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COPD Supplement
A practical guide for Primary Care Nurses

The Burden of COPD COPD Guide PDF
Spirometry
Smoking Cessation
Pulmonary Rehabilitation
Appendix One - Resources and contacts
Update on Managing Smoking Cessation - BMJ review July 2007

Spirometry

Spirometry in primary care | Which spirometer | Interpretation guide

Spirometry gives an objective measurement of airflow and lung volume when assessing lung function. It will distinguish between restrictive and obstructive lung diseases and is considered the gold standard for diagnosing, assessing and monitoring COPD. Accurate diagnosis requires the use of a regularly calibrated and validated quality spirometer (approx $4,000 plus GST) by someone who has undergone comprehensive training. In practice in New Zealand, this will usually require referral to a spirometry service. Good advice is available from the Asthma and Respiratory Foundation on how to set up a spirometry service1.

Whatever system is used for spirometry it is essential that smokers are not allowed to be complacent if a normal result is returned. Changes within the lung may be occurring despite the result still being within the normal range and the decision to quit smoking should not be delayed.

Spirometry in primary care

In our COPD faxback, practitioners asked about spirometry in primary care. Is there a place for spirometry in primary care which can augment evaluation of individual patients, but does not meet the high standards for accuracy required of diagnostic spirometry?

Monitoring spirometers are spirometers which do not meet the high standards required of diagnostic spirometers, but are suitable for monitoring progress in individual patients. These spirometers could also be used as part of the initial work up of those with respiratory problems, with the proviso that people who do not have unequivocal symptoms, signs and results confirming COPD or asthma are referred on for formal spirometric testing. Monitoring spirometers start at a cost of around $1,000.

A single spirometry result does not represent the complex clinical consequences of COPD and it is not a substitute for clinical judgment in the evaluation of the severity of disease in individual patients.
American Thoracic Society, European Respiratory Society, 2004.

Which spirometer?

This section is taken from the publication “Spirometry” of the International Primary Care Respiratory Group (IPCRG)2 . This two-page document is a useful source of information on spirometry.

Unfortunately we were unable to source any independent testing of low-cost spirometers available in New Zealand. The National Asthma Council of Australia has published a guide to spirometry use and purchase in Australia on their website. For more information on this excellent guide go to www.nationalasthma.org.au

Ideally, a spirometer should have a graphical display to allow technical errors to be detected. It should be able to produce a hard copy. Regular calibration is essential. Some spirometers need to be calibrated before each session using a calibration syringe. Others hold their calibration between annual services. Check the manufacturer's instructions.

Three types of spirometer are commonly used in primary care:

  • Small, hand held meters which provide digital readings. These are the cheapest option and small enough to fit into a medical bag, but the lack of graphs can make it difficult to judge when a blow is complete. Predicted charts and a calculator will be needed to interpret the results.
  • Portable meters with integral printers. These are more expensive but they will undertake all the calculations, including reversibility. Small displays of the volume time graph help monitor the blow and the printout includes a flow volume loop.
  • Systems designed to work with a computer which will display a graph, calculate predicted FEV1 and FVC, and reversibility and provide a print-out. Integral memories allow data to be recorded outside the practice and uploaded when convenient.

A guide to interpreting spirometry3

i) Normal spirometry

The Forced Vital Capacity (FVC) of the lung is the volume of air that can be forcibly expelled from the lung from maximum inspiration to maximum expiration.
Normal Male, 49yrs, 180cm
FVC = 4.90 litres
Predicted FVC = 4.95 litres
% predicted = 99%
Forced Expiratory Volume in 1 second = FEV1 . The FEV1 is the volume of air that can be forcibly expelled from maximum inspiration in the first second.
Normal Female, 33yrs, 165cm
FEV1 = 3.20 litres
Predicted FEV1 = 3.03 litres
%predicted = 105%

ii) Abnormal spirometry is divided into restrictive and obstructive ventilatory patterns

Restrictive: due to conditions in which the lung volume is reduced, e.g. fibrosing alveolitis, scoliosis. The FVC and FEV1 are reduced proportionately.
  Male, 49yrs, 180cm
FVC = 2.00 litres
(40% of predicted)
FEV1 = 1.80 litres
(45% of predicted)
Obstructive: due to conditions in which the airways are obstructed e.g. asthma or COPD. The FVC and FEV1 are reduced disproportionately.
  Female, 33yrs, 165cm
FVC = 3.50 litres
(98% of predicted)
FEV1 = 1.80 litres
(58% of predicted)

Severity of COPD: FEV1 as a % predicted may be used to classify the severity of COPD.

iii) Forced expiratory ratio (FEV1/FVC ratio, or FEV1 %)

The FEV1/FVC ratio is the FEV1 expressed as a percentage of the FVC (or VC if that is greater): i.e. the proportion of the vital capacity exhaled in the first second. It distinguishes between a reduced FEV1 due to restricted lung volume and that due to obstruction.
Obstruction is defined as an FEV1/FVC ratio less than 70%.

FVC = 2.00 litres
(40% of predicted)
FEV1 = 1.80 litres
(45% of predicted)
FEV1/FVC ratio = 90%
Restrictive ventilatory pattern FVC reduced <80%
FEV1 reduced
FEV1/FVC ratio normal
FVC = 3.50 litres
(98% of predicted)
FEV1 = 1.80 litres
(58% of predicted)
FEV1/FVC ratio = 51%
Obstructive ventilatory pattern FVC normal or reduced
FEV1 reduced <80%
FEV1/FVC ratio reduced <70%


1 Swanney M. Guidelines for setting up a spirometry service. Asthma and Respiratory Foundation of New Zealand, 2004. http://www.asthmanz.co.nz/files/PDF-files/setting_up_a_spirometry_service_pdf.pdf (Accessed March 2005).

2 Spirometry. Kaplan A, Pinnock H. International Primary Care Respiratory Group Opinion No 1. http://www.theipcrg.org/resources/spirometry.pdf (Accessed April 2005).

3 Adapted from: Kaplan A, Pinnock H. Spirometry. International Primary Care Respiratory Group Opinion No 1. http://www.theipcrg.org/resources/spirometry.pdf (Accessed April 2005).


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