1282 EFFECT OF CONSTANT DISTENDING PRESSURE (CDP) ON CARDIAC FUNCTION IN NEWBORN INFANTS

Abstract

The cardiac function of 11 newborn infants (mean gestational age 34 ± 3 weeks and mean birth weight 2500 ± 780 g) requiring CDP for respiratory distress was serially assessed by M mode echocardiogram prior to CDP and 1/2 hour after establishment of CDP at ± 5 cm of H2O. Six infants received constant negative pressure (CNP) and 5, constant positive airway pressure (CPAP). There were no significant changes in stroke index, left ventricular systolic time intervals, left atrium/aortic ratio, ejection fraction, and % dimension change of the left ventricle, with changes in CDP. The ratio of right ventricular preejection period to eject time (RVPEP/RVET) was constantly decreased after introduction of CDP, more so with CNP than with CPAP (0.49 ± 0.11 to 0.35 ± 0.07 after CNP, p<0.01; 0.45 ± 0.10 to 0.34 ± 0.01, after CPAP, p<0.05). Cardiac index decreased after CNP (1.98 ± 0.79 to 1.16 ± 0.50, p<0.05) but did not change after CPAP (1.38 ± 0.14 to 1.58 ± 0.52 p<0.9). PaO2 increased after both CNP and CPAP (61 ± 13 to 92 ± 22 after CPAP, p<0.01; 58 ± 9 to 82 ± 13 after CNP p<0.02). These results suggest that the increased PaO2 after CDP decreases pulmonary resistance as measured by RVPEP/RVET. Other parameters of mycocardial function are unaffected by CDP at a level of ± 5 cm of H2O.