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Keller:

zuurstofopname

ME/CVS-patiŽnten

bij tweede fietstest

beduidend lager

dan bij eerste fietstest

 

 

 

 


 

 

 

Uit een vandaag verschenen studie van Betsy Keller en anderen blijkt wederom (klik hier en hier)

dat de maximale zuurstofopname, maximale inspanning en/of zuurstofopname en inspanning bij de verzuringsdrempel bij een tweede fietstest significant (*) minder zijn dan bij de eerste, 24 uur eerder.

 

Bij de meeste patiŽnten neemt de maximale zuurstofopname (VO2max) sterk af.

Bij de patiŽnten bij wie de VO2max niet noemenswaardig afwijkt,

neemt de zuurstofopname bij de verzuringsdrempel (VO2@AT) beduidend af.

 

Dus bij alle ME/CVS-patiŽnten nam de VO2max of de VO2@AT bij de tweede fietstest significant (*) af.

 

De objectief vastgestelde invaliditeit op basis van het "verval" bij de tweede fietstest

was bij ca. 50% van de patiŽnten zwaarder dan op basis van ťťn fietstest zou worden geconstateerd.

 

VO2max

ml.kg-1.min−1

Mate van invaliditeit

Zuurstofopname

bij verzuringsdrempel

ml.kg-1.min−1

>20

A

Weinig of geen beperkingen

>14

16Ė20

B

Kleine/gemiddelde beperkingen

12Ė14

10Ė15

C

Gemiddelde tot ernstige beperkingen

9Ė10

<10

D

Ernstige beperkingen

6Ė7

 

Zoals Keller en collega's en eerder ook VanNess en collega's concludeerden:

alle ME- en/of CVS-criteria ontberen objectieve maatstaven om post-exertionele malaise vast te stellen.

 

PatiŽntenorganisaties zouden, roep dit al minstens 5 jaar, zich heel erg hard moeten maken voor

een objectieve vaststelling van de symptomen, m.b.v. dubbele fietstesten, cognitieve testen etc.

 

 

*

De maximale zuurstofopname (VO2max) wijkt bij de tweede fietstest normaliter minder dan 7% af van die bij de eerste fietstest. Dit geldt voor gezonde mensen, inactieven ťn patiŽnten met andere ziekten.

Op basis van ťťn fietstest zou de lage VO2max toegeschreven kunnen worden aan "inactiviteit".

 

Overigens was de zuurstofopname bij de eerste fietstest gemiddeld al erg laag: 21.9 (ml.kg-1.min-1).

Dit is slechts 77,1% van de VO2max die op basis van leeftijd en geslacht verwacht mag worden.

Eerder vonden VanNess e.a. (gem. VO2max: 21.51) en Vermeulen e.a. (22.3) vergelijkbare waarden.

 

 


 

Belangrijke citaten uit het uitgebreide studieverslag:

 

 

As pointed out by Snell et al. [17], the predominant ME/CFS case definitions fail to

operationally define, or provide guidance to assess responses to exertion.

 

 

It is well documented that

VO2peak is highly reliable (test-retest difference = 7%) and reproducible (r = 0.95-0.99)

in healthy active and inactive adults, children and many patient populations.

 

Thus, failure of ME/CFS patients

to reproduce VO2peak within the well-established normative variation of ≤7%

would indicate an underlying pathophysiology, and

could provide a metric of the effects of PEM on physical activity tolerance and physical function.

 

 

In this cohort, RER at maximal effort (RERpeak) was high (=1.1) and

did not differ between tests,

indicating that ME/CFS participant effort was very strong during both CPETs.

 

 

Examination of individual changes from test 1 to test 2 in Figure 3 reveal that

VO2peak decreased in most patients and

did not change in the remaining patients.

 

Patients whose VO2peak did not change instead

demonstrated a decrease in VO2@VT shown in Figure 4.

 

Thus, all patients demonstrated

clinically significant decreases in either VO2peak and/or VO2@VT

that exceed normative values for test-retest variability.

 

 

Overall,

classification of functional impairment

worsened in 50% of the ME/CFS cohort

due to post-exertional decrements in VO2peak and/or VO2 at VT.

 

Using only a single CPET,

13 of 22 were classified as "A" (little to no impairment) and

eight were classified as "B" (mild/moderate impairment),

which would typically be attributed to physical deconditioning.

 

Thus the actual functional impairment of ME/CFS patients is much greater

than is measured by a single CPET.

 

 


 

 

 

Inability of myalgic encephalomyelitis/chronic fatigue syndrome patients

to reproduce VO2peak indicates functional impairment.

Journal of Translational Medicine 2014, 12:104. doi:10.1186/1479-5876-12-104.

Keller BA, Pryor JL, Giloteaux L.

 

 

Abstract (provisional)

 

 

Background

 

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.

 

 

Methods

 

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).

 

 

Results

 

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 RERwas 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.

 

 

Conclusion

 

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.

 

 

Keywords

 

Chronic fatigue syndrome, Functional impairment, Cardiopulmonary exercise test,

Exercise intolerance, Post exertional malaise

 

 

http://www.translational-medicine.com/content/pdf/1479-5876-12-104.pdf

 

 


 

Met dank aan Manja, correspondente/ME-de-patiŽnte.