Spirometry is an examination that measures the function of our lungs, particularly the patency of the respiratory tract.

Everyone should have this examination done at least once in their life.

Not only is it performed to diagnose, monitor and determine the progression of bronchial asthma, but it also examines the bronchial airflow (the flow rate) as well as the volumes and capacities of the lung's air spaces. The examination is performed by means of a device known as spirometer.

During the examination, the patient stands or sits in an upright position, holding a mouthpiece tightly in the mouth. A nose clip is applied to prevent nose breathing.

The examination is not particularly bothersome for the patient, who breathes in and out through the mouthpiece and performs the instructions of the attending physician. The mouthpiece held in the patient’s mouth is connected to the spirometer by means of a tube (a flexible plastic pipe like the one used in vacuum cleaners but with a smaller diameter). There are different procedures for the examination. However, it mostly measures the vital capacity and its components, and registers the forced expiration. Spirometry helps to determine a number of parameters, the most important being: FEV1, FVC, PEF and the FEV1/FVC ratio (known as the Tiffeneau index). The normal values of these indices are specified on the basis of population tests and depend on: sex, age, height and race.

Forced expiratory volume in 1 second (FEV1):

The parameter refers to the amount of air exhaled from the lungs within the first second of forced exhalation. It shows the degree of airway obstruction, or the narrowing of bronchial passages. Obstruction occurs in bronchial asthma and COPD, and may be caused by bronchospasm, swelling of the bronchial mucosa or bronchial lining by mucosal secretion. Pulmonary obstruction can be mild (>70% of the predicted value), moderate (60-69%), moderate-severe (50-59%), severe (35-49%) and very severe (<35%)

Forced vital capacity (FVC):

It refers to the total amount of air exhaled from the lungs after a maximum inhalation. It shows the magnitude of restrictions, or conditions that limit expansion and contraction of the lungs in the course of various diseases and pathologies restraining chest mobility. Tiffaneau index: The index is calculated from multiplication of the absolute values of FEV1 and FVC (FEV1/FVC). Values below < 0.7 indicate obstruction of the bronchial tree.

Peak expiratory flow (PEF):

This parameter can be measured by means of a special simple device known as a peak flow meter. Similarly to the FEV1 index, it determines the degree of bronchial obstruction. Because the procedure can be performed using a cheap and simple apparatus, it can be carried out by the patient at home (which is recommended). The measurement is easy to carry out: After resetting the scale on the device, the patient makes a maximum exhalation which is followed by a maximum inhalation. Next, without holding breath, the patient exhales through the mouthpiece of the device. The indicator of the apparatus shows the flow value. The use of a peak flow meter is a good method of monitoring the course of bronchial asthma in a domestic environment by the patient (for more information see the ‘patient guide’ tab).

Bronchial obstruction reversibility test:

This test is performed in order to assess the reversibility degree of the patient’s bronchial obstruction. It is prescribed for patients with the FEV1 index below normal range. It involves administration of a specific dose of a bronchodilating agent to the patient and repetition of the spirometry examination after 15 minutes. Next, assessment is done on the extent to which the FEV1 indicator has improved (increased in value).


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