Effect of high-frequency jet ventilation on heart rate variability

We investigated the effects of high-frequency jet ventilation (HFJV) on heart rate variability in nine patients during fentanyl (10μg·kg^-1) anesthesia using power spectral density analysis. ECG and arterial pressure were recorded during intermittent positive pressure ventilation (IPPV) (tidal volume 8 ml·kg^-1, respiratory rate 0.25 Hz) and during HFJV [5 Hz, 2.5 kg·(cm²)^-1]. The R-R interval time series obtained were analyzed by the autoregressive method, and low-frequency (LF) (0.05-0.15 Hz) power and high-frequency (HF) (0.20-0.50 Hz) power from R-R interval spectra were used for statistical comparison. LF power did not change during IPPV and HFJV (108.8±41.6 ms² vs 105.8±22.4 ms², mean±SE). HF power was detected during IPPV (65.1±14.3 ms²); however, it was not detected during HFJV. Plasma levels of norepinephrine and epinephrine were significantly higher during HFJV than during IPPV. The mean R-R interval, arterial pressure, and arterial blood gas data did not differ between IPPV and HFJV. These data indicate that, during fentanyl anesthesia, HFJV influences mainly the respiratory frequency fluctuation of heart rate variability, and they suggest that alteration of breathing patterns caused by HFJV might be involved, as well as elevated sympathetic neural outflow to the heart.