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.
How to Take Melatonin. Three Methods: Understanding Melatonin Taking Melatonin for Sleep Taking Melatonin for Other Reasons Community Q&A. Melatonin is a natural hormone that controls your body's inner clock. It works by activating certain chemical receptors in the brain that encourage sleep. Melatonin production is controlled by light.