Physiological effects of high-flow oxygen in tracheostomized patients

Background High-flow oxygen therapy via nasal cannula (HFOT NASAL ) increases airway pressure, ameliorates oxygenation and reduces work of breathing. High-flow oxygen can be delivered through tracheostomy (HFOT TRACHEAL ), but its physiological effects have not been systematically described. We conducted a cross-over study to elucidate the effects of increasing flow rates of HFOT TRACHEAL on gas exchange, respiratory rate and endotracheal pressure and to compare lower airway pressure produced by HFOT NASAL and HFOT TRACHEAL. Methods Twenty-six tracheostomized patients underwent standard oxygen therapy through a conventional heat and moisture exchanger, and then HFOT TRACHEAL through a heated humidifier, with gas flow set at 10, 30 and 50 L/min. Each step lasted 30 min; gas flow sequence during HFOT TRACHEAL was randomized. In five patients, measurements were repeated during HFOT TRACHEAL before tracheostomy decannulation and immediately after during HFOT NASAL . In each step, arterial blood gases, respiratory rate, and tracheal pressure were measured. Results During HFOT TRACHEAL , PaO 2 /FiO 2 ratio and tracheal expiratory pressure slightly increased proportionally to gas flow. The mean [95% confidence interval] expiratory pressure raise induced by 10-L/min increase in flow was 0.2 [0.1–0.2] cmH 2 O ( ρ = 0.77, p