THE INFLUENCE OF HIGH-FREQUENCY JET VENTILATION WITH VARYING CARDIAC-CYCLE SPECIFIC SYNCHRONIZATION ON CARDIAC-OUTPUT IN ARDS

Background: Previous studies have shown ''beat-to-beat'' variation in systemic BP with high-frequency jet ventilation (HFJV). However, it is not clear if such changes are paralleled by changes in cardiac output . Objective: To characterize the effect of HFJV near or equal to the h eart rate (HR) on bent-to-beat cardiac output in an adult human subjec t with ARDS. Design: Case study. Setting: ICU, university teaching hos pital. Patients: One patient with end-stage liver disease complicated by sepsis, severe pancreatitis, ARDS, and multisystem organ failure. M ethods: The patient was intubated, sedated, paralyzed, and ventilated with controlled mechanical ventilation (CMV). Ventilatory mode was the n switched to HFJV at lived frequencies (f) near but not equal to the HR (f = 100, 110, and 120 beats/min; HR = 108/min). HFJV was then sync hronized to the ECG such that f and HR were equal. Continuous cardiac output (COc),vas monitored during change of ventilator mode from CMV t o fixed-rate HFJV to synchronized HFJV, then followed through progress ive delays in jet triggering within the cardiac cycle during the synch ronous HFJV mode. COc was monitored by arterial pulse-contour analysis , allowing assessment of beat-to-beat changes in cardiac output. Measu rements ana main results: A cyclic variation in COc equal to the beat frequency difference between f and HR was observed (harmonic interacti on) during fixed-rate HFJV. This COc oscillation was abolished during synchronous HFJV. COc was significantly greater dining systolic synchr onous HFJV as compared to diastolic synchronous HFJV or lived-rate HFJ V (10.1 to 9.0 [p < 0.05] and to 8.6 [p < 0.05] L/min, systolic synchr onous to diastolic synchronous and to fixed-rate HFJV, respectively). Conclusions: This study demonstrates instantaneous variations in cardi ac output in a human subject with fixed rates of HFJV near to the HR i n humans. These variations are abolished by synchronous HFJV but cardi ac output was dependent on the timing of the HFJV inspiration in relat ion to the cardiac cycle. COc is a potentially valuable method to moni tor sudden changes in cardiac output and facilitate attempts to maximi ze cardiac output during synchronized HFJV.