Detection of episodic nocturnal hypercapnia in patients with neurodegenerative disorders

Episodic nocturnal hypercapnia (eNH) in transcutaneous carbon dioxide pressure (PtcCO₂) corresponding to rapid eye movement sleep hypoventilation is a useful biomarker for detecting nocturnal hypoventilation. However, the relationship between eNH and neurodegenerative diseases with sleep-related breathing disorders (SRBDs) is unknown. The aim of this study was to evaluate the relationship between eNH and nocturnal hypoventilation in neurodegenerative diseases.

Patients with neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), multiple system atrophy (MSA), Parkinson's disease, progressive supranuclear palsy, corticobasal syndrome, and idiopathic normal pressure hydrocephalus, were enrolled and received overnight PtcCO₂ monitoring. The patients were divided into groups for eNH and sleep-associated hypoventilation (SH) prevalence analysis: A (ALS), B (MSA), and C (others).

Among 110 patients, twenty-three (21%) and 10 (9%) of the patients met eNH and SH criteria, respectively. eNH and SH were significantly more frequent in groups A and B than in C. The prevalence of SH in the patients with eNH was 39% whereas most of patients with SH (90%) presented with eNH. Among patients with daytime carbon dioxide pressure in arterial blood ≤ 45 mmHg, eNH frequency was 13%, whereas none of the patients met SH criteria. The frequency of noninvasive positive pressure ventilation after PtcCO₂ monitoring was significantly higher in those with than without eNH.

eNH is common in patients with MSA and ALS who present with SRBD. eNH with overnight PtcCO₂ monitoring is a useful biomarker to detect hypoventilation among neurodegenerative diseases with different SRBD mechanisms.