HEMODYNAMIC-EFFECTS OF HIGH-FREQUENCY OSC ILLATING VENTILATION IN PRETERM AND TERM INFANTS

To study the effects of high frequency oscillating ventilation (HFOV) on cerebral and abdominal circulation we measured blood flow velocitie s in three cerebral arteries and in the A. mesenterica superior by pul sed doppler ultrasound in 13 preterm (mean gestional age 28 weeks [25- 31]) and 3 term infants during conventional ventilation (intermittend positive pressure ventilation, IPPV) and HFOV. In the preterm infants systolic blood flow velocities decreased under HFOV in all cerebral ar teries. Statistically significant differences were found in the A. cer ebri anterior (45.8 cm/s [sd+/-20.6] versus 34.3 [sd+/-10.8]; p<0.02) and in the A. basilaris (52.8 cm/s [sd+/-26.4] versus 44.1[sd+/-18,7]; p<0.05). There was also a distinct decrease of systolic blood flow ve locity in the A. mesenterica (111 cm/s [sd+/-31.3] versus 61.8 cm/s [s d+/-18.6]; p<0.002). The enddiastolic blood flow velocity and the Resi stance Index of Pourcelot did not change significantly. The systemic b lood pressure did not change during conventional ventilation or HFOV. Mean airway pressure and pCO(2) were lower during HFOV, but there was not strong correlation with the reduction of now velocities in the stu died arteries (r=0.48). In the three term infants presenting with a pe rsistent pulmonary hypertension of the newborn, there was an increase in systolic and enddiastolic flow velocities in all studied arteries u nder HFOV.