Decreased oxygen extraction during cardiopulmonary exercise test in patients with chronic fatigue syndrome.
BACKGROUND
The insufficient metabolic adaptation to exercise in Chronic Fatigue Syndrome (CFS) is still being debated and poorly understood.


METHODS
We analysed the cardiopulmonary exercise tests of CFS patients, idiopathic chronic fatigue (CFI) patients and healthy visitors. Continuous non-invasive measurement of the cardiac output by Nexfin (BMEYE B.V. Amsterdam, the Netherlands) was added to the cardiopulmonary exercise tests. The peak oxygen extraction by muscle cells and the increase of cardiac output relative to the increase of oxygen uptake (ΔQ'/ΔV'O₂) were measured, calculated from the cardiac output and the oxygen uptake during incremental exercise.


RESULTS
The peak oxygen extraction by muscle cells was 10.83 ± 2.80 ml/100ml in 178 CFS women, 11.62 ± 2.90 ml/100 ml in 172 CFI, and 13.45 ± 2.72 ml/100 ml in 11 healthy women (ANOVA: P=0.001), 13.66 ± 3.31 ml/100 ml in 25 CFS men, 14.63 ± 4.38 ml/100 ml in 51 CFI, and 19.52 ± 6.53 ml/100 ml in 7 healthy men (ANOVA: P=0.008).The ΔQ'/ΔV'O₂ was > 6 L/L (normal ΔQ'/ΔV'O₂ ≈ 5 L/L) in 70% of the patients and in 22% of the healthy group.


CONCLUSIONS
Low oxygen uptake by muscle cells causes exercise intolerance in a majority of CFS patients, indicating insufficient metabolic adaptation to incremental exercise. The high increase of the cardiac output relative to the increase of oxygen uptake argues against deconditioning as a cause for physical impairment in these patients.
CFS/ME Medical Centre Amsterdam, Waalstraat 25-31, Amsterdam 1078BR, Netherlands. rv@cvscentrum.nl.
Ruud C W
RC
Vermeulen
Ineke W G
IW
Vermeulen van Eck
D000328:Adult; D003710:Demography; D005080:Exercise Test; D015673:Fatigue Syndrome, Chronic / Q000503:physiopathology*; D005260:Female; D006321:Heart / Q000503:physiopathology*; D006801:Humans; D008168:Lung / Q000503:physiopathology*; D008297:Male; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption
D010100:Oxygen