CARDIOPULMONARY INTERACTION DURING PARTIAL LIQUID VENTILATION IN SURFACTANT-TREATED PRETERM LAMBS

Gas ventilation following instillation of perfluorochemical (PFC) liqu id, partial liquid ventilation (PLV), improves gas exchange and pulmon ary mechanics in neonatal animals and humans with severe respiratory d istress, The effect of PLV on cardiac contractility, performance, pulm onary blood flow and ductal shunt has not been fully described. To thi s end, we evaluated these indices of cardiopulmonary function in eight conventionally gas ventilated, surfactant-treated premature lambs (12 5 days gestation) before and during PLV. Animals were instrumented wit h central venous and aortic lines. Serial evaluation of arterial blood chemistry/pressure, and pulmonary mechanics was performed, cardiac co ntractility, performance, pulmonary blood flow and ductal shunts were serially assessed by echocardiography, As compared to conventional gas ventilation, during PLV there was a significant decrease in left vent ricular meridian (22.5 +/- 6.6 SE vs 8.1 +/- 1.4 SE g/cm(2), P < 0.02) and circumferential wall stress (54.1 +/- 16.5 vs 24.4 +/- 3.8 SE g/c m(2), P < 0.04) at end systole. The fall in wall stress at end systole was associated with a significant decrease in left ventricular intern al diameter (1,2 +/- 0.05 SE vs 1.04 +/- 0.045 SE cm; P < 0.01). There were no significant changes in heart rate, systemic arterial and cent ral venous pressures, systemic vascular resistance, left ventricular s hortening and ejection fractions during PLV. The decrease in wall stre ss was associated with a significant decrease in mean airway pressures (15.9 +/- 1.1 SE vs 9.9 +/- 0.2 SE cmH(2)O; P < 0.05) and ostensibly a change in intrathoracic pressures during PLV, There were no signific ant differences in blood flows (pre vs during PLV; ml/min/kg): pulmona ry (226 +/- 62 SE vs 293 +/- 65 SE), aortic (237 +/- 36 SE vs 204 +/- 21 SE), and left to right ductal (119 +/- 25 SE vs 105.5 +/- 26 SE) me asured before and during PLV. Conclusion. Cardiac output and pulmonary blood flow do not change significantly during PLV and therefore do no t appear to contribute to improved gas exchange, This stable cardiac p erformance occurs at lower wall stress and thereby more advantageous e nergetic conditions.