List the reasons why it is recommended to perform a minimum of three spirometry tests and a maximum of eight spirometry tests for a trial.
Minimum:
A valid spirometry record requires that there be a minimum of three acceptable tests, per ATS recommendations.
Maximum:
The maximum number of manuvers for any one test period is eight manuvers.
As the number of trials increase, the lungs become more compliant, or stretched out, up to its anatomical limit. This is known as the 'Compliance' curve.
The more the test is repeated the better the subject understands what is required, therefore values increase. This is called the 'Learning' curve.
After the 5th trial, the 'Fatigue' and 'Subject Hostility' curve supercedes the 'Learning' and 'Compliance' curve; so data values tend to go down, see graph below.
Reference: 'Why Three Trials?' NIOSH Approved Spirometry, training course #051 Training Manual 9.1.06, 2007 http://www.palmerassociates.com