Chest
Clinical InvestigationsMiscellaneousBTPS Correction for Ceramic Flow Sensor
Section snippets
Methods
To investigate BTPS correction, five different experiments were conducted. Both the flow sensors and associated electronics were purchased (Tamarac Systems, Denver) and used with data acquisition software written specifically for our particular experiments. To calibrate the ceramic spirometry system, five runs of 30 different constant flows (6 L of volume injected at a constant flow) from 0.4 to 12 L/s were injected through each of the flow sensors (150 flow tests for each sensor). The
Results
Figure 3 shows the results for experiment 1 or the percent difference between room air and air heated-humidified for FEV1 vs the order in which the maneuvers were performed. The ten consecutive FVC maneuvers for each ATS waveform are connected by a line. For each successive FVC maneuver, the percent difference between room and heated air decreases, particularly for waveforms with larger volumes (ATS waveforms 1 and 2). Lower percent differences between room and heated air correspond to a
Discussion
The percent difference in FEV1, obtained using room vs heated-humidified air (proportional to the magnitude of BTPS correction factor needed), ranged from 0.3 percent to 6.2 percent and varied with the number of maneuvers previously performed, the time interval between maneuvers, the volume of the current and previous maneuvers, and the starting temperature of the sensor. Correspondingly, the temperature of the air leaving the sensor (exit) temperature) showed a steady rise with each successive
ACKNOWLEDGMENT
The authors wish to acknowledge the work of Jeff Rushford who spent many hours conducting the tests using the mechanical pump, and Elizabeth Knutti and Michael Lyman who assisted in the field data collection.
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Is my lung function really that good? Flow-type spirometer problems that elevate test results
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