Estimation of maximal work rate based on the 6-minute walk test and fat-free mass in chronic obstructive pulmonary disease

Estimating endurance training intensity prescription from the 6-minute stepper test in people with chronic obstructive pulmonary disease - a multicenter cross-sectional study with external validation

BACKGROUND

Home-based pulmonary rehabilitation (PR) can enhance accessibility to PR, but no at-home field exercise test has been validated for individualized endurance training prescriptions.

RESEARCH QUESTION

What is the accuracy of the six-minute stepper test (6MST) in estimating endurance training intensity as determined during cardiopulmonary exercise testing (CPET)?

STUDY DESIGN AND METHOD

This multicenter (N = 3) cross-sectional study included individuals with COPD. Participants performed CPET and two 6MSTs to evaluate the 6MST's ability to estimate endurance training intensity based on CPET-derived heart rate at the first ventilatory threshold (HRvt1), the corresponding power output (Pvt1), and peak power output (Ppeak). Predictive equations were tested for external validity using data from two prior studies.

RESULTS

105 patients were included (mean age 61 (SD 9) years; mean FEV1 61 (SD 21) %). Predictive equations moderately predicted HRvt1 (r² = 0.38), strongly predicted Pvt1 (r² = 0.63) and very strongly predicted Ppeak (r² = 0.75). External validity was small to moderate for HRvt1 and Pvt1 but was strong for 60% of Ppeak (mean absolute difference: 10W, 95% CI 5 to 10). Passing and Bablok regression confirmed interchangeability for Pvt1 and 60% of Ppeak.

INTERPRETATION

The 6MST offers a reliable method to set initial training intensity when CPET is unavailable.

CLINICAL TRIAL REGISTRATION

NCT02842463.

Estimating maximum work rate during cardiopulmonary exercise testing from the six-minute walk distance in patients with heart failure

Background

Exercise is recommended for patients with chronic heart failure (CHF) and its intensity is usually set as a percentage of the maximal work rate (MWR) during cardiopulmonary exercise testing (CPX) or a symptom-limited incremental test (SLIT). As these tests are not always available in cardiac rehabilitation due to logistic/cost constraints, we aimed to develop a predictive model to estimate MWR at CPX (estMWR@CPX) in CHF patients using anthropometric and clinical measures and the 6-min walk test (6 MWT), the most widely used exercise field test.

Methods

This is a multicentre cross-sectional retrospective study in a cardiac rehabilitation setting. Six hundred patients with HF in New York Heart Association (NYHA) functional class I-III underwent both CPX and 6 MWT and, through multivariable linear regression analysis, we defined several predictive models to define estMWR@CPX.

Results

The best model included 6 MWT, sex, age, weight, NYHA class, left ventricular ejection fraction (LVEF), smoking status and chronic obstructive pulmonary disease COPD (adjusted R2 = 0.55; 95% LoA -39 to 33 W). When LVEF was excluded as a predictor, the resulting model performed only slightly worse (adjusted R2 = 0.54; 95% LoA -42 to 34 W). Only in 34% of cases was the percentage difference between estMWR@CPX and real MWR@CPX <10% in absolute value. EstMWR@CPX tended to overestimate low values and underestimate high values of true MWR@CPX.

Conclusions

Our results showed a lack of accuracy in the predictive model evaluated; therefore, for an accurate prescription of cycle-ergometer exercise training, it is necessary to assess MWR by CPX or SLIT.

The relevance of body composition assessment for the rating of perceived exertion in trained and untrained women and men

Introduction: Mechanic power output (MPO) and oxygen consumption (VO2) reflect endurance capacity and are often stated relative to body mass (BM) but less often per skeletal muscle mass (SMM). Rating of perceived exertion (RPE) has previously shown conflicting results between sexes at submaximal intensities. Individual body composition, however, largely differs due to sex and training status. It was the aim of this study to evaluate RPE of untrained and trained individuals of both sexes considering body composition and to estimate whether RPE could be improved as a tool to determine endurance capacity. Methods: The study included 34 untrained adults (age 26.18 ± 6.34 years, 18 women) and 29 endurance trained (age 27.86 ± 5.19, 14 women) who were measured for body composition (InBody 770, InBody Europe B.V., Germany) and tested on a treadmill (Pulsar, H/P/Cosmos, Germany) for aerobic capacity (Metalyzer 3B, Cortex Biophysik GmbH, Germany) in an all-out exercise test applying the Bruce-protocol. VO2, MPO, heart rate (HR), and RPE were obtained at each exercise stage. VO2 and MPO were calculated per BM and SMM. RPE values were correlated with absolute VO2 and MPO, as well as relative to BM, and SMM. HR values and the parameters' standardized values served for comparison to standard procedures. Results: VO2 and MPO were higher in men compared to women and in trained compared to untrained participants. No differences between groups and sexes exist when VO2 and MPO were calculated per BM. When calculated per SMM, VO2 and MPO indicate opposite results already at low intensity stages of exercise test. RPE values had highest correlation with MPO per SMM (R2 = 0.8345) compared to absolute MPO (R2 = 0.7609), or MPO per BM (R2 = 0.8176). Agreement between RPE and MPO per SMM was greater than between RPE and HR (p = 0.008). Conclusion: Although RPE represents a subjective value at first glance, it was shown that RPE constitutes a valuable tool to estimate endurance capacity, which can be further enhanced if individual body composition is considered. Furthermore, MPO and VO2 should be considered relative to SMM. These findings might help to avoid over-exertion, especially among untrained people, by adjusting the training intensity for each subject according to the individual strain evaluated in an exercise test based on individual body composition.

Obstructive sleep apnea reduces functional capacity and impairs cardiac autonomic modulation during submaximal exercise in patients with chronic obstructive pulmonary disease: A follow-up study

BACKGROUND

Functional capacity and heart rate variability (HRV) are important prognostic markers in chronic obstructive pulmonary disease (COPD) and obstructive sleep apnea syndrome (OSA). However, the impact of the overlap of these diseases and the one-year clinical follow-up has not yet been evaluated.

OBJECTIVES

To assess whether the presence of OSA can impair functional performance and cardiac autonomic control during exercise in patients with COPD; and to verify whether the overlap of these diseases could lead to worse clinical outcomes during the one-year follow-up.

METHODS

Thirty-four patients underwent pulmonary function tests, echocardiography and polysomnography for diagnostic confirmation, disease staging, exclusion of any cardiac changes, and allocation between groups. The patients underwent the six-minute walk test (6MWT) to assess functional capacity and HRV during exercise. Subsequently, patients were followed up for 12 months to record outcomes such as exacerbation, hospitalization, and deaths. At the end of this period, the patients were revaluated to verify the hypotheses of the study.

RESULTS

The OSA-COPD group showed greater functional impairment when compared to the COPD group (p=0.003) and showed worse cardiac autonomic responses during the 6MWT with greater parasympathetic activation (p=0.03) and less complexity of the autonomic nervous system, in addition to being more likely to exacerbate (p=0.03) during one year of follow-up.

CONCLUSION

OSA-COPD produces deleterious effects on functional performance and a greater autonomic imbalance that impairs clinical outcomes.

Reduced exercise capacity and self-perceived health status in high-risk patients undergoing lung resection

BACKGROUND

Lung resection represents the main curative treatment modality of non-small cell lung cancer. Patients with high-risk to develop postoperative pulmonary complications have been classified as “high-risk patients.” Characterizing this population could be important to improve their approach and rehabilitation.

AIM

To identify the differences between high and low-risk patients in exercise capacity and self-perceived health status after hospitalization.

METHODS

A longitudinal observational prospective cohort study was carried out. Patients undergoing lung resection were recruited from the “Hospital Virgen de las Nieves” (Granada) and divided into two groups according to the risk profile criteria (age ≥ 70 years, forced expiratory volume in 1 s ≤ 70% predicted, carbon monoxide diffusion capacity ≤ 70% predicted or scheduled pneumonectomy). Outcomes included were exercise capacity (Fatigue Severity Scale, Unsupported Upper-Limb Exercise, handgrip dynamometry, Five Sit-to-stand test, and quadriceps hand-held dynamometry) and patient-reported outcome (Euroqol-5 dimensions 5 Levels Visual Analogue Scale).

RESULTS

In total, 115 participants were included in the study and divided into three groups: high-risk, low-risk and control group. At discharge high-risk patients presented a poorer exercise capacity and a worse self-perceived health status (P < 0.05). One month after discharge patients in the high-risk group maintained these differences compared to the other groups.

CONCLUSION

Our results show a poorer recovery in high-risk patients at discharge and 1 mo after surgery, with lower self-perceived health status and a poorer upper and lower limb exercise capacity. These results are important in the rehabilitation field.

Quali-quantitative analysis of adherence and perceived satisfaction of individuals with COPD after high-intensity training on land and in water: additional analysis from a randomized clinical trial

ABSTRACT Although patients with chronic obstructive pulmonary disease (COPD) benefit in many ways after participating in pulmonary rehabilitation programs, high dropout rates are still observed among participants. This study aims to analyze the adherence rate and perceived satisfaction in individuals with chronic obstructive pulmonary disease who underwent high-intensity physical training on land (LG) and in water (WG). This study is an additional analysis from a randomized controlled trial. In total, 36 subjects (51%) completed the intervention. All participants underwent six months of high-intensity endurance and strength training. Adherence was assessed by the proportion of patients who completed the training program. Perceived satisfaction was evaluated using a questionnaire composed of structured and semi-structured questions. The interviews were recorded, transcribed, and analyzed according to the criteria of our thematic analysis. The Shapiro-Wilk test was used to assess data normality, and dropout rates were compared using the chi-square test. Statistical significance was set at 5%. Regarding adherence, 59% of WG participants and 44% of LG participants completed the program, with no difference between the groups (p>0.05). Individuals from both groups were equally satisfied after six months of physical training (<90%); the therapist-patient relationship and treatment effectiveness being important factors for this perception. Qualitative analysis also showed that WG participants reported a more prominent improvement in their respiratory symptoms, leisure, sensation of pain, and sleep. In conclusion, patients with COPD were satisfied after six months of high-intensity physical training in water and on land, noting that water exercising promoted additional benefits compared to land exercising. There seems to be no superiority to any of the regimens (water or land) regarding the adherence to the training programs.

Effects of land- and water-based exercise programmes on postural balance in individuals with COPD: additional results from a randomised clinical trial

OBJECTIVE

To investigate the effects of water-based exercise training on postural balance in individuals with chronic obstructive pulmonary disease (COPD), and compare the effects of two similar protocols of land- and water-based exercise programmes on postural balance in this population.

DESIGN

Randomised clinical trial.

SETTING

University-based, outpatient, physical therapy clinic.

SUBJECTS

Fifty individuals with COPD.

INTERVENTIONS

Participants were assigned at random to the land group (LG; n=27) or the water group (WG; n=23), and underwent high-intensity endurance and strength training three times per week for 3months.

MAIN OUTCOME MEASURES

Functional balance was assessed by the timed up and go test (TUG), and static balance was assessed with a force platform in the following conditions: standing with feet hip-width apart and eyes open; standing with feet hip-width apart and eyes closed; standing on a short base; and one-legged stance.

RESULTS

Seventeen subjects completed the intervention in the LG {nine males, mean age 64 [standard deviation (SD) 8] years, mean forced expiratory volume in 1 second (FEV₁) 48 (SD 17) %predicted} compared with 14 subjects in the WG [nine males, mean age 65 (SD 8) years, FEV₁ 51 (SD 15) %predicted]. Water-based exercise training had a positive effect on functional balance [TUG: mean difference -1.17 (-1.93 to -0.41 95% confidence interval) seconds; P=0.006], whereas static balance remained unaltered for both groups. There was no between-group difference in postural balance after exercise training; however, a higher proportion of participants who had a clinically relevant improvement in the TUG were in the WG (LG 35%, WG 64%; P<0.001).

CONCLUSION

Functional balance improved after 3months of high-intensity exercise training performed in water. Despite the environment, non-specific training seems to be insufficient to improve static balance.

CLINICAL TRIAL REGISTRATION NUMBER

clinicalTrials.gov NCT01691131.

A new maximal bicycle test using a prediction algorithm developed from four large COPD studies

Background: Maximum exercise workload (W_MAX) is today assessed as the first part of Cardiopulmonary Exercise testing. The W_MAX test exposes patients with COPD, often having cardiovascular comorbidity, to risks. Our research project was initiated with the final aim to eliminate the W_MAX test and replace this test with a predicted value of W_MAX, based on a prediction algorithm of W_MAX derived from multicentre studies.

Methods: Baseline data (W_MAX, demography, lung function parameters) from 850 COPD patients from four multicentre studies were collected and standardized. A prediction algorithm was prepared using Random Forest modelling. Predicted values of W_MAX were used in a new W_MAX test, which used a linear increase in order to reach the predicted W_MAX within 8 min. The new W_MAX test was compared with the standard stepwise W_MAX test in a pilot study including 15 patients with mild/moderate COPD.

Results: The best prediction algorithm of W_MAX included age, sex, height, weight, and six lung function parameters. FEV₁ and DLCO were the most important predictors. The new W_MAX test had a better correlation (R² = 0.84) between predicted and measured W_MAX than the standard W_MAX test (R² = 0.66), with slopes of 0.50 and 0.46, respectively. The results from the new W_MAX test and the standard W_MAX test correlated well.

Conclusion: A prediction algorithm based on data from four large multicentre studies was used in a new W_MAX test. The prediction algorithm provided reliable values of predicted W_MAX. In comparison with the standard W_MAX test, the new W_MAX test provided similar overall results.

Comparative Assessment of CPET Versus Typical Work-related Activities in Women With and Without Mild COPD

BACKGROUND

Prevalence of chronic obstructive pulmonary disease (COPD) is increasing in Germany. This study examined the work performance of healthy women compared to those with mild COPD.

PATIENTS AND METHODS

Nineteen women suffering from COPD Global Initiative for Chronic Obstructive Lung Diseases stage I and 41 healthy women underwent standardised cardiopulmonary exercise test (CPET) in comparison to 5 typical work-related tasks. Oxygen uptake, carbon dioxide output, ventilation volume, breathing frequency, heart rate and respiratory exchange ratio (RER) were measured. The activities were quantified. Wilcoxon test and ANOVA were calculated using the SPSS software.

RESULTS

Patients with COPD had a lower exercise capacity compared to healthy women and also showed lower performance during work-related activities. Patients with COPD had a lower oxygen uptake (p<0.001), a higher breathing frequency was accompanied by a higher Borg scale. The heart rate and the ventilation volume as a percentage of maximum CPET were significantly higher in patients with COPD. Women suffering from progressive symptoms had lower oxygen uptakes and RER, whilst breathing frequency and Borg scale were elevated.

CONCLUSION

Even at an early stage of the disease, patients with COPD exhibited limitations in work-related tasks.

The six-minute walk test predicts cardiorespiratory fitness in individuals with aneurysmal subarachnoid hemorrhage

BACKGROUND

Peak oxygen uptake (VO_2peak) established during progressive cardiopulmonary exercise testing (CPET) is the "gold-standard" for cardiorespiratory fitness. However, CPET measurements may be limited in patients with aneurysmal subarachnoid hemorrhage (a-SAH) by disease-related complaints, such as cardiovascular health-risks or anxiety. Furthermore, CPET with gas-exchange analyses require specialized knowledge and infrastructure with limited availability in most rehabilitation facilities.

OBJECTIVES

To determine whether an easy-to-administer six-minute walk test (6MWT) is a valid clinical alternative to progressive CPET in order to predict VO_2peak in individuals with a-SAH.

METHODS

Twenty-seven patients performed the 6MWT and CPET with gas-exchange analyses on a cycle ergometer. Univariate and multivariate regression models were made to investigate the predictability of VO_2peak from the six-minute walk distance (6MWD).

RESULTS

Univariate regression showed that the 6MWD was strongly related to VO_2peak (r = 0.75, p < 0.001), with an explained variance of 56% and a prediction error of 4.12 ml/kg/min, representing 18% of mean VO_2peak. Adding age and sex to an extended multivariate regression model improved this relationship (r = 0.82, p < 0.001), with an explained variance of 67% and a prediction error of 3.67 ml/kg/min corresponding to 16% of mean VO_2peak.

CONCLUSIONS

The 6MWT is an easy-to-administer submaximal exercise test that can be selected to estimate cardiorespiratory fitness at an aggregated level, in groups of patients with a-SAH, which may help to evaluate interventions in a clinical or research setting. However, the relatively large prediction error does not allow for an accurate prediction in individual patients.

Is the six-minute walk test a useful tool to prescribe high-intensity exercise in patients with chronic obstructive pulmonary disease?

BACKGROUND

It is not yet completely known whether the 6MWT can be used to prescribe high-intensity exercise for patients with COPD.

OBJECTIVE

To evaluate the ability of the six-minute walk test (6MWT) to prescribe high-intensity exercise for patients with chronic obstructive pulmonary disease (COPD).

METHODS

Lung function, maximal inspiratory strength, symptoms and exercise capacity were evaluated in patients with COPD (n = 27) before and after a 12-week high-intensity exercise program. Criteria for high-intensity training were: 1) ≥75% of the 6MWT average speed; 2) American Thoracic Society/European Respiratory Society (ATS/ERS) criteria (≥60% of the maximal incremental shuttle walk test speed).

RESULTS

The 6MWT showed good positive and negative predictive values (0.69 and 0.71, respectively), and accuracy (0.70), good reliability (ICC 0.70 [95%CI 0.45-0.85]) and moderate agreement (k 0.41 [95%CI 0.13-0.67]) with the ATS/ERS criteria.

CONCLUSION

The 6MWT has good predictive ability and accuracy in relation to high-intensity exercise for patients with COPD.

Fatores associados à melhora da composição corporal em indivíduos com DPOC após treinamento físico

Introdução A redução da massa magra corpórea (MMC) é um fator independente de mortalidade em pacientes com Doença Pulmonar Obstrutiva Crônica (DPOC) e a literatura mostra que exercícios físicos aumentam a MMC. Objetivo Identificar fatores associados à melhora da composição corporal em indivíduos com DPOC após treinamento físico de alta intensidade. Métodos 37 pacientes com DPOC (19 H; 66 ± 7 anos; IMC = 27 ± 6 kg/m2; VEF1 = 38 ± 16 %pred) foram avaliados segundo sua composição corporal, função pulmonar, força muscular respiratória e periférica, capacidade funcional de exercício (teste de caminhada dos seis minutos, TC6M), nível de atividade física diária (DynaPort®), sensação subjetiva de dispneia (escala Medical Research Council) e qualidade de vida (Saint George Respiratory Questionnaire). O treinamento conteve exercícios de endurance e força muscular (3 vezes por semana por três meses). Após três meses, os pacientes foram reavaliados. Aqueles que apresentaram incremento de MMC incorporaram à estatística. Resultados No pré-treinamento, a MMC se correlacionou significativamente (p ≤ 0,05) com gasto energético total (r = 0,57), TC6M em %predito (r = 0,46), pressão expiratória máxima (PEmax) (r = 0,57), volume expiratório forçado no primeiro segundo em %predito (r = 0,47), força muscular de quadríceps femoral (r = 0,54), bíceps (r = 0,62) e tríceps braquial (r = 0,63). Contudo, o incremento da MMC após treinamento correlacionou-se significativamente somente com a melhora das escalas MRC (r = 0,4; p = 0,05) e PEmax (r = 0,35; p = 0,04). Conclusão Apesar de a MMC de pacientes com DPOC estar relacionada com a capacidade funcional de exercício, força muscular respiratória e periférica, obstrução pulmonar e gasto energético no pré-tratamento, a melhora da composição corporal está relacionada somente ao incremento da força muscular expiratória e sensação de dispneia após treinamento físico de alta intensidade.

Costs and benefits of pulmonary rehabilitation in chronic obstructive pulmonary disease: a randomized controlled trial

OBJECTIVE

The current study evaluated the costs and benefits of a simple aerobic walking program for patients with chronic obstructive pulmonary disease (COPD).

METHOD

This was a blinded randomized controlled clinical trial that recruited 72 patients diagnosed with COPD, 40 of whom were included in the study and divided into two groups [control group (CG) and pulmonary rehabilitation group (GPR)]. We assessed pulmonary function, distance covered during the 6-minute walk test (6MWT), respiratory and peripheral muscle strength, health-related quality of life (HRQOL), body composition, and level of activities of daily living (ADLs) before and after an 8-week walking program. The financial costs were calculated according to the pricing table of the Brazilian Unified Health System (SUS).

RESULTS

Only 34 of the 40 patients remained in the final sample; 16 in the CG and 18 in the GPR (FEV1: 50.9 ± 14% predicted and FEV1: 56 ± 0.5% predicted, respectively). The intervention group exhibited improvements in the 6MWT, sensation of dyspnea and fatigue, work performed, BODE index (p<0.01), HRQOL, ADL level (p<0.001), and lower limb strength (p<0.05). The final mean cost per patient for the GPR was R$ 148.75 (~US$ 75.00) and no patient significantly exceeded this value. However, 2 patients in the CG did exceed this value, incurring a cost of R$ 689.15 (~US$ 345.00).

CONCLUSION

Aerobic walking demonstrated significant clinical benefits in a cost-efficient manner in patients with COPD.

Relationship between the work developed in maximal and submaximal exercise capacity tests and the degree of airflow obstruction in individuals with Chronic Obstructive Pulmonary Disease

The aim of this study was to investigate the relationship between the work in two exercise capacity tests, a maximum and a submaximal exercise, and the level of airflow obstruction in patients with Chronic Obstructive Pulmonary Disease (COPD). Fifty-three subjects with COPD (29 men, 70±9 years old, 65±14 kg, forced expiratory volume in the first second [FEV1] 38[31-54]% predicted) had their lung function assessed by spirometry, and maximal and submaximal exercise capacity were evaluated by the Incremental Shuttle Walking test (ISWT) and the 6-Minute Walk Test (6MWT), respectively. The work in the tests was calculated by multiplying the covered distance and the individual's body weight (W). To evaluate the contribution of weight on the developed work, subjects were separated into two groups: higher weight (n=32), and lower weight (n=21). FEV1 correlated with the distance on the ISWT and with the ISWT*W (r=0.43 and r=0.49, respectively; p<0.05 for both). Moreover, the distance on the ISWT correlated with the ISWT*W (r=0.88, p<0.0001). Regarding the 6MWT, it was observed that FEV1 had a weak correlation with the covered distance (r=0.29, p=0.03) and a moderate one with the 6MWT*W (r=0.51, p<0.0001). Moreover, the distance covered in the 6MWT was moderately correlated with the 6MWT*W (r=0.47, p=0.0004). The higher weight group showed worse performance only in the 6MWT compared to the lower weight group (407±85 versus 469±64 meters, respectively; p=0.004). The work on the used exercise tests was similarly related to the level of airflow obstruction. The submaximal test, however, appears to have its performance more influenced by the individuals' body weight.

Is an individual prediction of maximal work rate by 6-minute walk distance and further measurements reliable in male patients with different lung diseases?

BACKGROUND

In patients with chronic lung diseases, the work rate for endurance training is calculated by the maximal work rate (Wmax). Because the assessment bears side effects, a prediction by easier accessible tests would be of practical use.

OBJECTIVE

We addressed the reliability of predicting Wmax on the basis of the 6-min walk distance (6MWD) test and a set of further parameters in patients with different lung diseases.

METHODS

Baseline data of a longitudinal study including 6MWD, Wmax, peripheral muscle force, lung function, fat-free mass and dyspnea (Modified Medical Research Council score) of 255 men with occupational lung diseases (104 asthma, 69 asbestosis, 42 silicosis, 40 chronic obstructive pulmonary disease) were evaluated.

RESULTS

6MWD correlated with Wmax (r = 0.51, p < 0.05). The product of 6MWD and body weight, in particular fat-free mass, led to an improvement in the correlation of Wmax with 6MWD. Muscle force, lung function and Modified Medical Research Council score correlated moderately but significantly with Wmax (p < 0.05 each). The maximum correlation gained by including 6MWD and further parameters in the prediction equations was r = 0.76 in patients with obstructive lung function impairment and r = 0.61 in asbestosis patients. The residual standard deviations of Wmax predicted by the calculated equations ranged between 20 and 28 W, and the 95% prediction intervals of Wmax ranged between ±47 and ±65 W.

CONCLUSIONS

A reliable prediction of individual Wmax by 6MWD or related measures and therefore a replacement by other tests is not possible. Nevertheless, it may be useful for the comparison of average values in epidemiological and clinical studies.