Measurement of maximum inspiratory pressure and airway occlusion pressure in a bench study of the adult star ventilator

Michael G. Winter, James D. Pike, Thomas A Dillard

Research output: Contribution to journalArticle

Abstract

INTRODUCTION: Maximum inspiratory pressure (MIP) is a clinical measure of respiratory muscle strength and pressure in the occluded airway at 0.1 seconds of tidal inspiration (P0.1) and is a reflection of ventilatory drive. Contemporary microprocessor-controlled ventilators permit measurement of MIP and P0.1 in intubated patients without removing the patient from the ventilator and without need for additional equipment. METHODS and MATERIALS: In a bench study of equipment accuracy, we compared MIP values from 3 Adult Star ventilators (ASVs) with an aneroid gauge, a respiratory pressure monitor, and a negative pressure ventilator and made similar comparisons for P0.1. RESULTS: Input values ranged from -10 to -55 cm H2O for MIP and from -1 to -9 cm H2O for P0.1. MIP values correlated strongly among all devices (r2 > 0.989, n = 30, p < 0.001). The average deviation from the reference value expressed as mean (SD) for MIP was +0.79 (0.68) for the respiratory pressure monitor; -1.46 (0.59) for the negative pressure ventilator; +1.34 (1.17) for the aneroid gauge; and -0.67 (0.84) for the ASVs (p < 0.05). The deviation in MIP among the 3 ASVs was -0.19, +0.42, and - 0.23 cm H2O after adjusting for device deviation in 2-factor ANOVA with covariate (p < 0.05). P0.1 values correlated strongly among all instruments (r2 > 0.931, n = 27, p < 0.001). The average deviation from reference values for P0.1 was +0.22 (0.30) for the respiratory pressure monitor; +0.03 (0.36) for the negative pressure ventilator; and -0.25 (0.55) for the ASVs. The deviation in P0.1 between individual ASVs was +0.04, - 0.15 and +0.11 cm H2O, by 2-factor ANOVA with covariate (p > 0.05). CONCLUSIONS: We conclude that the differences between devices were small and not likely to be clinically important and that the microprocessor-controlled ventilators compared favorably to the other devices.

Original languageEnglish (US)
Pages (from-to)946-951
Number of pages6
JournalRespiratory Care
Volume42
Issue number10
StatePublished - Oct 1 1997

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ASJC Scopus subject areas

  • Pulmonary and Respiratory Medicine
  • Critical Care and Intensive Care Medicine

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