Pulmonary function tests in children are one of the necessary tests for respiratory diseases. Children's lung function plays an important role in the diagnosis, differential diagnosis, severity evaluation, efficacy judgment and prognosis of asthma. At present, the pulmonary function test of children has the function of tidal breathing and lung function in infants and young children. The expiratory flow-volume curve is measured in school age and children. Main indicators useful peak expiratory flow rate (PEF), forced expiratory volume in 1 second (FEV1), peak time ratio (TPTEF/TE), peak volume ratio (VPEF/VE), flow rate-volume ring shape, etc. It can reflect airway obstruction in children with asthma.

Basic Information

Specialist classification: Respiratory examination classification: pulmonary function test

Applicable gender: whether men and women apply fasting: not fasting

Reminder: Children may be afraid of the test, and should be given comfort and guidance before and during the examination. Normal value

1. Bronchial challenge test without airway hyperresponsiveness. The airway is unobstructed and the gas is very easy to get in and out.

2. The bronchodilation test calculates that the improvement rate of FEV1 after drug administration is less than 12%, which is negative for the diastolic test.

Clinical significance

Abnormal results:

1. The bronchial provocation test has an increased airway responsiveness, and the diagnosis may be atypical asthma.

2. The bronchodilation test was stopped within 12 hours before the test, the long-acting β2 agonist was stopped, the long-acting β2 agonist was stopped within 48 hours, the theophylline sustained-release tablet should be stopped for 24 hours, and the atropine should be stopped for 8 hours. First, the subject's basic FEV1 was measured, and then the β2 agonist was inhaled. The FEV1 was measured repeatedly 15-20 minutes after inhalation, and the FEV1 improvement rate after drug administration was calculated. More than 12% of the positive diastolic test can help diagnose asthma. It is suggested that airway spasm and mild asthma attack are present.

Need to check the crowd:

Children with problems with lung function and respiratory problems. Cough for up to 1 month, antibiotic treatment is ineffective; or repeated wheezing more than 4 times in 1 year, after a period of acute asthma attack treatment, there is no child with cough symptoms.

Precautions

Precautions:

Not suitable for people: patients with cardiopulmonary dysfunction, hypertension, coronary heart disease, hyperthyroidism, pregnancy and other diseases.

Contraindications before the test: no history of respiratory infections in the month before the test; asthma patients were relieved of symptoms.

Requirements for inspection: Children may be afraid of inspections, and should be given comfort and guidance before and during the examination.

Inspection process

Children's respiratory diseases, like adults, are also reflected in lung function. The application of pulmonary function tests is the same as that of adults, but the lung function of children has its characteristics. Care should be taken when testing lung function.

1. Force-dependent lung function test

(1) The Force-Dependent Pulmonary Function Test (MEFV) is limited by the age of the child. The test requires active coordination of the subject, and the application of these lung function tests is limited due to poor fit, such as inability to breathe quickly, with poor repetitiveness.

(2) For the test of children's lung function, it may be necessary to perform multiple tests as long as the expiratory flow rate curve is straight (flow rate change <0.251/s).

(3) Children's lung function differs from that of adults in some aspects due to their growth and development. With the increase of age, height and weight, children's lung function indexes (such as FVC, FEV1, PEF, etc.) are also increasing. The evaluation of children's lung function can not refer to the adult lung function value and calculate according to the adult's prediction equation. Only the normal values ​​of lung function in the child group can be referred to.

2, does not cooperate with children

For some children who are unable to cooperate with the lung function test, or some need to continuously monitor the rate of change in lung function, the highest expiratory flow meter (peak speed meter) can be used to determine the peak expiratory flow rate.

3, infants (<3 years old) children

Because they can't actively cooperate, the current routine force-dependent lung function tests cannot be applied. Non-stress-dependent lung function such as tidal volume, minute ventilation, functional residual capacity, repetitive breathing lung diffusion, respiratory mechanics such as airway resistance, chest lung compliance, etc. can be applied to these children.

(1) Determination of tidal breathing flow capacity loop (TBFV). This technique does not require subjective force coordination. After connecting the mouthpiece, it only needs to breathe moisture. The lung function meter can continuously record the flow rate capacity loop.

(2) Measurement of airway resistance by pulse oscillation spectrum analysis. Through the pulse oscillation technology of the external signal source, the child only needs to take the mouthpiece for tidal breathing for several cycles, and can make multiple parameters such as airway viscous resistance, elastic resistance and inertial resistance, and chest and lung bronchial compliance. Evaluation.

4, blood gas analysis

Blood gas analysis is an important part of lung function and the most important lung function test item for infants and young children. Judging the gas exchange capacity of the child.

5, airway reactivity determination

For older children, multiple reference methods for adult airway responsiveness are performed. Zheng Jinping reported the airway responsiveness test (inhalation histamine bronchial provocation test) in older children (11-14 years old). The measurement method and judgment criteria were the same as those of adults, and the results were similar to those of adults. Exercise stimulation tests are also used in the clinic.

6, airway diastolic test

For infants and young children, the beta receptor development in the airway may be immature and may be less responsive to beta receptor agonists. While M receptors are relatively mature and may respond well to M receptor antagonists, it may be better to use M receptor antagonists (such as ipratropium bromide) in infant airway relaxation tests.

Not suitable for the crowd

Unsuitable for people: patients with heart and lung dysfunction, hypertension, coronary heart disease, hyperthyroidism and other diseases.

Adverse reactions and risks

Generally no complications and harm.