Change in pulmonary mechanics and the effect on breathing pattern of high flow oxygen therapy in stable hypercapnic Chronic Obstructive Pulmonary Disease

Chronic hypercapnic respiratory failure (CHF) represents a major issue in stable chronic obstructive pulmonary disease (COPD). Non-invasive Ventilation (NIV) improves pulmonary gas exchange function with decrease in PaCO2 and rise in pH. Long-term NIV reduces mortality in these patients and time to first exacerbations, but adherence to ventilatory therapy is poor. High Flow Oxygen Therapy (HFOT) could counterbalance the effect of intrinsic Positive End Expiratory Pressure (PEEPi) and optimize Ventilation/Perfusion ratio through the modification of breathing pattern; then, HFOT could be an appealing alternative to home NIV. Therefore, in order to assess HFOT effects on respiratory work of breathing, compared to NIV as gold standard, we studied the consequences of these two form of non-invasive respiratory support on: inspiratory effort, as assessed by measuring transdiaphragmatic pressure; breathing pattern; gas exchange. Fourteen patients with hypercapnic stable COPD underwent five 30-min trials, in a random order: HFOT at two flow rates (20 L/min and 30 L/min), both with open and closed mouth, and NIV. After each trial, standard oxygen therapy was reinstituted for ten min. Compared with baseline, HFOT and NIV significantly improved breathing pattern, although to different extents, and reduced inspiratory effort; however, arterial carbon dioxide oxygen tension decreased but not significantly. These results indicate a possible role for HFOT in the long-term management of patients with hypercapnic stable COPD, because of no rise in PaCO2, and improved respiratory mechanic