Tidal (T) and partial (P) LV can be applied without substantial adverse steady-state haemodynamic effects. In this study we quantify and compare phasic cardio-pulmonary interaction during T and P. Lung injury was induced by repeated saline lavage(PaO2 < 13.3 kPa, FiO2 1.0) in 7 anaesthetized and paralysed piglets (age: 9-15 days; BW:3.0-4.9 kg), instrumented with catheters and ultrasonic transit-time flow probes in order to measure systemic arterial(SAP), pulmonary arterial (PAP), left atrial (LAP), and central venous (CVP) pressure, left and right ventricular stroke volume (SVLV and SVRV) and cardiac output (Qao and Qpa). Haemodynamic data were collected successively during gas ventilation (G) (30 bpm; VT ≅ 12 ml/kg; I:E ratio = 1:1; FiO2 = 1.0), P (instillation of 30 ml/kg FC-75 (3M-Company) followed by G settings), and T (5 bpm; VT = 15 ml/kg; I:E ratio = 1:2; FiO2 = 1.0). To describe the effects of ventilation on each haemodynamic variable, we performed non-linear regression analysis of beat-to-beat trend data versus time. The regression model used was y(t)=b0+b1t+b2t2+b3sin(2π/T)t+b4cos(2π/T)t, with T the period of the ventilator. The amplitude of the harmonic function with pulsation 2π/T can be estimated as: A=(b32+b42)0.5. Amplitude was normalized by expressing it as a percentage of the mean value of the variable during the studied period. Data are presented as median [interquartile range]. Differences between paired data were analyzed using the Wilcoxon signed rank sum test. Median values of haemodynamic variables were not significantly different between the studied periods of G, P and T. The amplitude (%) of respiration-synchronous fluctuation was as follows:Table Conclusion: Within breath variability of left ventricular output and systemic blood pressure are increased during tidal liquid ventilation as compared to partial liquid ventilation.
