Lung compliance refers to changes in lung volume caused by changes in unit pressure, which represent the effect of changes in chest pressure on lung volume. It includes both static compliance and dynamic compliance. The former reflects the elasticity of lung tissue, which is affected by both lung tissue elasticity and airway resistance. The scope of lung compliance test is: 1 various types of lung disease such as pulmonary fibrosis and pleural fibrosis. 2 pulmonary edema, pulmonary congestion. 3 acute respiratory distress syndrome. 4 emphysema. 5 small airway function measurement. 6 mechanical ventilation and respiratory monitoring.

Basic Information

Specialist classification: Respiratory examination classification: pulmonary function test

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

Tips: Tell the doctor about the history of medication before the examination, the history of illness. Normal value

Normal value:

Male Clst (170 ± 60) ml / cm H2O, Cldyn20 (230 ± 60) ml / cm H2O (1 cm H20 ≈ 0.098 kPa).

Female Clst (110 ± 30) ml / cm H2O, Cldyn20 (150 ± 40) ml / cm H2O.

Clinical significance

Abnormal results:

(1) Reduced lung compliance is seen in:

1 restrictive lung disease, including various types of pulmonary fibrosis, pleural fibrosis and the like.

2 alveolar filling diseases, such as pulmonary edema, pulmonary congestion, alveolar hemorrhage, alveolar proteinosis.

3 acute respiratory distress syndrome.

(2) In emphysema, the static compliance is increased due to the destruction of the alveolar wall and the reduction of elastic tissue. Alveolar adhesion reduces the traction of the bronchial ring, and the lungs are inflated, so the dynamic compliance is reduced.

(3) The rate of alveolar inflation and emptying depends on the product of lung compliance and airway resistance, the time constant. In small airway disease, when the respiratory rate increases, lung compliance decreases, and the frequency dependence of dynamic compliance (FDC) is a sensitive indicator for measuring small airway function.

(4) When mechanical ventilation is performed, the optimal PEEP level is determined, that is, the PEEP pressure at which maximum lung compliance can be produced, and the oxygen transport and the smallest dead space of the maximum health search can be generated at this time.

Need to check the crowd:

Some diseases such as pulmonary fibrosis and emphysema are diagnosed or estimated for their severity.

Frequency-dependent dynamic compliance is sensitive to small airway function measurements.

Used for mechanical ventilation and respiratory failure monitoring to help determine the best PEEP levels.

Low results may be diseases: acute respiratory distress syndrome, emphysema, pulmonary fibrosis precautions

Requirements for inspection:

(1) The lung compliance values ​​were not completely consistent for different lung volumes. High lung volume is highly compliant, and low lung volume is less compliant, so compliance/FRC is required to truly represent the elasticity of the lung tissue.

(2) Under the same conditions of transpulmonary pressure, the change of expiratory lung volume is larger than that of inspiratory phase, which is called “hysteresis”, so the lung pressure-volume curve measured during inspiratory phase and expiratory phase ( PV curves) are not consistent.

(3) Alveolar surface tension is the main influencing factor of lung compliance in low lung volume.

(4) The elastic fibers of the lung tissue have a certain influence on lung compliance.

Preparation before inspection:

Inform the doctor about the history of the medication and the history of the illness.

Inspection process

After the anesthesia, the instrument catheter test is inserted, and the data is analyzed after the data is obtained.

Not suitable for the crowd

No taboos.

Adverse reactions and risks

Generally no complications and harm.