Validity of 2-Day Cardiopulmonary Exercise Testing in Male Patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Abstract

Introduction: Among the main characteristics of patients with myalgic en- cephalomyelitis/chronic fatigue syndrome (ME/CFS) are effort intolerance along with a prolonged recovery from exercise and post-exertional exacerba- tion of ME/CFS symptoms. The gold standard for measuring the severity of physical activity intolerance is cardiopulmonary exercise testing (CPET). Multiple studies have shown that peak oxygen consumption is reduced in the majority of ME/CFS patients. A consecutive day CPET protocol has shown a difference on day 2 in ME/CFS patients in contrast to sedentary controls. Because of the low number of male ME/CFS patients in the published literature, and because of a possible gender difference in the clinical phenotype, the aim of this study was to examine whether the response to a 2-day CPET protocol in a larger sample of male ME/CFS patients was similar to that observed in females. Methods: From 77 male patients, 25 male ME/CFS patients fulfilled the criteria of a 2-day CPET protocol for analysis. Measures of oxygen consumption (VO2), heart rate (HR), systolic and diastolic blood pressure, work-load (Work), and respiratory exchange ratio (RER) were made at maximal (peak) and ventilatory threshold (VT) intensities. Data were analysed using a paired t-test. Results: Baseline characteristics of the group were as follows. Mean age was 44 (12) years, mean BMI was 27.1 (4.4) kg/m2. Median disease duration was 10 years (IQR 7 - 13). Heart rate, systolic and diastolic blood pressure at rest and the RER did not differ significantly between CPET 1 and CPET 2. All other CPET parameters at the ventilatory threshold and maximum exercise differed significantly (p-value between <0.005 and <0.0001). All patients experienced a deterioration of performance on CPET2 as measured by the predicted and actual VO2 and workload at peak exercise and ventilatory threshold. Conclusion: This study confirms that male ME/CFS patients have a reduction in exercise capacity in response to a consecutive day CPET. These results are similar to published results in female ME/CFS populations.