Use of oxygen therapy in COPD

What is chronic obstructive pulmonary disease?

Chronic obstructive pulmonary disease (COPD) is a lung condition. It is almost always caused by smoking. Over time, your lungs get damaged and stiff: you feel breathless if you try to walk around and eventually breathless even when sitting down.

You may develop symptoms in your 50s and 60s although the changes in your lungs may have been taking place for some time if you have smoked from a young age. See the separate leaflet called Chronic Obstructive Pulmonary Disease.

The most important thing is to stop smoking.

Other things you can do if you have chronic obstructive pulmonary disease (COPD) are:

• Eat healthily.

• Try to keep moving: regular exercise can help.

• There are some medications which can help to relieve symptoms and these may be in the form of tablets or given by an inhaler.

In some cases, oxygen is used in COPD: it is prescribed by a doctor.

Oxygen is used to take the strain off your heart, not your lungs. It helps to prevent something called 'pulmonary artery hypertension'. This is quite an unusual condition where the right-hand side of your heart gets worn out by trying to pump blood harder and harder to your lungs. Some people think that oxygen helps them feel less breathless: this is a myth unfortunately.

Oxygen saturations can be measured easily in your home with a small electronic device that goes on your finger: they are called 'pulse oximeters', are readily available and can be bought in shops. Most people have a saturation level of 96% or more. In chronic obstructive pulmonary disease (COPD) it often goes down to 90%. There is another, more accurate way of measuring oxygen levels that is used by specialists in hospitals: it's called an 'arterial blood gas'.

It requires a small needle that takes blood from a blood vessel (an artery) which is usually in your wrist. This gives a more accurate reading than using the device on your finger. Rather than a percentage, it gives a number called 'PaO₂' which is a specialised way of testing oxygen. It is this 'PaO₂' that doctors use to work out if oxygen will help you.

Fortunately not. Oxygen doesn't help at all in some people with COPD and, in fact, can be harmful. A lung specialist will assess you. The criteria for needing oxygen are:

• A PaO₂ of less than 7.3 kPa when your COPD is stable (this means you have a low oxygen level in your blood); or

• A PaO₂ of between 7.3 kPa and 8.0 kPa when stable and one of:

  • A high red blood cell level.

  • A low oxygen level at night (less than 90% oxygen saturations for more than 30% of the time you're asleep).

  • Swollen legs and ankles.

  • Pulmonary artery hypertension.

This is a common misconception. When you've got chronic obstructive pulmonary disease (COPD) your body gets used to having a low oxygen level. Your brain gets good at detecting low levels of oxygen and keeps your lungs working at a stable rate. If you suddenly increase your oxygen levels, your brain 'gets confused' and stops your lungs working properly: your breathing rate can go really slow and you could fall unconscious. This is why it's important never to use someone else's oxygen or to try oxygen 'just in case'.

This is usually a doctor who specialises in breathing problems (a respiratory physician). It probably won't be your family doctor (your GP). Oxygen can only help in certain situations with COPD and even then it is not recommended if you smoke: if the oxygen catches fire it can be extremely dangerous and burn your face. It could even cause an explosion and be dangerous to other people in your house.

Your doctor doesn't provide it directly to you, nor does a chemist or pharmacist. Each country has a company that delivers oxygen canisters or a special machine called an oxygen concentrator to your house. Your doctor will fill out a form and send it to the company for you.

Oxygen canisters are only used if you're out and about: at the shops, for example. While you're at home you can use an oxygen concentrator. It's a box about the size of a big computer printer. It plugs into the wall and has a long tube for the oxygen that can reach most rooms in your home.

A lot of people think they only need the oxygen when they're feeling breathless or having a flare-up of their COPD. This is a bit of a myth. If your doctor does think you'll benefit from oxygen then you'll be advised to keep it on for at least 15 hours a day. In fact, some people are advised to have it on for 20 hours. You can appreciate this might get a bit inconvenient. The problem is, if you have it on for less then it doesn't do much good.