Sleeping and Breathing: REM Atonia Compromises Rib Cage Inspiratory Muscles

Sleeping and Breathing: REM Atonia Compromises Rib Cage Inspiratory MusclesRib cage inspiratory muscles (external intercostal, parasternal, scalene and sternocleidomastoid) contribute to a minor extent to normal breathing in adult males. Accordingly, loss of their action during REM sleep is compatible with maintenance of a normal alveolar ventilation during this stage of sleep, particularly in view of associated reduction in metabolic rate. This situation is drastically altered in diseases such as diaphragm paralysis or COPD. In the latter, changes in diaphragm configuration greatly compromise its pressure-generating capability. Both types of patients heavily recruit rib cage inspiratory muscles to maintain ventilation while awake. An interesting observation is that this heightened activity continues during non-REM sleep but is profoundly inhibited during REM sleep. Such loss of activity reflects the participation of motoneurons innervating rib cage inspiratory muscles in the overall postsynaptic inhibition of somatic motoneurons during REM sleep. The net result is a great diminution of rib cage excursion during REM in patients with COPD. If chemical feedback is heightened during non-REM, its loss during REM might evoke greater than normal shifts in breathing when the patient shifts from non-REM to REM. asthma inhalers