Spirometry – Lung Function Test Explained
Spirometry is a lung function test that measures breathing capacity and airflow. It helps diagnose conditions such as asthma and COPD quickly and non-invasively.
Things worth knowing about "Spirometry"
Spirometry is a lung function test that measures breathing capacity and airflow. It helps diagnose conditions such as asthma and COPD quickly and non-invasively.
What is Spirometry?
Spirometry is the most widely used diagnostic procedure for assessing lung function. Using a device called a spirometer, the test measures the volume and speed of air that is inhaled and exhaled. The procedure is painless, non-invasive, and provides valuable information about respiratory function within just a few minutes.
How Does Spirometry Work?
During the test, the patient breathes in as deeply as possible and then exhales as forcefully and quickly as they can into a mouthpiece connected to the spirometer. The device continuously records airflow and exhaled air volumes, generating a graphical representation known as the flow-volume curve.
The key measurements obtained from spirometry include:
- FEV1 (Forced Expiratory Volume in 1 second): The amount of air that can be exhaled in the first second of a forced breath out.
- FVC (Forced Vital Capacity): The total amount of air exhaled after a maximum inhalation.
- FEV1/FVC ratio (Tiffeneau index): The ratio of FEV1 to FVC, used to distinguish between obstructive and restrictive lung disorders.
- PEF (Peak Expiratory Flow): The maximum airflow rate during exhalation.
When is Spirometry Used?
Spirometry is used in a wide range of clinical situations, including:
- Diagnosis and monitoring of bronchial asthma
- Diagnosis and severity assessment of chronic obstructive pulmonary disease (COPD)
- Evaluation of shortness of breath, chronic cough, or exertional dyspnoea
- Preoperative risk assessment before lung or cardiac surgery
- Monitoring conditions that may affect the lungs, such as pulmonary fibrosis or cystic fibrosis
- Occupational health screenings for workers exposed to harmful substances
Interpreting the Results
Obstructive Pattern
A reduced FEV1/FVC ratio (below 0.7) indicates airway narrowing, which is typical of asthma or COPD. The airways are constricted, making it difficult to exhale air quickly.
Restrictive Pattern
A reduced FVC with a normal FEV1/FVC ratio suggests a restrictive ventilation disorder. The lungs cannot fully expand, as seen in pulmonary fibrosis, pleural effusion, or neuromuscular diseases.
Mixed Pattern
In some cases, both obstructive and restrictive components are present simultaneously, referred to as a mixed ventilatory defect.
Preparation and Procedure
To ensure accurate results, the following guidelines should be followed:
- Avoid strenuous physical activity immediately before the test
- Refrain from smoking for at least four hours prior to the examination
- Certain bronchodilator medications may need to be withheld before the test, depending on the clinical question -- always consult a physician first
- Wear loose-fitting clothing to allow unrestricted chest movement
The test is typically performed in a seated or standing position. To ensure reliable results, three to five attempts are usually required, with the best result being recorded.
Risks and Contraindications
Spirometry is generally very safe. In rare cases, the effort of forced exhalation may cause brief dizziness or coughing. Contraindications include:
- Recent myocardial infarction or unstable angina
- Acute pneumothorax
- Uncontrolled hypertension
- Recent eye, abdominal, or thoracic surgery
References
- Global Initiative for Chronic Obstructive Lung Disease (GOLD) – Global Strategy for the Diagnosis, Management, and Prevention of COPD (2024). Available at: www.goldcopd.org
- Miller MR et al. – Standardisation of spirometry. European Respiratory Journal, 26(2):319-338, 2005. DOI: 10.1183/09031936.05.00034805
- Pellegrino R et al. – Interpretative strategies for lung function tests. European Respiratory Journal, 26(5):948-968, 2005. DOI: 10.1183/09031936.05.00035205
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Related search terms: Spirometry-en