Task-related oxygen uptake and symptoms during activities of daily life in CHF patients and healthy subjects

Burn size and environmental conditions modify thermoregulatory responses to exercise in burn survivors

This project tested the hypothesis that burn survivors can perform mild/moderate-intensity exercise in temperate and hot environments without excessive elevations in core body temperature. Burn survivors with low (23 ± 5%TBSA; N = 11), moderate (40 ± 5%TBSA; N = 9), and high (60 ± 8%TBSA; N = 9) burn injuries performed 60 minutes of cycle ergometry exercise (72 ± 15 watts) in a 25°C and 23% relative humidity environment (ie, temperate) and in a 40°C and 21% relative humidity environment (ie, hot). Absolute gastrointestinal temperatures (TGI) and changes in TGI (ΔTGI) were obtained. Participants with an absolute TGI of >38.5°C and/or a ΔTGI of >1.5°C were categorized as being at risk for hyperthermia. For the temperate environment, exercise increased ΔTGI in all groups (low: 0.72 ± 0.21°C, moderate: 0.42 ± 0.22°C, and high: 0.77 ± 0.25°C; all P < .01 from pre-exercise baselines), resulting in similar absolute end-exercise TGI values (P = .19). Importantly, no participant was categorized as being at risk for hyperthermia, based upon the aforementioned criteria. For the hot environment, ΔTGI at the end of the exercise bout was greater for the high group when compared to the low group (P = .049). Notably, 33% of the moderate cohort and 56% of the high cohort reached or exceeded a core temperature of 38.5°C, while none in the low cohort exceeded this threshold. These data suggest that individuals with a substantial %TBSA burned can perform mild/moderate intensity exercise for 60 minutes in temperate environmental conditions without risk of excessive elevations in TGI. Conversely, the risk of excessive elevations in TGI during mild/moderate intensity exercise in a hot environment increases with the %TBSA burned.

Relationship between VO2peak, VO2 Recovery Kinetics, and Muscle Function in Older Adults

INTRODUCTION

The efficiency of the cardiovascular system to recover following an exercise bout is measured by oxygen (VO2) recovery kinetics. In older adults with a chronic disease, a higher aerobic capacity (VO2peak) and faster VO2 recovery kinetics are associated with higher muscle strength and physical capacity. Yet, this relationship in healthy older adults remains unclear. The aim of this cross-sectional study was to determine whether a higher VO2peak and faster VO2 recovery kinetics are associated with higher muscle strength and physical performance in healthy community-dwelling older adults.

METHODS

Thirty-five healthy older adults (female 25/male 10, mean age 73 ± 6 years) performed a graded exercise test on a cycle ergometer. VO2peak and VO2 recovery kinetics were assessed through gas exchange analysis. Muscle strength was determined by maximal leg (one-repetition maximum on leg press; 1RM) and grip strength, and physical performance was determined by the physical performance test (PPT) which assessed gait speed, stair ascent and descent, and timed up-and-go.

RESULTS

Higher VO2peak was associated with stronger leg (r = 0.59, p < 0.001) and grip strength (r = 0.39, p < 0.03), but no relationship to PPT (p > 0.05). There was also no relationship between VO2 recovery kinetics and leg and grip strength or PPT (p > 0.05).

CONCLUSION

In healthy community-dwelling older adults, VO2peak, but not VO2 recovery kinetics, is associated with muscle strength. This suggests that muscle strength may be an important factor related to aerobic capacity that could assist in identifying older adults who should be prioritized for resistance training.

Telerehabilitation in patients with recent hospitalisation due to acute decompensated heart failure: protocol for the Tele-ADHF randomised controlled trial

BACKGROUND

Cardiac rehabilitation in patients with chronic heart failure (CHF) has favourable effects on exercise capacity, the risk at hospital (re-)admission and quality of life. Although cardiac rehabilitation is generally recommended it is still under-utilised in daily clinical practice, particularly in frail elderly patients after hospital admission, mainly due to low referral and patient-related barriers. Cardiac telerehabilitation (CTR) has the potential to partially solve these barriers. The purpose of this study is to evaluate the effects of CTR as compared to standard remote care after hospital admission on physical functional capacity in CHF patients.

METHODS

In this randomised controlled trial, 64 CHF patients will be recruited during hospitalisation for acute decompensated heart failure, and randomised to CTR combined with remote patient management (RPM) or RPM alone (1:1). All participants will start with RPM after hospital discharge for early detection of deterioration, and will be up titrated to optimal medical therapy before being randomised. CTR will start after randomisation and consists of an 18-week multidisciplinary programme with exercise training by physical and occupational therapists, supported by a (remote) technology-assisted dietary intervention and mental health guiding by a physiologist. The training programme consists of three centre-based and two home-based video exercise training sessions followed by weekly video coaching. The mental health and dietary programme are executed using individual and group video sessions. A wrist-worn device enables remote coaching by the physical therapist. The web application is used for promoting self-management by the following modules: 1) goal setting, 2) progress tracking, 3) education, and 4) video and chat communication. The primary outcome measure is physical functional capacity evaluated by the Short Physical Performance Battery (SPPB) score. Secondary outcome measures include frailty scoring, recovery after submaximal exercise, subjective health status, compliance and acceptance to the rehabilitation programme, and readmission rate.

DISCUSSION

The Tele-ADHF trial is the first prospective randomised controlled trial designed for evaluating the effects of a comprehensive combined RPM and CTR programme in recently hospitalised CHF patients. We hypothesize that this intervention has superior effects on physical functional capacity than RPM alone.

TRIAL REGISTRATION

Netherlands Trial Registry (NTR) NL9619, registered 21 July 2021.

Relative Aerobic Load of Daily Activities After Stroke

OBJECTIVE

Individuals after stroke are less active, experience more fatigue, and perform activities at a slower pace than peers with no impairments. These problems might be caused by an increased aerobic energy expenditure during daily tasks and a decreased aerobic capacity after stroke. The aim of this study was to quantify relative aerobic load (ie, the ratio between aerobic energy expenditure and aerobic capacity) during daily-life activities after stroke.

METHODS

Seventy-nine individuals after stroke (14 in Functional Ambulation Category [FAC] 3, 25 in FAC 4, and 40 in FAC 5) and 22 peers matched for age, sex, and body mass index performed a maximal exercise test and 5 daily-life activities at a preferred pace for 5 minutes. Aerobic energy expenditure (mL O2/kg/min) and economy (mL O2/kg/unit of distance) were derived from oxygen uptake ($\dot{\mathrm{V}}{\mathrm{O}}_2$). Relative aerobic load was defined as aerobic energy expenditure divided by peak aerobic capacity (%$\dot{\mathrm{V}}{\mathrm{O}}_2$peak) and by $\dot{\mathrm{V}}{\mathrm{o}}_2$ at the ventilatory threshold (%$\dot{\mathrm{V}}{\mathrm{o}}_2$-VT) and compared in individuals after stroke and individuals with no impairments.

RESULTS

Individuals after stroke performed activities at a significantly higher relative aerobic load (39%-82% $\dot{\mathrm{V}}{\mathrm{o}}_2$peak) than peers with no impairments (38%-66% $\dot{\mathrm{V}}{\mathrm{o}}_2$peak), despite moving at a significantly slower pace. Aerobic capacity in individuals after stroke was significantly lower than that in peers with no impairments. Movement was less economical in individuals after stroke than in peers with no impairments.

CONCLUSION

Individuals after stroke experience a high relative aerobic load during cyclic daily-life activities, despite adopting a slower movement pace than peers with no impairments. Perhaps individuals after stroke limit their movement pace to operate at sustainable relative aerobic load levels at the expense of pace and economy.

IMPACT

Improving aerobic capacity through structured aerobic training in a rehabilitation program should be further investigated as a potential intervention to improve mobility and functioning after stroke.

Cardiac remodeling in well-healed burn survivors after 6 months of unsupervised progressive exercise training

Aerobic exercise is important in the rehabilitation of individuals with prior burn injuries, but no studies have examined whether adult burn survivors demonstrate cardiac remodeling to long-term aerobic exercise training. In this study, we tested the hypothesis that 6 months of progressive exercise training improves cardiac magnetic resonance imaging-based measures of cardiac structure and function in well-healed burn survivors. Secondary analyses explored relations between burn surface area and changes in cardiac structure in the cohort of burn survivors. V̇o2peak assessments and cardiac magnetic resonance imaging were performed at baseline and following 6 months of progressive exercise training from 19 well-healed burn survivors and 10 nonburned control participants. V̇o2peak increased following 6 months of training in both groups (Control: Δ5.5 ± 5.8 mL/kg/min; Burn Survivors: Δ3.2 ± 3.6 mL/kg/min, main effect of training, P < 0.001). Left ventricle (LV) mass (Control: Δ1.7 ± 3.1 g/m2; Burn survivors: Δ1.8 ± 2.7 g/m2), stroke volume (Control: Δ5.8 ± 5.2 mL/m2; Burn Survivors: Δ2.8 ± 4.2 mL/m2), and ejection fraction (Control: Δ2.4 ± 4.0%; Burn Survivors: Δ2.2 ± 4.3%) similarly increased following 6 months of exercise training in both cohorts (main effect of training P < 0.05 for all indexes). LV end-diastolic volume increased in the control group (Δ6.5 ± 4.5 mL/m2) but not in the cohort of burn survivors (Δ1.9 ± 2.7 mL/m2, interaction, P = 0.040). Multiple linear regression analyses revealed that burn surface area had little to no effect on changes in ventricular mass or end-diastolic volumes in response to exercise training. Our findings provide initial evidence of physiological cardiac remodeling, which is not impacted by burn size, in response to exercise training in individuals with well-healed burn injuries.NEW & NOTEWORTHY Aerobic exercise is important in the rehabilitation of individuals with prior burn injuries, but no studies have examined whether adult burn survivors demonstrate cardiac remodeling to long-term aerobic exercise training. In this study, we tested the hypothesis that 6 months of progressive exercise training would improve cardiac magnetic resonance imaging-based measures of cardiac structure and function in well-healed burn survivors. Our findings highlight the ability of exercise training to modify cardiac structure and function in well-healed burn survivors and nonburned sedentary controls alike.

The Impact of Cardiac Rehabilitation on Activities of Daily Life in Elderly Patients With Heart Failure

Background: In elderly chronic heart failure (HF) patients, activities of daily living (ADLs) require the use of a high proportion of patients’ peak aerobic capacity, heart rate, and ventilation.

Objectives: To assess the effects of short-term comprehensive cardiac rehabilitation (CR) on the metabolic requirement of ADLs in elderly patients with chronic HF.

Methods: The study population comprised 99 elderly chronic HF patients (mean age 72 ± 5 years, 80% male, 61% ejection fraction <40%, mean NT-proBNP 2,559 ± 4,511 pg/ml) participating in a short-term (mean days 19 ± 7) residential CR program. Before and after CR, participants, while wearing a portable ergospirometer, performed a standardized ADL battery: ADL1 (getting dressed), ADL2 (folding 8 towels), ADL3 (putting away 6 bottles), ADL4 (making a bed), ADL5 (sweeping the floor for 4 min), ADL6 (climbing 1 flight of stairs carrying a 1.5 Kg load), and ADL7 (a standard 6-min walking test).

Results: After CR, task-related oxygen uptake did not change in any of the domestic ADLs. Notably, there was a significant decrease in the cumulative time required to perform ADLs (ADL 1–4 and ADL6; from 412 ± 147 to 388 ± 141 s, p = 0.001) and a reduction in maximal heart rate in ADL1 and 3 (p = 0.005 and p = 0.027, respectively). Changes occurred in the 6MWT with an increase in oxygen uptake (p = 0.005) and in the distance covered (p < 0.001) and a significant decrease in the Borg scale of dyspnea (p = 0.004).

Conclusion: Elderly patients with chronic heart failure who are engaged in a short-term residential CR program improve the performance of routine ADLs.

Edward F. Adolph Distinguished Lecture. It's more than skin deep: thermoregulatory and cardiovascular consequences of severe burn injuries in humans

Each year, within the United States, tens of thousands of individuals are hospitalized for burn-related injuries. The treatment of deep burns often involves skin grafts to accelerate healing and reduce the risk of infection. The grafting procedure results in a physical disruption between the injured and subsequently debrided host site and the skin graft placed on top of that site. Both neural and vascular connections must occur between the host site and the graft for neural modulation of skin blood flow to take place. Furthermore, evaporative cooling from such burn injured areas is effectively absent, leading to greatly impaired thermoregulatory responses in individuals with large portions of their body surface area burned. Hospitalization following a burn injury can last weeks to months, with cardiovascular and metabolic consequences of such injuries having the potential to adversely affect the burn survivor for years postdischarge. With that background, the objectives of this article are to discuss 1) our current understanding of the physiology and associated consequences of skin grafting, 2) the effects of skin grafts on efferent thermoregulatory responses and the associated consequences pertaining to whole body thermoregulation, 3) approaches that may reduce the risk of excessive hyperthermia in burn survivors, 4) the long-term cardiovascular consequences of burn injuries, and 5) the extent to which burn survivors can "normalize" otherwise compromised cardiovascular responses. Our primary objective is to guide the reader toward an understanding that severe burn injuries result in significant physiological consequences that can persist for years after the injury.

Effects of resistance training on metabolic and cardiovascular responses to a maximal cardiopulmonary exercise test in Parkinson`s disease

Objective:

To evaluate the effects of resistance training on metabolic and cardiovascular responses during maximal cardiopulmonary exercise testing in patients with Parkinson’s disease.

Methods:

Twenty-four patients with Parkinson’s disease (modified Hoehn and Yahr stages 2 to 3) were randomly assigned to one of two groups: Control or Resistance Training. Patients in the Resistance Training Group completed an exercise program consisting of five resistance exercises (two to four sets of six to 12 repetitions maximum per set) twice a week. Patients in the Control Group maintained their usual lifestyle. Oxygen uptake, systolic blood pressure and heart rate were assessed at rest and during cycle ergometer-based maximal cardiopulmonary exercise testing at baseline and at 12 weeks. Assessments during exercise were conducted at absolute submaximal intensity (slope of the linear regression line between physiological variables and absolute workloads), at relative submaximal intensity (anaerobic threshold and respiratory compensation point) and at maximal intensity (maximal exercise). Muscle strength was also evaluated.

Results:

Both groups had similar increase in peak oxygen uptake after 12 weeks of training. Heart rate and systolic blood pressure measured at absolute and relative submaximal intensities and at maximal exercise intensity did not change in any of the groups. Muscle strength increased in the Resistance Training but not in the Control Group after 12 weeks.

Conclusion:

Resistance training increases muscle strength but does not change metabolic and cardiovascular responses during maximal cardiopulmonary exercise testing in patients with Parkinson’s disease without cardiovascular comorbidities.

Effect of Aerobic Exercise on Cardiopulmonary Responses and Predictors of Change in Individuals With Parkinson's Disease

OBJECTIVE

To determine the effect of aerobic exercise on maximal and submaximal cardiopulmonary responses and predictors of change in individuals with Parkinson's disease (PD).

DESIGN

Single-center, parallel-group, rater-blind study.

SETTING

Research laboratory.

PARTICIPANTS

Individuals with mild to moderate PD (N=100).

INTERVENTION

Participants were enrolled in a trial evaluating the effect of cycling on PD and randomized to either voluntary exercise (VE), forced exercise (FE), or a no exercise control group. The exercise groups were time and intensity matched and exercised 3×/wk for 8 weeks on a stationary cycle.

MAIN OUTCOME MEASURES

Cardiopulmonary responses were collected via gas analysis during a maximal graded exercise test at baseline and post intervention.

RESULTS

Exercise attendance was 97% and 93% for the FE and VE group, respectively. Average exercise heart rate reserve was 67%±11% for FE and 70%±10% for VE. No significant difference was present for change in peak oxygen consumption (VO₂peak) post intervention, even though the FE group had a 5% increase in VO₂peak. Both the FE and VE groups had significantly higher percentage oxygen consumption per unit time (V˙o₂) at ventilator threshold (VT) than the control group compared with baseline values (P=.04). Mean V˙O₂ at VT was 5% (95% CI, 0.1%-11%) higher in the FE group (P=.04) and 7% (2%, 12%) higher in VE group compared with controls. A stepwise linear regression model revealed that lower age, higher exercise cadence, and lower baseline VO₂peak were most predictive of improved VO₂peak. The overall model was found to be significant (P<.01).

CONCLUSIONS

Peak and submaximal cardiopulmonary function may improve after aerobic exercise in individuals with PD. Lower age, higher exercise cadence, and lower baseline VO₂peak were most predictive of improved VO₂peak in this exercise cohort. The improvements observed in aerobic capacity were gained after a relatively short aerobic cycling intervention.

How Patients With Heart Failure Perform Daily Life Activities

Background:

Cardiopulmonary exercise test and 6-minute walking test are frequently used tools to evaluate physical performance in heart failure (HF), but they do neither represent activities of daily living (ADLs) nor fully reproduce patients’ symptoms. We assessed differences in task oxygen uptake, both as absolute value and as percentage of peak oxygen consumption (peakVO 2 ), ventilation efficiency (VE/VCO 2 ratio), and dyspnea intensity (Borg scale) in HF and healthy subjects during standard ADLs and other common physical actions.

Methods:

Healthy and HF subjects (ejection fraction <45%, stable conditions) underwent cardiopulmonary exercise test. All of them, carrying a wearable metabolic cart, performed a 6-minute walking test, two 4-minute treadmill exercises (at 2 and 3 km/h), and ADLs: ADL1 (getting dressed), ADL2 (folding 8 towels), ADL3 (putting away 6 bottles), ADL4 (making a bed), ADL5 (sweeping the floor for 4 minutes), ADL6 (climbing 1 flight of stairs carrying a load).

Results:

Sixty patients with HF (age 65.2±12.1 years; ejection fraction 30.4±6.7%, peakVO 2 14.2±4.0 mL/[min·kg]) and 40 healthy volunteers (58.9±8.2 years, peakVO 2 28.1±7.4 mL/[min·kg]) were enrolled. For each exercise, patients showed higher VE/VCO 2 ratio, percentage of peakVO 2 , and Borg scale value than controls, while absolute values of task oxygen uptake and exercise duration were lower and higher, respectively, in all activities, except for treadmill (fixed execution time and intensity). Differently from Borg Scale data, metabolic values and exercise time length changed in parallel with HF severity, except for ADL duration in very short (ADL3) and composite (ADL1) activities. Borg scale values correlated with percentage of peakVO 2 .

Conclusions:

During ADLs, patients self-regulated activities in parallel with HF severity by decreasing intensity (VO 2 ) and prolonging the effort.

Physical activity assessment by accelerometry in people with heart failure

Background

International guidelines for physical activity recommend at least 150 min per week of moderate-to-vigorous physical activity (MVPA) for adults, including those with cardiac disease. There is yet to be consensus on the most appropriate way to categorise raw accelerometer data into behaviourally relevant metrics such as intensity, especially in chronic disease populations. Therefore the aim of this study was to estimate acceleration values corresponding to inactivity and MVPA during daily living activities of patients with heart failure (HF), via calibration with oxygen consumption (VO₂) and to compare these values to previously published, commonly applied PA intensity thresholds which are based on healthy adults.

Methods

Twenty-two adults with HF (mean age 71 ± 14 years) undertook a range of daily living activities (including laying down, sitting, standing and walking) whilst measuring PA via wrist- and hip-worn accelerometers and VO₂ via indirect calorimetry. Raw accelerometer output was used to compute PA in units of milligravity (mg). Energy expenditure across each of the activities was converted into measured METs (VO₂/resting metabolic rate) and standard METs (VO₂/3.5 ml/kg/min). PA energy costs were also compared with predicted METs in the compendium of physical activities. Location specific activity intensity thresholds were established via multilevel mixed effects linear regression and receiver operator characteristic curve analysis. A leave-one-out method was used to cross-validate the thresholds.

Results

Accelerometer values corresponding with intensity thresholds for inactivity (< 1.5METs) and MVPA (≥3.0METs) were > 50% lower than previously published intensity thresholds for both wrists and waist accelerometers (inactivity: 16.7 to 18.6 mg versus 45.8 mg; MVPA: 43.1 to 49.0 mg versus 93.2 to 100 mg). Measured METs were higher than both standard METs (34–35%) and predicted METs (45–105%) across all standing and walking activities.

Conclusion

HF specific accelerometer intensity thresholds for inactivity and MVPA are lower than previously published thresholds based on healthy adults, due to lower resting metabolic rate and greater energy expenditure during daily living activities for HF patients.

Trial registration

Clinical trials.gov NCT03659877, retrospectively registered on September 6th 2018.

Palliative care needs assessment in chronic heart failure

PURPOSE OF REVIEW

The unmet palliative care needs of patients with chronic heart failure (CHF) are well known. Palliative care needs assessment is paramount for timely provision of palliative care. The present review provides an overview of palliative care needs assessment in patients with CHF: the role of prognostic tools, the role of the surprise question, and the role of palliative care needs assessment tools.

RECENT FINDINGS

Multiple prognostic tools are available, but offer little guidance for individual patients. The surprise question is a simple tool to create awareness about a limited prognosis, but the reliability in CHF seems less than in oncology and further identification and assessment of palliative care needs is required. Several tools are available to identify palliative care needs. Data about the ability of these tools to facilitate timely initiation of palliative care in CHF are lacking.

SUMMARY

Several tools are available aiming to facilitate timely introduction of palliative care. Focus on identification of needs rather than prognosis appears to be more fitting for people with CHF. Future studies are needed to explore whether and to what extent these tools can help in addressing palliative care needs in CHF in a timely manner.

Timely recognition of palliative care needs of patients with advanced chronic heart failure: a pilot study of a Dutch translation of the Needs Assessment Tool: Progressive Disease - Heart Failure (NAT:PD-HF)

BACKGROUND

The Needs Assessment Tool: Progressive Disease - Heart Failure (NAT:PD-HF) was developed to identify and triage palliative care needs in patients with chronic heart failure. A Dutch version is currently lacking.

AIMS

The aim of this study was to investigate the feasibility and acceptability of a Dutch NAT:PD-HF in chronic heart failure outpatients; and to gain preliminary data regarding the effect of the NAT:PD-HF on palliative care referral, symptoms, health status, care dependency, caregiver burden and advance directives.

METHODS

A mixed methods study including 23 outpatients with advanced chronic heart failure and 20 family caregivers was performed. Nurses conducted patient consultations using a Dutch translation of the NAT:PD-HF and rated acceptability. Before this visit and 4 months later, symptoms, health status, performance status, care dependency, caregiver burden and recorded advance directives were assessed. A focus group with participating nurses discussed barriers and facilitators towards palliative care needs assessment.

RESULTS

Acceptability was rated as 7 (interquartile range 6-7 points) on a 10-point scale. All patients had palliative care needs. In 48% actions were taken, including two patients referred to palliative care. Symptoms, performance status, care dependency, caregiver burden and advance directives were unchanged at 4 months, while health status deteriorated in patients completing follow-up ( n=17). Barriers towards palliative care needs assessment included feeling uncomfortable to initiate discussions and concerns about the ability to address palliative care needs.

CONCLUSIONS

The NAT:PD-HF identified palliative care needs in all participants, and triggered action to address these in half. However, training in palliative care communication skills as well as palliative care interventions should accompany the introduction of a palliative care needs assessment tool.

NETHERLANDS NATIONAL TRIAL REGISTER (NTR)

5616. http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=5616.

Skeletal muscle fiber characteristics in patients with chronic heart failure: impact of disease severity and relation with muscle oxygenation during exercise

INTRODUCTION

Skeletal muscle function in patients with heart failure and reduced ejection fraction (HFrEF) greatly determines exercise capacity. However, reports on skeletal muscle fiber dimensions, fiber capillarization, and their physiological importance are inconsistent.

METHODS

Twenty-five moderately-impaired patients with HFrEF and 25 healthy control (HC) subjects underwent muscle biopsy sampling. Type I and type II muscle fiber characteristics were determined by immunohistochemistry. In patients with HFrEF, enzymatic oxidative capacity was assessed, and pulmonary oxygen uptake (VO₂) and skeletal muscle oxygenation during maximal and moderate-intensity exercise were measured using near-infrared spectroscopy.

RESULTS

While muscle fiber cross-sectional area (CSA) was not different between patients with HFrEF and HC, percentage of type I fibers was higher in HC (46±15% versus 37±12%, respectively, P=0.041). Fiber type distribution and CSA were not different between patients in New York Heart Association (NYHA) class II and III. Type I muscle fiber capillarization was higher in HFrEF compared with controls (capillary-to-fiber perimeter exchange (CFPE) index: 5.70±0.92 versus 5.05±0.82, respectively, P=0.027). Patients in NYHA class III had slower VO₂ and muscle deoxygenation kinetics during onset of exercise, and lower muscle oxidative capacity than those in class II (P<0.05). Also, fiber capillarization was lower, but not compared with HC. Higher CFPE index was related to faster deoxygenation (r_spearman=-0.682, P=0.001), however, not to muscle oxidative capacity (r=-0.282, P=0.216).

CONCLUSIONS

Type I muscle fiber capillarization is higher in HFrEF compared with HC, but not in patients with greater exercise impairment. Greater capillarization may positively affect VO₂ kinetics by enhancing muscle oxygen diffusion.

Oxygen uptake during functional activities after stroke-Reliability and validity of a portable ergospirometry system

Background

People with stroke have a low peak aerobic capacity and experience increased effort during performance of daily activities. The purpose of this study was to examine test-retest reliability of a portable ergospirometry system in people with stroke during performance of functional activities in a field-test. Secondary aims were to examine the proportion of oxygen consumed during the field-test in relation to the peak-test and to analyse the correlation between the oxygen uptake during the field-test and peak-test in order to support the validity of the field-test.

Methods

With simultaneous measurement of oxygen consumption, participants performed a standardized field-test consisting of five activities; walking over ground, stair walking, stepping over obstacles, walking slalom between cones and from a standing position lifting objects from one height to another. All activities were performed in self-selected speed. Prior to the field-test, a peak aerobic capacity test was performed. The field-test was repeated minimum 2 and maximum 14 days between the tests. ICC_2,1 and Bland Altman tests (Limits of Agreement, LoA) were used to analyse test-retest reliability.

Results

In total 31 participants (39% women, mean (SD) age 54.5 (12.7) years and 21.1 (14.3) months’ post-stroke) were included. The ICC_2,1 was ≥ 0.80 for absolute V̇O₂, relative V̇O₂, minute ventilation, CO₂, respiratory exchange ratio, heart rate and Borgs rating of perceived exertion. ICC_2,1 for total time to complete the field-test was 0.99. Mean difference in steady state V̇O₂ during Test 1 and Test 2 was -0.40 (2.12) The LoAs were -3.75 and 4.51. Participants spent 60.7% of their V̇O₂peak performing functional activities. Correlation between field-test and peak-test was 0.689, p = 0.001 for absolute and 0.733, p = 0.001 for relative V̇O₂.

Conclusions

This study presents first evidence on reliability of oxygen uptake during performance of functional activities after stroke, showing very good test-retest reliability. The secondary analysis showed that the amount of energy spent during the field-test relative to the peak-test was high and the correlation between the two test was good, supporting the validity of this method.

Submaximal oxygen uptake kinetics, functional mobility, and physical activity in older adults with heart failure and reduced ejection fraction

BACKGROUND

Submaximal oxygen uptake measures are more feasible and may better predict clinical cardiac outcomes than maximal tests in older adults with heart failure (HF). We examined relationships between maximal oxygen uptake, submaximal oxygen kinetics, functional mobility, and physical activity in older adults with HF and reduced ejection fraction.

METHODS

Older adults with HF and reduced ejection fraction (n = 25, age 75 ± 7 years) were compared to 25 healthy age- and gender-matched controls. Assessments included a maximal treadmill test for peak oxygen uptake (VO2peak), oxygen uptake kinetics at onset of and on recovery from a submaximal treadmill test, functional mobility testing [Get Up and Go (GUG), Comfortable Gait Speed (CGS), Unipedal Stance (US)], and self-reported physical activity (PA).

RESULTS

Compared to controls, HF had worse performance on GUG, CGS, and US, greater delays in submaximal oxygen uptake kinetics, and lower PA. In controls, VO2peak was more strongly associated with functional mobility and PA than submaximal oxygen uptake kinetics. In HF patients, submaximal oxygen uptake kinetics were similarly associated with GUG and CGS as VO2peak, but weakly associated with PA.

CONCLUSIONS

Based on their mobility performance, older HF patients with reduced ejection fraction are at risk for adverse functional outcomes. In this population, submaximal oxygen uptake measures may be equivalent to VO2 peak in predicting functional mobility, and in addition to being more feasible, may provide better insight into how aerobic function relates to mobility in older adults with HF.

Association between physical activity measurements and key parameters of cardiopulmonary exercise testing in patients with heart failure

BACKGROUND

A hallmark characteristic of heart failure (HF) is reduced physical activity (PA) patterns. The relationship between key cardiopulmonary exercise testing (CPX) variables and PA patterns has not been investigated. Therefore, we evaluated PA patterns in patients with ischemic HF and its relationship to peak oxygen consumption (VO2), the minute ventilation/carbon dioxide production (VE/VCO2) slope, and the oxygen uptake efficiency slope (OUES).

METHODS AND RESULTS

Sixteen patients with HF wore an accelerometer for six days to measure total steps/day as well as percentage of time at light, moderate, and vigorous PA. Symptom-limited CPX was performed on a treadmill using a ramping protocol. Total steps correlated with VO2 (r = 0.64 P < .05), the VE/VCO2 slope (r = -0.72; P < .05), and the OUES (0.63; P < .05). The percentage of time at light-intensity PA correlated with the VE/VCO2 slope (r = 0.58; P < .05) and the OUES (r = -0.51; P < .05). The percentage of time at vigorous-intensity PA correlated with peak VO2 (r = 0.55; P < .05) and the VE/VCO2 slope (r = -0.52; P < .05).

CONCLUSIONS

PA assessed by accelerometer is significantly associated with key CPX variables in patients with HF.

Effects of body mass index on task-related oxygen uptake and dyspnea during activities of daily life in COPD

BACKGROUND

Patients with COPD use a higher proportion of their peak aerobic capacity during the performance of domestic activities of daily life (ADLs) compared to healthy peers, accompanied by a higher degree of task-related symptoms. To date, the influence of body mass index (BMI) on the task-related metabolic demands remains unknown in patients with COPD. Therefore, the aim of our study was to determine the effects of BMI on metabolic load during the performance of 5 consecutive domestic ADLs in patients with COPD.

METHODOLOGY

Ninety-four COPD patients and 20 healhty peers performed 5 consecutive, self-paced domestic ADLs putting on socks, shoes and vest; folding 8 towels; putting away groceries; washing up 4 dishes, cups and saucers; and sweeping the floor for 4 min. Task-related oxygen uptake and ventilation were assessed using a mobile oxycon, while Borg scores were used to assess task-related dyspnea and fatigue.

PRINCIPAL FINDINGS

1. Relative task-related oxygen uptake after the performance of domestic ADLs was increased in patients with COPD compared to healthy elderly, whereas absolute oxygen uptake is similar between groups; 2. Relative oxygen uptake and oxygen uptake per kilogram fat-free mass were comparable between BMI groups; and 3. Borg symptom scores for dyspnea en fatigue were comparable between BMI groups.

CONCLUSION

Patients with COPD in different BMI groups perform self-paced domestic ADLs at the same relative metabolic load, accompanied by comparable Borg symptom scores for dyspnea and fatigue.