Key result
Large tidal volume ventilation produces a ~6 ml smaller decrease in LVEDV than IVCO.
Why the study?
Assessment of preload independent left ventricular function traditionally requires inferior caval vein balloon inflation, but alternative methods to achieve similar preload changes were not established.
Does positive pressure ventilation with large tidal volume provide similar preload changes as inferior vena cava occlusion for assessing left ventricular systolic function in a porcine model?
Does positive pressure ventilation with large tidal volume provide similar preload changes as inferior vena cava occlusion for assessing left ventricular systolic function in a porcine model?
Absolute Event Rate: 16.5% vs 22.4%
p-value: p=<0.0001
Positive pressure ventilation with large tidal volume can create transient preload changes similar to inferior vena cava occlusion for assessing left ventricular systolic function.
May serve as alternative preload maneuver in porcine models; leaves open validation for clinical conductance catheter use.
BACKGROUND: Assessment of preload independent left ventricular function with conductance volumetry is traditionally accomplished by inflating a balloon in the inferior caval vein. Our aim was to investigate if a similar change in preload could be achieved by positive pressure ventilation with large tidal volume. METHODS: Conductance volumetry generating left ventricular pressure-volume loops was used in seven pentobarbital-anesthetized pigs. Changes in preload recruitable stroke work were studied, comparing the effects of inferior vena cava occlusion (IVCO) or large tidal volume (LTV). Cardiodepression was induced by halothane anesthesia and halothane + phenylephrine, and stimulation by epinephrine infusion. RESULTS: Although the decreasis in left ventricular end diastolic volume was slightly less with LTV (16.5 +/- 1.7 ml, mean +/- SEM) than with IVCO (22.4 +/- 1.7 ml) (P < 0.0001) the PRSW-slopes showed a high degree of correlation (r=0.80, P < 0.0001). Although peak tracheal pressures increased significantly to 27.8 +/- 0.9 mmHg during LTV, esophageal pressures (used as an indicator of pericardial pressure) were unchanged. CONCLUSIONS: Positive pressure ventilation with LTV is similar to IVCO in creating transient changes in preload, necessary for assessment of left ventricular systolic function. This observation was valid also during drug-induced cardiac depression and stimulation. The preload recruitable stroke work used for this validation was shown to be a reliable and stable method.
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Sellgren et al. (2003) studied Assessment of left ventricular systolic function (n=7). Positive pressure ventilation with large tidal volume (LTV) vs. Inferior vena cava occlusion (IVCO) was evaluated on Decrease in left ventricular end diastolic volume (p=<0.0001). Positive pressure ventilation with large tidal volume produced slightly smaller decreases in left ventricular end-diastolic volume than inferior vena cava occlusion (16.5 vs 22.4 ml, P<0.0001).
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