During HFOV, selection of an appropriate MAP is essential to reach optimal lung volume. This is the key to successful and safe use of HFOV. Respitrace technology is a non-invasive volume measuring technique based on Respiratory Inductive Plethysmography (RIP). The purpose of this pilot study was to evaluate RIP technology in monitoring lung volume when weaning MAP on HFOV and to test the ability of the RIP to determine the critical closing pressure location on the Pressure/Volume (P/V) Curve. In a model of normal saline lavaged lungs, 8 anesthetized adult rabbits were ventilated with HFOV using the SensorMedics 3100A ventilator. After injury, lungs were clinically recruited and stabilized on HFOV. MAP was then weaned gradually as changes in lung volume were recorded with the RIP. These changes were plotted as a function of MAP in order to build the P/V Curve (Figure). X-rays were taken to assess lung volume at start and end of the weaning maneuver. The RIP was able to detect marked drop in lung volume before clinical deterioration occurred, as followed by pulse oximetry. Therefore, RIP could be a useful, non-invasive tool to monitor lung volume during HFOV and could be used to maintain the lung above the critical closing pressure during the weaning phase.

Figure 1
figure 1

P/V Curve from one experiment CCP = Critical Closing Pressure

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