Det har, 23 april 2014, blitt publisert en ny studie med tittel «Inability of myalgic encephalomyelitis / chronic fatigue syndrome patients to reproduce VO2 peak indicates functional impairment» i tidsskriftet Journal of Translational Medicine. Målsetningen med studien var blant annet å se om resultatene fra test-retest (to-etterfølgende dager) sykkeltest (CPETs) kunne dokumenteres, basert på tidligere studier, samt pasientenes subjektive symptombeskrivelse.Publikasjonen sammenligner også deres resultater med andre lignende studier, samt resultater i fra andre pasientgrupper med respirasjonsnedsettelse.
I denne studien ble det inkludert 22 pasienter diagnostisert etter fakuda-kriteriene. Forskerene konkluderer med at ME-pasientene ikke var i stand til å reprodusere de fleste fysiologiske målinger ved både maksimal og respiratorisk terkelnivåer etter å ha gjennomført en CPET 24 timer dagen før.
Videre konkluderer forskerne med at med denne studien så kan de verifisere at gjentatt CPETs kan brukes og betraktes som en klinisk indikator for å diagnostisere ME-pasienter. Videre blir det påpekt at resultatene viser at bare etter en CPET er sannsynligheten stor for at ME-pasienter kan bli misdiagnostisert og ikke identifisert med hensyn til den signifikante fysiologiske nedsettelsen (nedsatt arbeidskapasitet) som ble funnet etter 24 timers repitasjon av sykkel-treningstesten.
De nevner det lave antallet med deltakere og håper på en oppfølgingsstudie for å bedre det statistiske datagrunnlaget, samt å se om der er uliketer mellom kjønn mm.
Abstraket er som følger:
Myalgic 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.
22 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).
ME/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.
ME/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.
Noen sitater i fra publikasjonen:
Changes in physiological measures indicate a substantial post-exertional decrement in performance at ventilatory threshold in ME/CFS 24 hours after an initial CPET. Ventilatory or anaerobic threshold intensity indicates the workload, heart rate and/or oxygen consumption at which anaerobic metabolism begins to predominate. Thus, after induction of post- exertional malaise, the threshold lowers at which anaerobic metabolism accelerates in ME/CFS. This causes premature anaerobiosis in ME/CFS patients after they have endured an earlier physical challenge, further reducing the ability to do work. It is therefore not surprising that Snell et al.  found that work at ventilatory thr eshold contributed most substantially to differentiate ME/CFS from healthy controls.
Use of a single CPET only to indicate functional impairment in ME/CFS is problematic. The results of this study, and the consensus of the three previous studies of test-retest CPETs in ME-CFS patients, provide strong evidence of impaired physiological responses to exercise.
More specifically, the abnormal post-exertional responses to exercise in ME/CFS are marked by test-retest decreases in VO2 and work at both maximum and ventilatory threshold intensities. Data from a single CPET resulted in classification of 12 of 22 patients as having little or no impairment, and eight as having mild/moderate impairment. Such individuals would likely be prescribed graded exercise therapy (GET) to improve aerobic capacity.
However, data from the second CPET in this and prior studies [13,17,18] indicate that aerobic energy-producing processes fail to respond normally to exercise stress in ME/CFS patients. Thus, incautiously applied GET is likely to result in exacerbation of fatigue and other symptoms of ME/CFS patients.
Kilde: Betsy A Keller, John Luke Pryor and Ludovic Giloteaux (2014).Inability of myalgic encephalomyelitis / chronic fatigue syndrome patients to reproduce VO2peak indicates functional impairment. ournal of Translational Medicine 2014, 12:104 doi:10.1186/1479-5876-12-104
Full tekst (pdf): http://www.translational-medicine.com/content/pdf/1479-5876-12-104.pdf
However, data from the second CPET in this and prior studies [13,17,18] indicate that aerobic energy-producing processes fail to respond normally to exercise stress in ME/CFS patients.
Thus, incautiously applied GET is likely to result in exacerbation of fatigue and other symptoms of ME/CFS patients.
Nyttig lesning om belastingstester: Belastningsundersøkelse for vurdering av kardiopulmonal funksjon