Effects of high frequency oscillatory ventilation on cerebral hemodynamicsin neonates.

Background: The effects of high-frequency oscillatory ventilation (HFOV) on hemodynamic parameters have been shown in animal as well as in clinical st udies. In a further study we could demonstrate, that after change of a conv entionel positive pressure ventilation (CMV) to HFOV flow velocities in cer ebral arteries decreased. In the following we added to the dopplerflow meth od the continuous examination of cerebral oxygenation with near infrared sp ectroscopy (NIRS). Patients: 19 measurements were prospectively conducted i n 18 neonates. The infants were mechanically ventilated with HFOV and were in a stable condition. Methods: Before change from HFOV to CMV doppler sign als of the anterior cerebral artery were measured. We repeated this at the end of the study in each patient. NIRS-optodes were placed on the front and the os parietale of each infant. After stabilisation of the system we chan ged from HFOV to CMV without disconnection of the patient from the machine. PCO2 was registred continously via a transcutaneous probe, as well as oxyg en saturation via pulse oxymetry. Statistical analysis was performed with W ilcoxon test. Results: There were no significant changes of doppler-signals during the study (median vs. 25 cm/s (+/- 6) during HFOV, 28 cm/s (+/-/) d uring CMV). The parameter of NIRS, oxygenated hemoglobin HbO [-1.5U (+/-22. 78)] at 15 minutes after change), reduced hemoglobin HbR [-1.17 U (+/- 5.26 )] and total hemoglobin HbT [-2.68 U (+/- 18.7)] remained stable during the change from HFOV to CWV, too. In five infants there was a decrease and in two an increase of HbO 15 minutes after change, which correlated with decre ase or increase of pCO(2). Conclusion: In a combined measurement of doppler flow and NIRS we found no special effect of HFOV on cerebral hemodynamics c omparing with CMV. Changes of cerebral oxygenation in NIRS correlated with pCO(2).