Background: We analyzed phasic cardio-pulmonary interaction during gas ventilation (G), partial (P), and tibal (T) liquid ventilation. Subjects: Seven anaesthetized piglets, made respiratory insufficient by saline lung lavage. Intervention: G (30 bpm; VT ≅ 12 ml/kg; I:E ratio = 1:1), P (instillation of 30 ml/kg FC-75 followed by G), and T (5 bpm; VT = 15 ml/kg; I:E ratio = 1:2). Measurements: We performed non-linear regression analysis of beat-to-beat trend data versus time of systemic arterial [SAP], pulmonary arterial [PAP], left atrial [LAP], and central venous [CVP] pressure, left and right ventricular stroke volume[SVLV and SVRV]. Amplitude of the respiratory induced oscillation was normalized by expressing it as a% of the mean value of the variable during the studied period. Results: The normalized amplitude of respiratory induced oscillation was significantly higher for CVP and SVLV (and accordingly for SAP and Qao) during T when compared to P (Wilcoxon matched-pairs signed-rank test). Conclusion: Within breath variability of left ventricular output and systemic blood pressure are increased during T as compared to P.
