Open-label, phase II study of routine high-flow nasal oxygen therapy in cardiac surgical patients

Background. Respiratory complications after cardiac surgery increase morbidity, mortality, and length of stay. Studies suggest that routine delivery of positive airway pressure after extubation may be beneficial. We sought to determine whether the routine administration of nasal high-flow oxygen therapy (NHF) improves pulmonary function after cardiac surgery. Methods. A pragmatic randomized controlled trial; participants received either NHF (45 litre min(-1)) or usual care from extubation to Day 2 after surgery. The primary outcome was number of patients with Sp(O2)/FIO2 ratio >= 445 on Day 3 after surgery. The secondary outcomes included atelectasis score on chest X-ray; spirometry; intensive care and hospital length of stay; mortality on Day 28; oxygenation indices; escalation of respiratory support; and patient comfort. Results. We randomized 340 patients over 14 months. The number of patients with a Sp(O2)/FIO2 ratio of >= 445 on Day 3 was 78 (46.4%) in the NHF group vs 72 (42.4%) standard care [odds ratio (OR) 1.18,95% confidence interval (CI) 0.77-1.81, P = 0.45]. Pa-CO2 was reduced at both 4 h post-extubation and at 9 a. m. on Day 1 in the NHF group (5.3 vs 5.4 kPa, P = 0.03 and 5.1 vs 5.3 kPa, P = 0.03, respectively). Escalation in respiratory support at any time in the study occurred in 47 patients (27.8%) allocated to NHF compared with 77 (45%) standard care (OR 0.47, 95% CI 0.29-0.7, P = 0.001). Conclusions. Routine use of NHF did not increase Sp(O2)/FIO2 ratio on Day 3 but did reduce the requirement for escalation of respiratory support.