How do I assess Diffusing Capacity of the Lung for Carbon Monoxide (DLCO)?

From the Guidelines

To assess Diffusing Capacity of the Lung for Carbon Monoxide (DLCO), a single-breath DLCO measurement or rebreathing technique can be used, with the choice of method depending on the patient's ability to perform the test, particularly in cases of severe neurodegenerative dysfunction. When assessing DLCO, it is essential to consider the patient's clinical condition, as advanced diseases like ataxia telangiectasia may render certain tests unfeasible 1. The single-breath DLCO measurement is commonly used but may not be suitable for all patients, especially those with severe neurodegenerative dysfunction, in which case the rebreathing technique may be required.

Key Considerations for DLCO Assessment

• The test measures the difference between inhaled and exhaled CO concentration to determine gas transfer from the lungs into the bloodstream.
• Specialized equipment, including a spirometer with gas analyzers, is necessary for the test.
• Patients should avoid smoking for 24 hours before testing, as it can temporarily reduce DLCO values.
• Results are typically reported in ml/min/mmHg and compared to predicted values based on the patient's age, height, sex, and ethnicity.

Clinical Applications of DLCO Measurement

• Diagnosing conditions like pulmonary fibrosis, emphysema, and pulmonary hypertension.
• Monitoring disease progression and treatment response.
• Evaluating impaired gas exchange in patients with interstitial lung disease (ILD) 1.

In clinical practice, DLCO measurement is a valuable tool for assessing lung function and gas exchange capability, but it should be used in conjunction with other clinical assessments, such as respiratory rate, effort, and auscultation, particularly in patients with severe neurodegenerative diseases 1.

From the Research

Assessing DLCO

To assess the Diffusing Capacity of the Lung for Carbon Monoxide (DLCO), several methods can be used, including:

• The single-breath method, which is the most widely used and best standardized technique 2
• The intrabreath method, which is a useful and reliable alternative to the single-breath method 3

Measurement Techniques

The single-breath method involves the patient breathing quietly, inhaling the test gas, holding their breath for ten seconds, and then exhaling 4. The intrabreath method, on the other hand, does not depend on the length of time or other conditions during breath holding or expiration 3.

Interpretation of Results

The results of the DLCO test can be used to:

• Diagnose and monitor lung diseases, such as chronic obstructive pulmonary disease (COPD) and interstitial lung disease (ILD) 4
• Assess the severity and prognosis of lung diseases 4
• Evaluate the effectiveness of treatment 5

Clinical Applications

DLCO can be used in various clinical scenarios, including:

• Evaluating patients with dyspnea of unknown cause 4
• Assessing patients with spirometric restriction 4
• Monitoring patients with lung diseases, such as COPD and ILD 4, 5

Standardization and Quality Criteria

Standardization and quality criteria are essential to ensure accurate and reliable DLCO measurements 2, 6. This includes calibration routines, calculations, and adjustments to minimize inter-laboratory variability.