Hypothesis: Diaphragm spasms contribute to obstructive sleep apneas and pulmonary hypertension.

While in diaphragm spasm, which appears to happen most often in REM-sleep (in the form of apneas), the intercostal and other accessory inspiratory muscles are forced to resume the work of breathing independently. However, because the diaphragm is temporarily inactivated by the spasm (and with delayed relaxation occurring by diaphragm fatigue), it might be rendered immobile thus adding airway resistance as a novel form of respiratory obstruction. Partial closure of the upper airway by relaxation of the dilator muscles in sleep, well-identified in OSA, could also contribute to diaphragm fatigue and neuromuscular excitability in the form of spasms (and more).

Also, pulmonary hypertension and right-heart failure (cor pulmonale) have been identified in OSA but the mechanism is unknown [1]. Perhaps diaphragm spasms are the cause, via constriction of the thin-walled, pliable inferior vena cava through its diaphragmatic hiatus? Similarly, diaphragm tension and spasms could cause acid reflux (esophageal hiatus) [2] and even reduced cardiac output and left-heart failure (aortic hiatus).

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Image reproduced with permission by Dr. Luo