Physiological effects of high-flow oxygen in tracheostomized patients

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.

High-flow tracheal oxygen: what is the current evidence?

“…This makes it difficult to generate sufficient inspiratory airway pressure and positive end-expiratory pressure due to leakage from the expiratory port of the interface. Although both HFNC and HFT generate mean airway pressures of 50 L/min, HFNC generates a higher mean airway pressure (2.7 to 3.3 cmH 2 O) [19,20] than does HFT (−0.23 to 1.2 cmH 2 O) [14,15]. We believe that this gap in mean airway pressure between these two interfaces explains the different clinical outcomes.…”

“…The effect of HFT on clinical performance remains controversial. To assess the effects of HFT relative to COT at different flow rates, Natalini et al performed a randomized crossover trial [14]. Compared with the use of COT, that of HFT at 50 L/ min exhibited a significantly higher PaO 2 /FiO 2 ratio at 307 [IQR: 241-390] versus 277 [IQR: 247-344] (p =.01).…”

“…Notably, in this study, 5 participants underwent tracheostomy decannulation after being enrolled. Natalini et al performed the study protocol again on the day of decannulation with HFNC [14]. Compared with the use of HFT, that of HFNC exhibited a significantly higher peak and mean expiratory airway pressure.…”

“…Even though these two interfaces differ in some respects, both routes appear to share some benefits for high-flow therapy. In most trials, relative to COT, HFNC [22,23] and HFT [14,19] improved oxygenation.…”

High-flow nasal cannula for body rewarming in hypothermia

“…Use of high-flow nasal cannula (HFNC) is common in critically ill patients with or at risk of respiratory failure. Its benefits include accurate delivery of the set fraction of inspired oxygen (FiO 2 ), carbon dioxide washout from nasopharyngeal dead space, provision of small degree of positive end-expiratory pressure, and improved tolerance due to the comfortable interface [1][2][3]. To continuously deliver flows up to 60 l/min, inspired gas is actively conditioned through a heated humidifier, which increases gas temperature and absolute humidity up to 37°C and 44 mgH 2 O/l.…”