1 The normal value for the partial pressure of arterial oxygen (PaO2) irrespective of age is greater than 80 mmHg/10.6 kPa (Mellengard K, 1966, Sorbini CA et al, 1968).2  The normal PaO2 for a given age can be predicted from: -. The normal value for the partial pressure of arterial oxygen (PaO2) irrespective of age is greater than 80 mmHg/10.6 kPa (Mellengard K, 1966, Sorbini CA et al, 1968).
When to take: Depending on the severity of the sleep problem, take time-released melatonin 1 to 3 hours prior to the time you usually fall asleep. Since time release melatonin only lasts for 3 â 4 hours, any need to shift sleep schedules more than 3 hours may require taking another pill in 3 or 4 hours. Cautions: Melatonin should not be taken if eyes are exposed to bright sunlight, and melatonin should be avoided if operating any vehicle. If attempting sleep shifts of more than 1 hour, light therapy should also be used. Do not use melatonin for more than two weeks at a time.
Melatonin is a naturally occurring hormone synthesized in the brain that regulates normal sleep and wake cycles. Melatonin levels naturally start to rise in the evening and remain elevated for most of the night, signalling to our body that it is time to sleep.his is the really important thing you should understand about melatonin: Melatonin is a sleep and body clock regulator â NOT a sleep initiator. Melatonin works with your biological clock by telling your brain when it is time to sleep. Melatonin does not increase your sleep drive or need for sleep.