Cardiac output and arteriovenous oxygen difference contribute to lower peak oxygen uptake in patients with fibromyalgia

Abstract

BackgroundPatients with fibromyalgia (FM) exhibit low peak oxygen uptake (dot{text{V}}O2peak). We aimed to detect the contribution of cardiac output to (dot{text{Q}}) and arteriovenous oxygen difference [text{C}(text{a-v})text{O}_{2}] to dot{text{V}}text{O}_{2} from rest to peak exercise in patients with FM.MethodsThirty-five women with FM, aged 23 to 65 years, and 23 healthy controls performed a step incremental cycle ergometer test until volitional fatigue. Alveolar gas exchange and pulmonary ventilation were measured breath-by-breath and adjusted for fat-free body mass (FFM) where appropriate. dot{text{Q}} (impedance cardiography) was monitored. text{C}(text{a-v})text{O}_{2} was calculated using Fick’s equation. Linear regression slopes for oxygen cost (∆dot{text{V}}O2/∆work rate) and dot{text{Q}} to text{V}O2 (∆dot{text{Q}}/∆dot{text{V}}O2) were calculated. Normally distributed data were reported as mean ± SD and non-normal data as median [interquartile range].Resultsdot{text{V}}O2peak was lower in FM patients than in controls (22.2 ± 5.1 vs. 31.1 ± 7.9 mL∙min−1∙kg−1, P < 0.001; 35.7 ± 7.1 vs. 44.0 ± 8.6 mL∙min−1∙kg FFM−1, P < 0.001). dot{text{Q}} and C(a-v)O2 were similar between groups at submaximal work rates, but peak dot{text{Q}} (14.17 [13.34–16.03] vs. 16.06 [15.24–16.99] L∙min−1, P = 0.005) and C(a-v)O2 (11.6 ± 2.7 vs. 13.3 ± 3.1 mL O2∙100 mL blood−1, P = 0.031) were lower in the FM group. No significant group differences emerged in ∆dot{text{V}}O2/∆work rate (11.1 vs. 10.8 mL∙min−1∙W−1, P = 0.248) or ∆dot{text{Q}}/∆dot{text{V}}O2 (6.58 vs. 5.75, P = 0.122) slopes. ConclusionsBoth dot{text{Q}} and C(a-v)O2 contribute to lower dot{text{V}}O2peak in FM. The exercise responses were normal and not suggestive of a muscle metabolism pathology.Trial registrationClinicalTrials.gov, NCT03300635. Registered 3 October 2017—Retrospectively registered. https://clinicaltrials.gov/ct2/show/NCT03300635.