DECREASED PULMONARY DAMAGE IN PRIMATES WITH INHALATION INJURY TREATEDWITH HIGH-FREQUENCY VENTILATION

Objective This study compared two forms of high-frequency ventilation (HFV) with conventional volume ventilation (CON) in a primate model of inhalation injury to determine whether ventilatory mode was a determi nant of pulmonary damage. Summary Background Data The authors previous ly reported that the prophylactic use of high-frequency flow interrupt ion in patients with bronchoscopically diagnosed inhalation injury req uiring mechanical ventilatory support resulted in a significant decrem ent in mortality. They hypothesized that a reduction in ventilatory mo de induced pulmonary damage was in part responsible for their clinical results. Methods Fifteen adult baboons were randomized to one of thre e ventilatory modes (CON, high-frequency flow interruption [HFFI], or high-frequency oscillatory ventilation [HFO]) after moderate smoke inj ury. Ventilatory support was tailored to the same physiologic endpoint s. After 7 days, the animals were killed and pulmonary pathologic chan ges were scored and compared. Repetitive physiologic and biochemical d ata were compared using analysis of variance for repeated measures. Re sults Physiologic endpoints were achieved in CON and HFFI, but not in HFO. Hemodynamic variables did not diff er between CON and HFFI. The b arotrauma index was greater in CON compared to HFFI (p < 0.05), despit e similar PO2, FlO2, AA gradient, and PCO2. Animals treated with HFFI had significantly less parenchymal damage than those treated with CON (p = 0.03) or HFO (p = 0.0008). Conclusions The prophylactic use of HF FI led to a significant decrement in ventilatory mode induced pulmonar y damage and offers an explanation for the decreased mortality in inha lation injury patients treated with HFFI.