Acceptable Spirometry

acceptable spirometry

Spirometry is effort dependent and the spirometric technician should encourage the subjects to perform with the maximal possible effort. Certain criteria are recommended by the ATS-ERS Task Force on the Standardization of Lung Function Testing (2005) for obtaining acceptable and reproducible flow-volume loop.

1) Start of Test Criteria
The back extrapolated volume (EV) should be less than 5% of FVC or 0.150 liter whichever is greater. Spirometers generally alert the technician if the start of test criteria is not met while testing a subject.

2) End of Test Criteria
The test can be terminated if the volume time curve shows no change in volume for greater than one second and the subjects have exhaled for greater than or equal to 6 seconds (age>10 years). In children less than 10 years exhalation time of 3 seconds is sufficient. If the subjects cannot or should not continue the exhalation, they can stop at any time and terminate the maneuver.

3) Reproducibility Criteria
This is to check if the spirometric parameters  and flow-volume curve obtained can be reproduced by the individual subject. To test the reproducibility criteria, after three acceptable FVC maneuvers are obtained, the two largest FVC should be within 0.150 liters of each other and two largest FEV1 should be within 0.150 litres of each other. In case if this criteria is not met, the test is repeated for a maximum total of 8 attempts till FVC maneuver which satisfies the criteria of reproducibility is obtained.

4) Additional Criteria
Excessive hesitation at the start, cough during the first second, glottis closure, submaximal effort, leak, block in mouthpiece may render the maneuver unacceptable.


Wednesday, September 7, 2011