Certified Pulmonary Function Technologist (CPFT) Practice Exam

How can a Mueller maneuver affect DLCO results?

1. It has no effect on DLCO

2. It can decrease DLCO results

3. It can falsely increase DLCO because it increases pulmonary capillary blood flow

4. It can stabilize DLCO measurements

The correct answer is: It can falsely increase DLCO because it increases pulmonary capillary blood flow

The Mueller maneuver involves a forced inspiratory effort against a closed airway, which can lead to certain physiological changes in the lungs. When this maneuver is performed, it can increase pulmonary capillary blood flow due to increased intrathoracic negative pressure, which enhances blood flow into the pulmonary circulation. As a result, this increased blood flow means more hemoglobin is available to bind with carbon monoxide (the gas often used in DLCO testing). This can falsely elevate the measured DLCO values because the test detects the amount of carbon monoxide that diffuses across the alveolar-capillary membrane. Therefore, the manipulation of blood flow induced by the Mueller maneuver can lead to an artificially high DLCO result, which does not accurately reflect the true diffusion capability of the lungs in a resting state. Understanding this relationship is crucial in pulmonary function testing, as it highlights the importance of test conditions and patient maneuvering during DLCO measurements.