Nasal High Flow therapy reduces work of breathing compared to oxygen during sleep in COPD and smoking controls - prospective observational study.

Rationale: Patients with COPD endure excessive resistive and elastic loads leading to chronic respiratory failure. Oxygen supplementation corrects hypoxemia but is not expected to reduce mechanical loads. Nasal High Flow therapy (NHF) supports breathing by reducing dead space but it is unclear how it affects mechanical loads of patients with COPD. Objective: To compare the effects of low-flow oxygen and NHF on ventilation and work of breathing (WOB) in patients with COPD and controls during sleep. Methods: Patients with COPD (n=12) and controls (n=6) were recruited and submitted to polysomnography to measure sleep parameters and ventilation in response to administration of oxygen and NHF. A subset of 6 patients also had an esophageal catheter inserted for measuring WOB. Results: Patients with COPD had similar minute ventilation, but lower tidal volumes than matched controls. Under oxygen, SaO₂ was increased and minute ventilation was reduced in both controls and patients with COPD, but with an increase in transcutaneous CO₂ levels. NHF produced a greater reduction in minute ventilation, and was associated with a reduction in CO₂ levels. While NHF halved WOB, oxygen produced only minor reduction in this parameter. Conclusion: Oxygen produced little changes in WOB, which were associated with CO₂ elevations. On the other hand, NHF produced a large reduction in minute ventilation and WOB with a concomitant fall in CO₂ levels. Our data indicate that NHF improves alveolar ventilation during sleep compared to oxygen and room-air in patients with COPD and therefore can decrease their cost of breathing.

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