Chest

Chest

Volume 94, Issue 4, October 1988, Pages 755-762
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Pressure Controlled Inverse Ratio Ventilation in Severe Adult Respiratory Failure

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Thirty-one patients with severe respiratory failure who were failing volume controlled conventional ratio ventilation were placed on pressure controlled inverse ratio ventilation (PC-IRV) for a total of 4,426 patient-hours. The PC-IRV resulted in a reduction of minute ventilation from 22 ± 1.0 L/min (mean ± SEM) to 15 ± 0.7 L/min. Peak inspiratory pressure (PEP) was reduced from 66 ± 2.3 cm H2O to 46 ± 1.6 cm H2O and positive end expiratory pressures (PEEP) from 15 ± 1.0 cm H2O to 2.5 ± 0.5 cm H2O. Mean airway pressure increased from 30 ± 1.7 cm H2O to 35 ± 1.7 cm H2O. Oxygenation (PaO2) improved from 69 ± 4.0 mm Hg to 80 ± 4.5 mm Hg. The FaCO2 and arterial pH were not significantly changed. There were no significant changes in mean hemodynamic pressures. A lung compromise index (FIO2·PIP·10/PaO2) retrospectively distinguished between successful and unsuccessful PC-IRV episodes. These data suggest that PC-IRV can be successfully and safely implemented in critically ill patients with severe respiratory failure over prolonged periods of time resulting in significant improvement in oxygenation at lower minute volume, peak airway pressure and PEEP requirements. (Chest 1988; 94:755-62)

Section snippets

METHODS

Thirty three patients identified from Respiratory Therapy department records were placed on PC-IRV at the University of California, Davis Medical Center between July 1985 and December 1986. One medical record could not be located and one patient never was placed on PC-IRV although the equipment was set up at bedside. The remaining 31 patients who underwent 35 episodes of PC-IRV comprise the study group (Table 1). Two patients did not tolerate the attempt to institute PC-IRV leaving 29 patients

RESULTS

Table 1 summarizes the demographic characteristics of our study population. The average age was 38 ± 3.2 years (range 12 to 74). There was a significant difference in ages between male (42 ± 8.4 years) and female (22 ± 2.6 years) subjects. The patients were divided into medical and surgical subgroups on the basis of admitting diagnosis and the service that had primary responsibility for their care. There was no significant difference between subgroups with respect to average time to institution

DISCUSSION

Current management of ARDS utilizing mechanical ventilation, supplemental oxygen, and PEER has changed little over the last ten years.13 Limiting factors in this supportive therapy have included the development of normobaric oxygen toxicity,14 pulmonary barotrauma,15, 16 and hemodynamic instability17 from the positive pressures employed.

The overall goal in treatment of ARDS has been to recruit and stabilize closed, potentially functional alveolar units while minimizing inhomogeneity of

ACKNOWLEDGMENT

The authors wish to thank Kathy Grace, RRT, RCP, Rusty Reid, RCP, Vance Wilson, RRT, RCP, Steve Kutler, RRT, RCEP, and the respiratory therapists of the University of California Davis Medical Center intensive care units for their expert technical assistance in the management of the patients undergoing PC-IRV.

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    Presented in part at the 53rd Annual Scientific Assembly, American CoDege of Chest Physicians, Atlanta, October 26-30, 1987.

    Manuscript received October 12; revision accepted February 10.

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    Copyright © 1988 The American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.