High-Intensity vs Low-Intensity Noninvasive Positive Pressure Ventilation and Need for Endotracheal Intubation—Reply

In Reply For all patients in the trial, 1 an oronasal mask was the first choice with a nasal mask used as an alternative (reported in Supplement 1).An oronasal mask was used in 139 of 147 patients (95%) in the high-intensity NPPV group vs 143 of 153 patients (93%) in the low-intensity NPPV group (P = .69),and a nasal mask was used in 11 of 147 patients (7%) vs 18 of 153 patients (12%), respectively (P = .21).The FIo 2 data were reported in eTables 4 and 5 in Supplement 3. In both groups, the FIo 2 or flow rate of supplemental oxygen was adjusted to obtain oxygen saturation as measured by pulse oximetry (SpO 2 ) of 90% to 95% (Supplement 1). 1 We recorded and reported SpO 2 instead of SaO 2 .For the high-intensity NPPV group, the mean SpO 2 was 93% (SD, 5%) at 2 hours, 94% (SD, 4%) at 6 hours (n = 146), 95% (SD, 3%) at 24 hours (n = 144), 95% (SD, 3%) at 48 hours (n = 141), and 95% (SD, 3%) at 72 hours (n = 140).For the low-intensity NPPV group, the mean SpO 2 was 92% (SD, 7%) at 2 hours, 93% (SD, 4%) at 6 hours (n = 151), 93% (SD, 5%) at 24 hours (n = 147), 94% (SD, 3%) at 48 hours (n = 146), and 95% (SD, 3%) at 72 hours (n = 144).We reported PaO 2 :FIo 2 rather than PO 2 (eTables 7-8 in Supplement 3).For the high-intensity NPPV group, the mean PaO 2 was 72 mm Hg (SD, 16 mm Hg) at 2 hours (n = 146), 72 mm Hg (SD, 16 mm Hg) at 6 hours (n = 140), 74 mm Hg (SD, 15 mm Hg) at 24 hours (n = 143), 75 mm Hg (SD, 14 mm Hg) at 48 hours (n = 138), and 78 mm Hg (SD, 16 mm Hg) at 72 hours (n = 135).For the lowintensity NPPV group, the mean PaO 2 was 69 mm Hg (SD, 16 mm Hg) at 2 hours (n = 151), 70 mm Hg (SD, 14 mm Hg) at 6 hours (n = 139), 71 mm Hg (SD, 15 mm Hg) at 24 hours (n = 145), 72 mm Hg (SD, 15 mm Hg) at 48 hours (n = 139), and 74 mm Hg (SD, 16 mm Hg) at 72 hours (n = 139).Given that the NPPV failure rate of approximately 15% reported previously 2,3 might be partly associated with limited improvement in alveolar ventilation due to low-intensity NPPV using a tidal volume 6 mL/kg to 10 mL/kg of predicted body weight, a tidal volume of 10 mL/kg to 15 mL/kg of predicted body weight was initially used to guide the adjustments to inspiratory positive airway pressure (IPAP).Subsequent adjustments to IPAP were based on the results of arterial blood gases to achieve normocapnia if possible, or to decrease PaCO 2 toward normocapnia if normocapnia could not be achieved.We agree that high tidal volume might increase the risk of dynamic hyperinflation and subsequent physiological dead space.However, the protocol for high-intensity NPPV did not incorporate a high backup ventilatory rate and the actual respiratory rate exhibited only a minor increase, allowing patients to have sufficient expiratory time to achieve lung emptying.This approach likely contributed to a reduced likelihood of worsening dynamic hyperinflation. 4Hypotension was rare in both groups.