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Best Practices in Workplace Surveillance
Technique and Equipment Pitfalls in Spirometry Testing:
Serious Threats to Your Respiratory Surveillance Program
Mary C. Townsend
The goal of screening and surveillance programs is
to identify individuals, either singly or in groups, who have
developed obstructive or restrictive impairment or rapidly declining
lung function. However, both screening and surveillance will be
ineffective if spirometry quality is not monitored and if health
professionals at all levels, from those conducting the tests to those
interpreting the results, are not aware of the pitfalls of technique-
and equipment-related spirometry testing errors. Though most
technique-related testing errors and traditional equipment-related
errors cause the forced expiratory volumes to be under-estimated, some
errors in testing technique and problems with equipment, particularly
with some flow-type spirometers, will cause the expired volumes to be
over-estimated. Because the spirometry test is summarized by selecting
the largest FEV1, the largest FVC, and the single curve with the
largest sum of (FEV1 + FVC) for flow rate measurement, spirometry test
results are particularly vulnerable to errors that inflate the expired
volumes. In many commercially available spirometers, if erroneous
curves are not recognized and deleted as they occur, the inflated
erroneous values will be saved and reported as the subject's test
results, replacing accurate but lower values from that test session.
In contrast, if errors which reduce the measurements are corrected
within a test session, the erroneous curves are replaced by accurate
curves, and the errors have no impact on the subject's reported test
result. Recognition of test errors requires a real-time graphical
display and trained, competent technicians, whose spirograms and
calibration checks are periodically reviewed for technical quality and
to assure that the spirometer calibration remains within acceptable
limits. This paper summarizes and gives examples of technique- and
equipment-related testing errors, demonstrating the effects of these
errors on test results. Examples of the effects of testing errors on
screening and surveillance programs will also be presented.
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NOTE: This document is provided for historical purposes only.