A Comparison of Conventional Mechanical Hyperventilation with Two Forms of High-Frequency Ventilation for the Control of Intracranial Pressure in Closed-Head Injury

Abstract

Early, aggressive treatment of elevated intracranial pressure (ICP) reduces mortality. A major therapeutic intervention to achieve this is mechanical hyperventilation to produce hypocarbia, which promotes cerebral vasoconstriction and decreased cerebral blood volume. However, high peak airway pressure during conventional mechanical hyperventilation (CMHV) has been shown to have adverse effects on ICP and cerebral blood flow. We therefore compared the effectiveness of CMHV to the effectiveness of high-frequency jet ventilation plus intermittent mandatory ventilation (HFJV + IMV) and the effectiveness of high-frequency percussive ventilation (HFPV) in reducing ICP. Methods: Of 38 patients, 23 began on CMHV and were changed to HFJV + IMV-1, and 15 began on CMHV and were changed to HFPV; changes in ICP were recorded. Results: In the 23 patients changed to HFJV + IMV-1, ICP dropped from 20 ± 8 torr to 12 ± 8 torr (mean ± SD) after the change (P < 0.001). PaO2 dropped significantly, from 120 ± 46 torr to 102 ± 33 torr (P < 0.01). In the 15 patients who were changed from CMHV to HFPV, ICP dropped from 22 ± 12 torr to 14±9 torr after the transition (significant at P < 0.001). PaO2 did not change significantly in this group. Conclusion: Head-injured patients with intracranial hypertension and pulmonary dysfunction requiring increasing levels of CPAP may benefit from high-frequency ventilation for further reduction of ICP.