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Spirometry: the health test that’s often overlooked

June 26, 2012

By Patricia Nicholson

Spirometry is a simple and easy lung function test that can provide your doctor with crucial information about your lungs, yet it’s often overlooked and under-used – even in women who are at risk for lung disease.

“Spirometry is a test that measures the size of your lungs and how well you can empty them,” says Dr. Anna Day, a respirologist at Women's College Hospital.

Many respiratory conditions such as chronic obstructive pulmonary disease (COPD) cause changes in the size of the lungs or in the ability to blow air out. These changes can be caused by blocked or inflamed airways, or by damage to the supporting structure. Detecting these changes early is important.

“Unfortunately, people can have 50 to 60 per cent loss of lung function without noticing,” Dr. Day says. “Because it occurs gradually over time, they may attribute symptoms that they have to other things, such as deconditioning, weight gain or aging. So by the time people have symptoms, they actually have very significant disease.”

Spirometry, however, can detect early changes even before chronic lung disease develops. People who are at risk for lung damage should talk to their doctor about spirometry. That group includes:

  • smokers over age 40
  • former smokers over age 40
  • people with asthma

Smokers and former smokers

We all lose lung function as we age. However, people who smoke can lose lung function much more quickly, and there’s no way to tell who will be affected.

“We have no markers at this point that help us know if that person who has smoked for 20 years has no damage, or if they’ve got very rapidly progressive damage. When a person stops smoking, the rate of change in their lung function goes back to normal – which is phenomenal,” says Dr. Day.

They may not have any symptoms, so the only way to know if a person has early or moderate lung disease is by testing.

“For people who are currently smoking, it’s important to be able to find out if they are one of these people who are losing lung function fast, and inform them, and help them make an appropriate choice about whether they want to take the risk of developing symptomatic COPD, or preventing further deterioration,” Dr. Day says.

For people who have already stopped smoking, it’s important to find out how their lungs are functioning because if they do have signs of lung disease, there may be medications that can improve quality of life.

“We have some good therapies that can help people with their breathing and what they can do,” says Dr. Day. “We also have reactivation programs and rehabilitation programs.”

Dr. Day recommends that all smokers and former smokers over age 40 have at least one screening spirometry test. Those who continue to smoke should be assessed annually.

It may be particularly important for women to be screened. In recent years, illness and death from COPD have been rising in Canada.

“That’s primarily because of increasing numbers of women who are being hospitalized with COPD and dying from COPD. Whereas it’s gone down for men, it’s actually being going up for women,” Dr. Day says. “That’s despite the fact that there has been a decrease in smoking for both men and women.”

The reasons for this aren’t fully understood, but could be related to differences in how men and women smoke, or to an increased susceptibility to the effects of smoke in women.


Although spirometry may not always be necessary to diagnose asthma, it’s very useful to find out how asthmatic lungs are functioning.

“We know that asthma that has not been well controlled can cause irreversible damage to the airways,” Dr. Day says. However, it’s often difficult to tell from symptoms if asthma is well controlled.

“Often people will come in and say they’re fine and we do their spirometry and it’s quite clear that they are not well controlled,” Dr. Day says. There isn’t necessarily a strong correlation between the symptoms – or being ‘fine’ – and full control of the asthma.

“What we’re trying to do is move from a model that has used clinical descriptions to objective measurements,” she adds. That can be challenging because a lot of patients and their doctors still view asthma as a condition in which the goal is to deal with symptoms, rather than to ensure that the condition itself is under optimal control. An example would be a patient who says she only wheezes when she plays tennis. However, spirometry may show that she has airway obstruction even with no exertion.

“They may only be aware of it when they play tennis, but the rest of the time they’ve still got active disease and inflammation which can cause long-term damage to their lungs,” Dr. Day says. She recommends that all asthmatics have at least one baseline spirometry test, and periodic followup tests to ensure that their asthma is under optimal control.

What happens during spirometry

Spirometry testing is easy and non-invasive – there are no needles, no preparation and you don’t have to get undressed. Here is what’s involved:

  • The technician will need your age, height, gender and weight.
  • The apparatus includes a tube that you’ll be asked to exhale sharply into through your mouth. You may be asked to wear nose plugs so you don’t exhale through your nose.
  • The technician will give you instructions to blow and then push, push, push air from your lungs. You have to blow out for at least six seconds, and may be asked to keep blowing even after you think your lungs are empty.
  • You can’t study or prepare for the test, so there’s no need to feel stressed about it.






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  • A publication of:
  • Women's College Hospital