Dual Test Gas Pulmonary Diffusing Capacity Measurement During Exercise in Humans Using the Single-Breath Method
February 2nd, 2024
This protocol presents a method to assess pulmonary alveolar-capillary reserve measured by combined single-breath measurement of the diffusing capacity to carbon monoxide (DL,CO) and nitric oxide (DL,NO) during exercise. Assumptions and recommendations for using the technique during exercise form the foundation of this article.
Our research focuses on mechanism of impaired pulmonary gas exchange in various disease states and how knowledge of these may be used for diagnostic and target treatments. We aim to refine the understanding of acute exercise adaptation by assessing alveolar-capillary reserve through diffusion capacity measurements during exercise. Conventional lung function testing such as dynamic spirometry and diffusion capacity measurements during rest provide limited information about pulmonary limitations and adaptations to acute exercise.
Our protocol addresses this gap by introducing a more comprehensive and physiologically relevant measurement method that assesses the alveolar-capillary reserve. By providing a more detailed analysis of lung function during exercise, this research contributes to the development of target diagnostic and therapeutic strategies for pulmonary diseases, enhancing clinical management and treatment efficacy. By this technique, our studies will specifically elucidate how pulmonary gas exchange limitations contributes to the pathophysiology of chronic lung disease and how this may be affected by exercise training.
Our research group intends to extend this research to explore the impact of various therapeutic and training interventions on pulmonary function during exercise, and to investigate the specific responses in patients with chronic obstructive pulmonary disease. This will further elucidate the lungs'adaptability and resilience under stress. After performing a cardiopulmonary exercise test, instruct the participant to avoid vigorous exercise for the next 48 hours.
To calibrate single-breath diffusing capacity equipment, open the software program and initiate an automatic warmup period of 50 minutes to achieve a sufficient temperature in the pneumotach. Ensure that the containers with the test gases are open and the inspiratory bag is connected to the MS PFT analyzer unit. For gas calibration, connect the sampling line from the pneumotach to the MS PFT analyzer unit plugin termed CAL.
On the homepage, select Calibration, and choose Gas Calibration. Then press start or F1 and select calibration to start the calibration. Once the gas calibration is fulfilled and accepted, attach the sampling line to the pneumotach.
To perform volume calibration using a three-liter syringe, select Calibration, followed by Volume Calibration. Choose PFT and press start or F1.Then select Calibration to start the calibration and follow the onscreen instructions. To complete the calibration process, perform biological controls of spirometry and measurements of diffusing capacity to carbon monoxide at rest on an approved individual.
Monitor for any significant week-to-week variations in FEV1, FVC, and DLCO. Calculate the desired workload based on previous cardiopulmonary exercise test results. Choose the intensity for measuring DLCO by DLNO as percentage of the maximal workload.
After 48 hours of the cardiopulmonary exercise test, ask the participant to return to the laboratory for DLCO by DLNO measurement during exercise. Measure and record the patient's height in centimeters. On the homepage, select Patient, then New Patient.
Enter the last name, first name, date of birth, gender, height, and weight of the participant. Then press OK or F1 to continue. For analysis, open the software, and on the homepage, choose Measurement followed by NO membrane diffusing.
Enter hemoglobin concentration in the system, then press F1 to zero the gas analyzer for all test gases, and to initiate the mixing of the test gases in the connected inspiratory bag. When the software instructs to begin the procedure, ask the participant to sit in an upright chair equipped with a nose clip. Instruct the participant to start normal tidal respirations through a mouthpiece connected to the pneumotach.
After three normal respirations, instruct the participant to perform a rapid maximal expiration to reach residual volume. Now, instruct the participant to perform a rapid maximal inspiration to total lung capacity in less than four seconds, inhaling the pre-mixed test gases. Direct the participant to hold their breath for five seconds at total lung capacity, aiming for an inspired volume of at least 90%of their forced vital capacity during the breath hold time.
Then instruct the participant to perform a steady and strong maximal exhalation without any interruptions. Remove the participant's mouthpiece and nose clip. The software then calculates DLCO and DLNO without any command.
Calculate the percentage of the inspired volume of their forced vital capacity. Repeat the maneuver after a four-minute washout period until two maneuvers meet the acceptability criteria. Report the DLCO and DLNO data per the criteria explained in the given table.
Adjust the cycle ergometer's distance and height to ensure the participant can breathe through the mouthpiece comfortably while maintaining a proper cycling position. Ask the participant to sit on the cycle ergometer and place a heart rate monitor on their chest. Direct the participant to start cycling for five minutes at a sub-maximal workload as a warmup before the measurement.
Increase the workload to the target intensity and simultaneously press F1 to initiate automatic resetting of the device to allow the participant to reach a steady state. Next, turn the mouthpiece towards the participant. While the participant continues cycling at the target intensity, perform a maneuver to measure DLCO by DLNO.
Upon completion of the maneuver, remove the mouthpiece. Reduce the workload to 15 to 40 watts and engage the participant in an active recovery phase for two minutes. In the healthy individual, DLNO displayed a near linear increase, except for a plateau between 20%and 40%of maximum workload, whereas DLCO showed a slight consistent increase across all workloads.
Conversely, in chronic obstructive pulmonary disease, DLNO increase at the first workload and then plateau, suggesting full alveolar-capillary reserve utilization at just 20%maximum workload.
Overview
This protocol presents a method to assess pulmonary alveolar-capillary reserve measured by combined single-breath measurement of the diffusing capacity to carbon monoxide (D L,CO) and nitric oxide (D L,NO) during exercise. This research aims to refine the understanding of acute exercise adaptation by providing a more comprehensive measurement method.
Key Study Components
Area of Science
- Pulmonary physiology
- Exercise science
- Gas exchange mechanisms
Background
- Conventional lung function tests provide limited information.
- Understanding pulmonary gas exchange is crucial for diagnosing lung diseases.
- Acute exercise adaptation is not fully understood.
- There is a need for more physiologically relevant measurement methods.
Purpose of Study
- To assess alveolar-capillary reserve during exercise.
- To enhance diagnostic and therapeutic strategies for pulmonary diseases.
- To elucidate the impact of exercise training on pulmonary gas exchange limitations.
Methods Used
- Single-breath measurement of diffusing capacity.
- Assessment during exercise conditions.
- Comparison with conventional lung function tests.
- Analysis of gas exchange mechanisms.
Main Results
- Introduction of a comprehensive measurement method.
- Identification of pulmonary limitations during exercise.
- Insights into the pathophysiology of chronic lung disease.
- Potential for improved clinical management and treatment efficacy.
Conclusions
- The protocol addresses gaps in current lung function testing.
- Enhanced understanding of exercise adaptation is achieved.
- This research contributes to better diagnostic strategies.
