High-Flow Oxygen Therapy in Tracheostomized Subjects With Prolonged Mechanical Ventilation: A Randomized Crossover Physiologic Study

BACKGROUND:

High-flow oxygen therapy via tracheostomy (HFT) can be used in tracheostomized patients during ventilator disconnection. The physiologic effects of this technique are unknown. We hypothesized that HFT would reduce inspiratory effort and improve breathing pattern compared to conventional oxygen therapy via T-tube. This study aimed to evaluate the physiologic effects of HFT compared to conventional O₂ in patients with prolonged mechanical ventilation.

METHODS:

A randomized crossover physiologic study was conducted in adult tracheostomized patients who experienced temporary periods of ventilator disconnection. Subjects were ventilated with pressure support ventilation (PSV) for 15 min and were then randomly assigned to HFT or conventional O₂ via T-tube for 30 min. After a washout period, subjects were switched to the other system. Esophageal pressure (P_es), breathing frequency, blood pressure, heart rate, ${\mathrm{S}}_{{\mathbf{\text{pO}}}_2}$, and transcutaneously measured pressure of carbon dioxide (${\mathrm{P}}_{{\mathbf{\text{tcCO}}}_2}$) were recorded. The primary outcome was inspiratory effort as determined by the simplified esophageal pressure-time product (sPTP_es). Secondary outcomes were P_es swing, breathing frequency, heart rate, mean arterial pressure, ${\mathrm{S}}_{{\mathbf{\text{pO}}}_2}$, and ${\mathrm{P}}_{{\mathbf{\text{tcCO}}}_2}$ between groups.

RESULTS:

Twenty-two subjects were enrolled: sPTP_es per minute was significantly higher with HFT and conventional O₂ compared to PSV (153.5 ± 97.9, 163.5 ± 111.3, and 86.8 ± 51.1 cm H₂O × s/min, respectively, P = .001), but it was not different between HFT and conventional O₂ (P = .72). Breathing frequency increased significantly after switching from PSV to HFT and conventional O₂ (23 ± 4 vs 26 ± 6 and 23 ± 4 vs 27 ± 5 breaths/min, respectively, P = .001). ${\mathrm{S}}_{{\mathbf{\text{pO}}}_2}$ was higher with conventional O₂ compared to HFT (P = .02). No differences in ${\mathrm{P}}_{{\mathbf{\text{tcCO}}}_2}$, mean arterial pressure, or heart rate were observed between HFT and conventional O₂.

CONCLUSIONS:

Inspiratory effort and breathing frequency increased significantly during unassisted breathing compared to PSV in tracheostomized subjects, but HFT via tracheostomy provided no measurable additional physiologic benefit compared to O₂ therapy via T-tube.