The diffusion function is a measure of the ventilation function. It is used to evaluate the efficiency of gas exchange of alveolar capillary membranes. For early detection of lung and airway lesions, assess the severity and prognosis of the disease, assess the efficacy of drugs or other treatments, identify the cause of dyspnea, diagnose lesions, assess lung function tolerance to surgery, or labor intensity Tolerance and monitoring of critically ill patients have important guiding significance. Dissemination of the lungs refers to the process of gas exchange between oxygen and carbon dioxide in the lungs through the alveolar and pulmonary capillary walls. Dispersion pathways include alveolar air, alveolar capillary walls, intrapulmonary capillary plasma, red blood cells, and hemoglobin. The gas is exchanged along this path depending on which end is highly concentrated, so the process can be bidirectional. The rate of diffusion of oxygen is much slower than that of carbon dioxide because oxygen is not easily dissolved in body fluids. Therefore, when the patient's diffuse function is abnormal, the exchange of oxygen is more susceptible than carbon dioxide. In the clinical, the disorder of lung diffuse function can significantly affect the arterial blood oxygen level.

Basic Information

Specialist classification: Respiratory examination classification: pulmonary function test

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

Tips: Non-invasive examination, there is no suitable for the crowd. Normal value

Male is (28.84 ± 4.84) ​​ml / (mmHg · min).

Female is (22.13±3.09) ml/(mmHg·min).

(Note 1mmHg ≈ 0.33kPa).

Clinical significance

Need to check the crowd:

Pulmonary interstitial disease, chronic obstructive pulmonary disease, alveolar lesions such as pulmonary infection, pulmonary edema, alveolar hemorrhage, alveolar proteinosis, thoracic and pleural lesions, cardiovascular disease, anemia or polycythemia patients, repeated upper respiratory tract Infected patients, who have a history of smoking and long-term cough, patients with seasonal cough and asthma attacks.

Abnormal results:

(1) Diffusion function reduction can be seen in.

1 diffuse area reduction such as emphysema, lobectomy, pulmonary infection, pulmonary edema, pulmonary hemorrhage, pneumothorax, scoliosis and so on.

2 alveolar capillary membrane thickening such as pulmonary interstitial fibrosis, sarcoidosis, asbestosis, scleroderma and so on.

3 hemoglobin oxygen-carrying capacity decreased, such as anemia, carboxyhemoglobin.

(2) Increased diffuse function can be seen in polycythemia, intra-cardiac left to right shunt caused by increased pulmonary pressure.

Low results may be diseases: pneumothorax, pulmonary edema, sarcoidosis, asbestosis, scoliosis considerations

Taboo before inspection:


Requirements for inspection:

Keep your mouth breathing because your nose is caught.

Keep your mouth as tight as possible to ensure no air leaks during the test.

As much as possible with the operator's password, instant exhalation and inhalation.

Inhale as much as you can, then call out with maximum strength and speed.

Not suitable for people:

For non-invasive examinations, there is no suitable population.

Inspection process

Hold the nose with a clip, the patient has a tight mouth, with the operator's password, exhale, inhale.

Not suitable for the crowd

No taboos.

Adverse reactions and risks

No complications or harm.