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

Area of Science:

• Respiratory physiology
• Critical care medicine

Background:

• Tracheostomized patients may lose lung volume post-ventilation, increasing respiratory effort and hypoxemia risk.
• High-flow tracheal oxygen (HFTO) is explored to mitigate these changes.
• Previous studies with HFTO ≤60 L/min showed limited effects on end-expiratory lung volume.

Purpose of the Study:

• To evaluate the short-term physiological effects of HFTO at higher flows (70 and 80 L/min) on end-expiratory lung impedance (EELI).
• To compare HFTO effects with low-flow oxygen via a heat and moisture exchanger for tracheostomy (HMET).

Main Methods:

• Prospective physiological crossover study in 11 adult tracheostomized subjects.
• EELI measured by electrical impedance tomography (EIT) during sequential 20-min phases: low flow oxygen, HFTO at 70 L/min, low flow washout, HFTO at 80 L/min.
• Hemodynamic variables, breathing frequency, SpO2/FiO2 ratio, and tolerance recorded.

Main Results:

• HFTO at 70 and 80 L/min significantly increased global EELI compared to low flow oxygen.
• No significant difference in EELI between 70 and 80 L/min HFTO.
• Anterior-posterior impedance ratio, breathing frequency, oxygenation, and hemodynamics remained unchanged.
• All subjects tolerated the protocol without adverse events.

Conclusions:

• Short-term HFTO at 70-80 L/min modestly increased EELI in spontaneously breathing tracheostomized adults.
• No significant impact on ventilation distribution, breathing frequency, oxygenation, or hemodynamics observed.
• Current physiological effects do not demonstrate clear clinical benefit; further randomized studies are needed.