How often is it necessary?

Patients with moderate asthma should be seen at least twice a year.^{10 <LE I>} Their FEV₁ should be measured during every review appointment. Spirometry gives you an objective measure of a patient’s lung function and may identify a decline in asthma control before symptoms develop.^{11 <LE IV>, 12 <LE IV>} This is particularly useful when the dose of asthma medication is being back-titrated. Patients with severe asthma need to be seen more frequently.^{10 <LE I>}

How can I do it cost-effectively, and within a normal consultation?

As soon as you become aware in a consultation that the visit concerns asthma and that spirometry is appropriate, the pre-bronchodilator spirometry can be done even before finishing the history. Give the bronchodilator, and use this opportunity to check technique. After completing history-taking, examination and beginning to outline a management plan, enough time should have elapsed for a post-bronchodilator spirometry to be done. The consultation time is not unduly extended.¹³

The time between pre- and post-bronchodilator tests can be used to complete the written Asthma Action Plan, or to provide other asthma education in a longer consultation. Salbutamol works very quickly and valid results are obtained if the interval is about 10 minutes.¹³

Other suggestions:

• Do the pre-bronchodilator spirometry, history and exam, send the patient out, get the next patient in and when finished with that patient, get the first patient back in. Do the post-bronchodilator spirometry and then consider the management plan for the patient.
• Get your practice nurse to do the spirometry, then do the consultation following this.
• Send the patient to your local respiratory lab or pathology service for testing prior to your consultation. A respiratory laboratory will accurately calibrate their equipment each day and will also interpret the results for you.
• Send the patient away and get them to return specifically for spirometry.
• See if the local hospital physiotherapy department or asthma educators are prepared to perform spirometry on request.¹³

There is a rebate for pre- and post-bronchodilator spirometry: MBS Item No. 11506. The results should be documented in the patient’s medical record and it is also helpful to attach the print-out.

I’m not confident with interpretation – is there an easy way?

A full guide is available in Spirometry: The Measurement and Interpretation of Respiratory Function in Clinical Practice (Pierce & Johns, National Asthma Campaign, 1995). The interpretation table on p. 22 (see Figure 1 below) makes it simple. The publication can be downloaded from the NAC website: www.NationalAsthma.org.au

A respiratory laboratory can also perform the test accurately and interpret the results for you.

Figure 1  Interpretation of spirometry as a function of VC or FVC ( expressed as per cent predicted ) and the FEV₁/FVC% ratio. The vertical line represents the patients’ predicted FEV₁/FVC% (varies with age and sex) and the horizontal line is an estimate of the lower limit of normal for VC or FVC.¹

Normal and abnormal spirometry: A guide

What should I look for when choosing a spirometer?

There are now spirometers to fit every practice and pocket, from small, hand-held computerised models to full-size, traditional bellows spirometers. All reputable brands give good results.

• Ensure that the spirometer provides a graphic display and is calibrated at regular intervals. Your local hospital’s respiratory laboratory may assist you with calibration.
• Infection control is also very important. Disposable mouthpieces are recommended.
• A list of suppliers can be found in the spirometry publication detailed above.

You would not consider managing hypertension without a sphygmomanometer, or diabetes without a glucometer - accurate and objective assessment and management of asthma is not possible without a spirometer.^{3,12,14<LEIV>}  

Content Updated March 2005