Spirometry Test

A Spirometry Test measures the volume of air blown out against time and gives more specific information about lung function. This is done by a special technician or specialist using a machine into, which the patient’s age, gender, and height have been entered, so that a predicted value has already been made. The patient blows out into a mouthpiece connected to the machine, as fully and as long as possible, after a deep breath in. Various readings can then be taken and compared with the predicted values.

It is the single best diagnostic test for patients with airflow limitation. All new diagnoses of COPD have to be tested to fulfil scores in the new GP General Medical Services contract. Most GPs are now becoming familiar with this and have nurses who perform spirometry and reversibility testing.

A value is calculated for the amount of air blown out in one second (this is known as the “Forced Expiratory Volume” or FEV1). This is divided by the total amount of air blown out until all air is expired (known as Forced Vital Capacity or FVC). This is expressed as a percentage value and a value of less than 70% indicates COPD.

In asthma, the readings will be reduced, returning to normal between episodes, and again, the recorded result would be compared with what is predicted (according to age, height and gender, by the machine) and the results are then printed out.

Below are some approximate result ranges indicating the level of reduced FEV1.  These can only be considered approximate as factors such as height, age and weight are not considered.

 

Amended April 2008