CPET – Cardiopulmonary Exercise Test

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Understanding Biological Validation in CPET

Cardiopulmonary exercise testing (CPET or CPX) is a non-invasive, sensitive test to evaluate cardiopulmonary pathophysiology. CPET assesses functional capacity and exercise intolerance and plays a valuable role in diagnosis and clinical decision-making.

The American College of Sports Medicine (ACSM), American Thoracic Society/American College of Chest Physicians (ATS/ACCP), American Heart Association (AHA), and European Respiratory Society (ERS) have published CPET recommendations and guidelines.

All recommend a Biological Quality Control (BioQC) procedure whereby a healthy subject on a stable diet performs regular exercise tests at work rates below the ventilatory/anaerobic (V/AT) or lactate threshold.

A Biological Quality Control (BioQC) procedure is critical to ensure accurate results. 

What is Biological Validation?

Biological validation assures that biological processes, methods, or products consistently meet specified requirements and perform as intended. It requires thorough testing and documentation.

Regarding CPET, biological validation ensures that gas analyzers produce high-quality, valid, and reliable data. Over time, gas analyzers will fail and must be serviced or replaced. According to the American Heart Association (AHA), “Even when appropriate calibration procedures are followed, modern automated CPX systems can provide results that appear to be accurate yet may be erroneous.” A BioQC protocol will ensure the precision of high-quality metabolic output and inform when analyzers start to fail.

Who Should Perform Biological Validation?

To employ a quality assurance plan with biological validation, a healthy staff member should participate in regularly scheduled CPET protocols to observe metabolic responses. After each test, biological QC data are submitted to a database.  

Staff members should fast and avoid caffeinated drinks for at least two hours before testing and record their age, height, and weight.

If testing methods are consistent, gas exchange measurements are highly reproducible within a given subject and should match what we anticipate to occur in the body. 

BioQC Procedures

CPET/CPX systems should be calibrated according to the manufacturer’s instructions immediately before BioQC testing. 

VO2 (oxygen uptake), V̇CO2 (carbon dioxide production), and V̇E (minute ventilation) are sampled breath-by-breath using a facemask, and heart rate is obtained from an electrocardiogram (ECG). 

The first BioQC test uses a constant work rate step protocol on a cycle ergometer. This test consists of four minutes of unloaded cycling, followed by four minutes at stage 1 (40W) and four minutes at stage 2 (80W), both of which are at workloads below the ventilatory/anaerobic threshold (V/AT).  

The second BioQC test is a ramp protocol on a cycle ergometer that gradually increases work rate over time to look at the relationship between VO2 and workload (VO2/W slope).

Staff members should carry out BioQC procedures at monthly intervals. In a system requiring maintenance (analyzer replacement, software updates, etc.), an out-of-schedule BioQC test should occur, and patient testing should only be resumed when the system passes QC criteria. 

If multiple CPET/CPX systems or carts are available, the metabolic output obtained from one metabolic cart should be compared to the other. 

A maintenance and troubleshooting log should be used to record all preventative maintenance activities, faults, and repairs.

Accuracy and Precision of Gas Exchange and Ventilation Measurements

Physiologic responses should be logged using an average of the last 30-60 seconds during steady state at each stage for V̇O2, V̇CO2, and V̇E. The accepted variability should be no greater than 6-8% for all metabolic variables. In addition, the acceptable range for VO2/W slope is 8.5-11.

CPET at Workwell Foundation

Workwell Foundation uses CPET to document impairment in individuals with post-exertional malaise (PEM). We follow rigorous quality control protocols, including biological validation, to ensure our clients obtain accurate test results. 

CPET, a non-invasive and highly precise tool when BioQC is applied, offers valuable insights for detecting issues with aerobic capacity and unexplained breathlessness. It is especially beneficial for individuals dealing with various chronic fatiguing conditions.

Contact us today at 209-599-7194 to learn more.