Spirometry of the lungs: what is this procedure, how is it conducted

Evaluation of the function of external respiration is an integral component of a comprehensive clinical examination of a patient with pulmonary diseases. When collecting anamnesis and physical examination, signs of violations of respiratory function of the lungs are revealed, and then purposefully assess the severity of these changes through standardized methods.

Spirometry is a method of measuring lung volume when performing various respiratory maneuvers (quiet breathing, maximum inhalation and exhalation, forced exhalation, maximum ventilation). At present, volume measurements are carried out on the basis of measurement of airflows - pneumotachometry (pneumotachography) followed by automatic data processing. The most common are the recording of a calm deep inspiration and expiration and an evaluation of the parameters of forced expiration.

Other method names: recording the flow-volume curve of forced expiration, Votchal-Tiffno test, forced exhalation spirography, pneumotachography with integration.

At present, the use of such devices is unacceptable. Pneumatic tachometers measure airflow by measuring differential pressure using differential pressure gauges (Fleisch, Lily or Pitot tubes) or by using "turbines" - inertial-free propellers with light blades, while the patient breathes ambient air. Lips and oral cavity of the patient contact only with a disposable mouthpiece.

Objectives

• Diagnosis of violations of the ventilation function of the lungs.
• Identification of type (obstruction, restriction) and severity of disorders.
• Evaluation of the course of pulmonary disease and the effectiveness of the therapy (etiotropic, pathogenetic, in particular, bronchodilator).
• Evaluation of the reversibility of obstruction after inhalation of short-acting bronchodilators and evaluation of the response to provocative samples (methacholine, allergens).
• Determination of the possibility of surgical treatment and postoperative assessment.
• Objectification of the state (for medico-social expertise).
• Predicting the course of the disease.

Indications for the procedure

• Presence of complaints from the respiratory organs.
• Changes in the respiratory organs on the radiograph (or with other methods of diagnosis).
• Disorders of gas exchange (hypoxemia, hypercapnia, decreased saturation) and changes in laboratory parameters (polycythemia).
• Preparation for invasive methods of investigation or treatment ( bronchoscopy, surgery).
• Referral to medical and social expertise.

[1], [2], [3], [4]

Preparation

The study is performed on an empty stomach or after a light breakfast. The patient should not take medications that affect the state of the respiratory system (short-acting inhaled bronchodilators, cromoglycic acid for 8 hours, aminophylline, short-acting oral β ₂ -adrenomimetics for 12 hours, tiotropium bromide, inhaled and oral β ₂ -adrenomimetics of long-acting , blockers of leukotriene receptors for 24 hours, nedocromilated and prolonged forms of theophylline for 48 hours, second-generation antihistamines for 72 hours), tea, coffee containing caffeine bev- erages. Before the research, tie, belts and corsets should be relaxed, lipstick removed from the lips, dentures should not be removed. An hour before the procedure is forbidden to smoke. If the study is conducted in the cold season, the patient should be warmed for 20-30 minutes.

[5], [6], [7], [8]

Technique of the spirometry

The spirometer is calibrated daily with a syringe attached to it with a volume of 1-3 liters (the "gold" standard is a three-liter syringe with an error of volume of no more than 0.5%). Before the study, the patient is explained the stages of the procedure, demonstrating maneuvers using a mouthpiece. During the procedure, the operator comments on the maneuver and directs the patient's actions.

First, determine the vital capacity of the lungs by inhalation (ZHEL _piles ) or on exhalation (LIVES _vyd ). The nasal passages are blocked with a nasal clip, the patient inserts the mouthpiece of the device (mouthpiece) into the oral cavity and tightly grips the outside with teeth. This ensures the opening of the mouth during the maneuvers. The patient's lips should tightly surround the tube from the outside, avoiding air leakage (this can be difficult in elderly people and in persons with facial nerve damage). The patient is asked to breathe freely with his mouth for adaptation (at this time the spirometer calculates the respiratory volume, respiratory rate and minute volume of breathing, which are practically not used at present). Then the patient is asked to take a deep deep breath and calmly breathe deeply for at least three consecutive times. The patient should not take sudden breaths or exhalations. The maximum amplitude of breathing from total exhalation to full inspiration - WAS _halved, and from full inspiration to a full exhalation - ZHEL _vyd  . During this procedure, a spyogram is monitored on the screen or display (recording changes in volume versus time).

To record the forced expiration, the spirometer is transferred to the appropriate mode and a flow-volume test is carried out (recording the volumetric velocity relative to the expiratory volume). The patient makes a calm deep breath, holds his breath on inhalation and then exhales with the maximum effort and complete expulsion of air from the chest. The beginning of the exhalation should be a push character.

Practically, only a correctly recorded curve having a distinct vertex at the site not later than 25% of the beginning of recording of the forced vital capacity of the lungs (FVC) has practical value: the peak of the volumetric expiratory flow should be no later than 0.2 s from the beginning of the forced exhalation. The duration of the forced exhalation should be at least 6 seconds, the end of the curve should look like a "plateau", during the recording of which the air flow is minimal, but the patient continues exhaling with effort.

Perform at least three attempts to record forced expiration. Two attempts with the best results should not differ in the values of FVC and the volume of forced expiration in the first second (FEV ₁ ) by more than 150 ml.

Contraindications to the procedure

• Hemoplegia or pulmonary hemorrhage.
• Insufficiency of the venous valves of the lower extremities with varicose veins, trophic disorders and a tendency to high blood coagulability.
• Uncontrolled arterial hypertension (systolic blood pressure> 200 mmHg or diastolic blood pressure> 100 mmHg).
• Aneurysm of the aorta.
• Postponed during the last 3 months myocardial infarction (or stroke).
• Postoperative period (month after operations on the thoracic and abdominal cavity).
• Pneumothorax.

[9], [10], [11]

Normal performance

WISHED (FVC). FEV _1,  peak volumetric expiratory flow rate (PIC) and instantaneous volumetric rates of forced expiration at 25%, 50% and 75% of the beginning of the FVC curve (MOS25, MOC50, MOS75) are expressed in absolute values (liters and liters per second) and in percent of the required values. The device calculates the norms automatically according to the regression equations based on the sex, age and growth of the patient. For the LIFE (FVC). FEV ₁, PIC minimum normal value is 80% due, and for MOS25, MOS50, MOS75 - 60% due. СОС25-75 is the average volumetric flow rate of the forced expiratory flow in the middle half of the FVC (ie between 25% and 75% FVC). SOS25-75 reflects the state of the small airways and is more significant than FEV ₁  in detecting early airway obstruction. COC25-75 is a force-independent measure.

Isolated reduction of the ZHEL indicates a predominance of restrictive disorders, and a decrease in FEV ₁  and the ratio of FEV ₁ / FVC (or FEV ₁ / ZHEL) - about the presence of bronchial obstruction or obstruction.

By the ratio of the main indicators formulate a conclusion.

[12], [13], [14], [15], [16]

Complications after the procedure

Complications when writing spirograms of forced expiration are rare.

[17], [18], [19], [20], [21]

Factors affecting the outcome

The main factors are the cooperation of the medical worker and the patient during maneuvers, the accuracy of calibration, the recording of reproducible and correct curves.

[22], [23], [24], [25]