The Science Journal of the American Association for Respiratory Care

2001 OPEN FORUM Abstracts

BENCHCOMPARISON OF FOUR SPIROMETERS WHICH USE DISPOSABLE FLOW TRANSDUCERS

Bliss PL, Dirks AJ, McCoyRW, Adams AB Valley Inspired Products LLC Burnsville,MN

Background: In recent years many new, low-cost spirometers have become available. Some ofthese spiromters, in order to control cost and provide infection control, utilizea disposable resistance element as a flow transducer. Manufacturing tolerancedictates that each of these elements will be slightly different, so a calibrationnumber is input into the spirometer before use. This calibration number providesthe spirometer with the required information to accurately estimate instantaneousflow from the pressure data it receives. We wondered whether this system providesconsistent results.

Methods: Fourcommercially available spirometers, Renaissance II (Mallinckrodt), Simplicity(Mallinckrodt), SpiroCard (QRS Diagnostic), and Sensaire (QRS Diagnostic) werechallenged with a Flow ? Volume Simulator (Hans Rudolph Inc.) that delivereda known FVC and FEV1. Three of the standard ATS waveforms (volume waveforms2,12 and 17) were used. Five disposable flow elements were used for each device,selected from different manufacturing lots. The same selection of elements wasused for the two Mallinckrodt devices. FVC and FEV1 values were recorded fromeach trial as reported by the device, and compared to the values reported bythe simulator.

Results: Thespirometers reported different values than the simulator, as shown in the followingtable. The average and the range (maximum ? minimum) for each set of flow elementsis included. All data is expressed as % error.

%ERROR
Volume2
Volume12
Volume17
 
FVCFEV1FVCFEV1FVCFEV1Average
RenaissanceIIError1.52.1 1.7 3.51.72.5 2.1
Range2.11.81.01.50.91.01.4
SimplicityErrorError2.83.03.04.63.03.53.3
Range1.41.41.11.51.61.71.5
SpiroCardError-2.7-2.9-2.4-1.5-2.0-1.7-2.2
Range1.61.61.61.81.21.01.5
SensaireError0.1-0.2-0.51.6-0.9-0.30.0
Range0.60.60.90.61.61.61.0

 

Discussion: Theflow volume simulator delivers gas at ambient temperature and humidity. Spirometerson the other hand assume that the gas entering the flow element is at body temperatureand humidity, and must assume some amount of cooling. This may create a systematicerror in the measurements.

Conclusion: Theuncertainty introduced by the disposable flow elements is low, no greater than1.5%. The difference between spirometer models, however can be as high as 5.5%,which should be considered, especially when testing the same patient on differentdevices.

 

OF-01-161

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