Respiratory Oscillometry in Patients With Acute Hypoxemic Respiratory Failure.

Background: Assessing respiratory mechanics in patients with acute hypoxemic respiratory failure who are not intubated could provide useful information about illness trajectory. Oscillometry is a respiratory function test used to measure total respiratory impedance during tidal breathing, which reveals resistive and elastic properties of the lung. This study assessed the feasibility of oscillometry in patients with acute hypoxemic respiratory failure and described their respiratory mechanics. Methods: Adult participants with acute hypoxemic respiratory failure who were receiving noninvasive respiratory support with FIO2 ≥0.4 and flow ≥6 L/min underwent oscillometry at baseline and after resolution of acute hypoxemic respiratory failure. The primary end point was the number of participants who completed the baseline measurement. The feasibility criterion was in obtaining baseline oscillometry measurements in ≥80% of enrolled participants. Results: Of 183 patients screened between July 2022 and August 2023, 29% were unable to cooperate due to altered mental state, 20% with extreme hypoxemia were excluded because of clinical instability, and 12% declined participation. Of the 10 participants (5.4%) recruited, all tolerated oscillometry measurements. At baseline, the median (minimum, maximum) FIO2 was 0.8 (0.4, 0.8), median oxygen saturation of 94% dropped to a nadir of 82% at the end of oscillometry and recovered within 2 min. Lung reactance was increased, with a reactance area of 25 (15-32) cm H2O/L. Hypoxemia resolved in 9 participants. After resolution of acute hypoxemic respiratory failure in 8 (6-16) d, the median reactance area dropped to 15 (14-19) cm H2O/L. Conclusions: Respiratory mechanics in the participants with acute hypoxemic respiratory failure who were not intubated could be assessed by oscillometry in carefully selected cases.