Feasibility and effectiveness of cardiopulmonary exercise testing in people with type 2 diabetes mellitus
Authors: Kinoshita N , Yamada S , Uchiyama E 
Published: June 2024

Abstract

Background/Introduction
Physical activity and exercise training play an important role to reduce morbidity and mortality in people with type 2 diabetes mellitus (T2DM). However, impaired functional capacity, abnormal cardiovascular responses to exercise, and silent myocardial ischemia in T2DM are major obstacles to determine effective and safe intensity of exercise. Therefore, cardiopulmonary exercise testing (CPX) is recommended as the initial evaluation for exercise program (1). However, feasibility and effectiveness of CPX for risk stratification and exercise prescription are not established in T2DM.

Purpose
To characterize cardiovascular and respiratory response to maximal exercise testing and to evaluate the feasibility and effectiveness of CPX in T2DM.

Methods
Retrospective study was conducted using records of CPX performed for T2DM who were incorporated to the in-hospital T2DM education program of our hospital (2005–2021). Known cardiovascular diseases (old myocardial infarction, chronic Af, etc.), other systemic diseases (malignancy, anemia, etc.), beta blocker use, and technically difficult testing for evaluation were excluded. CPX was conducted by cycle ergometer using ramp protocol with individually optimized work rate (WR) (2). The test was regarded as incomplete when peak heart rate (HR) &lt;85% of age predicted maximal HR (apHRmax, 220-age). VO2max was determined when peak HR &gt;90% of apHRmax with volitional exhaustion and respiratory exchange ratio &gt;1.1 above ventilatory compensation point, otherwise VO2peak was referred to the highest VO2. CPX parameters were investigated according to age groups. The study was approved by the Research Ethics Committee of our hospital.

Results
We analyzed 491 CPX data of T2DM (M: 309, 60±13 y/o, BMI: 25.9±4.9 kg/m2). Peak HR, BP, and WR were 139±22 bpm, 209/92±28/18 mmHg, and 109±45 W, respectively. The tests resulted in positive in 14 (2.9%), incomplete in 200 (40.7%), and the maximal level achieved in 129 (26.3%) while no serious accidents occurred. Further evaluation found significant coronary stenosis in 4 cases (0.8%, PCI: 1; CABG: 1; medication: 2, all asymptomatic). There were trends of age-related declines in VO2peak, O2 uptake efficiency slope (OUES), WR at VT, and peak O2 pulse and increase in minimum VE/VCO2 (Table 1). Rate of the maximal level attained were decreased by age, whereas VT was obtained in 90–100% cases. HR, WR, and %VO2peak at VT varied widely regardless of age group.

Conclusions
Despite limited ability to exert the maximal level, CPX could be safely performed to detect high risk individuals with silent myocardial ischemia and effectively identify VT in T2DM. Also, the low level and age-related decline of functional capacity was suggested. Still, exercise at VT was feasible, while corresponding HR or %VO2peak zones to the level could not be generalized. Exercise prescription should be individualized with precisely evaluated intensity by CPX in T2DM. CPX parameters by age group (mean±SD).