The effect of high-flow oxygen via tracheostomy on respiratory pattern and diaphragmatic function in patients with prolonged mechanical ventilation: A randomized, physiological, crossover study

Compared to conventional oxygen devices, high-flow oxygen treatment (HFOT) through the nasal cannulae has demonstrated clinical benefits. Limited data exist on whether such effects are also present in HFOT through tracheostomy. Hence, we aimed to examine the short-term effects of HFOT through tracheostomy on diaphragmatic function and respiratory parameters in tracheostomized patients on prolonged mechanical ventilation. A randomized, crossover, physiological study was conducted in our ICU between December 2020 and April 2021, in patients with tracheostomy and prolonged mechanical ventilation. The patients underwent a 30-min spontaneous breathing trial (SBT) and received oxygen either via T-piece or by HFOT through tracheostomy, followed by a washout period of 15-min breathing through the T-piece and receipt of 30-min oxygen with the other modality in a randomized crossover manner. At the start and end of each session, blood gasses, breathing frequency (f), and tidal volume (VT) via a Wright's spirometer were measured, along with diaphragm ultrasonography including diaphragm excursion and diaphragmatic thickening fraction, which expressed the inspiratory muscle effort. Eleven patients were enrolled in whom 19 sessions were uneventfully completed; eight patients were studied twice on two different days with alternate sessions; and three patients were studied once. Patients were randomly assigned to start the SBT with a T-piece (n=10 sessions) or with HFOT (n=9 sessions). With HFOT, VT and minute ventilation (VE) significantly increased during SBT (from 465±119 mL to 549±134 mL, P <0.001 and from 12.4±4.3 L/min to 13.1±4.2 L/min, P <0.05, respectively), but they did not change significantly during SBT with T-piece (from 495±132 mL to 461±123 mL and from 12.8±4.4 mL to 12.0±4.4 mL, respectively); f/VT decreased during HFOT (from 64±31 breaths/(min∙L) to 49±24 breaths/(min∙L), P <0.001), but it did not change significantly during SBT with T-piece (from 59±28 breaths/(min∙L) to 64±33 breaths/(min∙L)); partial pressure of arterial oxygen increased during HFOT (from 99±39 mmHg to 132±48 mmHg, P <0.001), but it decreased during SBT with T-piece (from 124±50 mmHg to 83±22 mmHg, P <0.01). In addition, with HFOT, diaphragmatic excursion increased (from 12.9±3.3 mm to 15.7±4.4 mm, P <0.001), but it did not change significantly during SBT with T-piece (from 13.4±3.3 mm to 13.6±3.3 mm). The diaphragmatic thickening fraction did not change during SBT either with T-piece or with HFOT. In patients with prolonged mechanical ventilation, HFOT through tracheostomy compared with T-piece improves ventilation, pattern of breathing, and oxygenation without increasing the inspiratory muscle effort.