Inability of myalgic encephalomyelitis/chronic fatigue syndrome patients to reproduce VO2peak indicates functional impairment

Abstract

BackgroundMyalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a multi-system illness characterized, in part, by increased fatigue following minimal exertion, cognitive impairment, poor recovery to physical and other stressors, in addition to other symptoms. Unlike healthy subjects and other diseased populations who reproduce objective physiological measures during repeat cardiopulmonary exercise tests (CPETs), ME/CFS patients have been reported to fail to reproduce results in a second CPET performed one day after an initial CPET. If confirmed, a disparity between a first and second CPET could serve to identify individuals with ME/CFS, would be able to document their extent of disability, and could also provide a physiological basis for prescribing physical activity as well as a metric of functional impairment.Methods22 subjects diagnosed with ME/CFS completed two repeat CPETs separated by 24 h. Measures of oxygen consumption (VO2), heart rate (HR), minute ventilation (Ve), workload (Work), and respiratory exchange ratio (RER) were made at maximal (peak) and ventilatory threshold (VT) intensities. Data were analyzed using ANOVA and Wilcoxon’s Signed-Rank Test (for RER).ResultsME/CFS patients showed significant decreases from CPET1 to CPET2 in VO2peak (13.8%), HRpeak (9 bpm), Ve peak (14.7%), and Work@peak (12.5%). Decreases in VT measures included VO2@VT (15.8%), Ve@VT (7.4%), and Work@VT (21.3%). Peak RER was high (≥1.1) and did not differ between tests, indicating maximum effort by participants during both CPETs. If data from only a single CPET test is used, a standard classification of functional impairment based on VO2peak or VO2@VT results in over-estimation of functional ability for 50% of ME/CFS participants in this study.ConclusionME/CFS participants were unable to reproduce most physiological measures at both maximal and ventilatory threshold intensities during a CPET performed 24 hours after a prior maximal exercise test. Our work confirms that repeated CPETs warrant consideration as a clinical indicator for diagnosing ME/CFS. Furthermore, if based on only one CPET, functional impairment classification will be mis-identified in many ME/CFS participants.

Metabolic profiling indicates impaired pyruvate dehydrogenase function in myalgic encephalopathy/chronic fatigue syndrome

“…Our data, suggesting that ME/CFS is associated with impaired efficiency of energy metabolism combined with lactate overproduction, may explain why many ME/CFS patients reach anaerobic threshold at a low workload (9)(10)(11). This is supported by an individual patient report (35) and our own observations of patients with severe ME/CFS that had lactate levels elevated to more than 8 mM from just standing upright for 10 minutes.…”

An Accurate Diagnosis of Myalgic Encephalomyelitis and Chronic Fatigue Syndrome requires strict Clinical Case definitions and Objective Test Methods

“…It is very unlikely that all patients meeting specific diagnostic criteria will show abnormal results for all specific objective tests, e.g. repeated exercise tests [41,42], cognitive tests [43,44], tilt table tests [45,46], muscle power (endurance) tests [47,48], but it is essential to establish physiological and neurocognitive abnormalities in the individual patients impartially, both in clinical practice as in research studies.…”

“…repeated exercise tests [41,42], cognitive tests [43,44], tilt table tests [45,46], muscle power (endurance) tests [47,48], for diagnosing patients [49] and determining the effect of interventions [50], to find correlations between symptoms/subjective measures and objective test outcomes, and to define symptomatic subgroups of the ME and CFS patient population [51].…”

“…between post-exertional malaise and the effect of exercise on the exercise capacity [41] and cognitive test scores [54], between orthostatic intolerance and tilt table test results [55], and between cognitive deficits and cognitive test performance during orthostatic stress [56].…”

Persistent Burnout Theory of Chronic Fatigue Syndrome

“…A meta-analysis by Malouff et al found that including cognitive elements in a treatment did not lead to a greater effect, and there appeared to be no empirical basis for including cognitive components in the treatment of CFS [6]. Exercise avoidance and de-conditioning do not adequately explain findings such as abnormal performance in repeated cardiopulmonary exercise tests [7] [8]. A review by Wiborg et al found that the effectiveness of cognitive behavioral therapy (CBT) was independent of any persistent change in physical activity [9].…”