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Difference between occluded airway pressure and generated muscle pressure

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Abstract

During the measurement of occluded airway pressure (Pao), the gas in the lung expands. This volume change causes Pao to underestimate the generated inspiratory muscle pressure (Pmus), which has been recommended as an index of respiratory drive. Analysis shows that the error is proportional to the thoracic gas volume at occlusion and to the effective respiratory system elastance (E ′rs ) and is inversely proportional to the dry atmospheric pressure. Examples of potential error in various species are presented. In normal human subjects at sea level measurement of Pao would underestimate Pmus on the order of 5 percent depending on E ′rs . In subjects with large functional residual capacity due to obstructive lung disease, the error can be as large as 20 percent. It is recommended that, in all studies of occlusion pressure, an estimation of this error be made.

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Authors and Affiliations

  1. Department of Medicine, University of North Carolina, 724 Clinical Sciences Bldg. 229H, 27514, Chapel Hill, NC

    R. L. Pimmel & F. L. Eldridge

  2. Department of Physiology, University of North Carolina, Chapel Hill, N.C.

    R. L. Pimmel & F. L. Eldridge

Authors
  1. R. L. Pimmel
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  2. F. L. Eldridge
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Additional information

This work was supported by the U.S. Public health Service Grants HL-19118 and HL-17689. R. L. Pimmel is supported by an RCDA (HL-00207)

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Pimmel, R.L., Eldridge, F.L. Difference between occluded airway pressure and generated muscle pressure. Ann Biomed Eng 7, 67–72 (1979). https://doi.org/10.1007/BF02364440

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  • DOI: https://doi.org/10.1007/BF02364440

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