High-frequency jet ventilation cooling in a canine hyperthermia model

A study was undertaken to evaluate high-frequency jet ventilation (HFJV) as an adjunct for the treatment of heatstroke. Eleven mongrel dogs were anesthetized, shaved, and externally heated until core temperature reached 43 C (109.4 F). Control animals (n = 6) were cooled passively in room air. Treatment animals (n = 5) were cooled with the addition of HFJV using a flow-interrupter, high-frequency jet ventilator with a rate of 200, a driving pressure of 40 psi, and an inspiratory to expiratory ratio of .5 to deliver room air. Temperatures were measured in brain, pulmonary artery, rectum, and subcutaneous tissue of the chest wall. Serial arterial blood gases, cardiac outputs, and mean arterial pressures were measured at baseline, maximal heating, and at .5, 1, 2, and 12 hours after heating. Animals were sacrificed 12 hours after heatstroke induction. Cooling rates for brain, pulmonary artery, and rectum achieved in the HFJV group were 1.7 times faster than those for the control group (P less than .05), although slower than previously reported cooling rates with gastric and peritoneal lavage. A higher PO2, a lower PCO2, and a more physiologic pH was maintained in the HFJV group than in the control group at 30 and 60 minutes after onset of cooling (P less than .05). Gross and histopathologic examination showed characteristic changes of heatstroke in both groups; no deleterious findings could be attributed to the use of HFJV itself. HFJV warrants clinical investigation as an adjunct for treatment of hyperthermia.