A novel method for improving gas exchange by applying percussive ventilation in the expiratory phase

Abstract

<b>Background:</b> While high-frequency percussive ventilation (HFPV) improves gas exchange, concerns remain about the added lung tissue strain caused by the oscillations. We compared a modified percussive ventilation modality induced by superimposing high-frequency oscillations to the conventional ventilation waveform during expiration only (eHFPV) to conventional mechanical ventilation (CMV) and standard HFPV. <b>Methods:</b> Hypoxia and hypercapnia were established by decreasing CMV frequency in rabbits. Periods of CMV were followed by HFPV and eHFPV sequences with different oscillatory amplitudes (2 or 4 cmH₂O) and frequencies (5 or 10 Hz). Arterial partial pressures of oxygen (PaO₂) and carbon dioxide (PaCO₂) were assessed. Ventilation dead space, phase 2 slope (S2), and minute-elimination of CO2 (VCO₂) were measured by volumetric capnography. Respiratory mechanics were characterized by forced oscillations. <b>Results:</b> The application of eHFPV with a superimposed oscillatory frequency of 5 Hz and an amplitude of 4 cmH₂O improved gas exchange similar to the improvement observed after HFPVon PaO₂ (58.6±7.2 vs. 47.3±5.5 mmHg, p&lt;0.05) and PaCO₂ (50.1±2.9 vs. 54.7±2.3 mmHg, p&lt;0.05). These benefits were associated with decreased ventilation dead space and S2, and increased VCO₂ without affecting respiratory mechanics. <b>Conclusions:</b> Improvement in gas exchange using eHFPV as a novel mechanical ventilation modality was demonstrated via combining the advantages of conventional and small-amplitude high-frequency oscillatory ventilation. The benefits of eHFPV are due to improved longitudinal gas transport rather than increased lung surface area available for gas exchange. <b>Funding:</b> OTKA-NKFIH K138032