Introduction
Spirometry is a physiologic method that helps to measure how an individual inhales or exhales volumes of air as a function of time. It assesses the function of the lung, respiratory muscles, and the chest wall by measuring the total volume of air exhaled from a lung or total lung capacity (TLC) to maximal expiration or residual volume (RV). It is a technique used to measure airflow in and out of the lungs. It records lung volumes and capacities defined by the respiratory process. These recordings may be static or dynamic. It is the most commonly used pulmonary function test. It is the gold standard for diagnosing, assessing, and monitoring chronic obstructive pulmonary disease (COPD).
What Is Spirometry?
It assesses lung function by measuring the volume of air the patient can expel from the lungs after maximal inspiration. It is a simple, safe, and non-invasive method that measures lung function with a graphical display. Spirometry may be required if an individual complains of breathlessness or chronic persistent cough.
The patient should sit upright. A small tube is attached to the mouth, and a nose clip is placed onto the nose to prevent air escape. The tube is attached to the spirometer. It is also important that the lips make a seal around the tube. The patient is asked to inhale fully so that the lungs are filled with air and exhale as quickly and forcibly as possible, ensuring that the lungs have been emptied. The process is repeated at least three times to obtain the same result. The entire procedure takes around 15 minutes.
What Are the Conditions That Can Be Diagnosed With Spirometry?
Conditions that can be diagnosed are:
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Chronic obstructive pulmonary disease (COPD).
What Are the Indications of Spirometry?
Based on the clinical presentation, spirometry is indicated in the following situations:
Symptoms Include:
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Dyspnea or difficulty in breathing.
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Cough.
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Sputum production.
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Chest pain.
Signs Include:
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Clubbing.
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Chest deformity.
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Diminished chest expansion.
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Diminished breath sounds.
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Hyperinflation.
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Prolongation of expiratory phase and crackles.
Diagnostic Purpose:
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To evaluate the signs, symptoms, and abnormal laboratory tests.
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To measure the effect of disorder on pulmonary function.
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To screen the individuals at high risk of having pulmonary disease.
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To assess the pre-operative risk.
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To assess the prognosis.
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To assess the health status before beginning strenuous physical activity programs.
Monitoring Purpose:
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To assess the therapeutic interventions.
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To describe the course of diseases that affect lung function.
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To monitor people exposed to harmful agents.
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To monitor the adverse drug reactions with known pulmonary toxicity.
Disability or Impairment Evaluation:
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To assess the patients as part of a rehabilitation program.
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To assess risk as part of an insurance evaluation.
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To assess individuals for legal reasons.
Public Health:
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Epidemiological surveys.
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Clinical research.
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Derivation of reference equations.
When Not to Perform a Spirometry?
1) Absolute Contraindications:
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Recent Pneumothorax.
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Active respiratory infection.
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Recent myocardial infarction.
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Unstable angina pectoris.
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Hemoptysis of unknown origin.
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Retinal detachment.
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Thoracic, abdominal, or cerebral aneurysm.
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Recent abdominal surgery.
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Intracranial hypertension.
2) Relative Contraindications:
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Problems holding the mouthpiece.
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Facial hemiparesis.
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Poor mental condition.
What Does the Spirometry Measure?
It measures two key measurements:
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FEV1
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FVC
FEV1:
The volume of air an individual can expire during a forced breath in t seconds. For example, forced expiratory volume in one second (FEV1) is the maximum amount of air an individual can forcibly exhale during the first second following a maximal inhalation. Likewise, forced expiratory volume in six seconds (FEV6) is the maximum amount of air an individual can exhale during the sixth second following a maximal inhalation. A lower than normal value indicates obstructive lung disease such as COPD. According to the American Thoracic Society guidelines, a percentage of FEV1 value:
of 80 % or more - is normal.
70 %–79 % - mildly abnormal.
60 %–69 % - moderately abnormal.
50 %–59 % - moderate to severely abnormal.
35 %–49 % - severely abnormal.
less than 35 % - very severely abnormal.
FVC:
Forced vital capacity (FVC) is the total amount of air that can be forcibly exhaled out of the lungs after taking the deepest possible inhalation. A lower than normal indicates restrictive lung disease such as pulmonary fibrosis.
What Are the Basic Types of Pulmonary Function Abnormalities Using a Spirometry?
Two basic pulmonary function abnormalities are described using spirometric parameters:
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Obstructive lung disease.
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Restrictive lung disease.
Obstructive Lung Disease:
It is a chronic inflammatory lung disease that causes obstructed airflow from the lungs.
Types of obstructive lung disease:
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COPD.
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Asthma.
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Cystic fibrosis.
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Bronchiectasis.
Factors that obstruct the airflow include
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Swelling and inflammation of the airways.
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Thick mucus plugging in the airways.
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Damage to the alveolar sac.
Obstructive lung disease is characterized by:
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Reduced FEV1 of less than 80 %.
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Normal or reduced vital capacity.
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Normal or reduced FVC.
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Reduced FEV1/FVC ratio by less than 70 %.
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Concave flow-volume loop on spirometry trace.
Restrictive Lung Disease:
Reduced expansion of the lung parenchyma is accompanied by decreased total lung capacity.
Types of restrictive lung disease:
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Interstitial lung disease.
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Idiopathic pulmonary disease.
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Pulmonary fibrosis.
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Pneumoconiosis.
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Sarcoidosis.
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Scoliosis.
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Neuromuscular causes such as amyotrophic lateral sclerosis.
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Muscular dystrophy.
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Marked obesity.
Restrictive lung disease is characterized by:
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Reduced FEV1 and FVC.
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Normal or more than normal FEV1/FVC.
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The normal-looking shape on spirometry trace.
What Are the Complications of Spirometry?
Complications of spirometry include:
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Syncope.
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Dizziness.
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Lightheadedness.
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Pneumothorax.
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Chest pain.
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Coughing.
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Bronchospasm.
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Contraction of infection.
Conclusion
Spirometry is used to detect early signs of diseases and also provides physiological confirmation for diagnosis. It can be used to assess the disease progression and response to therapy. It is also used to screen individuals at high risk of having pulmonary diseases. Therefore, it is not only used as a diagnostic tool but it can also be used as a screening test. With the introduction of portable spirometers, they can be performed anywhere and by anyone with proper training.