Sleep-Related Hypoventilation 389
Gender-Related Diagnostic Issues
Gender distributions for sleep-related hypove ntilation occurring in association with co-
morbid conditions reflect the gender distributions of the co morbid conditions. For exam-
ple, COPD is more frequently present in males and with increasing age. 
Diagnostic Markers 
Sleep-related hypoventilation is diagnosed using polysomnography showing sleep-related
hypoxemia and hypercapnia that is not better explained by another breathing-related sleep
disorder. The documentation of increased arterial pCO2 levels to greater than 55 mmHg
during sleep or a 10 mmHg or greater increase in pCO2 levels (to a level that also exceeds
50 mmHg) during sleep in comparison to awake supine values, for 10 minutes or longer, is
the gold standard for diagnosis. However, obtaining arterial blood gas determinations dur-
ing sleep is impractical, and non-invasive measures of pCO2 have not been adequately val-
idated during sleep and are not widely used during polysomnography in adults. Prolonged
and sustained decreases in oxyg en saturation (oxygen saturation of less than 90% for more
than 5 minutes with a nadir of at least 85%, or oxygen saturation of less than 90% for at least
30% of sleep time) in the absence of evidence of upper airway obstruction are often used as
an indication of sleep- related hypoventilation; however, this  finding is not sp ecific, as there
are other potential causes of hypoxemia,  such as that due to lung disease.
Functional Consequences of 
Sleep-Related Hypoventilation
The consequences of sleep-related hypoventilati on are related to the effects of chronic ex-