High-Flow Tracheal Oxygen Therapy Effect on End-Expiratory Lung Impedance

Tracheostomized patients undergoing liberation from invasive mechanical ventilation may experience lung volume loss during ventilator disconnection, which can increase respiratory effort and the risk of hypoxemia. High-flow tracheal oxygen (HFTO) therapy has been proposed as a strategy to attenuate these physiological alterations. However, previous studies using flows ≤60 L/min have demonstrated limited or absent effects on end-expiratory lung volume. This study evaluates the short-term physiological effects of HFTO delivered at higher flows (70 and 80 L/min) on end-expiratory lung impedance (EELI), assessed by electrical impedance tomography (EIT), compared with low-flow oxygen delivered via a heat and moisture exchanger for tracheostomy (HMET).

A prospective physiological crossover study was conducted in 11 adult tracheostomized subjects previously liberated from invasive ventilation. EELI was measured by EIT during 4 sequential 20-min phases low flow oxygen (baseline), HFTO at 70 L/min, washout with low flow oxygen, and HFTO at 80 L/min. Hemodynamic variables, breathing frequency, S_pO2/F_IO2 ratio, and short-term tolerance were recorded.

HFTO at both 70 and 80 L/min produced a statistically significant increase in global EELI compared with low flow oxygen, without a significant difference between the two high-flow conditions. The anterior-to-posterior impedance ratio, breathing frequency, oxygenation, and hemodynamic variables remained unchanged. All subjects completed the protocol without adverse events or signs of respiratory distress.

In tracheostomized adults breathing spontaneously after ventilator liberation, short-term HFTO at 70-80 L/min modestly increased global EELI versus low flow oxygen, without affecting ventilation distribution, breathing frequency, oxygenation, or hemodynamics. These physiological effects do not demonstrate clinical benefit. Larger randomized studies with longer exposure and integrated outcomes are needed to define the role of very-high-flow tracheal oxygen in this setting.