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The effect of temperature on recording spirograms
The American Review of Respiratory Disease
|November 1, 1983
Summary
Spirometers may inaccurately measure lung function due to temperature differences. Heated pneumotachographs offer more precise spirometry readings than rolling seal or water seal devices, especially in research settings.
Area of Science:
- Pulmonary Function Testing
- Respiratory Physiology
- Medical Instrumentation
Background:
- Accurate spirometry relies on correcting measurements to Body Temperature and Pressure Saturated (BTPS).
- This correction assumes spirometers have a minimal cooling time constant.
- The accuracy of spirometers under varying temperature conditions requires further investigation.
Purpose of the Study:
- To evaluate the accuracy of different spirometer types under simulated physiological conditions.
- To assess the impact of temperature and device type on spirometric measurements.
- To determine the significance of observed errors in clinical and research contexts.
Main Methods:
- Simulated spirograms were generated using a computer-driven servo-controlled pump with regulated internal temperature.
- Three devices were tested: a rolling seal spirometer (RSS), a water seal spirometer (WSS), and a heated pneumotachygraph (PT).
- Measurements were taken with simulated air at ambient (19°C) and body (37°C) temperatures.
Main Results:
- At 19°C, all devices measured forced expiratory volume in one second (FEV1) within 1% accuracy.
- At 37°C, RSS and WSS overestimated FEV1 by 6% and 5% respectively after BTPS correction.
- PT demonstrated consistent accuracy across temperatures, while RSS and WSS showed significant underestimation of mean transit time.
Conclusions:
- Rolling seal and water seal spirometers exhibit temperature-dependent errors, potentially affecting spirometry accuracy.
- Heated pneumotachographs maintain precision across temperatures, making them suitable for research and epidemiological studies.
- While clinical judgments may be minimally impacted, precise spirometric recordings for research necessitate accounting for these instrumental errors.