Effect of the thermodynamics of an infant plethysmograph on the measurement of thoracic gas volume

Sly, P. D., Lanteri, C. and Bates, J. H. (1990) Effect of the thermodynamics of an infant plethysmograph on the measurement of thoracic gas volume. Pediatric pulmonology, 8 3: 203-208. doi:10.1002/ppul.1950080312


Author Sly, P. D.
Lanteri, C.
Bates, J. H.
Title Effect of the thermodynamics of an infant plethysmograph on the measurement of thoracic gas volume
Journal name Pediatric pulmonology   Check publisher's open access policy
ISSN 8755-6863
1099-0496
Publication date 1990
Sub-type Article (original research)
DOI 10.1002/ppul.1950080312
Volume 8
Issue 3
Start page 203
End page 208
Total pages 6
Place of publication Hoboken, NJ, United States
Publisher John Wiley & Sons
Language eng
Formatted abstract
Adult plethysmographs have frequency responses that are essentially flat over the range of frequencies encountered in the measurement of thoracic gas volume (TGV). An infant plethysmograph is necessarily much smaller than an adult model. This means that there is a smaller mean distance over which heat diffusion must occur between the air in the plethysmograph and its walls. This in turn leads to a much reduced thermal time constant. We examined the effects of thermal time constant of a 60 L infant plethysmograph on measurements of TGV in infants. The thermal time constant was measured by rapidly injecting 20 mL of air into the plethysmograph, and found to be 0.16 +/- 0.09s when the box was empty. We calculated from this time constant that measurements of TGV should be quite dependent on the frequency at which the associated panting maneuvers are performed. TGV was measured in 5 infants less than 6 months old in the recovery phase following acute viral bronchiolitis. When we performed a digital correction of the measurements, to compensate for the thermal time constant of the plethysmograph, the TGV values decreased by a mean of 12%. Agitating the air in the plethysmograph with a fan decreased the thermal time constant of the box and reduced measured TGV by a mean of 8.4%. These results indicate that thermodynamics of infant plethysmographs can be an important source of error in TGV measurements.
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: Faculty of Health and Behavioural Sciences -- Publications
 
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Created: Wed, 17 Nov 2010, 11:50:59 EST