Definition - What does Transfer Factor mean?
Transfer factor is a test of the diffusing capacity of the lungs for gases like oxygen, carbon dioxide, and carbon monoxide.
The process involves six stages: ventilation of airways, diffusion of gases in alveolar ducts, transfer of gases across alveolar membrane, diffusion in the lung parenchyma, chemical reaction with blood components, and circulation of blood between vascular beds.
Safeopedia explains Transfer Factor
The test measures the ability of the lungs to transfer gases from inhaled air to red blood cells. The functional dimensions for the test are determined after considering the volume of the lungs, the thickness of alveolar capillary membrane, and the volume of blood in capillaries.
The transfer factor test is mainly performed on people suspected of having any chronic lung disease or infection. The factors that contribute to a decrease in reduced transfer factor include reduced volume of alveoli, reduced pulmonary blood flow, anemia, cardiac insufficiency, pulmonary hypertension, pneumonia, lung resection, muscle illnesses, pulmonary edema, emphysema, disease affecting lung tissue and airway geometry, pulmonary embolism, sarcoidosis, and smoking.
The factors that contribute to transfer factor include increased pulmonary blood flow, disease associated with left-right shunt, polyglobulia, asthma bronchiale, and hemoptysis.
The test is now measured using carbon monoxide (CO) under single-breath methods, which helps in determining the partial pressure of driving CO from the inhaled air into the blood and the rate of absorption of CO.
The method requires a person to breathe a gas mixture consisting of around 0.2% CO. Since the partial pressure of CO in the alveoli fluctuates throughout the respiratory cycle, it cannot be measured directly. It is calculated by partitioning the concentration in the expired gas into alveolar and dead-space compartments.