Lung diffusion capacity refers to the efficiency with which gases, specifically oxygen and carbon dioxide, move between the air in your lungs and your bloodstream. When this capacity is decreased, it means that the transfer of oxygen into your blood, and carbon dioxide out of it, is not happening as effectively as it should. This can impact your body’s ability to get enough oxygen for its needs and remove waste carbon dioxide.
Understanding Lung Diffusion Capacity
The process of gas exchange in the lungs occurs primarily in millions of tiny air sacs called alveoli. These alveoli are surrounded by an intricate network of very small blood vessels known as capillaries. Oxygen from the air you inhale travels down your airways into these alveoli.
Once in the alveoli, oxygen must cross a very thin barrier, the alveolar-capillary membrane, to enter the bloodstream within the capillaries. This membrane is typically only about one cell thick, which facilitates rapid gas movement. Simultaneously, carbon dioxide, a waste product carried by the blood from the body’s tissues, moves from the capillaries across this same membrane into the alveoli to be exhaled. This movement of gases occurs through simple diffusion.
Common Causes of Reduced Lung Diffusion Capacity
A decrease in lung diffusion capacity can stem from various underlying medical conditions that affect the delicate structure of the lungs and blood. One primary mechanism involves damage to the alveolar-capillary membrane itself. For instance, in conditions like pulmonary fibrosis, scarring and thickening of this membrane make it difficult for gases to pass through. Sarcoidosis, another restrictive lung disease, can also lead to similar thickening and impaired diffusion.
Another significant cause is a reduction in the available surface area for gas exchange. Emphysema, a type of chronic obstructive pulmonary disease (COPD), causes destruction of the alveoli. Lung surgeries where parts of the lung are removed can also physically reduce this surface area. Conditions affecting blood flow to the lungs also play a role, such as pulmonary hypertension, which involves high blood pressure in the arteries of the lungs, or pulmonary embolism, a blockage in a lung artery. These issues can reduce the volume of blood in the pulmonary capillaries.
Problems with hemoglobin, the protein in red blood cells that carries oxygen, can also lower diffusion capacity. Anemia, a condition characterized by a lack of healthy red blood cells or hemoglobin, means less capacity for oxygen uptake. Additionally, heart conditions like congestive heart failure can lead to fluid buildup in the lungs, known as pulmonary congestion. Certain lung infections, as well as exposure to specific medications like amiodarone or bleomycin, can also contribute to reduced diffusion capacity.
Identifying Decreased Lung Diffusion Capacity
Recognizing decreased lung diffusion capacity involves observing specific symptoms and utilizing specialized diagnostic tests. Individuals often experience shortness of breath, also known as dyspnea, particularly during physical activity. This symptom arises because the impaired gas exchange means the body is not receiving enough oxygen to meet the increased demands of exertion.
Another common symptom is fatigue, as the body’s cells and tissues become deprived of adequate oxygen, affecting overall energy levels. Reduced exercise tolerance is also frequently reported, making routine physical activities more challenging.
The primary diagnostic tool used to assess lung diffusion capacity is the Diffusion Capacity of the Lungs for Carbon Monoxide (DLCO) test, also sometimes referred to as the TLCO test. This test measures how much carbon monoxide transfers from the inhaled air in the lungs into the red blood cells in the pulmonary capillaries per minute. Carbon monoxide is used because it binds strongly to hemoglobin. The DLCO value is then compared to predicted values for a person of similar age, height, and gender with healthy lungs. A lower-than-expected DLCO value indicates that the lungs are less efficient at transferring gases.
Managing Decreased Lung Diffusion Capacity
Managing decreased lung diffusion capacity primarily focuses on addressing the underlying medical condition. For instance, if heart failure is contributing to reduced diffusion, treating the heart condition with appropriate medications can help improve fluid balance in the lungs. Similarly, managing pulmonary fibrosis with antifibrotic medications or treating anemia can lead to improvements.
Beyond treating the root cause, supportive therapies play a role in managing symptoms and improving quality of life. Supplemental oxygen therapy may be prescribed when blood oxygen levels are consistently low, especially during exertion. Pulmonary rehabilitation programs, which include exercise training, education, and breathing strategies, can help individuals improve their exercise tolerance and overall physical function. Additionally, lifestyle adjustments are often recommended, such as avoiding smoking and minimizing exposure to other lung irritants.