Spirometry Measures how much and how quickly you can move air out of your lungs. For the test you breathe into a mouthpiece attached to a recording device (spirometer). The information collected many be printed out onto a sheet (spirogram).
The more common lung function values measured are:
Forced Vital Capacity (FVC) This measures the amount of air you can exhale with force after you inhale as deeply as possible.
Forced Expiratory Volume (FEV) this measures how much air you can expel from your lungs in the first second of breathing out. It can help tell whether your breathing is obstructed by narrowing of the bronchial tubes (as found in asthma or chronic obstructive pulmonary disease (COPD)). The FEV1 is useful in diagnosing COPD, telling how severe it is and how it might develop. The amount of air you exhale may be measured at 1 second (FEV1), 2 seconds (FEV2), or 3 seconds (FEV3).
Peak Expiratory Flow (PEF) This measures how quickly you can exhale.
Maximum Voluntary Ventilation (MVV) This measures the greatest amount of air you can breathe in and out in one minute.
Total Lung Capacity (TLC) This measures the amount of air in your lungs after you inhale as deeply as possible.
Residual Volume (RV) This measures the amount of air in your lungs after you exhale with force.
Other Tests Gas Diffusion tests. These measure the amount of oxygen and other gases that cross the lungs air sacs (alveoli) per minute. The tests evaluate how well gases are being absorbed into your blood stream. Tests include, arterial blood gas which determines the amount of oxygen and carbon dioxide in your blood stream. Carbon monoxide diffusing capacity, which measures how well your lungs transfer a small amount of carbon monoxide into the blood.
Body Plethysmography This measures the total amount of air your lungs can hold. For this you test you sit in an airtight booth and breathe into a mouthpeice whilst pressure and air flow measurements are collected. Inhalation Challenge tests These are done to identify substances (allegens) that may be causing severe respiratory allergies or asthma.
Exercise Stress tests These evaluate the effect of exercise on lung function tests. Spirometry tests are done before and after exercise and some tests may be done after you inhale medication that enlarges the airways (bronchodilators).
When we exercise, it has an effect on our breathing. When we are physically active, we need to breathe more. To check your breathing, the tester will ask you to do some exercise and take measurements while you're exercising, and afterwards. This might involve: - Walking at your own pace for six minutes, taking as many rests as you need
- Doing a test called a 'shuttle walking test'. This involves walking between two points set 10 metres (about 30 feet) apart. This is timed with the times gradually get faster, until you can't keep up
- Walking on a treadmill, while the tester monitors your heart and lungs
- Doing a test on an exercise bike. This is done occasionally if the doctors need more detailed information about your breathing. Usually you will be asked to breathe through a mouthpiece while you cycle. The amount of oxygen you breathe in and the carbon dioxide you breathe out are measured, as well as your breathing rate, pulse and sometimes your blood gases.
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