Abstract
BackgroundHigh-flow oxygen therapy via nasal cannula (HFOTNASAL) increases airway pressure, ameliorates oxygenation and reduces work of breathing. High-flow oxygen can be delivered through tracheostomy (HFOTTRACHEAL), but its physiological effects have not been systematically described. We conducted a cross-over study to elucidate the effects of increasing flow rates of HFOTTRACHEAL on gas exchange, respiratory rate and endotracheal pressure and to compare lower airway pressure produced by HFOTNASAL and HFOTTRACHEAL.MethodsTwenty-six tracheostomized patients underwent standard oxygen therapy through a conventional heat and moisture exchanger, and then HFOTTRACHEAL through a heated humidifier, with gas flow set at 10, 30 and 50 L/min. Each step lasted 30 min; gas flow sequence during HFOTTRACHEAL was randomized. In five patients, measurements were repeated during HFOTTRACHEAL before tracheostomy decannulation and immediately after during HFOTNASAL. In each step, arterial blood gases, respiratory rate, and tracheal pressure were measured.ResultsDuring HFOTTRACHEAL, PaO2/FiO2 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] cmH2O (ρ = 0.77, p < 0.001). Compared to standard oxygen, HFOTTRACHEAL limited the negative inspiratory swing in tracheal pressure; at 50 L/min, but not with other settings, HFOTTRACHEAL increased mean tracheal expiratory pressure by (mean difference [95% CI]) 0.4 [0.3–0.6] cmH2O, peak tracheal expiratory pressure by 0.4 [0.2–0.6] cmH2O, improved PaO2/FiO2 ratio by 40 [8–71] mmHg, and reduced respiratory rate by 1.9 [0.3–3.6] breaths/min without PaCO2 changes. As compared to HFOTTRACHEAL, HFOTNASAL produced higher tracheal mean and peak expiratory pressure (at 50 L/min, mean difference [95% CI]: 3 [1–5] cmH2O and 4 [1–7] cmH2O, respectively).ConclusionsAs compared to standard oxygen, 50 L/min of HFOTTRACHEAL are needed to improve oxygenation, reduce respiratory rate and provide small degree of positive airway expiratory pressure, which, however, is significantly lower than the one produced by HFOTNASAL.
Highlights
High-flow oxygen therapy via nasal cannula (HFOTNASAL) increases airway pressure, ameliorates oxygenation and reduces work of breathing
Samples of tracheal pressure tracings are displayed in Discussion In the present cross-over study, we show that, as compared to standard oxygen, HFOTTRACHEAL mitigates the negative swing in airway pressure during inspiration, and, when flow is set at 50 L/min, ameliorates oxygenation and slightly reduces respiratory rate
Tracheal expiratory pressure is significantly lower with HFOTTRACHEAL than with HFOTNASAL, suggesting that the physiologic effects of H FOTTRACHEAL are milder than H FOTNASAL
Summary
High-flow oxygen therapy via nasal cannula (HFOTNASAL) increases airway pressure, ameliorates oxygenation and reduces work of breathing. We conducted a cross-over study to elucidate the effects of increasing flow rates of HFOTTRACHEAL on gas exchange, respiratory rate and endotracheal pressure and to compare lower airway pressure produced by HFOTNASAL and H FOTTRACHEAL. Nasal high-flow oxygen therapy (HFOTNASAL) has been proposed to treat acute hypoxemic respiratory failure [1,2,3,4], to facilitate weaning from mechanical ventilation [5,6,7,8] and to prevent hypoxemia during endotracheal intubation [9, 10]. With HFOTNASAL, up to 60 L/min of heated and humidified air/oxygen mixture are continuously delivered to the patient through designed nasal prongs [11]. Active heating/humidification and the comfortable interface improve comfort related to airway dryness and optimize device tolerability [16,17,18]
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