induction/recovery during routine surgery. accordingly, most citizens are likely to be "bagged" at least once during their lifetime as they undergo procedures involving general anesthesia. additionally, a significant number of newborns are ventilated with infant-sized manual resuscitators to help stimulate normal breathing, making manual resuscitators among the first therapeutic medical devices encountered upon birth. as previously stated, manual resuscitators are the first-line device recommended for emergency artificial ventilation of critical care patients, and are thus used not only throughout hospitals but also in out-of-hospital care venues by firefighters, paramedics and outpatient clinic personnel. inability of professional providers to use manual resuscitators within established safety guidelines manual resuscitators have no built-in tidal volume control — the amount of air used to force-inflate the lungs during each breath depends entirely on how much the operator squeezes the bag. in response to the dangers associated with the use of manual resuscitators, specific guidelines from the american heart association and european resuscitation council were issued that specify recommended maximal tidal volumes (or breath sizes) and ventilation rates safe for patients. while no studies are known that have assessed the frequency of complications or deaths due to uncontrolled manual resuscitator use, numerous peer-reviewed studies have found that, despite established safety guidelines, the incidence of provider over-inflation with manual resuscitators continues to be "endemic" and unrelated to provider training or skill level. another clinical study found "the tidal volume delivered by a manual resuscitator shows large variations", concluding that "the manual resuscitator is not a suitable device for accurate ventilation." a separate assessment of another high-skilled group with frequent emergency use of manual resuscitators (ambulance paramedics) found that "despite seemingly adequate training, ems personnel consistently hyperventilated patients during out-of-hospital cpr", with the same research group concluding that "unrecognized and inadvertent hyperventilation may be contributing to the currently dismal survival rates from cardiac arrest." a peer-reviewed study published in 2012 assessed the possible incidence of uncontrolled over-inflation in newborn neonates, finding that "a large discrepancy between the delivered and the current guideline values was observed for all parameters," and that "regardless of profession or handling technique ... 88.4% delivered excessive pressures, whereas ... 73.8% exceeded the recommended range of volume", concluding that "the great majority of research group concluding that "unrecognized and inadvertent hyperventilation from all professional groups delivered excessive pressures and volumes." a further examination has recently been made to assess whether a solution to the over-ventilation problem may lie with the use of pediatric-sized manual resuscitators in adults or use of more advanced flow-inflation (or "mapleson c") versions of manual resuscitators: while "the paediatric self-inflating bag delivered the most guideline-consistent ventilation", it did not lead to full guideline compliance as "participants hyperventilated patients' lungs in simulated cardiac arrest with all three devices." guideline non-compliance due to excessive rate versus excessive lung inflation "hyperventilation" can be achieved through delivery of (1) too many breaths per minute; (2) breaths that are too large and exceed the patient's natural lung capacity; or (3) a combination of both. with use of manual resuscitators, neither rate nor inflating volumes can be physically controlled through built-in safety adjustments within the device, and as highlighted above, studies show providers frequently exceed designated safety guidelines for both ventilation rate (10 breaths per minute) and volume (5–7 ml/kg body weight) as outlined by the american heart association and european resuscitation council. numerous studies have concluded that ventilation at rates in excess of current guidelines are capable of interfering with blood flow during cardiopulmonary resuscitation, however the pre-clinical experiments associated with these findings involved delivery of inspiratory volumes in excess of current guidelines, e.g., they assessed the effects of hyperventilation via both excessive rate and excessive volumes simultaneously. a more recent study published in 2012 expanded knowledge on this topic by evaluating the separate effects of (1) isolated excessive rate with guideline-compliant inspiratory volumes; (2) guideline-compliant rate with excessive inspiratory volumes; and (3) combined guideline non-compliance with both excessive rate and volume. this study found that excessive rate more than triple the current guideline (e.g., 33 breaths per minute) may not interfere with cpr when inspiratory volumes are delivered within guideline-compliant levels, suggesting that ability to keep breath sizes within guideline limits may individually mitigate clinical dangers of excessive rate. it was also found that when guideline-excessive tidal volumes were delivered, changes in blood flow were observed that were transient at low ventilation rates but sustained when both tidal volumes and rates were simultaneously excessive, suggesting that guideline-excessive tidal volume is the principal mechanism of side effects, with ventilation rate acting as a multiplier of these effects. consistent with previous studies where both excessive rate and volumes were found to produce side effects of blood flow interference during cpr, a complicating factor may be inadequate time to permit full expiration of oversized breaths in between closely spaced high-rate breaths, leading to the lungs never being permitted to fully exhale between ventilations (also called "stacking" of breaths). a recent advancement in the safety of manual ventilation may be the growing use of time-assist devices that emit an audible or visual metronome tone or flashing light at the proper guideline-designated rate interval for breath frequency; one study found these devices may lead to near 100% guideline compliance for ventilation rate. while this advancement appears to provide a solution to the "rate problem" associated with guideline-excessive manual resuscitator use, it may not address the "volume problem", which may continue to make manual resuscitators a patient hazard, as complications can still occur from over-inflation even when rate is delivered within guidelines. currently, the only devices that can deliver pre-set, physician-prescribed inflation volumes reliably within safety guidelines are mechanical ventilators that require an electrical power source or a source of compressed oxygen, a higher level of training to operate, and typically cost hundreds to thousands of dollars more than a disposable manual resuscitator. additional components and features filters a filter is sometimes placed between the mask and the bag (before or after the valve) to prevent contamination of the bag. positive end-expiratory pressure some devices have peep valve connectors, for better positive airway pressure maintenance. medication delivery a covered port may be incorporated into the valve assembly to allow inhalatory medicines to be injected into the airflow, which may be particularly effective in treating patients in respiratory arrest from severe asthma. airway pressure port a separate covered port may be included into the valve assembly to enable a pressure-monitoring device to be attached, enabling rescuers to continuously monitor the amount of positive-pressure being generated during forced lung inflation. pressure relief valves a pressure relief valve (often known as a "pop-up valve") is typically included in pediatric versions and some adult versions, the purpose of which is to prevent accidental over-pressurization of the lungs. a bypass clip is usually incorporated into this valve assembly in case medical needs call for inflation at a pressure beyond the normal cutoff of the pop-up valve. device storage features some bags are designed to collapse for storage. a bag not designed to store collapsed may lose elasticity when stored compressed for long periods, reducing its effectiveness. the collapsible design has longitudinal scoring so that the bag collapses on the scoring "pivot point," opposite to the direction of normal bag compression. manual resuscitator alternatives in a hospital, long-term mechanical ventilation is provided by using a more complex, automated ventilator. however, a frequent use of a manual resuscitator is to temporarily provide manual ventilation whenever troubleshooting of the mechanical ventilator is needed, if the ventilator circuit needs to be changed, or if there is a loss of electrical power or source of compressed air or oxygen.a rudimentary type of mechanical ventilator device that has the advantage of not needing electricity is a flow-restricted, oxygen-powered ventilation device (fropvd). these are similar to manual resuscitators in that oxygen is pushed through a mask to force-inflate the patient's lungs, but unlike a manual resuscitator where the pressure used to force-inflate the patient's lungs comes from a person manually squeezing a bag, with the fropvd the pressure needed to force-inflate the lungs comes directly from a pressurized oxygen cylinder. these devices will stop functioning when the compressed oxygen tank becomes depleted. types of manual resuscitators self-inflating bags: this type of manual resuscitator is the standard design most often used in both in-hospital and out-of-hospital settings. the material used for the bag-portion of a self-inflating manual resuscitator has a "memory", meaning after it is manually compressed it will automatically re-expand on its own in between breaths (drawing in air for the next breath). these devices can be used alone (thus delivering room-air) or can be used in connection with an oxygen source to deliver nearly 100% oxygen. as a result of these features, this type of manual resuscitator is appropriate for in-hospital use and in out-of-hospital settings e.g., ambulances. flow-inflating bags: also termed "anesthesia bags", these are a specialized form of manual resuscitator with a bag-portion that is flaccid and does not re-inflate on its own. this necessitates an external flow source of pressurized inflation gas for the bag to inflate; once inflated the provider can manually squeeze the bag or, if the patient is breathing on his/her own, the patient can inhale directly through the bag. these types of manual resuscitators are used extensively during anesthesia induction and recovery, and are often attached to anesthesia consoles so anesthesia gases can be used to ventilate the patient. they are primarily utilized by anesthesiologists administering general anesthesia, but also during some in-hospital emergencies which may involve anesthesiologists or respiratory therapists. they are not typically used outside hospital settings. as per a recent indian study, these flow inflation bags can also be used to provide cpap in spontaneously breathing children.the study quotes that this mode of cpap is cost effective in limited resource settings