178 Circulatory performance in neonates on high-frequency oscilliation

Abstract

High-frequency oscillation (HFOV) is used to manage respiratory failure in critical ill newborns. To determine whether HFOV alters cardiac and cerebral performance we studied 18 infants (gestational age 34±3 wk, postnatal age 47±12 hours; birth weight 2350g±450) before and during HFOV (Stephan SHF 3000) for severe respiratory failure that has been unresponsive to IMV-ventilation. Dopplerechocardiography was used to determine changes in left ventricular output (LVO), cerebral and intestinal blood flow. Primary indications for HFOV included intractable airleaks (n=6), lung hypoplasia (n=1), meconium aspiration (n=1), pulmonary hypertension (n=2) and RDS (n=8). During HFOV, mean airway pressure was maintained at the same level as with IMV-ventilation Mean blood pressure (RR) increased from 45±5 to 50±6 mmHg (p<0.05). Flow resistance (RR:LVO) increased from 204±13 to 231±18 (p<0.05). Shortening fraction did not change (28% and 27%, respectively). Heart rate decreased from 138±15 to 127±13 1/min (p<0.05). LVO (220±54 and 216±48 ml/kg/min, respectively) remained unchanged. Mean blood flow velocity increased from 0.15±0.04 to 0.21±0.05 m/s in the A. carotis interna, from 0.16±0.05 to 0.22±0.04 m/s in the A. cerebri anterior and from 0.25±0.07 to 0.31±0.09 m/s in the coeliac trunc (p<0.05). PaCO2 decreased from 56±14 to 38±12 mmHg (p<0.05). Oxygenation index (OI=PaO2/FiO2) increased markedly. The results indicate that adequate ventilation and oxygenation can be maintained with HFOV in critically ill neonates without compromising their circulation.