In a full-term newborn, fingernails will extend beyond the end of the fingertip and are often slightly adhered to the skin. The nurse counts all the digits in each hand. The abnormal condition of extra digits in the hand is known as polydactyly . Another abnormal finding of the hand, syndactyly , is the presence of webbing, or fusion, of fingers and toes that can be associated with trisomy 21 ( Down syndrome ) or be the result of heredity (Figure 23.11). Hands are assessed for palmar creases. A single palmer crease is associated with newborns with trisomy 21.
A partial or complete paralysis of portions of the arm that results from trauma to the brachial plexus nerve is called brachial palsy . This can be caused by too much downward pressure being applied during the delivery of the head to deliver the shoulders. From this same motion, it is possible to fracture the clavicle. A fractured clavicle does not always indicate brachial plexus injury. It is important that the nurse assess for full range of motion in both limbs. Brachial palsy occurs most often when there is strong traction applied to the newborn’s head to dislodge the shoulder behind the symphysis pubis in the presence of shoulder dystocia. The portion of the arm affected is determined by the nerves damaged.
Erb-Duchenne paralysis, also known as Erb palsy , involves damage to the upper arm and is the most common nerve injury for newborns. With this injury, the newborn’s arm may lie limply at the side of the body, or the newborn may avoid moving their arm when encouraged to do so. The nurse can see this by initiating the startle reflex. The nurse will place their fingers on the newborn’s clavicle, starting in the center of body and then palpating to the outer body and feeling for crepitus, lumps, or masses on the clavicle, paying attention to grimaces or crying from the newborn. (For a full discussion of Erb-Duchenne paralysis and brachial plexus injury, see Chapter 25 Care of the Newborn at Risk.)
Assessment of Legs and Feet
Newborn legs should be of equal length and with symmetrical folds. The newborn’s legs will likely still be in a flexed position, but the nurse should be able to extend the legs with ease. Range of motion should be symmetrical. The nurse performs the Barlow maneuver to assess the newborn for congenital hip dysplasia by placing the newborn in a supine position in a warm, well-lit place. The nurse will then bring the newborn’s thighs to their chest, adducting the hip while applying pressure on the knee to direct the force posteriorly. If the hip can be dislocated, it will pop out of the socket, and the nurse will hear and feel a click or pop. This is considered a positive test that needs to be reported and documented. The Ortolani maneuver is the second assessment for congenital hip dysplasia, in which the nurse keeps the newborn’s thighs at the midline in the Barlow position, places anterior pressure on the greater trochanters, then uses their thumbs to abduct the newborn’s legs gently and smoothly. If the hips can be dislocated, the nurse will hear or feel a pop. That is considered a positive test that needs to be documented and, though it is not highly sensitive, reported to the health-care provider. A negative exam is free of clicking.
Examination of the newborn includes the Ortolani and Barlow maneuvers for assessing for hip dysplasia.
The nurse assesses the newborn feet for symmetry and mobility. An abnormal finding of asymmetry or lack of movement may indicate a talipes deformity , also known as clubfoot . If this condition is noted (see Figure 25.11), the nurse should document it and notify a clinician for follow-up. See Chapter 25 Care of the Newborn at Risk for more information on this topic.
Back and Spine
To assess the back and spine, the nurse rotates the newborn to a prone position. The nurse places one finger on either side of the newborn’s spine, gently pressing as they run their fingers down the length of the spine. In doing so, the nurse assesses that the spine is straight and flat, with no deviations to the right or left. At the base of the spine, there should be no hair tufts, dimples, or breaks in the skin. During fetal development the spinal column comes together caudal to pedal (head to toe). If this process is stopped prior to full alignment, a dimple, cyst, or opening may be found at the base of the spine, potentially indicating misplacement of the nerves found at the base of the spinal column, or spina bifida . Spina bifida is a condition that may not be diagnosed until late childhood, but it will be monitored by pediatric health-care providers. Any deviations should be reported to the health-care provider.
The Hepatitis B Vaccine
A large part of the nurse’s responsibility during their time with the new family on the postpartum unit is providing education about the newborn’s first vaccination, hepatitis B. The hepatitis B vaccine is given to the newborn within the first 24 hours after birth and is the first in a three-dose series the newborn will receive over an 18-month period. The nurse should allow plenty of time to answer any questions from the new parents before administering the injection to the newborn.
- Generic Name: Hepatitis B immune globulin
- Trade Name: Engerix-B , Recombivax HB , Heplisav-B
- Class/Action: vaccines, inactivated, viral
- Route/Dosage: 5 mcg/0.5 mL (Recombivax HB), 10 mcg/0.5mL (Engerix-B).
- The hepatitis B vaccine is given to the infant as a 0.5 mL intramuscular injection in the anterior thigh. It is a three-dose immunization: The first dose is administered to the newborn within 24 hours of birth, the second between 1 and 2 months of age, and the third and final dose between 6 and 18 months of age.
- High Alert/Black Box Warning:
- Indications : The Centers for Disease Control and Prevention (CDC) recommends administration of the hepatitis B vaccine to all newborns within 24 hours of birth or at hospital discharge, whichever comes first.
- Mechanism of Action: Immunization with hepatitis B vaccine stimulates the immune system to produce specific humoral antibodies (HBsAG) against the hepatitis B virus.
- Contraindications: hypersensitivity to yeast
- Adverse Reactions/Side Effects: soreness at the site of the injection, severe itching, redness at the injection site, weakness, feeling unwell, nausea, vomiting
- Nursing Implications: Witness consent. Review patient education with the family. Administer the IM injection in the middle vastus lateralis muscle. Document in the patient’s chart.
- Parent/Family Education: The nurse will provide education to the parents via the CDC vaccine information statement (VIS). It is mandatory that, while providing this information to the parents, the nurse provide a copy of the VIS statement to them so that they can follow along and make an informed decision. The nurse should educate the parents that the risk of reaction for this injection is soreness at the site of the injection. The nurse will also advise the parents that they will need to follow up with their pediatrician and schedule the next appointment for immunization between 1 and 2 months of age and then again for the newborn’s final dose between 6 and 18 months.
Skin Assessment
Newborn skin should look well perfused and an appropriate color for the race of the newborn. Capillary refill for newborns should be less than 3 seconds (Singh, 2015), and well-hydrated newborns have flat fontanelles and moist mucosal membranes. It is a normal variation to see dry, cracked skin on hands, legs, and feet. Some variations in newborn skin are identified and defined in Table 23.2.
| Skin Presentation | Assessment Findings | Comments |
|---|---|---|
| Acrocyanosis | Bluish discoloration of hands and feet after birth | Peripheral cyanosis is normal in the first 24–48 hours after birth and resolves on its own. This is due to an immature cardiac system. If this is seen after that period, it is due to cold stress or sepsis and requires further evaluation. |
| Erythema toxicum | Normal newborn rash abruptly occurring as yellow or white papules over an erythematous base on the newborn’s body except the palms; occurs in 30%–70% of newborns | This condition is of unknown cause but thought to be an awakening of the immature immune system. |
| Milia | Exposed sebaceous glands that look like “baby acne” on the newborn’s face, nose, or chin, or all three | Milia disappear within the first month of life; no additional treatment is needed. |
| Telangiectatic nevus (stork bite) | Pale pink or reddish discoloration at the base of the neck, lower axilla, nasal bridge, or eyelids | Stork bites are often more noticeable when the newborn is crying or upset; they usually disappears by the second birthday but sometimes do not; they require no intervention. |
| Dermal melanocytosis | Formerly referred to as Mongolian spots, bluish-gray spots that can occur across the shoulders, on the hips, on the lower back near the buttocks, and on the legs | Commonly seen in newborns with darker skin, these spots will resolve on their own in the first few years of life; they resemble bruising and so can be confused with nonaccidental trauma, so the nurse should document location and size during neonatal assessment. |
| Strawberry hemangioma | Raised capillary nevi, occurring anywhere on the body, that often increase in size for the first few months of life, slowly decreasing in size over time, and disappearing by 10 years of age | No referral is needed unless these are interfering with vision or are very close to the eyes. |
| Lanugo | Fine, soft hair that covers the newborn’s back, shoulders, cheeks, forehead, and scalp; more common in newborns that are born early and often disappears within the 4 weeks after birth | No referral is needed. |
| Vernix caseosa | Cheesy, white substance covering and protecting the skin during intrauterine life; coverage at birth related to gestational age | Vernix caseosa diminishes the closer to term the fetus gets. |
Skin Color in Black and Biracial Newborns
Newborns of Black or biracial descent are born with variations in skin color. These newborns often have very sensitive skin that is prone to dryness and hyperpigmentation. Their skin is likely to be a shade or two lighter than their eventual skin color will be. This is so because it takes melanin 2 to 3 weeks to appear at the surface of the skin after being produced by cells called melanocytes (Lucock, 2023). If parents are concerned about the newborn’s light skin color, the nurse can use this as a teaching opportunity.
Assessing Jaundice in a Newborn
The condition of neonatal jaundice arises from an excess of bilirubin in the blood due to an increase in breakdown of red blood cells and manifests in a newborn as a yellowish discoloration of the skin, sclera, and mucous membranes. Approximately 75 percent of jaundice cases in newborns is caused by physiologic jaundice, which results from an increased bilirubin load, decreased ability to clear the bilirubin, and impaired activity from the enzyme needed for bilirubin conjugation in immature newborn livers. Physiologic jaundice typically appears after 24 hours of age, peaks at around 48 to 96 hours, and resolves by 2 to 3 weeks in full-term newborns.
To assess for newborn jaundice, the nurse will press on the newborn’s forehead and nose for 1 second with a gloved finger and observe for any underlying yellow tinge to the skin. If there is a yellow tinge, the nurse will also assess the sternum, palms, and soles by blanching the skin. In darker skinned newborns, jaundice may be more difficult to assess. Under the tongue and the sclera of the newborn’s eyes are other areas that should be assessed for jaundice or yellowing, as those areas work equally well for all skin colors. Jaundice progresses from head to toe. Jaundice is observable in the face and neck when bilirubin levels reach 4 to 8 mg/dL and can be seen on hands and feet when levels are greater than 15 mg/dL. The first notable finding is often seen in the sclera, and it is also the last area to clear. If the newborn appears jaundiced, a total serum bilirubin or transcutaneous bilirubin (TcB) level needs to be checked with the transcutaneous bilirubin meter (Figure 23.13). A diagnosis of pathologic jaundice, or nonphysiologic jaundice, occurs if the jaundice is present on the first day of life, and the newborn’s total serum bilirubin (TSB) rises by more than 5 mg/dL, more than 0.2 mg/dL/hour, or is higher than 17 mg/dL, or when the newborn has signs and symptoms suggestive of serious illness, like lethargy, respiratory distress, and decreased feeding. (For further discussion, refer 24.2 Care of Common Problems in the Newborn.)
Assessment of Neurologic Status
The assessment of neurologic status should be ongoing throughout the entire assessment of the newborn and throughout the nurse’s shift. Neurologic assessment of a newborn is different from a neurologic assessment in an adult. In the newborn, the nurse assesses physical characteristics including resting posture, muscle tone, motor activity, state of alertness, cry, and, most importantly, the ability to be consoled. Newborns like to be in a flexed position and should be using their extremities bilaterally. Typical newborns move their upper extremities erratically with uncoordinated movements. Any decreased, absent, or unilateral movements need further evaluation, as they may be indicative of a neurologic issue.
Any observation of consistently long-lasting, ongoing tremors or jitteriness in a full-term newborn must be evaluated for a cause. Tremors can be related to hypoglycemia , hypocalcemia , substance withdrawal, or convulsions. Neonatal seizure s can look like many things but can also simply be chewing or swallowing movements, deviations of the eyes, rigidity, or flaccidity due to immaturity of the central nervous system.
To assess the sucking reflex, the nurse will insert a gloved finger into the newborn’s mouth to elicit a response. Once the newborn is sucking, the nurse will assess hearing and vision responses by noting sucking changes in the presence of noise by a rattle or voice, and a change in sucking when a penlight is shined near the newborn’s eyes. The newborn responds with a brief stop in sucking followed by restarting sucking.
A normal neurologic examination indicates a functional neurologic system in the newborn. Nurses will be on alert for neurologic changes to be recognized as possible alterations and injuries that have occurred. Table 23.3 lists possible injuries that could occur during birth or after and the signs that a nurse may observe during a physical examination.
Immaturity of the central nervous system in the newborn is demonstrated by reflex responses. The newborn’s movements are uncoordinated, and methods of communication are very limited, so reflexes in newborns serve specific purposes. Some of them are protective, like blink, gag, and sneeze. Some newborn reflexes help with feeding, such as rooting and sucking, and some are for stimulating human interaction, such as yawning. Additionally, newborns can draw back from pain (protective), and they can even push up and try to crawl (prone crawl).
| Potential Injury | Example |
|---|---|
| Eye injuries | Subconjunctival and retinal hemorrhages |
| Intracranial hemorrhage | Subdural, subarachnoid |
| Bone fracture | Clavicle, facial bone, skull, humerus, femur |
| Nasal injuries | Dislocation, fractures |
| Scalp laceration abscess | Fetal scalp electrode, scalpel injuries related to cesarean birth |
| Soft-tissue injuries | Cephalohematoma, brachial plexus |
Moro Reflex
The Moro, or startle, reflex is present at birth and usually disappears around 2 months of age. This is a primitive protective reflex that occurs when the newborn is startled by a loud sound or sudden movement. The newborn will throw back their head, extend arms and legs, and sometimes begin to cry. A lack of Moro reflex warrants a call to the primary health-care provider for further evaluation (Figure 23.14).
Palmar Grasp Reflex
The palmar grasp reflex , present at 16 weeks’ gestation in utero, is a primitive reflex that can be elicited in preterm newborns as early as 25 weeks (Anekar & Brodoni, 2022). This reflex integrates with other newborn behaviors at 4 to 6 months to allow grasping of objects. It is possible that this reflex began as a way create interaction and bonding between the newborn and the parent (Anekar & Brodoni, 2022). The nurse can assess for the grasp reflex by placing their finger into the newborn’s palm. The newborn will grasp hard enough bilaterally that the nurse will be able to raise the newborn’s trunk for a few seconds (Figure 23.15).
Rooting Reflex
The rooting reflex that assists the infant in eating is present at birth and disappears around 3 to 4 months of age. The nurse can elicit this response by stroking the newborn’s cheek or the corner of the newborn’s mouth. The newborn will turn toward the nurse and open their mouth, anticipating the nipple or a bottle (Figure 23.16). Lack of response can indicate facial paralysis or neurologic depression, and the nurse should contact the primary care practitioner for follow-up.
Sucking Reflex
The sucking reflex begins in utero around 23 weeks’ gestation but does not fully develop until 36 weeks’ gestation. Premature newborns may have a weak, uncoordinated sucking ability, and it may be difficult for them to feed (Stanford Medicine, Childrens Health, 2022).  During this assessment, the nurse can also assess for any soft and hard palate abnormalities. Absence of a suck reflex may indicate neurologic depression from CNS conditions, neonatal abstinence syndrome, or developmental immaturity, and the nurse will report this to the primary care practitioner for further follow-up.
Tonic Neck Reflex
The tonic neck reflex is present at birth and integrates at 4 to 6 months with other newborn behaviors like rolling over, sitting up, and developing hand-eye coordination to reach for items (Frothingham, 2020). Some hypotheses suggest that this reflex occurs to help the fetus move down the birth canal (Frothingham, 2020). The nurse can assess for tonic neck reflex by placing the newborn supine, gently rotating the head to one side, and holding it in position for 15 seconds. A positive response is when the arm and leg extend on the facial side and flex on the other (Figure 23.18). No response to the assessment indicates the need to report that finding to the newborn’s primary clinician.
Stepping Reflex
The final reflex assessed is the stepping reflex , present from birth and designed to assist the newborn in moving to the birthing person’s breast to begin feeding. The nurse can assess this reflex in two ways. They can leave the newborn prone on the birthing person’s abdomen and observe the newborn crawl to the birthing person’s breast using the toes and knees, as though they are taking steps (Stanford Medicine, Childrens Health, 2022). Alternatively, the nurse can hold the newborn, place their feet on the bed, and observe the newborn try to stand on their feet and take steps (Figure 23.19). This reflex will disappear at around 8 weeks of age.
QSEN Competency: Patient-Centered Care: Use of a Pacifier
Definition: Recognize the patient or designee as the source of control and full partner in providing compassionate and coordinated care based on respect for patients’ preferences, values, and needs.
Knowledge: The nurse integrates understanding of multiple dimensions of patient-centered care:
- patient/family/community preferences, values
- coordination and integration of care
- information, communication, and education
- physical comfort and emotional support
- involvement of family and friends
- transition and continuity
Describe how diverse cultural, ethnic, and social backgrounds function as sources of patient family and community values
Skill: Communicate patient values, preferences, and expressed needs to other members of health-care team. The nurse will do the following:
- Listen to the patient and explore any concerns they may express.
- Share the preference the birthing parent has for the newborn to utilize a pacifier to self-soothe when not feeding.
- Provide the materials requested.
Attitude: Respect and encourage individual expression of patient values, preferences, and expressed needs.
(QSEN Institute, n.d.)


15.4: Pólya's Theorem
Before getting to the full version of Pólya's formula, we must develop a generating function as promised at the beginning of the chapter. To do this, we will return to our example of Section 15.1.
15.4.1 The cycle index
Unlike the generating functions we encountered in Chapter 8, the generating functions we will develop in this chapter will have more than one variable. We begin by associating a monomial with each element of the permutation group involved. In this case, it is \(D_8\), the dihedral group of the square. To determine the monomial associated to a permutation, we need to write the permutation in cycle notation and then determine the monomial based on the number of cycles of each length. Specifically, if \(\pi\) is a permutation of \([n]\) with \(j_k\) cycles of length \(k\) for \(1≤k≤n\), then the monomial associated to \(\pi\) is \(x_1^{j_1}x_2^{j_2} \cdot \cdot \cdot x_n^{j_n}\). Note that \(j_1+2j_2+3j_3+ \cdot \cdot \cdot +nj_n=n\). For example, the permutation \(r_1=(1234)\) is associated with the monomial \(x_4^1\) since it consists of a single cycle of length 4. The permutation \(r_2=(13)(24)\) has two cycles of length 2, and thus its monomial is \(x_2^2\). For \(p=(14)(2)(3)\), we have two 1-cycles and one 2-cycle, yielding the monomial \(x_1^2x_2^1\). In Figure 15.10 , we show all eight permutations in \(D_8\) along with their associated monomials.
Figure 15.10. Monomials arising from the dihedral group of the square
Now let's see how the number of 2-colorings of the square fixed by a permutation can be determined from its cycle structure and associated monomial. If \(\pi(i)=j\), then we know that for \(\pi\) to fix a coloring \(C\), vertices \(i\) and \(j\) must be colored the same in \(C\). Thus, the second vertex in a cycle must have the same color as the first. But then the third vertex must have the same color as the second, which is the same color as the first. In fact, all vertices appearing in a cycle of \(\pi\) must have the same color in \(C\) if π fixes \(C!\) Since we are coloring with the two colors white and gold, we can choose to color the points of each cycle uniformly white or gold. For example, for the permutation \(v=(12)(34)\) to fix a coloring of the square, vertices 1 and 2 must be colored the same color (2 choices) and vertices 3 and 4 must be colored the same color (2 choices). Thus, there are \(2 \cdot 2=4\) colorings fixed by \(v\). Since there are two choices for how to uniformly color the elements of a cycle, letting \(x_i=2\) for all i in the monomial associated with \(\pi\) gives the number of colorings fixed by \(\pi\). In Figure 15.10 , the “Fixed colorings” column gives the number of 2-colorings of the square fixed by each permutation. Before, we obtained this manually by considering the action of \(D_8\) on the set of all 16 colorings. Now we only need the cycle notation and the monomials that result from it to derive this!
Recall that Burnside's Lemma states that the number of colorings fixed by the action of a group can be obtained by adding up the number fixed by each permutation and dividing by the number of permutations in the group. If we do that instead for the monomials arising from the permutations in a permutation group \(G\) in which every cycle of every permutation has at most \(n\) entries, we obtain a polynomial known as the cycle index \(P_G(x_1,x_2,…,x_n)\). For our running example, we find
\(P_{D_8}(x_1,x_2,x_3,x_4)=\dfrac{1}{8}(x_1^4+2x_1^2x_2^1+3x_2^2+2x_4^1)\).
To find the number of distinct 2-colorings of the square, we thus let \(x_i=2\) for all i and obtain \(P_{D_8}(2,2,2,2)=6\) as before. Notice, however, that we have something more powerful than Burnside's lemma here. We may substitute any positive integer \(m\) for each \(x_i\) to find out how many nonequivalent \(m\)-colorings of the square exist. We no longer have to analyze how many colorings each permutation fixes. For instance, \(P_{D_8}(3,3,3,3)=21\), meaning that 21 of the 81 colorings of the vertices of the square using three colors are distinct.
15.4.2 The full enumeration formula
Hopefully the power of the cycle index to count colorings that are distinct when symmetries are considered is becoming apparent. In the next section, we will provide additional examples of how it can be used. However, we still haven't seen the full power of Pólya's technique. From the cycle index alone, we can determine how many colorings of the vertices of the square are distinct. However, what if we want to know how many of them have two white vertices and two gold vertices? This is where Pólya's enumeration formula truly plays the role of a generating function.
Let's again consider the cycle index for the dihedral group \(D_8\):
\(P_{D_8}(x_1,x_2,x_3,x_4)=\dfrac{1}{8}(x_1^4+2x_1^2x_2^1+3x_2^2+2x_4^1)\).
Instead of substituting integers for the \(x_i\), let's consider what happens if we substitute something that allows us to track the colors used. Since \(x_1\) represents a cycle of length 1 in a permutation, the choice of white or gold for the vertex in such a cycle amounts to a single vertex receiving that color. What happens if we substitute \(w+g\) for ?\(x_1\)? The first term in \(P_{D_8}\) corresponds to the identity permutation \(ι\), which fixes all colorings of the square. Letting \(x_1=w+g\) in this term gives
\((w+g)^4=g^4+4g^3w+6g^2w^2+4gw^3+w^4\),
which tells us that \(ι\) fixes one coloring with four gold vertices, four colorings with three gold vertices and one white vertex, six colorings with two gold vertices and two white vertices, four colorings with one gold vertex and three white vertices, and one coloring with four white vertices.
Let's continue establishing a pattern here by considering the variable \(x_2\). It represents the cycles of length 2 in a permutation. Such a cycle must be colored uniformly white or gold to be fixed by the permutation. Thus, choosing white or gold for the vertices in that cycle results in two white vertices or two gold vertices in the coloring. Since this happens for every cycle of length 2, we want to substitute \(w^2+g^2\) for \(x_2\) in the cycle index. The \(x_1^2x_2^1\) terms in \(P_{D_8}\) are associated with the flips \(p\) and \(n\). Letting \(x_1=w+g\) and \(x_2=w^2+g^2\), we find
\(x_1^2x_2^1=g^4+2g^3w+2g^2w^2+2gw^3+w^4\),
from which we are able to deduce that p and n each fix one coloring with four gold vertices, two colorings with three gold vertices and one white vertex, and so on. Comparing this with Figure 15.2 shows that the generating function is right on.
By now the pattern is becoming apparent. If we substitute \(w^i+g^i\) for \(x_i\) in the cycle index for each \(i\), we then keep track of how many vertices are colored white and how many are colored gold. The simplification of the cycle index in this case is then a generating function in which the coefficient on \(g^sw^t\) is the number of distinct colorings of the vertices of the square with \(s\) vertices colored gold and \(t\) vertices colored white. Doing this and simplifying gives
\(P_{D_8}(w+g,w^2+g^2,w^3+g^3,w^4+g^4)=g^4+g^3w+2g^2w^2+gw^3+w^4\).
From this we find one coloring with all vertices gold, one coloring with all vertices white, one coloring with three gold vertices and one white vertex, one coloring with one gold vertex and three white vertices, and two colorings with two vertices of each color.
As with the other results we've discovered in this chapter, this property of the cycle index holds up beyond the case of coloring the vertices of the square with two colors. The full version is Pólya's enumeration theorem:
Let \(S\) be a set with \(|S|=r\) and \(\mathcal{C}\) the set of colorings of \(S\) using the colors \(c_1,…,c_m\) . If a permutation group \(G\) acts on \(S\) to induce an equivalence relation on \(\mathcal{C}\) , then
\(P_G ( \displaystyle \sum_{i=1}^m c_i, \sum_{i=1}^m c_i^2, \cdot \cdot \cdot, \sum_{i=1}^m c_i^r)\)
is the generating function for the number of nonequivalent colorings of \(S\) in \(\mathcal{C}\) .
If we return to coloring the vertices of the square but now allow the color blue as well, we find
\(P_{D_8}(w+g+b,w^2+g^2+b^2,w^3+g^3+b^3,w^4+g^4+b^4)=b^4+b^3g+2b^2g^2+bg^3+g^4+b^3w+2b^2gw+2bg^2w+g^3w+2b^2w^2+2bgw^2+2g^2w^2+bw^3+gw^3+w^4\).
From this generating function, we can readily determine the number of nonequivalent colorings with two blue vertices, one gold vertex, and one white vertex to be 2. Because the generating function of Pólya's Enumeration Theorem records the number of nonequivalent patterns, it is sometimes called the pattern inventory .
What if we were interested in making necklaces with 500 (very small) beads colored white, gold, and blue? This would be equivalent to coloring the vertices of a regular 500-gon, and the dihedral group \(D_{1000}\) would give the appropriate transformations. With a computer algebra system such as Mathematica ®, it is possible to quickly produce the pattern inventory for such a problem. In doing so, we find that there are
\(36360291795869936842385267079543319118023385026001623040346035832580600191583895484198508262979388783308179702534404046627287796430425271499270313565347234741708546745333417930824781980702852692187253642441292279756575936040804567103229 \approx 3.6 \times 10^{235}\)
possible necklaces. Of them,
\(252949184234046077349041318620101048779141729407880866280363896567824471388337043268753932294423230859058382000714795759057317766605088026968640797415175535033372572682057214340157297357996345021733060 \approx 2.5 \times 10^{200}\)
have 225 white beads, 225 gold beads, and 50 blue beads.
The remainder of this chapter will focus on applications of Pólya's Enumeration Theorem and the pattern inventory in a variety of settings.


3.8: The Metric in General Relativity
So far we’ve considered a variety of examples in which the metric is predetermined. This is not the case in general relativity. For example, Einstein published general relativity in 1915, but it was not until 1916 that Schwarzschild found the metric for a spherical, gravitating body such as the sun or the earth.
When masses are present, finding the metric is analogous to finding the electric field made by charges, but the interpretation is more difficult. In the electromagnetic case, the field is found on a preexisting background of space and time. In general relativity, there is no preexisting geometry of spacetime. The metric tells us how to find distances in terms of our coordinates, but the coordinates themselves are completely arbitrary. So what does the metric even mean? This was an issue that caused Einstein great distress and confusion, and at one point, in 1914, it even led him to publish an incorrect, dead-end theory of gravity in which he abandoned coordinate-independence.
With the benefit of hindsight, we can consider these issues in terms of the general description of measurements in relativity given in section 3.4 :
- We can tell whether events and world-lines are incident.
- We can do measurements in local Lorentz frames.
The Hole Argument
The main factor that led Einstein to his false start is known as the hole argument. Suppose that we know about the distribution of matter throughout all of spacetime, including a particular region of finite size — the “hole” — which contains no matter. By analogy with other classical field theories, such as electromagnetism, we expect that the metric will be a solution to some kind of differential equation, in which matter acts as the source term. We find a metric \(g(x)\) that solves the field equations for this set of sources, where \(x\) is some set of coordinates. Now if the field equations are coordinate-independent, we can introduce a new set of coordinates x', which is identical to \(x\) outside the hole, but differs from it on the inside. If we reexpress the metric in terms of these new coordinates as \(g'(x')\), then we are guaranteed that \(g'(x')\) is also a solution. But furthermore, we can substitute \(x\) for \(x'\), and \(g'(x)\) will still be a solution. For outside the hole there is no difference between the primed and unprimed quantities, and inside the hole there is no mass distribution that has to match the metric’s behavior on a point-by-point basis.
We conclude that in any coordinate-invariant theory, it is impossible to uniquely determine the metric inside such a hole. Einstein initially decided that this was unacceptable, because it showed a lack of determinism; in a classical theory such as general relativity, we ought to be able to predict the evolution of the fields, and it would seem that there is no way to predict the metric inside the hole. He eventually realized that this was an incorrect interpretation. The only type of global observation that general relativity lets us do is measurements of the incidence of world-lines. Relabeling all the points inside the hole doesn’t change any of the incidence relations. For example, if two test particles sent into the region collide at a point x inside the hole, then changing the point’s name to x' doesn’t change the observable fact that they collided.
A Machian Paradox
Another type of argument that made Einstein suffer is also resolved by a correct understanding of measurements, this time the use of measurements in local Lorentz frames. The earth is in hydrostatic equilibrium, and its equator bulges due to its rotation. Suppose that the universe was empty except for two planets, each rotating about the line connecting their centers. 13 Since there are no stars or other external points of reference, the inhabitants of each planet have no external reference points against which to judge their rotation or lack of rotation. They can only determine their rotation, Einstein said, relative to the other planet. Now suppose that one planet has an equatorial bulge and the other doesn’t. This seems to violate determinism, since there is no cause that could produce the differing effect. The people on either planet can consider themselves as rotating and the other planet as stationary, or they can describe the situation the other way around. Einstein believed that this argument proved that there could be no difference between the sizes of the two planets’ equatorial bulges.
Note
The example is described in Einstein’s paper “The Foundation of the General Theory of Relativity.” An excerpt, which includes the example, is given in Appendix A .
The flaw in Einstein’s argument was that measurements in local Lorentz frames do allow one to make a distinction between rotation and a lack of rotation. For example, suppose that scientists on planet A notice that their world has no equatorial bulge, while planet B has one. They send a space probe with a clock to B, let it stay on B’s surface for a few years, and then order it to return. When the clock is back in the lab, they compare it with another clock that stayed in the lab on planet A, and they find that less time has elapsed according to the one that spent time on B’s surface. They conclude that planet B is rotating more quickly than planet A, and that the motion of B’s surface was the cause of the observed time dilation. This resolution of the apparent paradox depends specifically on the Lorentzian form of the local geometry of spacetime; it is not available in, e.g., Cartan’s curved-spacetime description of Newtonian gravity .
Einstein’s original, incorrect use of this example sprang from his interest in the ideas of the physicist and philosopher Ernst Mach. Mach had a somewhat ill-defined idea that since motion is only a well-defined notion when we speak of one object moving relative to another object, the inertia of an object must be caused by the influence of all the other matter in the universe. Einstein referred to this as Mach’s principle. Einstein’s false starts in constructing general relativity were frequently related to his attempts to make his theory too “Machian.” Section 8.3 discusses an alternative, more Machian theory of gravity proposed by Brans and Dicke in 1951.


Chapter 24: Metabolism and Nutrition
This chapter will take you through some of the chemical reactions essential to life, the sum of which is referred to as metabolism. The focus of these discussions will be anabolic reactions and catabolic reactions. You will examine the various chemical reactions that are important to sustain life, including why you must have oxygen, how mitochondria transfer energy, and the importance of certain “metabolic” hormones and vitamins.
-
- 24.1: Introduction
- Eating is essential to life. Many of us look to eating as not only a necessity, but also a pleasure. You may have been told since childhood to start the day with a good breakfast to give you the energy to get through most of the day. You most likely have heard about the importance of a balanced diet, with plenty of fruits and vegetables. But what does this all mean to your body and the physiological processes it carries out each day?
-
- 24.2: Overview of Metabolic Reactions
- Metabolic processes are constantly taking place in the body. Metabolism is the sum of all of the chemical reactions that are involved in catabolism and anabolism. The reactions governing the breakdown of food to obtain energy are called catabolic reactions. Conversely, anabolic reactions use the energy produced by catabolic reactions to synthesize larger molecules from smaller ones, such as when the body forms proteins by stringing together amino acids. Both sets of reactions are critical.
-
- 24.3: Carbohydrate Metabolism
- Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen atoms. The family of carbohydrates includes both simple and complex sugars. Glucose and fructose are examples of simple sugars, and starch, glycogen, and cellulose are all examples of complex sugars. The complex sugars are also called polysaccharides and are made of multiple monosaccharide molecules. Polysaccharides serve as energy storage and as structural components.
-
- 24.4: Lipid Metabolism
- Fats (or triglycerides) within the body are ingested as food or synthesized by adipocytes or hepatocytes from carbohydrate precursors (Figure 24.3.1). Lipid metabolism entails the oxidation of fatty acids to either generate energy or synthesize new lipids from smaller constituent molecules. Lipid metabolism is associated with carbohydrate metabolism, as products of glucose (such as acetyl CoA) can be converted into lipids.
-
- 24.5: Protein Metabolism
- Much of the body is made of protein, and these proteins take on a myriad of forms. They represent cell signaling receptors, signaling molecules, structural members, enzymes, intracellular trafficking components, extracellular matrix scaffolds, ion pumps, ion channels, oxygen and CO2 transporters (hemoglobin).  How does the body meet this constant demand for energy? Your body processes the food you eat both to use immediately and, importantly, to store as energy for later demands. If there were no method in place to store excess energy, you would need to eat constantly in order to meet energy demands.
-
- 24.7: Energy and Heat Balance
- The body tightly regulates the body temperature through a process called thermoregulation, in which the body can maintain its temperature within certain boundaries, even when the surrounding temperature is very different. The core temperature of the body remains steady at around 36.5–37.5 °C. In the process of ATP production by cells throughout the body, approximately 60 % of the energy produced is in the form of heat used to maintain body temperature.
-
- 24.8: Nutrition and Diet
- The carbohydrates, lipids, and proteins in the foods you eat are used for energy to power molecular, cellular, and organ system activities. Importantly, the energy is stored primarily as fats. The quantity and quality of food that is ingested, digested, and absorbed affects the amount of fat that is stored as excess calories.


6.5: Fermentation
By the end of this section, you will be able to do the following:
- Discuss the fundamental difference between anaerobic cellular respiration and fermentation
- Describe the type of fermentation that readily occurs in animal cells and the conditions that initiate that fermentation
In aerobic respiration, the final electron acceptor is an oxygen molecule, O 2 . If aerobic respiration occurs, then ATP will be produced using the energy of the high-energy electrons carried by NADH or FADH 2 to the electron transport chain. If aerobic respiration does not occur, NADH must be reoxidized to NAD + for reuse as an electron carrier for glycolysis to continue. How is this done? Some living systems use an organic molecule as the final electron acceptor. Processes that use an organic molecule to regenerate NAD + from NADH are collectively referred to as fermentation. In contrast, some living systems use an inorganic molecule (other than oxygen) as a final electron acceptor to regenerate NAD + ; both methods are anaerobic (do not require oxygen) to achieve NAD + regeneration and enable organisms to convert energy for their use in the absence of oxygen.
Lactic Acid Fermentation
The fermentation method used by animals and some bacteria like those in yogurt is lactic acid fermentation (Figure \(\PageIndex{1}\)). This occurs routinely in mammalian red blood cells and in skeletal muscle that has insufficient oxygen supply to allow aerobic respiration to continue (that is, in muscles used to the point of fatigue). In muscles, lactic acid produced by fermentation must be removed by the blood circulation and brought to the liver for further metabolism. The chemical reaction of lactic acid fermentation is the following:
\[\ce{Pyruvic\: acid + NADH ↔ lactic\: acid + NAD+}\nonumber\]
The enzyme that catalyzes this reaction is lactate dehydrogenase. The reaction can proceed in either direction, but the left-to-right reaction is inhibited by acidic conditions. This lactic acid build-up causes muscle stiffness and fatigue. Once the lactic acid has been removed from the muscle and is circulated to the liver, it can be converted back to pyruvic acid and further catabolized for energy.
ART CONNECTION
Tremetol, a metabolic poison found in white snake root plant, prevents the metabolism of lactate. When cows eat this plant, Tremetol is concentrated in the milk. Humans who consume the milk become ill. Symptoms of this disease, which include vomiting, abdominal pain, and tremors, become worse after exercise. Why do you think this is the case?
Alcohol Fermentation
Another familiar fermentation process is alcohol fermentation (Figure \(\PageIndex{2}\)), which produces ethanol, an alcohol. The alcohol fermentation reaction is the following:
In the first reaction, a carboxyl group is removed from pyruvic acid, releasing carbon dioxide as a gas. The loss of carbon dioxide reduces the molecule by one carbon atom, making acetaldehyde. The second reaction removes an electron from NADH, forming NAD + and producing ethanol from the acetaldehyde, which accepts the electron. The fermentation of pyruvic acid by yeast produces the ethanol found in alcoholic beverages (Figure \(\PageIndex{3}\)). If the carbon dioxide produced by the reaction is not vented from the fermentation chamber, for example in beer and sparkling wines, it remains dissolved in the medium until the pressure is released. Ethanol above 12 percent is toxic to yeast, so natural levels of alcohol in wine occur at a maximum of 12 percent.
Anaerobic Cellular Respiration
Certain prokaryotes, including some species of bacteria and Archaea, use anaerobic respiration. For example, the group of Archaea called methanogens reduces carbon dioxide to methane to oxidize NADH. These microorganisms are found in soil and in the digestive tracts of ruminants, such as cows and sheep. Similarly, sulfate-reducing bacteria and Archaea, most of which are anaerobic (Figure \(\PageIndex{4}\)), reduce sulfate to hydrogen sulfide to regenerate NAD + from NADH.
Other fermentation methods occur in bacteria. Many prokaryotes are facultatively anaerobic. This means that they can switch between aerobic respiration and fermentation, depending on the availability of oxygen. Certain prokaryotes, like Clostridia bacteria, are obligate anaerobes. Obligate anaerobes live and grow in the absence of molecular oxygen. Oxygen is a poison to these microorganisms and kills them upon exposure. It should be noted that all forms of fermentation, except lactic acid fermentation, produce gas. The production of particular types of gas is used as an indicator of the fermentation of specific carbohydrates, which plays a role in the laboratory identification of the bacteria. The various methods of fermentation are used by different organisms to ensure an adequate supply of NAD + for the sixth step in glycolysis. Without these pathways, that step would not occur, and no ATP would be harvested from the breakdown of glucose.
Contributors and Attributions
Remixed and/or curated from the following works:
Fowler, S., Roush, R., & Wise, J. (2013). 4.4 Fermentation . In Concepts of Biology . OpenStax (CC BY 4.0; Access for free at https://openstax.org/books/concepts-biology/pages/1-introduction ).


11.5: Carbon monoxide
CO Fate in the Atmosphere
CO is one of the most common air pollutants, and its concentration in contaminated continental air masses reaches up to several ppmv ( Badr and Probert, 1994 ). CO is emitted to the atmosphere through anthropogenic processes, such as biomass combustion, fossil fuels, waste incineration, industrial processes, and transport. Additional contributors are natural sources (oceans, soils, plants, forest fires), atmospheric oxidation of CH 4 , and other non-CH 4 hydrocarbons (NMHC) ( Badr and Probert, 1995 ; Tarr et al., 1995 ; Schade and Crutzen, 1999 ; Bruhn et al., 2013 ). CH 4 oxidation has the largest share of these sources, producing approximately 700 Tg-CO·yr −1 ( Bergamaschi et al., 2000 ; Monson and Holland, 2001 ); fossil fuel combustion together with biofuel use and other industrial emissions are responsible for 500–900 Tg-CO·yr −1 , while biomass burning–for 400–800 Tg ( Duncan et al., 2007 ). Photochemical CO production due to the oxidation of naturally emitted and anthropogenic NMHC equals 450 and 110 Tg-CO·yr −1 , respectively, ( Rozante et al., 2017 ). In general, global CO levels rose from the Industrial Revolution until 1980; then a gradual decrease in its concentration, especially in the Northern Hemisphere, was observed in measurements from the global surface network from the National Oceanic and Atmospheric Administration (NOAA), caused by both the use of catalytic converters in cars and technological advances in combustion since 2000 ( Bakwin et al., 1994 ; Voiland, 2015 ; Gaubert et al., 2017 ). More recently, the downward trends in CO observed for both the Northern and Southern Hemispheres have shown good consistency with long-term trends in bottom-up emissions in Europe, the United States, and China; where an improvement in combustion efficiency and a reduction in emissions from anthropogenic sources was observed ( Gaubert et al., 2017 ). It is worth noting, however, that despite its main global sources, atmospheric CO levels show spatial as well as seasonal variability. While the oxidation of CH 4 , a gas that is evenly distributed around the world, provides a similarly constant CO background of around 25 ppb, the remaining emission groups depend on space-time aspects. Thus, inter alia, CO from fossil fuels shows higher levels in the northern mid-latitudes, mainly in winter, while biomass combustion in tropical continents contributes to higher CO concentrations in the summer, during the dry season, along with the rainforests ( Andreae et al., 2012 ). Additionally, the spatial variation in CO concentration is also characteristic on a smaller scale, e.g., in urban areas, where it depends not only on meteorological conditions or thermal inversion but also directly on atmospheric turbulence and traffic intensity ( Oliveira et al., 2003 ).
CO is mainly utilized by the tropospheric reaction with the OH hydroxyl radical ( Logan et al., 1981 ; Khalil and Rasmussen, 1984 ; Badr and Probert, 1995 ). CO is oxidized to CO 2 in the stratosphere, where it migrates via convection, turbulence, and mixing ( Seiler and Warneck, 1972 ; Seiler, 1974 ). The reaction is fast and independent of temperature; thanks to it, the residence time of CO in the atmosphere is relatively short, from 2 weeks to 3 months ( Rozante et al., 2017 ; Rakitin et al., 2021 ). Soils and oceans are also involved in CO capture ( Ingersoll et al., 1974 ; Conrad et al., 1982 ) and higher plants and algae ( Krall and Tolbert, 1957 ; Chappelle, 1962 ).
Taking into account the characteristics of greenhouse gases, CO is not considered one of them as it is not capable of absorbing infrared radiation ( Rozante et al., 2017 ). However, because of the primary mechanism for removing atmospheric CO by reaction with the OH radical, CO is recognized as an essential trace gas that controls the oxidative ability of the atmosphere ( Bruhn et al., 2013 ). An increase in CO concentration in the troposphere causes changes in the distribution and amount of OH; reactions of the radical with CO and CH 4 constitute about 97% of its destruction ( Logan et al., 1981 ; Levine et al., 1985 ; Badr and Probert, 1995 ). The change in the atmospheric OH affects the concentration of other gases, including CH 4 and O 3 ( Hameed et al., 1980 ). Thus, CO indirectly affects the energy budget of the atmosphere ( Evans and Puckrin, 1995 ), increasing the concentration of GHGs and the time of their utilization in the troposphere, as well as controlling the transfer to the stratosphere, which in turn has an impact on stratospheric O 3 ( Ramanathan et al., 1985 ; Thompson, 1992 ; Bruhn et al., 2013 ). The radiative forcing from CO is estimated more than from N 2 O and halogenated hydrocarbons ( Rakitin et al., 2021 ).
Further detailed information at Sobieraj, K., Stegenta-Dąbrowska, S., Luo, G., Koziel, J. A., & Białowiec, A. (2022). Carbon monoxide fate in the environment as an inspiration for biorefinery industry: A review. Frontiers in Environmental Science , 10 , 822463. https://www.frontiersin.org/articles/10.3389/fenvs.2022.822463/full
CO Fate in Soil
CO is constantly supplied to the atmosphere, which results from both natural and anthropogenic sources. Despite the significant amount of gas emitted, its concentration in the atmosphere does not seem to increase ( Bartholomew and Alexander, 1979 ). It’s because natural processes are responsible for utilizing CO shortly after its release ( Inman et al., 1971 ).
Soil is considered one of the main sinks of atmospheric CO, responsible for 40% of total consumption ( Seiler, 1978 ). However, soils can also be a CO source in the global CO cycle, as noted, especially in the savannas and deserts ( Conrad and Seiler, 1985a ; Kuhlbusch et al., 1998 ). For this reason, CO uptake by soils is a net flux consisting simultaneously of consumption and production ( Figure 1 ) ( Seiler, 1978 ; King and Crosby, 2002 ; Bruhn et al., 2013 ; van Asperen et al., 2015 ; Pihlatie et al., 2016 ). Simultaneous chemical, physical and microbiological processes ( Kuhlbusch et al., 1998 ) depend on many climatic, biological, and physical soil factors, making the equilibrium CO vary between a few ppbv up to hundreds of ppbv (parts per billion by volume) ( Conrad and Seiler, 1979 ; Conrad and Seiler, 1980b ; Conrad and Seiler, 1982a ). The most important soil parameters include water content, temperature, organic matter content, pH, soil type, the depth of CO consumption horizon, and CO concentration in the gas phase ( Potter et al., 1996 ). Even small changes in this balancing between CO production and soil uptake can severely impact tropospheric chemistry ( Moxley and Smith, 1998b ).
Further detailed information at Sobieraj, K., Stegenta-Dąbrowska, S., Luo, G., Koziel, J. A., & Białowiec, A. (2022). Carbon monoxide fate in the environment as an inspiration for biorefinery industry: A review. Frontiers in Environmental Science , 10 , 822463. https://www.frontiersin.org/articles/10.3389/fenvs.2022.822463/full
CO Fate in Water
The ocean has been recognized as a source of CO released into the atmosphere since the early 1970s ( Swinnerton et al., 1970 ; Lamontagne et al., 1971 ). Despite the low ocean share (0.4–9%) among all sources of CO in the atmosphere ( Bates et al., 1995 ), it can constitute up to 50% of the load in the marine boundary layer ( Erickson and Taylor, 1992 ; Stubbins et al., 2006a ). The southern hemisphere is particularly important here, in which CO production accounts for almost 60% of the total CO flux from the ocean surface ( Erickson, 1989 ). Surface ocean waters are saturated with CO compared to atmospheric equilibrium, which causes a net flux of this gas at the ocean-atmosphere interface ( Linnenbom et al., 1973 ; Logan et al., 1981 ; Zuo et al., 1998 ). The CO emissions to air are controlled mainly by the concentration of this gas in water ( Bates et al., 1995 ). It depends on several factors such as photochemical production, consumption by microorganisms, exchange between air and water, and physical mixing ( Figure 2 ) ( Wilson et al., 1970 ; Conrad et al., 1982 ; Butler et al., 1987 ; Jones, 1991 ). Due to the impact of these factors, CO concentration in waters shows diurnal, seasonal, and regional diversification ( Bates et al., 1995 ).
CO was identified as the second most important product of dissolved organic matter (DOM) photolysis in water bodies ( Mopper and Kieber, 2000 ; Stubbins et al., 2006b ). The rate of CO formation is one order of magnitude higher compared to other low molecular weight carbon photoproducts produced under aqueous conditions ( Mopper et al., 1991 ; Zuo and Jones, 1995 ). It is the photodegradation of the DOM by part of the UV solar radiation that is indicated as the main source of CO from both ocean and sea waters, as well as from the surface of lakes, rivers, wetlands, and coastal waters ( Zuo and Jones, 1997 ; Pos et al., 1998 ; Zuo et al., 1998 ; Stubbins et al., 2006a ; Blomquist et al., 2012 ).
Further detailed information at Sobieraj, K., Stegenta-Dąbrowska, S., Luo, G., Koziel, J. A., & Białowiec, A. (2022). Carbon monoxide fate in the environment as an inspiration for biorefinery industry: A review. Frontiers in Environmental Science , 10 , 822463. https://www.frontiersin.org/articles/10.3389/fenvs.2022.822463/full
CO Impact on Plants
Biosynthesis and photoproduction of CO in plants were observed in the second half of the 20th century ( Wilks, 1959 ; Schade et al., 1999 ). This compound is formed during oxidative heme catabolism due to the activity of the enzyme heme oxygenase (HO). The result is three products: CO, biliverdin, and free iron Fe 2 + ( Figure 3 ). The second one is immediately transformed into bilirubin, while the iron is involved in ferritin induction ( Bilban et al., 2008 ). Among the three isoforms of HO discovered so far, HO-1, HO-2 and HO-3 have been distinguished, the last two of which are characterized by low activity ( Maines, 1997 ).
Further detailed information at Sobieraj, K., Stegenta-Dąbrowska, S., Luo, G., Koziel, J. A., & Białowiec, A. (2022). Carbon monoxide fate in the environment as an inspiration for biorefinery industry: A review. Frontiers in Environmental Science , 10 , 822463. https://www.frontiersin.org/articles/10.3389/fenvs.2022.822463/full
Source
Sobieraj, K., Stegenta-Dąbrowska, S., Luo, G., Koziel, J. A., & Białowiec, A. (2022). Carbon monoxide fate in the environment as an inspiration for biorefinery industry: A review. Frontiers in Environmental Science , 10 , 822463. CC-BY accessed December 2023 https://www.frontiersin.org/articles/10.3389/fenvs.2022.822463/full