I. Clinical significance of pulmonary function measurement
1. To make an objective clinical evaluation of the degree and type of pulmonary function impairment and treatment effect of patients with respiratory system diseases, as well as the development of the disease.
2. To evaluate the feasibility of surgical procedures, especially thoracic and abdominal procedures, and the occurrence of postoperative complications in elderly patients.
3. Differential diagnosis of the causes of clinical symptoms, mainly dyspnea, and assessment of pulmonary function in patients with occupational diseases.
4. Sports medicine guidance: it can guide sports rehabilitation, and also the selection of our national outstanding athletes, it is also a good indicator.
Second, the indications for doing pulmonary function tests
1, chest tightness dyspnea, continuous cough, severe rhinitis;
2, suspected of bronchial, lung, heart, chest or spine diseases;
3. Diminished motor ability, difficulty in breathing at rest.
III. Pulmonary function test for younger children – tidal respiration
(i) Principle: Tidal breathing test is mainly a method to analyze the volume and expiratory flow rate during calm breathing, and the data measured by flow rate sensor.
(ii) Main parameters.
1, tidal respiratory flow rate volume ring (TBFV ring) morphology;
2, %V-PF: the exhalation volume/tidal volume when reaching the peak tidal expiratory flow rate;
3. 25/PF: expiratory flow rate at 75% of tidal volume exhaled/peak tidal expiratory flow rate;
4. ME/MI: mid-tidal expiratory flow rate/mid-tidal inspiratory flow rate;
5. PF/Ve: peak tidal expiratory flow rate/tidal volume;
6. Ventilation function in tidal breathing state: including respiratory rate (RR), tidal volume per kilogram of body weight (Vi/kg), generally 6-10 ml/kg in pediatric patients, and peak tidal expiratory flow rate (PTEF). Among them, %V- PF, 25/PF, PTEF can be used as sensitive indicators to reflect small airway function, ME/MI is an indicator of large airway function, RR and Vi/kg are simple and reliable clinical indicators to reflect ventilatory function.
(iii) Test method
Calm breathing is required, without special breathing movements, especially suitable for infants and young children. After the infant is sedated and hypnotized with chloral hydrate, the infant is placed in the supine position, the child’s mouth and nose are held tightly with the mask, the head is tilted back slightly, the flow rate sensor is checked, the computer calculates the measured value, and the best (the smoothest respiratory curve) test results are selected four times, the difference between each time is less than 5%-10%, and the average value is taken by the computer for the final calculation. For those who need to do bronchodilatation test, the compressed nebulizer inhaler produced by PARI GmbH, Germany, was used to nebulize the rapid-acting β2 agonist for about 10 min, and the tidal flow rate volume ring was checked by each line 5 minutes before and after the inhalation, respectively.
(iv) Results
(1) The horizontal coordinate of the TBFV ring is the volume axis and the vertical coordinate is the flow velocity axis, the lower half of the ring represents the inspiratory phase and the upper half of the ring represents the expiratory phase, reflecting the respiratory kinetic information. The TBFV ring in healthy infants and children is approximately elliptical in shape. The morphological changes of TFv ring in obstructive ventilatory dysfunction: the inspiratory ring is full, the ascending branch of the expiratory phase is steep, the peak of the curve is obviously shifted forward, the descending branch of expiration is inclined, the maximum expiratory flow rate is decreased, the expiratory time is prolonged, and the figure forms a stumpy shape.