Spirometry

The following parameters analysed during spirometry precisely evaluate lung capacity: 

• FEV1 (forced expiratory volume in the first second): measures the volume of air exhaled in the first second of a forced breath. 

• FVC (forced vital capacity): total air volume forcibly exhaled after maximum inhalation. 

These data help to detect ventilatory disturbances of an obstructive, restrictive or mixed type; and are fundamental for clinical diagnosis and monitoring. 

Spirometry has a number of uses: 

• Diagnosis and monitoring of respiratory diseases such as asthma, COPD, pulmonary fibrosis and other chronic lung conditions. 

• Assessment of the response to pharmacological or non-pharmacological treatment. 

• Pre-surgical functional evaluation, especially for thoracic and abdominal operations. 

• Early detection of respiratory conditions in smokers or people exposed to workplace toxins. 

• Respiratory functional assessment in patients with non-pulmonary diseases, as part of a prognosis or pre-transplant study. 

Spirometry can also be requested in patients with autoimmune or immuno-rheumatological systemic diseases (such as lupus, rheumatoid arthritis and scleroderma), chronic heart disease or as part of a pretransplant evaluation of other organs apart from the lung, such as the kidney, liver and heart; since it estimates pulmonary functional reserve and can highlight potential risks during complex treatments or major surgery. 

The test is performed sitting down, using a mouthpiece connected to a spirometer. A clip is placed on your nose to prevent air from escaping. 

The typical sequence is: 

1. Breathe normally at the start. 

2. Breathe out and empty the lungs smoothly. 

3. Inhale deeply until the lungs are full. 

4. Exhale quickly, forcefully and continuously for a few seconds. 

This procedure is repeated a minimum of 3 times to ensure the quality and reproducibility of the results. In many cases, the test is repeated 15 minutes after administering a bronchodilator, such as salbutamol, to check for possible changes in the volume of air exhaled. 

To ensure reliable results, the following should be observed. You should: 

• Avoid smoking within two hours of the test. 

• Avoid eating or drinking too much.  

• Not do any intense physical exercise before the study.  

• Wear comfortable clothing that does not restrict breathing.  

You must also inform the health team if you are using inhalers or bronchodilators; as this may have to be temporarily suspended before the test. 

Spirometry must not be performed in the following cases: 

• Pulmonary thromboembolism or a recent pneumothorax.  

• Bleeding in the mouth. 

• Active respiratory infection (tuberculosis or flu). 

• Cardiovascular problems, such as a recent myocardial infarction, unstable angina or a thoracic aorta aneurysm that has grown or is large. 

Other factors that will postpone examination are: 

• Very high intracranial or systemic blood pressure. 

• Acute retinal detachment. 

• Confusion or dementia syndromes. 

• Abdominal, thoracic, cerebral, ocular or recent ear, nose or throat surgery. 

• Diarrhoea or vomiting. 

• Oral or facial problems that prevent or hinder the placement and fastening of the mouthpiece. 

The test is performed by trained health personnel: nurses, technicians or physiotherapists specialising in respiratory function. 

The results are interpreted by a pneumologist, who will include them within the patient's general clinical context to guide diagnosis, therapeutic decision-making and prognosis. 

Spirometry is usually well-tolerated, although some people may notice a slight feeling of tiredness, cough or chest tightness due to the effort of forced breathing. Occasionally, there may be slight dizziness or a transitory headache. These effects are rare and usually disappear in a few minutes. Health personnel will be present throughout the test to guarantee your well-being and safety.