Identification of optimal lung volume during high-frequency oscillatory ventilation using respiratory inductive plethysmography

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Abstract
First, to define the relationships between critical opening and closing pressures and oxygenating efficiency, and second, to address whether respiratory inductive plethysmography (RIP) could be used to monitor changes in thoracic volume that follow changes in mean airway pressure during high- frequency oscillatory ventilation (HFOV). Prospective, interventional animal study. University research laboratory. Five anesthetized, paralyzed, and ventilated pigs. The animals were ventilated by using HFOV after lung injury. Pre- and post-HFOV pressure-volume curves were obtained by supersyringe. A pressure-volume curve was constructed during HFOV as mean airway pressure was increased from 10 to 40 cm H2O and then weaned back down to the minimum sustainable. Hemodynamic and oxygenation data were obtained at each data point. RIP-derived thoracic volumes correlated with known lung volumes during supersyringe (r2 = .78, p 10% predicted the decrease in oxygenation associated with reaching the critical closing pressure. The ability of RIP to detect optimal lung volume during the weaning of mean airway pressure may allow clinicians to more directly monitor lung volume changes during HFOV and use the lowest possible airway pressures after lung recruitment.