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

Objective: We conducted a prospective study to assess the hemodynamic effec ts of conventional mechanical ventilation (CMV) compared with high-frequenc y oscillation (HFO) in newborn babies with respiratory distress syndrome. Methods: A total of 18 consecutive term and preterm infants were examined b y two-dimensional M-mode and pulsed Doppler echocardiography. Results: Five patients had to be excluded, three of them because of increas ing cardiovascular support after initiation of HFO. The remaining 13 infant s (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 th e 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 inotro pic support. HFO was used as a rescue therapy in infants who failed with CM V. In all 13 patients, HFO significantly impaired cardiac performance compa red 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: med ian, 3.8 mt (range, 1.6-6.8) vs. 3.2 mt (range, 1.3-5.9; p < .002); and car diac 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 dia stolic diameter during HFO: median, 1.4 cm (range, 1.0-1.9) vs. 1.4 cm (ran ge, 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 ven tricular election time: median, 0.25 sec (range, 0.23-0.28) vs. 0.23 sec (r ange, 0.21-0.26; p < .02) and heart rate-corrected velocity of circumferent ial 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 stre ss (LVESWS; g/cm(2)) remained stable. The correlation between Vcfc and LVES WS did not show any significance (CMV, r(2) = .2; HFO, r(2) = .09). The reg ression line between Vcfc and LVESWS showed a higher y-intercept and steepe r 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 ventricula r cardiac output caused by reduced left ventricular filling and HFO decreas ed contractility at higher mean airway pressures than with CMV.