conventional ventilation versus high-frequency oscillation: Hemodynamic effects in newborn babies

Objective: We conducted a prospective study to assess the hemodynamic effects of conventional mechanical ventilation (CMV) compared with high-frequency oscillation (HFO) in newborn babies with respiratory distress syndrome. Methods: A total of 18 consecutive term and preterm infants were examined by two-dimensional M-mode and pulsed Doppler echocardiography. Results: Five patients had to be excluded, three of them because of increasing cardiovascular support after initiation of HFO. The remaining 13 infants (seven males, six females) had a median gestational age of 33 wks (range, 25-40) and a birth weight of 2350 g (range, 790-3600). Patients entered the study at 21 hrs (range, 5-69) of life, receiving total maintenance fluid of 90 mL/kg/day (range, 60-120). Five babies (38%) needed continuous inotropic support. HFO was used as a rescue therapy in infants who failed with CMV. In all 13 patients, HFO significantly impaired cardiac performance compared with CMV by decreasing aortic velocity-time integral: median, 10.2 cm (range, 6.0-14.6) vs. 8.3 cm (range, 5.3-12.4; p <.002); stroke volume: median, 3.8 mL (range, 1.6-6.8) vs. 3.2 mL (range, 1.3-5.9; p <.002); and cardiac index: 281 mL/min/kg of body weight (range, 177-579) vs. 200 mL/min/kg of body weight (range, 156-591; p <.002). Fractional shortening was also significantly reduced: median, 0.31% (range, 0.24-0.44) vs. 0.29% (range, 0.20-0.34; p <.01), because of a significantly smaller left ventricular diastolic diameter during HFO: median, 1.4 cm (range, 1.0-1.9) vs. 1.4 cm (range, 0.9-1.8; p <.05), with a median difference of -0.07 cm (range, -0.4-0.2). HFO also causes a significant decrease in heart rate-corrected left ventricular ejection time: median, 0.25 sec (range, 0.23-0.28) vs. 0.23 sec (range, 0.21-0.26; p <.02) and heart rate-corrected velocity of circumferential fiber shortening (Vcfc): median, 1.3 circ/sec (range, 1.0-1.6) vs. 1.2 circ/sec (range, 0.9-1.4; p <.05). Left ventricular end-systolic wall stress (LVESWS; g/cm 2 ) remained stable. The correlation between Vcfc and LVESWS did not show any significance (CMV, r 2 =.2; HFO, r 2 =.09). The regression line between Vcfc and LVESWS showed a higher y-intercept and steeper slope during CMV than during HFO. Heart rate, mean arterial pressure, and left ventricular systolic diameter remained unchanged. Conclusions: In newborn babies, HFO significantly decreased left ventricular cardiac output caused by reduced left ventricular filling and HFO decreased contractility at higher mean airway pressures than with CMV.