Comparison of four methods of lung volume recruitment during high frequency oscillatory ventilation

Abstract

Purpose: To compare four methods of volume recruitment upon initiation of high frequency oscillatory ventilation (HFOV). Methods: Anesthetized intubated neonatal piglets (n = 10) underwent repeated saline lavage, followed by conventional mechanical ventilation (CMV). After transition to HFOV at a mean airway pressure 8 cmH 2O above CMV (P basal), four methods of lung volume recruitment were tested in each animal in random order: Escalating - step-wise pressure increments over 6 min to a peak mean airway pressure 12 cmH 2O above P basal; Sustained dynamic inflation (DI) - a 20 s inflation to the same peak pressure; DI repeated six times for 1 s; Standard - mean airway pressure set directly at P basal. After each recruitment method, HFOV continued at P basal for 15 min. Thoracic gas volume and distribution of aeration were determined by single slice computed tomography, and oxygenation by arterial blood gas sampling. Results: Escalating recruitment resulted in the greatest thoracic gas volume 15 min post-recruitment [77 ± 3.3% of total lung capacity vs. 70 ± 4.2% (Sustained DI), 65 ± 3.5% (Repeated DI), 63 ± 5.1% (Standard); mean ± SEM; P = 0.042, ANOVA]. All methods resulted in a reduction in non-aerated lung, with the greatest redistribution to normally aerated lung being with Escalating recruitment. Oxygenation 15 min post-recruitment was better with the Escalating method than with Repeated DI or Standard recruitment (pO 2 307 ± 41 vs. 159 ± 36 vs. 134 ± 39 mmHg, respectively; P = 0.016, ANOVA). Conclusions: Escalating recruitment produced the greatest increase in lung volume and resolution of atelectasis, and is recommended for lung volume recruitment upon initiation of HFOV. © Springer and ESICM 2009.