Spirometry: When is it necessary?
Reasons for spirometric testing include:
- Clarification of the cause of chronic cough or shortness of breath (dyspnea)
- Suspicion of diseases of the respiratory tract, lungs or heart
- Suspicion of diseases of the respiratory muscles
- chronic tobacco use
- pulmonary function testing before surgery
- general preventive health care
- occupational health check-up for prevention and diagnosis of occupational diseases
Spirometry: Execution
During spirometry, the patient is given a mouthpiece, which becomes a measuring device for and which he should hold tightly with both lips. His nose is closed with a nose clip. On the doctor’s instructions, the patient now breathes in and out through the mouthpiece for about five to ten minutes: After inhaling as deeply as possible, the patient should exhale as quickly and forcefully as possible.
In order for the findings to be meaningful, it is very important that the patient follows the physician’s instructions exactly during the examination and cooperates well.
Bronchospasmolysis test
In some cases (e.g. for the diagnosis of COPD or asthma) the physician combines spirometry with another measurement:
Comparing the readings before and after drug administration helps the physician narrow down the diagnosis of a respiratory disorder. If the one-second capacity has improved to a certain extent in the second measurement compared with the first measurement, the bronchodilator has widened previously narrowed airways – the patient is probably suffering from asthma.
Spirometry: evaluation
Diseases with narrowed airways, for example, show prolonged and reduced exhalation. The Tiffeneau index (= ratio between one-second capacity and vital capacity) is then lowered.
If the vital capacity is reduced, this may be due to a reduced distensibility of the lungs (restriction) or pulmonary hyperinflation (emphysema). Further investigations are then necessary to distinguish between these two possible causes.
Spirometry: What are the risks?
Spirometry is a simple and virtually risk-free procedure. Deep breathing can sometimes cause an irritated cough and dry mouth or slight dizziness. However, both of these quickly disappear.