Journal of IiME Volume 5 Issue 1 (May 2011) Using Cardiopulmonary Exercise Testing to Evaluate Fatigue and Post-Exertional Malaise in ME/CFS The absence of reliable diagnostic laboratory tests or biomarkers presents significant problems for persons with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS), treating physicians, and the ME/CFS research community alike. Typically ME/CFS diagnoses rely on self-report measures where patients describe the extent and duration of their fatigue and attendant symptoms either verbally or on a questionnaire. An alternative to the current binary approach (i.e., fatigue or no fatigue) or use of paper and pencil inventories for evaluation of symptoms in ME/CFS is to employ direct, objective multisystem, measures of physical function that may also provide insights to the underlying pathophysiology of fatigue in ME/CFS. One such methodology is cardiopulmonary exercise testing (CPET). With a long history of use by exercise physiologists in research settings, this non-invasive, integrative assessment approach is now increasingly endorsed for the clinical evaluation of undiagnosed exercise intolerance and for the objective determination of functional capacity and impairment.[1] An early definition conceptualizes fatigue as reduced efficiency after doing work.[2] CPET is uniquely able to quantify this reduction in efficiency with measures of both workload and the metabolic cost of that work. Additionally, other available cardiovascular, pulmonary and symptom data further enhance the value of CPET for diagnostic, clinical and research purposes. As a corollary to extreme fatigue, postexertional malaise (PEM) or exacerbation of symptoms following physical exertion, is considered one of the most common and recognizable aspects of ME/CFS. For the objective assessment of PEM, CPET has the advantage of serving as both an indicator of clinical status and a quantifiable model of physical exertion. The principles underlying CPET are simple. Invest in ME (Charity Nr. 1114035) Chris Snell is scientific director of the Pacific Fatigue Laboratory, and chairs the federal Chronic Fatigue Syndrome Advisory Committee (CFSAC). He was one of the presenters at the recent state of knowledge workshop organised by the NIH. Christopher R. Snell, PhD1,2; Staci R. Stevens, MA2; Todd E. Davenport, DPT, OCS2,3; J. Mark Van Ness, PhD1,2 1 Department of Sport Sciences, University of the Pacific, 3601 Pacific Avenue, Stockton, CA 95211, USA 2 Pacific Fatigue Laboratory, 3601 Pacific Avenue, Stockton, CA 95211, USA 3 Department of Physical Therapy, Thomas J. Long School of Pharmacy and Health Sciences, 3601 Pacific Avenue, Stockton, CA 95211, USA Physical exertion requires that the cardiovascular system supply oxygen (O2) to active muscles and the pulmonary system remove carbon dioxide (CO2) from the blood. Taxing these systems has the capacity to reveal abnormalities that may not be apparent at rest and thus elucidate the mechanisms underlying exercise intolerance in ME/CFS. Procedures for CPET are widely available [1] as are results profiles for a variety of disabling conditions. [3] These data can facilitate differential diagnosis to rule out conditions that could otherwise explain patient symptoms. CPET is generally performed using a motorized treadmill or stationary cycle ergometer. For reasons of safety, the cycle is preferable when testing ME/CFS patients. Possible orthostatic intolerance and the extreme exhaustion patients usually experience post-testing can make using a treadmill particularly hazardous. Individualized ramp protocols, which involve Continued page 11 www.investinme.org Page 10/58
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