Tag: cardiopulmonary test

Inability of myalgic encephalomyelitis/chronic fatigue syndrome patients to reproduce VO₂peak indicates functional impairment

Abstract:

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 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.

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.

 

Source: Keller BA, Pryor JL, Giloteaux L. Inability of myalgic encephalomyelitis/chronic fatigue syndrome patients to reproduce VO₂peak indicates functional impairment. J Transl Med. 2014 Apr 23;12:104. doi: 10.1186/1479-5876-12-104. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4004422/ (Full article)

 

Decreased oxygen extraction during cardiopulmonary exercise test in patients with chronic fatigue syndrome

Abstract:

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.

CONCLUSION: 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.

 

Source: Vermeulen RC, Vermeulen van Eck IW. Decreased oxygen extraction during cardiopulmonary exercise test in patients with chronic fatigue syndrome. J Transl Med. 2014 Jan 23;12:20. doi: 10.1186/1479-5876-12-20. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3903040/ (Full article)’

 

Postexertional malaise in women with chronic fatigue syndrome

Abstract:

OBJECTIVE: Postexertional malaise (PEM) is a defining characteristic of chronic fatigue syndrome (CFS) that remains a source of some controversy. The purpose of this study was to explore the effects of an exercise challenge on CFS symptoms from a patient perspective.

METHODS: This study included 25 female CFS patients and 23 age-matched sedentary controls. All participants underwent a maximal cardiopulmonary exercise test. Subjects completed a health and well-being survey (SF-36) 7 days postexercise. Subjects also provided, approximately 7 days after testing, written answers to open-ended questions pertaining to physical and cognitive responses to the test and length of recovery. SF-36 data were compared using multivariate analyses. Written questionnaire responses were used to determine recovery time as well as number and type of symptoms experienced.

RESULTS: Written questionnaires revealed that within 24 hours of the test, 85% of controls indicated full recovery, in contrast to 0 CFS patients. The remaining 15% of controls recovered within 48 hours of the test. In contrast, only 1 CFS patient recovered within 48 hours. Symptoms reported after the exercise test included fatigue, light-headedness, muscular/joint pain, cognitive dysfunction, headache, nausea, physical weakness, trembling/instability, insomnia, and sore throat/glands. A significant multivariate effect for the SF-36 responses (p < 0.001) indicated lower functioning among the CFS patients, which was most pronounced for items measuring physiological function.

CONCLUSIONS: The results of this study suggest that PEM is both a real and an incapacitating condition for women with CFS and that their responses to exercise are distinctively different from those of sedentary controls.

Source: VanNess JM, Stevens SR, Bateman L, Stiles TL, Snell CR. Postexertional malaise in women with chronic fatigue syndrome. J Womens Health (Larchmt). 2010 Feb;19(2):239-44. doi: 10.1089/jwh.2009.1507. https://www.ncbi.nlm.nih.gov/pubmed/20095909

 

Subclassifying chronic fatigue syndrome through exercise testing

Abstract:

PURPOSE: The purpose of this study was to examine physiological responses of persons with chronic fatigue syndrome (CFS) to a graded exercise test.

METHODS: Cardiopulmonary exercise tests were performed on 189 patients diagnosed with CFS. Based on values for peak oxygen consumption, patients were assigned to one of four impairment categories (none, mild, moderate, and severe), using American Medical Association (AMA) guidelines. A one-way MANOVA was used to determine differences between impairment categories for the dependent variables of age, body mass index, percentage of predicted [OV0312]O(2), resting and peak heart rates, resting and peak systolic blood pressure, respiratory quotient (RQ), and rating of perceived exertion.

RESULTS: Significant differences were found between each impairment level for percentage of predicted [OV0312]O(2) and peak heart rate. Peak systolic blood pressure values for the “moderate,” and “severe” groups differed significantly from each other and both other groups. The more impaired groups had lower values. The no impairment group had a significantly higher peak RQ than each of the other impairment levels (all P < 0.001). Peak [OV0312]O(2) values were less than predicted for all groups. Compared with the males, the women achieved actual values for peak [OV0312]O(2) that were closer to their predicted values.

CONCLUSION: Despite a common diagnosis, the functional capacity of CFS patients varies greatly. Stratifying patients by function allows for a more meaningful interpretation of the responses to exercise and may enable differential diagnosis between subsets of CFS patients.

Comment in: Physiological factors limiting exercise performance in CFS. [Med Sci Sports Exerc. 2004]

 

Source: Vanness JM, Snell CR, Strayer DR, Dempsey L 4th, Stevens SR. Subclassifying chronic fatigue syndrome through exercise testing. Med Sci Sports Exerc. 2003 Jun;35(6):908-13. http://www.ncbi.nlm.nih.gov/pubmed/12783037