Acute Responses to Oxygen Delivery via High Flow Nasal Cannula in Patients with Severe Chronic Obstructive Pulmonary Disease-HFNC and Severe COPD

Differences in oxygen delivery methods to treat hypoxemia have the potential to worsen CO2 retention in chronic obstructive lung disease (COPD). Oxygen administration using high flow nasal cannula (HFNC) has multiple physiological benefits in treating respiratory failure including reductions in PaCO2 in a flow-dependent manner. We hypothesized that patients with COPD would develop worsening hypercapnia if oxygen fraction was increased without increasing flow rate. We evaluated the acute response to HFNC in subjects with severe COPD when flow remained constant and inspired oxygen was increased. In total, 11 subjects with severe COPD (FEV1 < 50%) on supplemental oxygen with baseline normocapnia (PaCO2 < 45 mm Hg; n = 5) and hypercapnia (PaCO2 >= 45 mm Hg; n = 6) were studied. Arterial blood gas responses were studied at three timepoints: Baseline, HFNC at a flow rate of 30 L/min at resting oxygen supplementation for 1 h, and FiO(2) 30% above baseline with the same flow rate for the next hour. The primary endpoint was the change in PaCO2 from baseline. No significant changes in PaCO2 were noted in response to HFNC applied at baseline FiO(2) in the normocapnic and hypercapnic group. At HFNC with FiO(2) 30% above baseline, the normocapnic group did not show a change in PaCO2 (baseline: 38.9 +/- 1.8 mm Hg; HFNC at higher FiO(2): 38.8 +/- 3.1 mm Hg; p = 0.93), but the hypercapnic group demonstrated significant increase in PaCO2 (baseline: 58.2 +/- 9.3 mm Hg; HFNC at higher FiO(2): 63.3 +/- 10.9 mm Hg; p = 0.025). We observed worsening hypercapnia in severe COPD patients and baseline hypercapnia who received increased oxygen fraction when flow remained constant. These data show the need for careful titration of oxygen therapy in COPD patients, particularly those with baseline hypercapnia when flow rate is unchanged.