Effects of temperature on Vitalograph spirometer readings

Area of Science:

• Pulmonary Function Testing
• Respiratory Physiology
• Medical Device Calibration

Background:

• Spirometry is crucial for assessing lung function.
• Standardization of spirometry measurements often involves correction to body temperature and pressure, saturated (BTPS).
• The impact of ambient temperature on spirometer accuracy, particularly with BTPS correction, requires further investigation.

Purpose of the Study:

• To evaluate the effect of ambient temperature on spirometric variables measured by Vitalograph spirometers.
• To assess the accuracy of spirometric measurements before and after correction to BTPS under varying temperatures.
• To determine if BTPS correction enhances measurement accuracy for Vitalograph spirometers.

Main Methods:

• Nine symptomless subjects performed forced expiratory maneuvers.
• Measurements were taken using three Vitalograph spirometers at three ambient temperatures: 36.5°C, 24.1°C, and -7.3°C.
• A Latin square design was employed over three days, with data analyzed using analysis of variance.

Main Results:

• No significant difference in spirometric values was observed at different ambient temperatures when measured at ambient temperature and pressure, saturated (ATPS).
• Correction to BTPS resulted in significant differences for most measurements (except Vmax25) across the tested temperatures.
• The mean error introduced by BTPS conversion ranged from 7% (SD 5%) for FVC at 24.1°C to 30% (21%) for Vmax50 at -7.3°C.

Conclusions:

• There is no evidence that converting Vitalograph spirometer measurements to BTPS improves accuracy.
• BTPS conversion can introduce significant errors, especially at low ambient temperatures.
• Further studies are needed to determine the appropriateness of BTPS correction for other spirometer models.