Respiratory disorders (RD) remain incompletely described and understood in multiple sclerosis (MS), although they might play an important role in the burden of MS. RD are the first cause of mortality in MS patients, and could suddenly worsen with acute respiratory failure, for example during an infectious pneumopathy. However, they are underestimated especially due to the motor disability and cognitive disorders.
The primary objective was to assess the categories of RD in MS patients:
i) isolated respiratory muscles impairment (decrease of inspiratory maximal pressure or sniff nasal inspiratory pressure < 60%)
ii) diaphragmatic dysfunction (upright vital capacity (VC) - supine VC > 20% of upright VC and/or phasic activation of respiratory muscles during sleep and/or opposition of the thoracic and abdominal respiratory movements during sleep and/or orthopnea and/or respiratory muscles impairment )
iii) nocturne alveolar hypoventilation (PaCO2 > 45 mmHg and/or during the sleep : > 10 min of sleep with PtcCO2 > 55 mmHg or PaCO2 > 50 mmHg if increasing of PaCO2 > 10 mmHg between awake and the sleep).
The secondary objectives were to evaluate the correlation between RD and i) disability scores, including fatigue and cognitive evaluation, and ii) MRI encephalic and spinal lesion load.
Patients with severe MS (EDSS ≥ 6.5), with or without respiratory complaint, were included in this prospective monocentric study. Comprehensive pulmonary function tests, polysomnography with specific electromyography of accessory respiratory muscles, cognitive tests, brain and cervical spinal cord MRI were performed within 24 hours.
71 patients (39 F/32 M) were included: median age 53,9 years (IQR: 48.40-60.95), median EDSS 7.5 (IQR: 6.5 - 8), median disease duration 21.4 years (IQR: 16-31.35). 46 patients (65%) had diaphragmatic dysfunction, including 36 patients (50%) with isolated respiratory muscles impairment. 9 patients (13%) had nocturnal alveolar hypoventilation. 21 (30 %) patients had no RD. Correlation studies with disability scores and MRI lesion load are on going.
Using specific technics of polysomnography and respiratory muscle testing, this study highlights the frequency of respiratory disorders in MS patients with EDSS ≥ 6.5, but also provides innovative insight into the different types of RD. These findings should lead to specific multidisciplinary care, such as non-invasive ventilation or preventive measures (vaccination against pulmonary infections for patients and families).