Spirometry is a relatively simple measure of how much air a person can breathe in and out and how fast the air can be exhaled, yet a Canadian Lung Association survey found that 90 per cent of Canadians are unaware of spirometry.
Recent studies have shown that misdiagnosis occurs in the absence of spirometry. Furthermore, many cases of lung disease go undiagnosed because of the lack of spirometry testing. While hypertension would not be diagnosed and managed without the measurement of blood pressure, and diabetes would not be managed without the measurement of blood sugar levels, all too frequently asthma and chronic obstructive pulmonary disease (COPD) are diagnosed and managed without spirometry.
The importance of spirometry is stressed in the Canadian Thoracic Society guidelines for the management of asthma and COPD –the new name for emphysema and chronic bronchitis, ( www.respiratoryguidelines.ca).
The term “spirometry” comes from the Latin spirare (breathe) and the Greek metron (measure). The results of spirometry provide information on how well the lungs are working from a mechanical point of view.
The air flow and volume are measured by a device called a spirometer. Spirometers either measure volume and calculate the flow or measure flow and calculate the volume. Spirometers that measure flow are more portable and more commonly found in physician’s offices. Most of the newer equipment, including equipment found in tertiary pulmonary function labs, uses spirometers that measure flow.
Spirometry is different from many other standard lab tests in that it requires well-motivated participation from the patient. The basic manoeuvre used in spirometry is for the patient to inhale as much air as possible and then exhale as rapidly as possible until no more air can be exhaled. The patient then inhales as rapidly as possible until the lungs are full. The technician conducting the test must be an excellent coach and cheerleader to guide the patient through the manoeuvre in order to obtain the best results. (See the Lung Association YouTube channel for video demonstrations of spirometry at www.youtube.com/TheLungAssociation
Far more interaction with the patient is required than for tests such as blood pressure measurement or collecting a blood sample. Specific spirometry training is required. Quality control considerations cover the preparation and coaching of the patient in addition to equipment calibration and testing procedures. Special considerations are required for spirometry in children. An experienced technician working primarily with children can obtain acceptable spirometry results in children as young as three years old.
To encourage the use of spirometry as a diagnostic tool for lung diseases, the Lung Association has responded to the deficiency of access to spirometry in three main ways. Firstly, there have been publicity campaigns, especially using World Spirometry Day (June 28th, 2012), to raise public awareness about the need for spirometry and which persons should be tested. Secondly, the Lung Association developed and delivers the SpiroTrec® course to train health care workers to conduct quality spirometry (www.resptrec.org). More than 400 health care workers have been trained by SpiroTrec to conduct spirometry across Canada in the past three years. Thirdly, the Lung Association Spirometry Interpretation Course was developed to teach family physicians and nurse practitioners to interpret the results of spirometry.
Spirometry interpretation requires knowledge of the expected lung volumes and flows for each individual patient. The size of the lungs varies with age, height, gender and ethnic origin. Lung growth continues from birth to age 18 – 22 years in females and 20 – 24 years in males. Lung volume remains relatively steady for the next 10 to 15 years and then declines with age. Height is a major predictor of lung volume – the taller the person, the bigger the lungs. An adult male will have larger lung volumes that a female of the same age, height and ethnic origin. African Americans have lung volumes about 10 per cent lower than whites, and Asians about 8 per cent lower, although Northeast Asians are closer to Caucasians and the differences are less in females. Currently, there are no reference values for Canadian First Nations, Métis or Inuit peoples.
What’s new in spirometry?
Later this year, new world-wide reference values for spirometry will be published that will cover the range from 3 to 95 years of age, for Caucasians, African Americans, Northeast Asians and Southeast Asians. The major thoracic societies around the world are recommending its widespread adoption. Canadian research is being done on reference values for First Nations, Métis or Inuit peoples.
The Canadian Thoracic Society is working on a new position paper to make recommendations about the factors to be considered for accrediting labs, clinics and physician offices conducting spirometry; a standardised report for spirometry results; and considerations for spirometry equipment.
New methods of measuring lung volume are being developed. One novel approach is to project a grid pattern on the patient’s torso and calculate lung volume changes by analysing data from stereoscopic cameras. This non-contact system was originally developed for measuring lung volumes in infants. Its accuracy and utility in other applications is under investigation.
COPD is the fourth leading cause of death in Canada, but it’s on the rise and will soon be the third. Because the development of COPD lags the onset of smoking addiction by 25 – 40 years, the predictable, growing wave of COPD will continue. More spirometry testing will be required (see the Canadian Lung Health Test) and disparities in spirometry access will need to be addressed.
Established in 1900, The Canadian Lung Association is one of Canada’s oldest and most respected health charities, and the leading national organization for science-based information, research, education, support programs, and advocacy on lung health issues.
For more information on spirometry, visit www.lung.ca