Background: The physiological effects of high-flow nasal cannula O2 therapy (HFNC) have been evaluated mainly in patients with hypoxemic respiratory failure. In this study, we compared the effects of HFNC and conventional low-flow O2 therapy on the neuroventilatory drive and work of breathing postextubation in patients with a background of chronic obstructive pulmonary disease (COPD) who had received mechanical ventilation for hypercapnic respiratory failure.
Methods: This was a single center, unblinded, cross-over study on 14 postextubation COPD patients who were recovering from an episode of acute hypercapnic respiratory failure of various etiologies. After extubation, each patient received two 1-h periods of HFNC (HFNC1 and HFNC2) alternated with 1 h of conventional low-flow O2 therapy via a face mask. The inspiratory fraction of oxygen was titrated to achieve an arterial O2 saturation target of 88-92%. Gas exchange, breathing pattern, neuroventilatory drive (electrical diaphragmatic activity (EAdi)) and work of breathing (inspiratory trans-diaphragmatic pressure-time product per minute (PTPDI/min)) were recorded.
Results: EAdi peak increased from a mean (±SD) of 15.4 ± 6.4 to 23.6 ± 10.5 μV switching from HFNC1 to conventional O2, and then returned to 15.2 ± 6.4 μV during HFNC2 (conventional O2: p < 0.05 versus HFNC1 and HFNC2). Similarly, the PTPDI/min increased from 135 ± 60 to 211 ± 70 cmH2O/s/min, and then decreased again during HFNC2 to 132 ± 56 (conventional O2: p < 0.05 versus HFNC1 and HFNC2).
Conclusions: In patients with COPD, the application of HFNC postextubation significantly decreased the neuroventilatory drive and work of breathing compared with conventional O2 therapy.
Keywords: Chronic obstructive pulmonary disease; High-flow nasal cannula oxygen therapy; Neuroventilatory drive; Weaning from mechanical ventilation; Work of breathing.