Tests your doctor may perform

Your doctor is likely to ask you questions about your symptoms, specifically coughing, how much mucus you produce, and whether you smoke. The answers to these questions will indicate whether you are at risk of COPD, but your doctor will then want to confirm the diagnosis by doing tests to check how well the lungs are working.

The spirometer gives an accurate picture of how much air is able to move into and out of the lungs during normal breathing, which shows whether airways are obstructed. You will be asked to blow very hard into a tube that is connected to a machine known as a spirometer. The spirometer takes two measurements:

• Forced vital capacity (FVC) is the total volume of air that can be breathed out of the lungs with maximum effort in one breath
• Forced expiratory volume (FEV₁) is a measure of how much of this air is breathed out in the first second
  

The spirometer represents these two findings as a graph.

If there is no obstruction in the airways, the air is breathed out fastest at the beginning (blue line). If the airways are obstructed, the outward breath will be more gradual (red line).

Blood gas measurements

If you have severe COPD your doctor may want to test the oxygen and carbon dioxide levels in your blood. Your doctor will be testing for hypoxaemia (too little oxygen) and hypercapnia (too much carbon dioxide). This is usually done by taking a sample of blood from an artery, to gain an accurate measurement of how much oxygen is being delivered to the body.

Gas-analysis

Usually doctors use a needle to withdraw blood from an artery in the wrist or leg. If you are on oxygen therapy, this may be turned off for 20 to 30 minutes before blood is collected, or, if you cannot cope without oxygen, the amount of oxygen you are receiving will be recorded. The blood taken in this sample is then analysed for the levels of oxygen and carbon dioxide.

Pulseoxymetry

Doctors can also measure oxygen levels using an instrument called a pulse oximeter. This does not use a needle, but instead a small sensor is attached to the end of a finger or an ear lobe. The sensor determines how much oxygen there is in the blood by recording the amount of light that can be transmitted through the skin.

X-rays

You may find that your doctor sends you for a chest X-ray. X-rays are another way of ‘seeing’ what is inside the body. Your doctor may be looking to see if there is infection, or if part of the lung has deflated or become overinflated. Your doctor may also want to exclude the possibility of other diseases.

Mucus test

If you have a respiratory infection your doctor may ask you to undergo a mucus test. You will be asked to provide a sample of mucus, which he will send to a laboratory. Here the mucus will be examined for signs suggesting inflammation or infection.

Exercise test

You may be asked to do an exercise test. This will measure how much exercise you are able to do. The commonest exercise test requires you to walk as far as you can in six minutes. If you use portable oxygen, you are allowed continue using it during the test.

Sometimes doctors also want to measure what happens to the oxygen levels in your blood when you exercise. This is normally done using a small device known as a pulse oximeter, which is clipped onto the end of a finger while you exercise. This measurement is painless and tells the doctor how much oxygen in is your blood.

What stage is the disease?

Test results are used to classify COPD into different stages – early stage, moderate or severe and very severe. These stages are sometimes referred to as stage I, stage II or stage III and stage IV respectively.

• In early stage COPD (stage I), there is usually a chronic cough and mucus production
• In moderate COPD (stage II) you are likely to notice that you get short of breath when you exert yourself. This is the stage at which most people start to see their doctor
• In severe COPD (stage III) there will be a serious shortness of breath on the mildest exertion. There may be signs of other organs being affected by respiratory failure, possibly heart or blood pressure problems
• In very severe COPD (stage IV) there will be a severe shortness of breath even at rest, and there are likely to be other problems in addition to breathing difficulties. Some people may have heart problems
  

Some doctors also refer to a stage 0, which covers people who are at risk of COPD, and have symptoms of cough and excessive mucus, even though their spirometry tests are normal.

These stages were defined by doctors who see a lot of people with COPD. You can find out more technical information about COPD by going to their website www.goldcopd.com