In COPD, Nocturnal Noninvasive Ventilation Reduces the FIO2 Delivered Compared With Long-Term Oxygen Therapy at the Same Flow

BACKGROUND: Nocturnal noninvasive ventilation is recommended for patients with hypercapnic COPD. Long-term oxygen therapy improves survival in patients with hypoxemic disease. However, leaks during noninvasive ventilation are likely to reduce the fraction of inspired oxygen. OBJECTIVES: To compare nocturnal inspired O-2 fractions during noninvasive ventilation with daytime pharyngeal inspired O-2 fractions during nasal cannula oxygen therapy (with the same O-2 flow) in patients with COPD at home (ie, real-life conditions). METHODS: This single-center prospective observational study included 14 subjects with COPD who received long-term O-2 therapy. We analyzed pharyngeal inspired O-2 fractions in the evening, with a nasopharyngeal probe (sidestream gas analyzer). The O-2 flow was measured with a precision flow meter, at the usual flow. Then, the same O-2 flow was implemented for noninvasive ventilation with a study's home ventilator. The all-night noninvasive ventilation parameters were delivered in pressure mode with a single-limb leaking circuit. Daytime and nighttime inspired O-2 fractions were compared. RESULTS: The mean +/- SD daytime pharyngeal inspired O-2 fraction, measured with normobaric basal O-2 flow, 0.308 +/- 0.026%, was significantly higher than the mean +/- SD nighttime inspired O-2 fraction, measured during noninvasive ventilation (0.251 +/- 0.011; P < .001). CONCLUSIONS: The nighttime inspired O-2 fraction decreased with a modern noninvasive ventilation pattern, pressure target, and intentional leaks. This partial lack of O-2 therapy is likely to be harmful. It might explain the poor results in all but 2 randomized controlled trials on long-term noninvasive ventilation in COPD.