BTPS Correction for Ceramic Flow Sensor: Recommendations

BTPS Correction for Ceramic Flow Sensor: RecommendationsOne study has reported it to be closer to 34°C and we have measured approximately 35.5°C. In addition, the subject’s exhaled air contains approximately 5 percent CO2 that was not present in our experiments using the mechanical simulator, filled with air from the room.
Another possible explanation for the maneuver order effect is the subjects may be exhibiting a learning effect or somehow varying their efforts in this uncoached environment, thereby increasing their values with each successive maneuver However, feedback based on peak flow was provided to the subject after each maneuver to encourage a maximal effort.
Although the volume spirometer-determined values of FEVi and FEVe were slightly higher than those obtained on the flow spirometer, these differences were not statistically significant. These differences may be due in part to an absence, with the flow spirometer, of immediate feedback of the FEVi and other values as maneuvers are performed. When using the volume spirometer, the FEVi, FVC, peak flow, and other values are provided to the technician as each maneuver was completed. Regardless, additional studies are necessary to explain the slight differences between results obtained using the mechanical pump vs human subjects.
We believe the best explanation for our results is that the sensor is warming from its initial room temperature with each successive FVC maneuver. Therefore, some measure of sensor temperature other than ambient temperature is warranted and a dynamic, rather than a static, BTPS correction factor should be used. This approach is needed for accurate estimations of forced expiratory volumes and to reduce the erroneous variability in FVC and FEVi between successive maneuvers. These results also highlight the need for spirometer testing using heated-humidified air.

This entry was posted in BTPS Correction and tagged air temperature, btps correction, ceramic element.