Relationship between Mean Airways Pressure, Lung Mechanics, and Right Ventricular Output during High-Frequency Oscillatory Ventilation in Infants.

Objective: To characterize changes in lung mechanics and right ventricular output (RVO) during incremental/decremental continuous distending pressure (CDP) maneuvers in newborn infants receiving high-frequency oscillatory ventilation, with the aim of evaluating when open lung maneuvers are needed and whether they are beneficial.

Study Design: Thirteen infants on high-frequency oscillatory ventilation were studied with a median (IQR) gestational age of 26 (25-29) weeks and median (IQR) body weight of 810 (600-1020) g. CDP was increased stepwise from 8 cmHO to a maximum pressure and subsequently decreased until oxygenation deteriorated or a CDP of 8 cmHO was reached. The lowest CDP that maintained good oxygenation was considered the clinically optimal CDP. At each CDP, the following variables were evaluated: oxygenation, respiratory system reactance (Xrs), and RVO by Doppler echocardiography.

Results: At maximal CDP reached during the trial, 19 [1] cmHO (mean [SEM]), oxygenation markedly improved, and Xrs and RVO decreased. During deflation, oxygenation remained stable over a wide range of CDP settings, Xrs returned to the baseline values, and RVO increased but the baseline values were not readily restored in all patients.

Conclusion: These results suggest that Xrs and RVO are more sensitive than oxygenation to overdistension and they may be useful in clinical practice to guide open lung maneuvers.