Evolution of daytime PaCO2 in patients with neuromuscular disorders and OSA using CPAP: a retrospective study.

BACKGROUND

Neuromuscular disorders (NMD) are frequently complicated by obstructive sleep apnea (OSA), which may add an obstructive ventilatory load and contribute to CO2 retention. While non-invasive ventilation (NIV) is recommended for established hypoventilation, the impact of continuous positive airway pressure (CPAP) on daytime PaCO2 in NMD remains poorly documented.

METHODS

We conducted a retrospective single-center cohort study in a tertiary neuromuscular referral center. Consecutive adults with NMD undergoing respiratory assessment were included if they had (i) OSA treated with CPAP and (ii) daytime PaCO2 measurements before and after CPAP initiation. The primary outcome was paired PaCO2 change. Prespecified analyses were performed in patients with baseline PaCO2 ≥42 and ≥ 45 mmHg. Predictors of PaCO2 decrease were explored using logistic regression.

RESULTS

One hundred patients were included, median AHI was 36.9/h. At a median follow-up of 13.6 months, PaCO2 decreased from 42.0 [39.0-44.0] to 40.5 [38.3-43.0] mmHg, corresponding to a paired reduction of 1.0 mmHg (95%CI 0.3-2.0; p = 0.01). PaCO2 decreased in 61% of patients, remained unchanged in 9%, and increased in 30%. In patients with baseline PaCO2≥45 mmHg (n = 18), the median PaCO2 reduction was 1.3 mmHg (95%CI 0.25-2.5; p = 0.016) and 8 patients normalized their PaCO2 but 4 experienced a deterioration. Baseline PaCO2 was the only independent predictor of PaCO2 decrease.

CONCLUSIONS

In NMD patients with OSA, CPAP was associated with a modest but significant reduction in daytime PaCO2. Responses were heterogeneous, supporting careful patient phenotyping and structured reassessment after CPAP initiation to avoid delayed NIV escalation in non-responders.