Description of automatic-voluntary dissociation of breathing in multiple sclerosis

Respiratory dysfunction in people with multiple sclerosis (PwMS) is often attributed to respiratory pump failure, yet central respiratory drive and automatic breathing control remain underexplored. We assessed the prevalence of breathing automatic-voluntary dissociation (AVD) in PwMS.

We analyzed prospectively collected data from a tertiary care rehabilitation center observational cohort. All adult PwMS, who underwent pulmonary function testing, including a CO₂ ventilatory response test, while relapse-free for ≥ 3 months, between January 2018 and December 2024 were screened. AVD was defined by maximal tidal volume (VTmax) during CO₂ response test higher than vital capacity (VC)(VTmax/VC>1), reflecting discordance between voluntary and automatic respiratory response. Univariate analysis and multivariate logistic regression were performed to identify variables associated with AVD.

Fifty-five PwMS were included (age 59 ±7 years, disease duration 23 ± 11 years, women 64 %, median EDSS 8[7,5;8,5]). Restrictive ventilatory pattern was observed in 65 %, 32 % being severely impaired, and with cough impairment in 64 %. Eighteen (33 %) presented AVD. It was associated with significantly lower VC, inspiratory capacity, peak cough flow (p < 0.001), higher EDSS scores and greater use of respiratory support devices (CPAP/NIV, p = 0.002; mechanical in-exsufflation, p = 0.002).

Breathing AVD is frequent in PwMs with severe disease, underscoring the relevance of thorough respiratory assessment to individualize respiratory care.