Spirometer calibration checks: is 3.5% good enough?

BACKGROUND: Current standards for spirometry require daily calibration checks to come within 3.5% of the inserted volume but do not require evaluation of trends over time. We examined the current guidelines and candidate quality control rules to determine the best method for identifying spirometers with suboptimal performance. METHODS: Daily calibration checks on seven volume spirometers recorded over 4 to 11 years were reviewed. Current guidelines and candidate quality control rules were applied to determine how well each detected suboptimal spirometer performance. RESULTS: Overall, 98% of 7,497 calibration checks were within 3.5%. However, based on visual inspection of calibration check data plots, spirometers 3 and 5 demonstrated systematic sources of error, drift, and bias. The +/- 3.5% criteria did not identify these spirometers. The application of +/- 2% criteria identified these spirometers (9% out-of control values in spirometers 3 and 5 vs < 5% in other spirometers). A rule stipulating out-of-control conditions when four consecutive checks exceeded 1% deviation identified suboptimal spirometers (14% and 20% out-of-control values) but maintained low error detection rates in other spirometers (< or = 2%). Other candidate rules were less effective or required longer times to error detection. CONCLUSIONS: The current recommendation that calibration checks come within +/- 3.5% of the inserted volume did not detect subtle errors. Alternative candidate rules were more effective in detecting errors and maintained low overall error-detection rates. Our findings emphasize the need for laboratories to systematically review calibration checks over time and suggest that more stringent guidelines for calibration checks may be warranted for volume spirometers. Although our general approach may also be appropriate for flow-type spirometers, the details are likely to differ since flow-type spirometers are a much more varied category of equipment.

Technical and functional assessment of 10 office spirometers: A multicenter comparative study.

STUDY OBJECTIVES: To investigate the technical properties and user friendliness of 10 office spirometers devoted for use in general practice, and to compare the results with standard diagnostic spirometers. DESIGN: Multicenter study. SETTING: Ten spirometer models were tested independently in three pulmonary function laboratories and by three general practitioners (GPs). MEASUREMENTS: The laboratories studied the technical quality of the office spirometers in terms of precision and agreement with standard spirometers, whereas the three GPs assessed their user friendliness. The spirometers tested were as follows: Spirobank (Medical International Research; Rome, Italy); Simplicity (Puritan Bennett; Pleasanton, CA); OneFlow (Clement Clarke International; Harlow, Essex, UK); Datospir 70 (Sibelmed; Barcelona, Spain); Datospir 120 (Sibelmed); SpiroPro (SensorMedics; Yorba Linda, CA); EasyOne (NDD; Zurich, Switzerland); MicroLoop (Micro Medical; Chatham, Kent, UK); SpiroStar (Medikro; Kuopio, Finland); and Pneumotrac (Vitalograph; Maids Moreton, Buckingham, UK). FVC and FEV1 were measured in 399 subjects. User friendliness was assessed by the three GPs using a questionnaire. RESULTS: The precision of FEV1 of the office and standard spirometers was comparable, but three office spirometers had > 200 mL limits of precision for FVC. Some devices presented a proportional difference on the FEV1 with standard spirometers, underestimating the small values. The limits of agreements between standard and some office spirometers for FEV1/FVC ratio was > 10%. The overall user friendliness was estimated as good. CONCLUSIONS: The global quality and user friendliness of several office spirometers make them acceptable for the detection of COPD, although differences between the laboratory and some of the office spirometers values suggest that the misclassification rates may be increased when using some models of office spirometers.

[The information content of bronchial reactivity tests (acetylcholinetest) for screening purposes]. / Zum Informationsgehalt bronchialer Reaktivitätsprüfungen (Azetylcholintest) in der Screeningebene

It is described a methodology of the test of bronchial reactivity (acetyl choline test) in the area of occupational medicine. Experiments of retesting resulted in a good reproducibility without regard to the fact that the problems of aerosol dosage and retention are not exactly to be clarified at present. Concerning the information value of tests of bronchial reactivity their value in early diagnosis is emphasized compared with the spirometry without provocation. As essential factors of influence for the results of the tests proved to be the eventually existing diseases of the respiratory tract and the ventilatory initial values. Habits of smoking and age are of less influence.