Detecting lung overdistention in newborns treated with high-frequency oscillatory ventilation

Positive airway pressure (Paw) during high-frequency oscillatory ventilatio n (HFOV) increases lung volume and can lead to lung overdistention with pot entially serious adverse effects. To date, no method is available to monito r changes in lung volume (Delta VL) in HFOV-treated infants to avoid overdi stention. In five newborn piglets (6-15 days old, 2.2-4.2 kg), we investiga ted the use of direct current-coupled respiratory inductive plethysmography (RIP) for this purpose by evaluating it against whole body plethysmography . Animals were instrumented, fitted with RIP bands, paralyzed, sedated, and placed in the plethysmograph. RIP and plethysmography were simultaneously calibrated, and HFOV was instituted at varying Paw settings before (6-14 cm H(2)O) and after (10-24 cmH(2)O) repeated warm saline lung lavage to induce experimental surfactant deficiency. Estimates of Delta VL from both method s were in good agreement, both transiently and in the steads state. Maximal changes in lung Volume (Delta VLmax) from all piglets were highly correlat ed with Delta VL measured by RIP (in ml) = 1.01 x changes measured by whole body plethysmography - 0.35; r(2) = 0.95. Accuracy of RIP was unchanged aR er lavage. Effective respiratory system compliance (Ceff) decreased aRer la vage, yet it exhibited similar sigmoidal dependence on Delta VLmax, pre- an d postlavage. A decrease in Ceff (relative to the previous Paw setting) as Delta VLmax was methodically increased from low to high Paw provided a quan titative method for detecting lung overdistention. We conclude that RIP off ers a noninvasive and clinically applicable method for accurately estimatin g lung recruitment during HFOV. Consequently, RIP allows the detection of l ung overdistention and selection of optimal HFOV from derived Ceff data.