Abstract
BACKGROUND: High-flow tracheal oxygen (HFTO) is being used as supportive therapy during weaning in tracheostomized patients difficult to wean from invasive mechanical ventilation. There is, however, no clinical evidence for such a strategy. Therefore, we conducted a systematic review to summarize studies evaluating the physiologic effects of HFTO during tracheostomy-facilitated weaning and to identify potential areas for future research in this field. METHODS: Observational and interventional studies on critically ill subjects weaning from mechanical ventilation via tracheostomy published until December 22, 2022, were eligible. Studies on high-flow oxygen, only in children, non-human models or animals, on clinical outcome only, abstracts without full-text availability, case reports, and reviews were excluded. Main outcomes were end-expiratory lung volume (EELV) and tidal volume using electrical impedance tomography, respiratory effort assessed by esophageal manometry, work of breathing and neuroventilatory drive as assessed by electrical activity of the diaphragm (EA(di)) signal, airway pressure (P(aw)), oxygenation (P(aO(2)) /F(IO(2)) or S(pO(2)) /F(IO(2)) ), breathing frequency, tidal volume, and P(aCO(2)) . RESULTS: In total, 1,327 references were identified, of which 5 were included. In all studies, HFTO was administered with flow 50 L/min and compared to conventional O(2) therapy in a crossover design. The total average duration of invasive ventilation at time of measurements ranged from 11-27 d. In two studies, P(aO(2)) /F(IO(2)) and mean P(aw) were higher with HFTO. EELV, tidal volumes, esophageal pressure swings, and EA(di) were similar during high-flow tracheal oxygen and conventional O(2) therapy. CONCLUSIONS: The main physiological effect of HFTO as compared to conventional O(2) therapy in tracheostomized subjects weaning from mechanical ventilation was improved oxygenation that is probably flow-dependent. Respiratory effort, lung aeration, neuroventilatory drive, and ventilation were similar for HFTO and conventional O(2) therapy. Future studies on HFTO should be performed early in the weaning process and should evaluate its effect on sputum clearance and patient-centered outcomes like dyspnea.