Tidal Volume (VT): The amount of air inhaled or exhaled each time when breathing calmly. The normal reference value is 500? Milliliter.
Supplementary inspiratory volume (IRV): the maximum amount of air that can be inhaled after calm inhalation, reflecting the elasticity of the chest and lungs and the strength of the inspiratory muscles. The normal reference value for men is about 2. 16? L, female about 1.5? l .
Deep inspiratory volume (IC): the maximum air volume that can be inhaled when trying to inhale at the end of a calm breath, which consists of tidal volume and supplementary inspiratory volume, that is, IC=? VT+？ The normal reference value of IRV. Male is about 2.6. L, female about 1.9? L. When there are some factors, such as respiratory muscle insufficiency, decreased chest or lung activity, airway obstruction, etc., ic can be reduced.
Vital capacity (VC): the maximum amount of air exhaled at the end of deep breathing. The normal reference value for men is about 3.47. L, female about 2.44? L all kinds of lung parenchymal lesions, emphysema, pleural lesions, thoracic malformation, respiratory muscle weakness or paralysis can all lead to the decrease of VC. It should be noted that vital capacity is affected by age, sex, body length and body surface area. , and should be judged as a percentage of the expected value. The normal population is (10020)%, and < 80% is decreasing.
Total lung volume (TLC): The total amount of gas contained in the lungs after deep inhalation is equal to vital capacity plus residual volume. The normal range is (5.09 0.87) liters for males and (4.00 0.83) liters for females. The increase of TLC in patients with emphysema and various restrictive ventilation disorders can significantly reduce the total lung volume. It should be noted that normal lung capacity does not necessarily mean normal lung function, because the increase and decrease of vital capacity and residual volume can make up for each other.
Pulmonary ventilation refers to the amount and flow of air in and out of the lungs per unit time, which shows the relationship between time and volume and is related to breathing amplitude, breathing frequency and exertion. It is a dynamic index to reflect the pulmonary ventilation function.
Forced vital capacity (FVC): refers to the maximum forced and fastest expiratory volume from the maximum inspiratory volume to TLC, which is consistent with VC under normal circumstances and can reflect the expiratory resistance of the larger airway. FVC can be used as an auxiliary diagnostic means for chronic bronchitis, COPD, asthma and emphysema, and can also be used to evaluate the efficacy of bronchodilators.
One-second forced expiratory volume (FEV 1): refers to the expiratory volume within 1 second after the maximum inspiratory volume reaches the TLC position. It is not only a volume measurement, but also an average flow velocity measurement within one second, which is the main index of lung function impairment. The normal range is (3.18 0.12) for males and (2.3 1.05) for females. In normal subjects, FEV 1 = FVC. When there is airway obstruction, fev 1 < FVC, when there is obstructive ventilation disorder, fev 1 decreases and the expiratory time is prolonged.
FEV 1/FVC: refers to the ratio of FEV 1 to FVC, which is a commonly used index to judge airway obstruction and can reflect the type and degree of ventilation disorder. FEV 1/FVC is a sensitive index of COPD, which can detect mild airflow restriction. The percentage of FEV 1 in the predicted value is a good indicator of moderate and severe airflow restriction, and it is the basic item of pulmonary function examination of COPD. After inhaling bronchodilator, the predicted FEV 1 < 80% and FEV 1/FVC < 70% can be determined as completely irreversible airflow restriction.