Lung ventilation

Lung ventilation is a dynamic indicator of the process by which air enters the alveoli and exhausts from the alveoli, containing the concept of time. Commonly used indicators include resting ventilation, alveolar ventilation, maximum ventilation, time vital capacity, and some flow rate indicators. 1 As a reference for the diagnosis of certain diseases or to estimate its severity. 2 to determine the type and extent of ventilatory dysfunction, to help diagnose clinical disease. 3 Conduct labor ability identification. 4 disease treatment efficacy evaluation.

Basic Information

Specialist classification: Respiratory examination classification: pulmonary function test

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

Tips: Severe cardiopulmonary disease, physical weakness, mental disorders or poor coordination is not suitable for this examination. Normal value

(1) Resting minute ventilation (MV) refers to the amount of gas exhaled per minute in the case of basal metabolism, which is obtained by tidal volume multiplied by the number of breaths per minute. The normal value of adults is 3 to 10L. For example, the number of breaths per minute is about 15 times, the tidal volume is 500 ml, and the resting ventilation is 7.5 L/min.

(2) Alveolar ventilation (VA) refers to the effective ventilation of air bubbles that can reach the alveoli in the amount of inhaled air per minute under basal metabolism. The normal value of adults is about 3 to 7L. The number of breaths per minute is about 15 times, and the amount of tidal volume minus the dead space is about 350 ml. The multiplication of the alveolar ventilation is about 5.5 L/min.

(3) Maximum ventilation (maximalvoluntary ventilation) (MVV) refers to the amount of air measured at the fastest speed and maximum amplitude per unit time. The normal value is about 104L for men and about 82L for women.

(4) Forced vital capacity (FVC) refers to the amount of gas obtained by exhaling with the greatest effort and the fastest speed after inhaling to the total amount of lungs. The expiratory volume in the first second of a normal person (the ratio of the fertility of the FEV1 occupancy is greater than 80%.

(5) The maximum flow rate of the maximal mid-expiratory flow curve (MMEF) calculated from the forced vital capacity curve is 25% to 75% (ie, half of the middle) of the forced expiratory lung capacity.

Clinical significance

Abnormal results:

(1) Reduction of alveolar ventilation is seen in chronic obstructive pulmonary disease, pneumonia, atelectasis, anesthesia, myasthenia gravis and other hypoventilation diseases, blood gas analysis shows type II respiratory failure and respiratory acidosis; alveolar ventilation increases, seen in ketone Alveolar hyperventilation, such as acidosis, rickets, hyperventilation syndrome, and blood gas analysis showed respiratory alkalosis.

(2) The maximum ventilation can reflect the severity of airway obstruction, and can also understand the patient's respiratory reserve, muscle strength and power level, which can be used as preoperative evaluation. Its reduction is seen in

1 increased airway resistance such as various chronic obstructive pulmonary disease, bronchial asthma or bronchial tumors.

2 lung tissue damage such as pneumonia, tuberculosis, alveolar hemorrhage, pulmonary edema, pulmonary interstitial fibrosis.

3 thoracic and pleural lesions such as severe posterior scoliosis, rib fractures, pneumothorax, and massive pleural effusion.

4 nervous system and respiratory muscle activity disorders such as anesthesia, encephalitis, poliomyelitis and myasthenia gravis.

(3) forced vital capacity, maximum expiratory mid-flow or FEV1/FVC reduction, indicating obstructive ventilatory dysfunction, the reduction is seen in

1 tracheal and bronchial diseases, such as A. tracheal tumors, stenosis; B. bronchial asthma; C. chronic obstructive bronchitis; D. occlusive bronchioles.

2 emphysema, pulmonary bullae.

3 Other diseases with unknown causes, such as ciliary dyskinesia.

(4) Can be used for the judgment of the type of ventilation dysfunction. Obstructive ventilatory dysfunction showed normal or decreased lung capacity, decreased FEV1/FVC, increased residual volume, normal or increased lung volume, and markedly increased residual-to-resume ratio; restricted ventilatory dysfunction showed decreased vital capacity and normal or increased FEV1/FVC . The amount of residual gas is reduced, the total amount of lungs is reduced, and the residual amount is higher than normal or slightly elevated.

Need to check the crowd:

Patients with respiratory disorders, patients with dyspnea, and those with asthma symptoms.

Low results may be diseases: obstructive emphysema, pediatric atelectasis, food allergic asthma, emphysema in the elderly, bronchial asthma in children, bronchial asthma, cotton pneumoconiosis

Preparation before inspection:

(1) Before the examination, the subjects should be explained in detail about the inspection methods and essentials, and adaptive training should be done.

(2) Quiet rest before the measurement of resting ventilation, should be carried out completely under the basal metabolic state, the surrounding environment is quiet, and the breathing is required to be stable.

Requirements for inspection:

(1) Since the dead volume can not be directly measured, the dead air volume can be calculated by measuring the minute resting ventilation and the exhaled CO 2 partial pressure, thereby obtaining alveolar ventilation. Clinically, PaCO2 is often used to reflect the adequacy of alveolar ventilation.

(2) Due to the difference in measurement methods and instruments, and the degree of cooperation of the subjects, the maximum range of maximum ventilation is large. The normal range is generally taken as a percentage of the predicted value of ±20%.

(3) The forced vital capacity and the maximum expiratory mid-flow were all affected by the degree of forced exhalation during the examination. The former had a greater impact.

(4) The sex, age, height and muscle strength of the subject may affect the results of the above examination.

Not suitable for people:

1, severe heart and lung disease, physical weakness.

2, mental abnormalities or can not be well coordinated.

Inspection process

Open inspection is suitable for large-scale screening screening at the grassroots level. The subject takes the standing position and is connected with the swelling meter. After 4 to 5 times of calm breathing, the breathing is repeated for 12 seconds or 15 seconds with the fastest breathing speed and the maximum breathing amplitude, and the number of breathing requests is 10-15 times. Repeat after 10 minutes of rest. In order to make the measurement successful, it is necessary to fully explain to the subject beforehand, and timely instructions and continuous guidance and encouragement are given to the subject to obtain the best result.

Not suitable for the crowd

Taboo people:

1, severe heart and lung disease, physical weakness.

2, mental abnormalities or can not be well coordinated.

Adverse reactions and risks

No complications or harm.