This study evaluates the correlation between the 6-min walking test (6MWT) with gases measurement, and the peak cardiopulmonary exercise testing (CPET) using incremental cycling with gases and workload measurement, in order to determine if the 6MWT detects impairment in exercise tolerance and if it avoids the post-exertional malaise that the peak CPET causes on decreasing levels of physical activity, in participants affected by chronic fatigue syndrome/ myalgic encephalomyelitis (CFS/ME). Physical activity level at baseline (usual activity, the parcipant will not be given any directions) will be recorded during 7 days, 24 hours/day. Afterwards, the 6MWT will be performed. After this test, the physical activity level will be collected again during 7 days, 24 hours/day. Peak CPET will be carried out 14 days after 6MWT to make sure that the basal levels are recovered, and finally, physical activity level will be collected again during 7 days, 24 hours/day.
Chronic fatigue syndrome/ myalgic encephalomyelitis presents with a significant deterioration of functional capacity, which seriously affects the quality of life. The peak or maximal incremental CPET is considered valid for the evaluation of exercise tolerance of those affected by CFS/ME, but its performance causes worsening of its symptomatology, decreasing its physical activity level after the test. It has not been verified whether the 6MWT (submaximal exercise test) with gases measurement is able to assess the exercise tolerance of those affected by SFC/EM without increasing their symptoms. So far, only the correlation between another submaximal test and a peak CPET in two different groups of participants have been analyzed and proven, which it makes necessary to check adequately whether there is a correlation by performing both tests on the same participants. In addition, it is necessary to compare the degree of worsening in physical activity level that both tests produce in participants, because they have not been objectively evaluated in any previous study. It could be useful to have a more innocuous and simple test for the assessment of exercise tolerance in CFS/ME in clinical practice, in order to evaluate the benefits of treatments like rehabilitation programs. 6MWT could respond to these characteristics because it reaches an identical value in peak VO2 than in the peak CPET in other pathologies and it generates less physical stress. This research will be developed with the utmost respect for individual human rights, according to the postulates accepted internationally by the United Nations and the European Commission (Helsinki Act of 1964 and the Oviedo Convention of 1997) and Regulation (EU) 2016/679 of the European Parliament and the Council of April 27, 2016 on Data Protection (RGPD). Participation in this study is entirely voluntary and does not imply any risk to health. Participants are entitled to refuse to participate or to leave the study at any time they choose. All information will be treated confidentially. If it is decided to publish the results of the study, in these publications will not include individual data or the names of the participants, only information considered globally will be included. This study has been approved in August 2018 by the Ethics and Research Committee of the La Paz University Hospital in Madrid (HULP Code: PI-3320). The sample sizes were calculated in order to find the significance of the Pearson linear correlation coefficient between two variables, for a unilateral hypothesis test according to the formula: n = \[Z1-α + Z1- β / ½ ln (1 + r / 1-r)\]\^2 + 3 and the largest has been chosen, which involve studying 22 participants. Taking into account the data of a previous study with participants of similar characteristics, a correlation of the parameters that set up the primary outcome, peak VO2 of r = 0.7 is assumed. An expected drop out in rate of 0.474 has been estimated from the data obtained in another related study. Accepting an alpha risk of 0.05 and a beta risk of 0.20 in a unilateral contrast, 22 participants are required to detect a positive correlation between the variables of the exercise tests, equal to or greater than those found in the study used as reference. This size will guarantee sufficient power to detect correlation in the purpose of the study. To guarantee this power, and since there is not enough information about the previous values, an intermediate analysis of the data, will be carried out in the middle of the study to recalculate the size of the final sample. The incidental sampling will be carried out according to a non-probabilistic system of consecutive cases of people diagnosed with CFS/ME. Data analysis / Statistical methods: 1. Descriptive: Descriptive analysis of all variables collected will be carried out. For quantitative data, centralization and dispersion measures will be calculated according to the distribution of each variable, such as mean, standard deviation, minimum and maximum median. The qualitative data will be described by absolute frequency and percentage. It will be checked if the variables are distributed normally by means of the Kolmogórov-Smirnov test for a single sample. 2. Correlation: A bivariate analysis will be performed to observe the association between the variables obtained in the 6MWT with gases measurement and those of the peak incremental CPET; between peak VO2 in the peak CPET and the distance achieved during the 6MWT; between peak VO2 and physical activity level at baseline and after each test; and between distance achieved in the 6MWT and physical activity level at baseline and after each test. In case of normality, the Pearson product-moment correlation coefficient will be used, and if any variable is not distributed normally, the Spearman correlation analysis will be used. 3. Linear regression: If some variables of the 6MWT are strongly correlated with the corresponding variables of the peak incremental CPET, a linear regression analysis will be performed to construct a regression equation for the prediction of the peak test performance. If necessary, a multiple linear regression analysis will be carried out to control the possible confounding variables: medication intake, time of disease evolution, quality of life, multidimensional fatigue, physical activity level at baseline, age, sex, profession, weight, height and body mass index. 4. Comparison: a comparative analysis of physical activity level at baseline and physical activity levels after each of the tests and between physical activity levels after each of the tests to compare decrease in physical activity level that generate both tests; using repeated measures ANOVA for related samples, if they meet the normal distribution or, if not, the Friedman test. In case of drop out, the data collected will be taken into account for the analysis. The analysis will assume a confidence level (1 - α) of 0.95 (significance level α = 0.05). The program SPSS® Statistics version 20.0 (SPSS Incorporation, Chicago, USA) will be used.
Study Type
OBSERVATIONAL
Enrollment
22
Escuela Universitaria de Fisioterapia de la ONCE
Madrid, Spain
RECRUITINGMean Value of the Peak VO2 in both Exercise Tests (6MWT and Peak CPET) in Milillitres/ Minute.
The portable spirometer Oxycon Mobile CPET from JaegerTM during 6MWT or the fixed spirometer Mijnhart Oxycon during peak CPET will be used for its measuring. Those instruments are validated. Mean and standard deviation will be calculated.
Time frame: 3 hours one day and 2 hours another day.
Mean Age of Participants in Years.
It will be measured with the date of birth, collected by data collection sheet. Mean and standard deviation will be calculated.
Time frame: 5 minutes.
Percentage of Males and Females.
It will be collected by data collection sheet. The percentage by gender will be calculated.
Time frame: 5 minutes.
Percentage of Participants´ Professions.
Profession is an open field, works, with or without salary. It will be collected by data collection sheet. The percentage by profession will be calculated.
Time frame: 5 minutes.
Mean of Time of Evolution of the Disease in Years.
It will be measured from the date of medical diagnosis. It will be collected by data collection sheet. Mean and standard deviation will be calculated.
Time frame: 5 minutes.
Percentage of Participants with Autonomic Dysfunction.
Options yes or not, presence of orthostatic postural tachycardias and/or alterations in the Heart Rate Variability. It will be collected by data collection sheet. Percentage of participants with or without autonomic dysfunction will be calculated.
Time frame: 5 minutes.
Percentage of Medications Intake.
The type of medications consumed is an open field. It will be collected by data collection sheet. Percentage by name of medication will be calculated.
Time frame: 10 minutes.
Mean of Weight in Kilograms.
It will be measured with the Pesperson precision scale. Range 200 grams-160 kilograms. Sensitivity 100 grams. Mean and standard deviation will be calculated.
Time frame: 5 minutes.
Mean of Height in Meters.
It will be measured with the Pesperson tape height meter, range 82-200cm. Sensitivity 1mm. Mean and standard deviation will be calculated.
Time frame: 5 minutes.
Mean of Body Mass Index in Kilograms/ Meters^2.
It is calculated by dividing the weight by the square of the height with the data obtained by the two previous outcomes. Mean and standard deviation will be calculated.
Time frame: 5 minutes.
Mean of Physical Activity Level at Baseline on ActivPAL 4 Micro.
The time that participant spends lying, sitting, standing or walking is measured 7 days, 24 hours/day before both exercise tests. It will be registered with the activity meter ActivPAL4 micro, which is validated as an instrument for detecting the activity and as a tool for estimating energy expenditure, and whose data are reproducible. Mean and standard deviation will be calculated.
Time frame: 7 days.
Mean Forced Vital Capacity (FVC) on Forced Spirometry in Milillitres.
It will be performed according to the American Thoracic Society protocol with three forced spirometries The portable spirometer Oxycon Mobile CPET from JaegerTM will be used for its measuring. Mean and standard deviation will be calculated.
Time frame: 15 minutes.
Mean Forced Expiratory Volume in the First Second (FEV1) on Forced Spirometry in Milillitres.
It will be performed according to the American Thoracic Society protocol with three forced spirometries. The portable spirometer Oxycon Mobile CPET from JaegerTM will be used for its measuring. Mean and standard deviation of FEV1 will be calculated.
Time frame: 15 minutes.
Mean Tiffeneau Index (FEV1 / FVC) on Forced Spirometry in Percentage.
It is calculated with the data provided by the two previous outcomes. Mean and standard deviation will be calculated.
Time frame: 15 minutes.
Mean Change from Baseline in Medications Dosage at After Both Exercise Tests (6MWT and Peak CPET).
Open field, daily medications dosage consumed before and after both tests. It will be collected by data collection sheet. Mean and standard deviation of the differences in the dose intake by type of medication will be calculated.
Time frame: 10 minutes on day and 10 minutes another day.
Mean Change from Baseline in Quality of Life Related to Health on SF-36v2 at After Both Exercise Tests.
It is measured from 0 to 100 points by the SF-36v2 (internal consistency value α of Cronbach of 0.94). This instrument provides a profile of health status, it is usually used in studies of research in the international field in the SFC/EM and a validated version is available in Spanish. Mean and standard deviation of the differences in the total questionnaire score and in the subscales of the questionnaire will be calculated.
Time frame: 20 minutes one day and 20 minutes another day.
Mean Change from Baseline in Multidimensional Fatigue on MIF:S at After Both Exercise Tests.
It is measured from 4 to 20 points with the Multidimensional Inventory of Fatigue in Spanish (MIF: S) (internal consistency value α of Cronbach of 0.91). Mean and standard deviation of the differences will be calculated.
Time frame: 10 minutes one day and 10 minutes another day.
Mean Change from Baseline in Physical Activity Level on ActivPAL 4 Micro at After each of the Exercise Tests.
The mean change in values of the time that participant spends lying, sitting, standing or walking is measured 7 days, 24 hours/day before both exercise tests and 7 days, 24 hours/day after the 6MWT and after the peak CPET. It will be registered with the activity meter ActivPAL4 micro, which is validated as an instrument for detecting the activity and as a tool for estimating energy expenditure, and whose data are reproducible.
Time frame: 21 days, in 3 periods of 7 days.
Mean Value of the Peak VO2 Body Weight Adjusted in 6MWT and in Peak CPET in Milillitres/ Kilograms/ Minute.
The portable spirometer Oxycon Mobile CPET from JaegerTM during 6MWT or the fixed spirometer Mijnhart Oxycon during peak CPET will be used for its measuring. Those instruments are validated. Mean and standard deviation will be calculated.
Time frame: 3 hours one day and 2 hours another day.
Percentage of Exercise Tolerance.
Class 1, 2, 3 or 4, classification of the impairment in exercise tolerance of the American Medical Association that is based on the values of percentage of peak VO2 body weight adjusted achieved during the exercise tests in accordance with the values of overall population. Percentage of participants in each class will be calculated.
Time frame: 3 hours one day and 2 hours another day.
Mean Distance on the 6MWT in Metres.
It will be obtained by the 6MWT with the American Thoracic Society protocol. Mean and standard deviation will be calculated.
Time frame: 3 hours.
Mean Peak Work Load on the Peak CPET in Watts.
It is measured through the Jaeger 900 cycle ergometer during the peak CPET with Snell CR. et al protocol. Mean and standard deviation of participants´ peak work load will be calculated.
Time frame: 2 hours.
Mean Change from Baseline in O2 Saturation on Spirometer at After each of the Exercise Tests.
It is measured in percentage with a portable spirometer Oxycon Mobile CPET of JaegerTM in the 6MWT or with a fixed spirometer Mijnhart Oxycon in the peak CPET. Mean and standard deviation will be calculated.
Time frame: 3 hours one day and 2 hours another day.
Mean Change from Baseline in Heart Rate on Pulsiometer or Electrocardiogram at Maximum Hearth Rate in both Exercise Tests.
It is measured in beats per minute with the heart rate sensor of the Polar TM31 band in 6MWT or with the 12-lead JaegerTM ECG in the peak CPET. Mean and standard deviation will be calculated.
Time frame: 3 hours one day and 2 hours another day.
Mean Change from Baseline in Heart Rate on Pulsiometer or Elecrocardiogram at After each of the Exercise Tests.
It is measured in beats per minute with the heart rate sensor of the Polar TM31 band in the 6MWT or with the 12-lead JaegerTM ECG in the peak CPET. Mean and standard deviation of the differences in hearth rate between baseline and after the 6MWT or peak CPET will be calculated.
Time frame: 3 hours one day and 2 hours another day.
Mean Change from Baseline in Blood Pressure on Tensiometer at After each of the Exercise Tests.
It is measured in mmHg with Suntech Oscar 2 tensionmeter in the 6MWT or Riester tensionmeter in the peak CPET. Mean and standard deviation will be calculated.
Time frame: 3 hours one day and 2 hours another day.
Mean Change from Baseline in Total Heart Rate Variability on Pulsiometer or Electrocardiogram at After each of the Exercise Tests.
It will be measured in milliseconds, standard deviation of all the variations in the time interval between heartbeats measured with the heart rate sensor of the TM31 Polar band in the 6MWT or with the 12-lead JaegerTM ECG in the peak CPET. Mean and standard deviation will be calculated.
Time frame: 3 hours one day and 2 hours another day.
Mean of the Maximum Heart Rate in Percentage.
It will be calculated with the value of the maximum heart rate reached and the maximum theoretical heart rate (220-patient's age) in the 6MWT and in the peak CPET. Mean and standard deviation will be calculated.
Time frame: 3 hours one day and 2 hours another day.
Mean Change from Baseline in VO2 on Spirometer at the Peak VO2 of the 6MWT and the Peak CPET.
It is measured in millilitres/ minute with a portable spirometer Oxycon Mobile CPET of JaegerTM in the 6MWT or with a fixed spirometer Mijnhart Oxycon in the peak CPET. Mean and standard deviation will be calculated.
Time frame: 3 hours one day and 2 hours another day.
Mean Change from Baseline in VO2 Body Weight Adjusted on Spirometer at the Peak VO2 of both Exercise Tests.
It is measured in millilitres/ minute /kilograms with a portable spirometer Oxycon Mobile CPET of JaegerTM in the 6MWT or with a fixed spirometer Mijnhart Oxycon in the peak CPET. Mean and standard deviation will be calculated.
Time frame: 3 hours one day and 2 hours another day.
Mean Change from Baseline in Oxygen Pulse on Spirometer at the Peak VO2 of both Exercise Tests.
It will be measured in millilitre/ cycle with a portable spirometer Oxycon Mobile CPET of JaegerTM in the 6MWT or with a fixed spirometer Mijnhart Oxycon in the peak CPET. Mean and standard deviation in differences in oxygen pulse at baseline and at peak VO2 in both exercise tests will be calculated.
Time frame: 3 hours one day and 2 hours another day.
Mean Change from Baseline in CO2 Production on Spirometer at the Peak VO2 of both Exercise Tests.
It will be measured in millilitre/ min with a portable spirometer Oxycon Mobile CPET of JaegerTM in the 6MWT or with a fixed spirometer Mijnhart Oxycon in the peak CPET. Mean and standard deviation in differences in CO2 production between baseline and peak VO2 in both exercise tests will be calculated.
Time frame: 3 hours one day and 2 hours another day.
Mean Change from Baseline in Respiratory Exchange Ratio (RER) at the Peak VO2 of both Exercise Tests.
It will be measured in millilitres/ minute, is calculated with the values of O2 consumption and CO2 production before tests and at peak VO2 of both exercise tests. Mean and standard deviation will be calculated.
Time frame: 3 hours one day and 2 hours another day.
Mean Change from Baseline in Minute Ventilation at the Peak VO2 of both Exercise Tests.
It will be measured in litres/ minute with a portable spirometer Oxycon Mobile CPET of JaegerTM in the 6MWT or with a fixed spirometer Mijnhart Oxycon in the peak CPET. Mean and standard deviation of differences between baseline and at peak VO2 of both exercise tests will be calculated.
Time frame: 3 hours one day and 2 hours another day.
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