Use of Combined Higb-Frequency Oscillation and Intermittent Mandatory Ventilation in Rabbits with Saline-Lavaged Lungs

Abstract

We combined high-frequency oscillation ventilation (HFOV) with intermittent mandatory ventilation (IMV) in rabbits with surfactant-depleted lungs by saline la vage. Thirteen rabbits were initially ventilated with con stant-flow, time-cycled, pressure-limited ventilators and 100% oxygen at a peak inspiratory pressure to keep arterial carbon dioxide tension (PaCOz) below 50 mm Hg. Group 1 (n = 6) received only IMV for 3 hours and Group 2 ( n = 7), combined HFOV/IMV for 3 hours. HFOV was delivered at 15 Hz and a tidal volume of 2 ml/ kg. Arterial blood gases were measured every 15 min utes. In Group 1, arterial oxygen tension (PaO 2) de creased from 71 ± 5 to 60 ± 7 mm Hg (mean ± standard error of the mean), PaCO2 increased from 34 ± 2 to 50 ± 9 mm Hg, and the ventilatory index (PaO 2/mean airway pressure x fraction of oxygen in in spired air) decreased from 5.9 ± 0.8 to 4.3 ± 0.6 mm Hg/cm H2O over the 3-hour period (nonsignificant). In Group 2, PaO2 increased from 61 ± 6 to 141 ± 12 mm Hg (p < .01), PaCO 2 decreased from 35 ± 2 to 25 ± 7 mm Hg (nonsignificant), and the ventilatory index in creased during HFOV/IMV from 5.1 ± 0.6 to 12.7 ± 2.2 mm Hg/cm H2O (p < .001) at a lower mean airway pressure than Group 1 over 3 hours. This indicates that the combination of HFOV and IMV is advantageous in improving pulmonary gas exchange in rabbits' saline- lavaged lungs.