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.
Nocturnal Hypoxemia. Nocturnal hypoxemia is a condition where the blood oxygen levels fall at night when the person is sleeping. This may be seen in sleep apnea wherein the partial pressure of oxygen in the blood may fall to such an extent, that it may lead to disruption of sleep patterns of the individuals.