Experiences of carers of youth, adult children and spouses with ME/CFS.

OBJECTIVES: The debilitating nature of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) means that family members often take on a caring role. This study compared the experiences of people caring for three groups: youth, young adults, spouses. METHODS: An opportunistic sample of 36 carers completed an online survey of open-ended questions asking about their experiences. Thematic analysis was used to consider the three sets of responses separately and Thematic Comparison was used to identify points of connection and disconnection across the sets. RESULTS: The themes identified were very similar to those identified in past studies. Two super-ordinate themes were identified: "Lack of knowledge and understanding" and "Holistic Impact". Though most sub-ordinate themes were evident across all three groups, important differences were found. The sub-ordinate themes "Caring Blindly", "Emotional and physical health cost", and "Impact on the whole family" were more evident amongst carers of youth while the theme "Worry for the future" was more evident from carers of young adults and spouses. DISCUSSION: Differences seemed to be related to both the time since diagnosis and the life stage. A longitudinal study would help to understand how carer experiences change over the life course of caring for someone with ME/CFS.

Does short-term whole-body vibration training affect arterial stiffness in chronic stroke? A preliminary study.

[Purpose] Previous studies have shown that stroke is associated with increased arterial stiffness that can be diminished by a program of physical activity. A novel exercise intervention, whole-body vibration (WBV), is reported to significantly improve arterial stiffness in healthy men and older sedentary adults. However, little is known about its efficacy in reducing arterial stiffness in chronic stroke. [Subjects and Methods] Six participants with chronic stroke were randomly assigned to 4 weeks of WBV training or control followed by cross-over after a 2-week washout period. WBV intervention consisted of 3 sessions of 5 min intermittent WBV per week for 4 weeks. Arterial stiffness (carotid arterial stiffness, pulse wave velocity [PWV], pulse and wave analysis [PWA]) were measured before/after each intervention. [Results] No significant improvements were reported with respect to carotid arterial stiffness, PWV, and PWA between WBV and control. However, carotid arterial stiffness showed a decrease over time following WBV compared to control, but this was not significant. [Conclusion] Three days/week for 4 weeks of WBV seems too short to elicit appropriate changes in arterial stiffness in chronic stroke. However, no adverse effects were reported, indicating that WBV is a safe and acceptable exercise modality for people with chronic stroke.

Human temperature regulation when given the opportunity to behave.

This study aimed to test the primary hypotheses that human thermoregulatory behavior is: (1) initiated before changes in rectal or esophageal temperatures; and (2) accompanied by indiscernible differences in sweating or shivering. This was achieved by placing nine, healthy, males in a situation where they were free to move between a cold (~8 °C) and a hot (~46 °C) environment. Upon behaving [i.e., move from cold to hot (C→H) or from hot to cold (H→C)], skin, rectal, and esophageal temperatures, indices of cutaneous vasomotor tone, metabolism and evaporation, and local and whole-body thermal discomfort were recorded. Rectal temperatures were similar at H→C (37.1 ± 0.2 °C) and C→H (37.1 ± 0.2 °C); yet esophageal temperatures were higher at C→H (36.9 ± 0.2 vs. 36.8 ± 0.2 °C). Skin temperature (C→H, 28.4 ± 0.9 vs. H→C, 35.0 ± 0.6 °C) and vasomotor tone were drastically different upon the decision to behave. Metabolic heat production was lower at H→C (79 ± 10 W/m(2)) than at C→H (101 ± 20 W/m(2)), yet there were no statistical differences in evaporative heat loss (C→H, 23 ± 33 W/m(2) vs. H→C, 52 ± 36 W/m(2)). Whole-body thermal discomfort was similar at C→H and H→C, yet there were inter-segmental differences. These findings indicate that skin temperature, not core temperature, plays a signaling role in the decision to behaviorally thermoregulate. However, this behavior does not occur in the complete absence of autonomic thermoregulatory responses.

Comparison study of treadmill versus arm ergometry.

The Bruce treadmill test is used worldwide to assess cardiovascular disease. However, because of the high increments of intensity between the stages of this test, it is not best suited to a number of populations. Therefore, the aim of the study was to determine the difference between physiological outcomes of the arm crank test and Bruce treadmill test and to provide a regression equation to account for this. Thirty subjects (16 men and 14 women) performed both an arm crank test and the Bruce treadmill test, on two separate days, in a random order. Peak values of oxygen uptake (VO(2) ), respiratory exchange ratio (RER), ventilation rate (V(E) ), heart rate (HR) and ratings of perceived exertion (RPE) were recorded. Arm crank VO(2peak) and peak V(E) were significantly lower compared with treadmill VO(2peak) and peak VE, in both men and women (P<0·001). Arm crank HR(peak) was significantly lower than treadmill HR(peak) in men (P<0·001). The following is the regression equation to estimate treadmill: VO(2peak) = 0·8*arm crank VO(2peak) + 0·019*body weight + 2·025*gender-0·038*gender*body weight + 0·852, with gender being '0' for males and '1' for females. This model has a r(2) of 0·832 (SEE = 0·471). This strong correlation indicates that an accurate prediction of treadmill VO(2peak) can be made by arm crank VO(2peak) , which is a good estimate of a person's maximal oxygen uptake (VO(2max) ). Therefore, the arm crank test can be of great importance for evaluation of cardiovascular disease in many people.

Peak cardiac power output in healthy, trained men.

Previous investigations into peak cardiac power output (CPO peak) have been limited to clinical populations and healthy, but non-athletic adults, and normative data on trained individuals would allow a greater understanding of this parameter. Therefore, we recruited eight healthy, well-trained male cyclists. Peak oxygen consumption ((.)VO2 peak) was assessed using an incremental ergometer test, and following a 40-min recovery period, peak cardiac output ((.)QT peak) was measured during a constant load test that elicited (.)VO2 peak (±5%) using the Defares CO2 rebreathing technique. CPO peak was calculated as described by Cooke et al. (1998). Mean (±SD) values during the constant load test were: (.)VO2 peak, 4.94 ± 0.41 l min⁻¹; (.)QT peak, 36.5 ± 3.7 l min⁻¹; mean arterial pressure, 123 ± 8 mmHg and CPO peak, 9.9 ± 1.0 W. These results demonstrate CPO peak in a well-trained population to be approximately twice those observed in healthy, but non-athletic adults. The current data provide useful information regarding the upper limits and possible 'trainability' of cardiac pumping capacity for sedentary and clinically compromised individuals.

Validity and reliability of short-term heart-rate variability from the Polar S810.

PURPOSE: : To assess the validity and the reliability of short-term resting heart-rate variability (HRV) measures obtained using the Polar S810 heart-rate monitor and accompanying software. METHODS: : Measures of HRV were obtained from 5-min R to R wave (RR) interval data for 19 males and 14 females during 10 min of quiet rest on three separate occasions at 1-wk intervals using the Polar S810. Criterion measures of HRV were obtained simultaneously using the CardioPerfect (CP; Medical Graphics Corporation, St Paul, MN) 12-lead ECG module. Measures of validity of the Polar S810 were estimated by regression analysis, and measures of reliability of both devices were estimated by analysis of change scores. Measures of the SD of normal-to-normal intervals (SDNN), the root mean square of successive differences (RMSSD), and the low-frequency (LF) and the high-frequency (HF) spectral power and their ratio (LF/HF) were analyzed after log transformation, whereas mean RR and LF and HF in normalized units were analyzed without transformation. RESULTS: : There were marginal differences between the Polar and the CP mean measures of HRV, and the uncertainty in the differences was small. The Polar S810 demonstrated high correlations (0.85-0.99) with CP for all measures of HRV indicating good to near-perfect validity. Except for the low- and the high-frequency normalized units, Polar S810 did not add any substantial technical error to the within-subject variability in the repeated measurements of HRV. CONCLUSION: : HRV measures obtained with the Polar S810 and accompanying software have no appreciable bias or additional random error in comparison with criterion measures, but the measures are inherently unreliable over a 1-wk interval. Reliability of HRV from longer (e.g., 10 min) and/or consecutive 5-min RR recordings needs to be investigated with the Polar and criterion instruments.

Levels of agreement for RR intervals and short-term heart rate variability obtained from the Polar S810 and an alternative system.

The aim of this study was to assess the agreement between HRV measures derived from a time series of RR intervals recorded by a standard 12-lead ECG (CP) and a commercially available RR interval recorder (S810). Thirty-three participants (19 males) (median age 36, range 20-63) underwent simultaneous, 5-min, supine RR-interval recordings. Each RR interval time series was analysed using the software supplied with the recording equipment. Two comparisons were then made. First, a comparison of RR interval data recording and editing only was made. Second, comparisons were made for measures of HRV derived from edited RR interval data. Agreement between RR intervals and standard HRV measures were assessed using intraclass correlation coefficient and limits of agreement. Agreement of HRV measures derived from RR intervals recorded and edited by individual systems was not acceptable. Agreement analyses for the number of RR intervals recorded and edited by each systems software showed excellent intraclass correlation coefficients (ICC lower 95% CI > 0.75) and acceptably narrow limits of agreement (LoA). These data indicate that the number of RR intervals recorded by S810 can agree well those recorded from a standard 12-lead ECG. This is true even after application of system specific data editing procedures. Commercial RR-interval recorders may offer a simple, inexpensive alternative to full 12-lead ECG in the recording and editing of RR intervals for subsequent HRV analysis in healthy populations.

Comparison of cardiac output determined by different rebreathing methods at rest and at peak exercise.

Several rebreathing methods are available for cardiac output (Q (T)) measurement. The aims of this study were threefold: first, to compare values for resting Q (T) produced by the equilibrium-CO(2), exponential-CO(2) and inert gas-N(2)O rebreathing methods and, second, to evaluate the reproducibility of these three methods at rest. The third aim was to assess the agreement between estimates of peak exercise Q (T) derived from the exponential and inert gas rebreathing methods. A total of 18 healthy subjects visited the exercise laboratory on different days. Repeated measures of Q (T), measured in a seated position, were separated by a 5 min rest period. Twelve participants performed an incremental exercise test to determine peak oxygen consumption. Two more exercise tests were used to measure Q (T) at peak exercise using the exponential and inert gas rebreathing methods. The exponential method produced significantly higher estimates at rest (averaging 10.9 l min(-1)) compared with the equilibrium method (averaging 6.6 l min(-1)) and the inert gas rebreathing method (averaging 5.1 l min(-1); P < 0.01). All methods were highly reproducible with the exponential method having the largest coefficient of variation (5.3%). At peak exercise, there were non-significant differences between the exponential and inert gas rebreathing methods (P = 0.14). The limits of agreement were -0.49 to 0.79 l min(-1). Due to the ability to evaluate the degree of gas mixing and to estimate intra-pulmonary shunt, we believe that the inert gas rebreathing method has the potential to measure Q (T) more precisely than either of the CO(2) rebreathing methods used in this study. At peak exercise, the exponential and inert gas rebreathing methods both showed acceptable limits of agreement.

Lack of agreement between gas exchange variables measured by two metabolic systems.

The purpose of this study was to assess the agreement and consistency between gas exchange variables measured by two online metabolic systems during an incremental exercise test. After obtaining local ethics approval and informed consent, 15 healthy subjects performed an incremental exercise test to volitional fatigue using the Bruce protocol. The Innocor (Innovision, Denmark) and CardiO2 (Medical Graphics, USA) systems were placed in series, with the Innocor mouthpiece attached to the pneumotach of the CardiO2. Metabolic data were analysed during the last 30 seconds of each stage and at peak exercise. There were non- significant differences (p > 0.05) between the two systems in estimation of oxygen consumption (VO2) and in minute ventilation (VE). Mean Cronbach's alpha for VO2 and VE were 0.88 and 0.92. The Bland-Altman analysis revealed that limits of agreement were -0.52 to 0.55 l.min(-1) for VO2, and -8.74 to 10.66 l.min(-1) for VE. Carbon dioxide production (VCO2) and consequently respiratory exchange ratio (RER) measured by the Innocor were significantly lower (p < 0.05) through all stages. The CardiO2 measured fraction of expired carbon dioxide (FeCO2) significantly higher (p < 0.05). The limits of agreement for VO2 and VE are wide and unacceptable in cardio-pulmonary exercise testing. The Innocor reported VCO2 systematically lower. Therefore the Innocor and CardiO2 metabolic systems cannot be used interchangeably without affecting the diagnosis of an individual patient. Results from the present study support previous suggestion that considerable care is needed when comparing metabolic data obtained from different automated metabolic systems. Key pointsThere is general concern regarding the limited knowledge available about the accuracy of a number of commercially available systems.Demonstrated limits of agreement between key gas exchange variables (oxygen consumption and minute ventilation) as measured by the two metabolic systems were wide and unacceptable in cardio-pulmonary exercise testing.Considerable care is needed when comparing metabolic data obtained from different automated metabolic systems.

The impact of short term supervised and home-based walking programmes on heart rate variability in patients with peripheral arterial disease.

The aims of the study were to determine whether heart rate variability (HRV) measured at rest and during exercise could be altered by an exercise training programme designed to increase walking performance in patients with peripheral arterial disease. Forty-four volunteers were randomised into 12 weeks of either: supervised walking training twice weekly for 30 min at 75% VO2peak (SU), home-based walking training sessions: twice weekly, 30 min per week (HB) or no exercise (CT). HRV measures were calculated from a 5-min resting ECG. Each patient then underwent maximal, graded exercise treadmill testing. All measures were repeated after 12 weeks. The SU group showed significantly (p < 0.001) increased maximal walking time (MWT) but no change in VO2peak. There were no statistically significant changes in any of the measures of HRV in any group. Effect sizes for change in HRV measures were all very small and in some cases negative. Improved walking performance was not accompanied by central cardiorespiratory or neuroregulatory adaptations in the present study. The lack of any change in HRV was possibly due to either the low intensity or discontinuous nature of exercise undertaken. Key pointsIt is known that exercise can positively influence heart rate variability in some cardiac patients.It is known that exercise can increase walking performance in peripheral vascular disease patients.Exercise training improved walking performance in peripheral vascular disease patients but HRV was unaltered.This may be due to low overall physiological demands on the cardiovascular system or the intermittent nature of the exercise.

Physiological range of peak cardiac power output in healthy adults.

AIMS: The purpose of this study was to indicate the normal range for peak cardiac power output (CPO(peak)) in healthy adults and to explore age- and sex-related variations of this parameter. METHODS AND RESULTS: Using the non-invasive exponential CO(2) rebreathing technique [J.G. Defares, J Appl Physiol13 (1958) 159], cardiac output was measured at an exercise intensity determined to coincide with > or =95% of peak oxygen consumption in 102 healthy adults (mean +/- SD, age 43 +/- 13 years, body mass 74 +/- 13 kg). Peak cardiac power was then computed from measurements of peak cardiac output (Q(Tpeak)) and peak mean arterial pressure (MAP(peak)) using the equation described by Cooke et al. [Heart79 (1998) 289]. Peak oxygen consumption in the study population was 2.42 (+/-0.74) l min(-1) and subjects achieved 101 +/- 7% of this value during the measurement of . was 17.3 (+/-4) l min(-1), and CPO(peak) was computed as 4.5 (+/-1.2) W. CPO(peak) ranged from 3.11 to 7.94 W in men and 2.53 to 5.57 W in women. Additionally, ageing appears to be associated with a significant loss of peak cardiac power in men that is not apparent in women. CONCLUSION: Although the sample size remains moderate, the CPO values attained were normally distributed and these values provide a useful indication of the normal range for CPO(peak) in healthy adults.