EFFECT OF CPAP VIA ENDOTRACHEAL TUBE ON ORGAN BLOOD FLOWS IN NEWBORN LAMBS

Abstract

Although CPAP is widely used in newborns, little is known of its effects on organ blood flows. We have shown head-box CPAP with a loose neck collar adversely affects cardiac output (C.O.) and retinal and renal blood flows in newborn lambs. The purpose of this study was to evaluate changes in C.O. and organ flows during endotracheal CPAP. Organ blood flows were measured with labeled 25 μ microapheres at CPAP pressures of 0, 6, 11, and 0 mnHg in 8 spontaneously breathing lambs, 3 to 8 days old. Twenty-three to 44% of the airway pressure was transmitted to the esophagus. Heart rate, left ventricular pressure and arterial blood gaaes were unchanged. Cardiac output (ml/min·kg) fell from a control of 248 ± 22 (mean ± SE) to 206 ± 11* and 202 ± 15† at 6 and 11 mmHg, respectively. Central venous pressure (CVP, mmHg) rose from 7.0 ± 1.4 to 10.9 ± 3.1% and 12.0 ± 2.7*, and jugular venous pressure (JVP) from 11.5 ± 1.8 to 13.9 ± 2.1† and 15.3 ± 2.2* at 6 and 11 mnHg, respectively. Blood flow to spleen, heart, brain, and choroid-retina did not change. Renal and gastrointestinal blood flows were unchanged at 6 mmHg, but fell 16.6 ± 5.1%* and 23.9 t 6.4%* at 11 mmHg. These data show that endotracheal CPAP caused moderate falls in C.O. and renal and gastrointestinal flows. However, endotracheal CPAP did not result in the fall in ocular blood flow or the extreme rise in CVP and JVP observed with head-box CPAP.* p < 0.05, † 0.10 > p > 0.05.