Increasing numbers of patients are receiving hyperbaric oxygen therapy as an intensive care treatment, some of whom have pre-existing airway obstruction. Spirometers are the ideal instruments for measuring airway obstruction, but peak flow meters are useful and versatile devices. The behaviour of both types of device was therefore studied in a hyperbaric unit under conditions of increased pressure. It is important to have a non-electrical indicator of airway obstruction, to minimize the fire risk in the hyperoxic environment. The hypothesis was tested that, assuming that dynamic resistance is unchanged, both the Wright's standard and mini-peak flow meters would over-read peak expiratory flow (PEF) under increased pressure when compared with a volumetric spirometer, as the latter is unaffected by air density. It was postulated that a correction factor could be derived so that PEF meters could be used in this setting. Seven normal subjects performed volume-dependent spirometry to derive PEF, and manoeuvres using both standard and mini PEF meters at sea level, under hyperbaric conditions at 303, 253 and 152 kPa (3, 2.5 and 1.5 atmospheres respectively; 1 atmosphere absolute = 101.08 kPa), and again at sea level. There was a progressive and significant decline in PEF with increasing pressure as measured by the spirometer (69.46±0.8% baseline at 303 kPa compared with 101 kPa), while the PEF meters showed a progressive increase in their readings (an increase of 7.86±1.69% at 303 kPa with the mini PEF meter). Using these data points, a correction factor was derived which allows appropriate values to be calculated from the Wright's meter readings under these conditions.
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Research Article|
December 13 1999
Peak expiratory flow at increased barometric pressure: comparison of peak flow meters and volumetric spirometer
Paul S. THOMAS;
*Faculty of Medicine, University of New South Wales, Sydney, NSW 2052, Australia
Correspondence: Dr Paul S. Thomas, Department of Respiratory Medicine, Prince of Wales Hospital, Randwick, NSW 2031, Australia (e-mail [email protected]).
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Clifford NG;
Clifford NG
*Faculty of Medicine, University of New South Wales, Sydney, NSW 2052, Australia
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Michael BENNETT
Michael BENNETT
†Department of Hyperbaric Medicine, Prince of Wales Hospital, Randwick, NSW 2031, Australia
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Publisher: Portland Press Ltd
Received:
May 13 1999
Revision Received:
September 08 1999
Accepted:
October 19 1999
Online ISSN: 1470-8736
Print ISSN: 0143-5221
The Biochemical Society and the Medical Research Society © 2000
2000
Clin Sci (Lond) (2000) 98 (1): 121–124.
Article history
Received:
May 13 1999
Revision Received:
September 08 1999
Accepted:
October 19 1999
Citation
Paul S. THOMAS, Clifford NG, Michael BENNETT; Peak expiratory flow at increased barometric pressure: comparison of peak flow meters and volumetric spirometer. Clin Sci (Lond) 1 January 2000; 98 (1): 121–124. doi: https://doi.org/10.1042/cs0980121
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