In contrast, Manser says, a person's passive vocabulary consists of the words whose meanings they knowâso that they do not have to look the words up in a dictionaryâbut which they would not necessarily use in ordinary conversation or writing (The Penguin Writer's Manual, 2004).
Sleep Apnea, Night Terrors, and Nightmares. Sleep apnea may also be to blame for your nightmares. During sleep apnea, your brain senses the low oxygen and realizes that you are under a very real threatâyou are being choked or smothered by your own bodyâand if nothing is done you will die.
Low oxygen levels in the blood are referred to as hypoxemia, a condition that can make you feel unusually sleepy and may even produce intermittent bouts of confusion.Low oxygen levels in your blood can also cause shortness of breath, headaches, fluid retention and insomnia.In some cases, low oxygen levels can be fatal when sleep apnea or cardiac complications become a factor.entilation Problems. Ventilation problems in the lungs can lead to low oxygen levels in the blood especially if the alveoli in the lungs are not functioning properly. Sometimes lung ventilation is disrupted when alveolar ventilation is not working in a pattern of uniformity.