Causes of hyperventilation
Sleep factors

If you have healthy relatives or friends, you can see that their breathing is very light. In fact, the breathing of the healthy person is noiseless and so quiet, that it may scare some people to death ("Is he alive?") Vice versa, breathing in the sleeping sick people is easy to hear and see, while the effects of morning hyperventilation were already discussed. What are the causes of morning hyperventilation?
Mouth breathing
This is the most destructive sleep factor. It was considered before and is easy to check. Is your mouth dry when you wake up?
Sleeping on one's back
Among body positions, sleeping on one's back (supine position) is worst (some people start snoring in this position). Sleeping on the right side also causes increased ventilation in comparison with sleeping on the left side or on the chest. Children's ventilation is minimum when they are sleeping on their tummies (Buteyko, 1977).
There are no physiological studies known to me in which such parameters of breathing, as minute ventilation and aCO2, are monitored in different sleeping body positions. Meanwhile, there are at least 8 studies devoted to the physiological effects of different body night positions on the stomach. All these investigations, trials included, advocate the left position due to the least night-time recumbent reflux (e.g., Khoury et al, 1999). That means that the liquid content of the stomach, for the left position cannot escape or leak due to the absence of physical contact with any of the stomach valves. This position is also the most favourable for general peristaltic waves in the large intestine due to the gravitational effect in the transverse colon. There are, possibly, some other reasons to explain the advantages of the left position (e.g., the influence of the heart position). Some people, due to congenital reasons, have their hearts on the right side. In such cases the effects of sleeping positions are also in reverse.
Presence of disease and existing damage in the body
“The horizontal position, lying intensifies breathing. Patients with asthma, heart disease, hypertension, and stenocardia often have acute states at night. If they lie down during the day time, or lie for 2-3 hours – the breathing gets heavier, the attacks come. Many severely sick patients sit, afraid to lie down. This is sensible. We should lie down only for sleeping. Our patients cannot control their breathing at night, and hence, sleep is poison for them” (Buteyko , 1977).
Sleeping too long
Sleeping too long, according to Buteyko, intensifies breathing causing prolonged periods of gradually increasing hyperventilation (p.177, Khoroscho, 1982)
Other causes
Among other causes are mouth breathing (considered before), poor air quality (especially due to carpets), soft beds, abnormal thermoregulation (e.g., too warm blankets), etc.
During sleep, as each hour passes, breathing gets deeper and heavier for most people. That is easy to check using the CP. The CP drop is especially noticeable after 4-6 hours of sleep. (We are physiologically created to sleep less than 4-5 hours.)
A simple "sleeping positions" self-test. By measuring breath holding time in different sleeping positions, one can find out what is the optimum position for breathing and health. Note that one needs to spend about 10-15 minutes in a certain position in order to achieve a stable metabolism correspondent to this position. A ticking mechanical clock can be used for that purpose. Generally, sleeping on the left side will produce the highest BHT, followed by sleeping on the tummy. Sleeping on the back is worst and causes lowest BHT.
For the list of the quoted references click here