Lung Diffusion Test: Purpose, Procedure, Normal Values, and Interpretation
Lung diffusion testing, specifically the Diffusing Capacity of the Lungs for Carbon Monoxide (DLCO) test, plays a crucial role in evaluating the efficiency of gas transfer from inhaled air into the bloodstream. This non-invasive test is essential for diagnosing, monitoring, and assessing several respiratory and related conditions.
The DLCO test is particularly useful in the diagnosis and management of Chronic Obstructive Pulmonary Disease (COPD). By measuring the lungs' ability to transfer gases, the test helps assess the severity and progression of COPD, a condition in which this ability is often impaired [1][3].
In addition, the test is valuable for those with Interstitial Lung Disease (ILD) and Pulmonary Fibrosis, conditions that affect the lung tissue and the surface area available for gas exchange, leading to reduced diffusion capacity [1][3].
For individuals with Pulmonary Vascular Disorders, such as pulmonary hypertension, the DLCO test can help detect reductions in the lung's ability to transfer gases [1]. The test is also beneficial in evaluating lung involvement in systemic conditions like connective tissue diseases (e.g., scleroderma, rheumatoid arthritis) [1][2].
Moreover, the DLCO test can help identify conditions that affect the Alveolar-Capillary Membrane, such as sarcoidosis, which can reduce diffusion and be reflected in test results [1]. It can also be used to assess or monitor less common conditions like pulmonary hemorrhage or polycythemia, which may alter the lung’s ability to transfer gases [1].
The DLCO test is often conducted in conjunction with spirometry and lung volume measurements to provide a complete assessment of lung function and disease status [1][2].
During a DLCO test, a person inhales a small amount of air containing carbon monoxide and a tracer gas, then exhales into a tube. The healthcare professional collects and tests the exhaled air to determine how much gas the person has breathed out, which shows how well the body has absorbed the tracer gas [2].
People may need to wait for 10 minutes between readings, repeat the test several times for accurate results, and abstain from smoking, eating, and drinking for several hours before the test [2]. The test is typically conducted using a special device that measures the amounts of exhaled carbon monoxide and tracer gas [2].
Normal ranges for DLCO can vary based on several factors, including age, sex, height, and hemoglobin levels [2]. For men, the normal range is typically 80-120% of its predicted value, while for women, it is 76-120% [2].
If abnormal results are obtained, it may indicate that the lungs are not exchanging gases efficiently, which can be caused by various conditions such as emphysema, pulmonary hypertension, or congestive heart failure [2]. It is always advisable to consult with a healthcare professional for a proper interpretation of the test results and any necessary follow-up actions.
The DLCO test, being a key evaluation tool for gas transfer efficiency from inhaled air into the bloodstream, is particularly useful in diagnosing and managing medical-conditions such as Chronic Obstructive Pulmonary Disease (COPD) and Interstitial Lung Disease (ILD), where gas exchange might be impaired. This test can also help identify other health-and-wellness conditions like pulmonary vascular disorders, connective tissue diseases, and alveolar-capillary membrane conditions, as they may cause reduced diffusion capacity.
