Temperature corrections in routine spirometry.

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Abstract
Forced expiratory volume (FEV1) and forced vital capacity (FVC) were measured in 9 normal subjects with 3 Vitalograph and 3 rolling seal spirometers at 3 different ambient temperatures (4.degree., 22.degree. and 32.degree. C). When the results obtained with the rolling seal spirometer were converted to BTPS [body temperature and pressure] the agreement between measurements in the 3 environments improved, but when the Vitalograph measurements obtained in the hot and cold rooms were converted an error of up to 13% was introduced. The error was similar whether ambient or spirometer temperatures were used to make the conversion. In an attempt to explain the behavior of the Vitalograph spirometers the compliance of their bellows was measured at the 3 temperatures. It was higher at the higher temperature (32.degree. C) and lower at the lower temperature (4.degree. C) than at the normal room temperature. These changes in instrument compliance could account for the differences in measured values between the 2 types of spirometer. The ATPS[ambient temperature and pressure]-BTPS conversion is valid and necessary for measurements made with rolling seal spirometers, but can cause substantial error if it is used for Vitalograph measurements made under conditions other than normal room temperature.

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