Decreased gas diffusion

Introduction The diffusion function is a measure of the ventilation function. It is used to evaluate the efficiency of gas exchange of alveolar capillary membranes. The process of gas exchange between alveoli and blood through the alveolar-capillary membrane (hereinafter referred to as alveolar membrane) is a physical diffusion process. The amount of gas per unit time depends on the difference in partial pressure of the gas on both sides of the alveolar membrane, the area and thickness of the alveoli, and the diffusion constant of the gas. The diffusion constant is in turn related to the molecular weight and solubility of the gas. In addition, the total amount of gas diffusion is also determined by the time the blood is in contact with the alveoli. The amount of dispersion depends on the partial pressure difference of the gas on the membrane, the area of dispersion, the distance, the time, the molecular weight of the gas and its solubility in the dispersion medium. Emphysema and other lung tissue lesions, diffuse pulmonary interstitial fibrosis and other diseases can cause a decrease in diffuse function. Clinically, when the pulmonary lesions produce diffuse dysfunction, there is often a significant ventilatory/blood flow imbalance, which results in hypoxia. A diagnosis can be made by a clinical examination of vital capacity. Males were (28.84±4.84) ml/(mmHg/min) and females were (22.13±3.09) ml/(mmHg/min). Below this value, the gas diffusion function decreases.

Cause

Diffusion function reduction can be seen in:

1, reduced diffuse area: 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.

4, the blood and alveolar contact time is too short: normal resting, the blood flow through the alveolar capillaries is about 0.75 sec, because the alveolar membrane is very thin, and the contact surface with the blood is wide, so only 0.25 sec hemoglobin can be Completely oxygenated. When the blood flows through the alveolar capillaries for too short a time, the amount of gas diffusion will decrease. In patients with reduced alveolar membrane area and increased thickness, although the oxygen partial pressure in the blood of the pulmonary capillaries rises slowly, the gas exchange in the lungs can still reach equilibrium at rest, so that hypoxemia is not caused, often only in When the physical load is increased, the blood flow will be accelerated, the blood and alveolar contact time will be shortened, and a significant diffusion disorder will occur, thereby causing hypoxemia. It is currently believed that respiratory failure occurs in alveolar lesions, mainly due to the imbalance of blood flow in alveolar ventilation.

an examination

Related inspection

Blood routine chest CT examination

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.

Pulmonary diffusion function measurement (DL) 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 of lung diffusion function measurement (DL):

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.

Differential diagnosis

Physiological factors have a certain influence on the diffusion function due to gender, age, body position and exercise.

Dispersion barriers are found in:

1 Reduced diffuse membrane area, such as obstructive emphysema.

2 pulmonary interstitial edema, alveolar wall thickening, alveolar capillary fibrosis, such as diffuse pulmonary interstitial fibrosis, pneumoconiosis, sarcoidosis and diffuse bronchiole-alveolar cancer. A diagnosis can be made by a clinical examination of vital capacity.

Males were (28.84±4.84) ml/(mmHg?min) and females were (22.13±3.09) ml/(mmHg?min). Below this value, the gas diffusion function decreases.

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