Sleep-related hypoventilation and hypercapnia in multiple system atrophy detected by polysomnography with transcutaneous carbon dioxide monitoring

Purpose We aimed to evaluate sleep-related hypoventilation in multiple system atrophy (MSA) using polysomnography (PSG) with transcutaneous partial pressure of carbon dioxide (PtcCO 2 ) monitoring. Methods This prospective study included 34 patients with MSA. Motor and autonomic function, neuropsychological tests, PSG with PtcCO 2 monitoring, and pulmonary function tests were performed. Sleep-related hypoventilation disorder (SRHD) was defined according to the International Classification of Sleep Disorders, third edition. Results Nine (27%) of the 34 patients met the diagnostic criteria of SRHD. Twenty-nine (85%) patients had sleep-related breathing disorders based on an Apnea–Hypopnea Index of ≥ 5/h. The patients with MSA and SRHD had a higher arousal index ( p = 0.017) and obstructive apnea index ( p = 0.041) than those without SRHD. There was no difference in the daytime partial pressure of carbon dioxide in arterial blood or respiratory function between MSA patients with and without SRHD. Conclusion Sleep-related hypoventilation may occur in patients with MSA even with a normal daytime partial pressure of carbon dioxide. This can be noninvasively detected by PSG with PtcCO 2 monitoring. SRBD and sleep-related hypoventilation are common among patients with MSA, and clinicians should take this into consideration while evaluating and treating this population.