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Above: Micro Medical spirometers undergoing Quality Assurance testing

The measurement accuracy of Turbine Flow Heads manufactured by Micro Medical remains unaffected by changes in environmental conditions. In consequence their factory-set calibration remains extremely stable(2) and they do not require routine calibration adjustment. In accordance with international guidelines,(1) however, their accuracy can be quickly verified by using a 3 litre calibration syringe or by performing a 'biological quality control check' (guidance outlined below)

Volume accuracy check

A summary of the key ATS/ERS 2005(1) recommendations when performing a volume accuracy check for flow measuring devices (such as Micro Medical Spirometers) follows;
  • A volume accuracy check should be performed daily(1)
  • A 3-L calibration syringe should be used(4)
  • This calibration syringe should have an accuracy of +/- 0.5% (15 mL for a 3-L syringe) (1)
  • The syringe should be discharged through the device at least three times to give a range of flows varying between 0.5 and 12 L.s-1 (with 3-L injection times of approximately 6s for the lower flow limit and less than 0.5 s for the upper flow limit) (1)
  • The volume at each flow should meet the accuracy requirement of +/- 3.5%(1)
  • For Micro Medical pocket Spirometers where a calibration check screen is not available, the device can be checked in the patient 'blow' mode and the accuracy range will be between 2.97L and 3.15L (requiring a 2% offset)

Biological quality control check

A 'biological quality control check' involves performing 3 technically correct Spirometry manoeuvres on the device, (using the same healthy individual for each biological check) and is also recommended as an indicator of the instruments accuracy performance (1)

(1) Standardisation of Spirometry M.R Miller et al. ATS/ERS Task Force: Standardisation of Lung Function ;Testing Eur Respir J 2005; 26: 319-338.
(2) Dirksen A, Madsen F, Pedersen OF, Vedel, Jensen AK. Long term performance of a hand held Spirometer. Thorax 1996; 52:973-976.
(3) Technical and Functional assessment of 10 Office Spirometers. A Multicenter Comparative Study Giuseppe Liistro, Carl Vanwelde et al CHEST/30/3/ September 2006.
(4) A 3 litre calibration syringe (catalogue number SM2125) can be obtained from Micro Medical Ltd in  the UK or from one of their approved distributors internationally. For more information please click here