John L Hankinson | Search PubMed

PubMed2004

Is my lung function really that good? Flow-type spirometer problems that elevate test results.

Most spirometry errors reduce test results, and it is widely assumed that measurement accuracy is guaranteed by frequent spirometer calibrations or calibration checks. However, zero errors and changes in flow-type spirometer sensors may occur during testing that significantly elevate test results, even though the spirometer was calibrated recently. To draw attention to these often-unrecognized problems, this report presents anomalous spirograms and test results obtained from occupational medicine clinics and hospital pulmonary function laboratories during quality assurance spirogram reviews. The spurious results appear to have been caused by inaccurate zeroing of the flow sensor, or by condensation, mucus deposition, or unstable calibration of various flow-type spirometers. These errors elevated some FVCs to 144 to 204% of predicted and probably caused 40% of 121 middle-aged working men in respirator medical clearance programs to record both FVC and FEV1 > 120% of predicted. Since spirometers report the largest values from a test, these errors must be recognized and deleted to avoid false-negative interpretations. Flow-type spirometer users at all levels, from the technician to the interpreter of test results, should be aware of the potential for and the appearance of these errors in spirograms.

Adult↗

PubMed2003

Spirometric reference values for the 6-s FVC maneuver.

STUDY OBJECTIVES: The guidelines of the National Lung Health Education Program for COPD screening proposed a shorter FVC maneuver (forced expiratory volume at 6 s of exhalation [FEV(6)]). Although reference values for FEV(6) are available from the third National Health and Nutrition Examination Survey, forced expiratory flow between 25% and 75% of FVC (FEF(25-75%)) reference values for the shorter 6-s maneuver are not available and are needed. In particular, calculation of largest observed volume during the first 6 s of an FVC maneuver (FVC(6)), from a shortened FVC maneuver, is necessary because the FEF(25-75%) measurement is based on a percentage of FVC or, for a shorter maneuver, FVC(6). DESIGN: We reanalyzed the raw volume-time curves from the third National Health and Nutrition Examination Survey to calculate FVC(6), forced expiratory volume at 0.5 s of exhalation, forced expiratory volume at 3 s of exhalation, ratio of the FEV(1) to largest observed volume during the first 6 s of an FVC maneuver expressed as a percentage (FEV(1)/FEV(6)%), and forced expiratory flow between 25% and 75% of the largest observed volume during the first 6 s of an FVC maneuver (FEF(25-75%6)) in addition to the previously reported values for FEV(1), FEV(6), and FEV(1)/FEV(6)%. PATIENTS OR PARTICIPANTS: Using the same normal, asymptomatic, nonsmoking reference population from a previous study, reference values for these parameters were derived from best values. RESULTS: A total of 2,261 white, 2,564 African-American, and 2,666 Mexican-American subjects aged 8 to 80 years were included in the analysis. Fifty-four subjects from the previous study were not included due to missing raw volume-time curves. CONCLUSIONS: These reference values, utilizing the FVC(6), provide investigators with the means of evaluating the relative merits of using the shorter FVC maneuver as a surrogate for the traditional FVC. They are needed particularly for calculating FEF(25-75%), as statistically significant differences were observed between the FEF(25-75%) and FEF(25-75%6).

Adolescent↗