Introduction: An alveolar hypoventilation physiologically occurs during sleep and more specifically during REM sleep.
State of the art: During obstructive chronic respiratory failures, increases in PaCO2 that are associated with REM sleep can participate to the severity of daytime hypercapnia and in a subgroup of patients lead to an indication of nocturnal non-invasive ventilation (NIV) in association with the long-term oxygen therapy. A REM sleep hypoventilation generally appears during the early course of restrictive chronic respiratory failures. This REM sleep hypoventilation represents one of the most frequent reasons for initiating NIV in restrictive respiratory insufficiencies. Obesity-hypoventilation syndrome (OHS) refers to a hypercapnic chronic respiratory failure in which REM sleep hypoventilation is one of the main determinants. In France, in 2004, OHS is the primary chronic respiratory failure leading to at home NIV. NIV on OHS aims to maintain upper airway patency as sleep apnoea is frequently associated and to allow sufficient alveolar ventilation during REM sleep.
Perspectives: Thus, sleep alveolar hypoventilation should be systematically assessed in obese patients and during the time curse evolution of all the chronic respiratory failures. This can be done relatively easily by using nocturnal oximetry concurrently with a transcutaneous PCO2 measurement.
Conclusion: The understanding of exact mechanisms underlying abnormal respiratory events occurring during sleep allows optimising adjustments in NIV parameters.