Evaluation of novel indices of walking performance taking oxygen desaturation into account during six-minute walk test in cardiovascular disease patients

In pulmonary disease patients since oxygen desaturation during 6-min walk test (6MWT) affects walk distance (6MWD), some novel indices such as desaturation/distance ratio [DDR, oxygen desaturation area (DAO2)/6MWD] and distance-saturation product [DSP, 6MWD × minimum peripheral oxygen saturation (SpO2)] are evaluated. However, there has been no study examining these indices that consider exercise-induced desaturation (EID) in patients with cardiovascular disease. In 94 cardiovascular disease patients without pulmonary complications, 6MWT and echocardiography were performed at the entry of cardiac rehabilitation. SpO2 was measured during 6MWT using a continuously monitorable pulse oximeter, and DSP and DDR were calculated using minimum SpO2 and DAO2 [sum of (100-SpO2) per second during 6MWT], respectively. EID was defined as SpO2 decrease of ≥ 4% or minimum SpO2 of < 90% during 6MWT. DSP was slightly lower and DDR was markedly higher in patients with EID than in those without. When examining correlations of DSP and DDR with their components, DSP was correlated with 6MWD much closely than minimum SpO2, while DDR was correlated as closely with DAO2 as 6MWD. Furthermore, DAO2, but not minimum SpO2, had a direct correlation with 6MWD. As for associations with cardiac function, DSP was correlated with several cardiac parameters, but DDR was not correlated with any of these parameters. Our findings suggest that oxygen desaturation during 6MWT affects walking distance in cardiovascular disease patients even without pulmonary complications and that DDR is more appropriate than DSP as an index of walking performance that takes EID into consideration, independently of cardiac function.

Five multivariate Duchenne muscular dystrophy progression models bridging six-minute walk distance and MRI relaxometry of leg muscles

The study aimed to provide quantitative information on the utilization of MRI transverse relaxation time constant (MRI-T2) of leg muscles in DMD clinical trials by developing multivariate disease progression models of Duchenne muscular dystrophy (DMD) using 6-min walk distance (6MWD) and MRI-T2. Clinical data were collected from the prospective and longitudinal ImagingNMD study. Disease progression models were developed by a nonlinear mixed-effect modeling approach. Univariate models of 6MWD and MRI-T2 of five muscles were developed separately. Age at assessment was the time metric. Multivariate models were developed by estimating the correlation of 6MWD and MRI-T2 model variables. Full model estimation approach for covariate analysis and five-fold cross validation were conducted. Simulations were performed to compare the models and predict the covariate effects on the trajectories of 6MWD and MRI-T2. Sigmoid Imax and Emax models best captured the profiles of 6MWD and MRI-T2 over age. Steroid use, baseline 6MWD, and baseline MRI-T2 were significant covariates. The median age at which 6MWD is half of its maximum decrease in the five models was similar, while the median age at which MRI-T2 is half of its maximum increase varied depending on the type of muscle. The models connecting 6MWD and MRI-T2 successfully quantified how individual characteristics alter disease trajectories. The models demonstrate a plausible correlation between 6MWD and MRI-T2, supporting the use of MRI-T2. The developed models will guide drug developers in using the MRI-T2 to most efficient use in DMD clinical trials.

Minimal clinically important differences in six-minute walking distance in late-onset Pompe disease

BACKGROUND

The minimal clinically important difference (MCID) is the smallest change in outcome that physicians or patients would consider meaningful and is relevant when evaluating disease progression or the efficacy of interventions. Studies of patients with late-onset Pompe disease (LOPD) have used the 6-min walk distance (6MWD) as an endpoint to assess motor function. However, an MCID for 6MWD (% predicted and meters) has yet to be established in LOPD. The objective of the study was to derive 6MWD MCID (% predicted and meters) with different analysis methods and for subgroups of different disease severity for LOPD.

METHODS

Data from the PROPEL trial were used to calculate 6MWD MCID in the overall PROPEL population and subgroups of baseline severity as assessed by walking distance and body mass index (BMI), using anchor- and distribution-based approaches.

RESULTS

The 6MWD MCIDs varied widely, depending on the method and subgroup, ranging from 2.27%-8.11% predicted for the overall LOPD population (23.7 m-57.2 m). For patients with baseline 6MWD < 150 m, MCIDs ranged from -0.74%-3.37% (-2.1 m-11.3 m). MCIDs increased with distance walked at baseline until a plateau was reached. For BMI subgroups, the MCIDs were generally lowest in obese patients.

CONCLUSION

Our analysis shows that MCID depends on the chosen method and disease severity. The findings suggest that applying a single MCID to all patients can be misleading; consequently, a range of possible MCIDs should be considered. This may also be highly relevant for other neuromuscular diseases. This study provides a range of 6MWD MCIDs for LOPD, with lower MCIDs for more severe patients.

Longitudinal significance of six-minute walk test in patients with nontuberculous mycobacterial pulmonary disease: an observational study

BACKGROUND

The long-term exercise tolerance changes in patients with nontuberculous mycobacterial pulmonary disease (NTM-PD) are of great interest because of its chronic course. This study aimed to characterize the associations between changes over time in six-minute walking test (6MWT) parameters and clinical parameters in patients with NTM-PD.

METHODS

Overall, 188 patients with NTM-PD, visiting outpatient clinics at Keio University Hospital from April 2012 to March 2020 were included in the study. Data were collected using the St. George's Respiratory Questionnaire (SGRQ), pulmonary function test (PFT), blood tests, and the 6MWT at registration and at least once after that. The association of the anchors and clinical indicators with the 6MWT parameters was assessed.

RESULTS

The median age [interquartile range] of the patients was 67 [63-74] years. The median baseline six-minute walk distance (6MWD) and final Borg scale (FBS) were 413 [361-470] m and 1 [0-2], respectively. In the correlation analysis, ΔSGRQ total/year (yr), Δforced vital capacity (FVC, % predicted)/yr, Δforced expiratory volume in 1 s (FEV₁, % predicted)/yr, and Δdiffusing capacity for carbon monoxide (DL_CO, % predicted)/yr correlated with both Δ6MWD/yr and ΔFBS/yr in the longitudinal analysis (|Rho| > 0.20). When stratified into three quantiles of changes in each anchor, the 6MWT parameters worsened over time in the bottom 25% group by mixed-effects model. Specifically, Δ6MWD was affected by SGRQ activity, SGRQ impacts, PFT (FVC, FEV₁, and DL_CO), and C-reactive protein (CRP). ΔFBS was affected by all SGRQ components, total score, and PFT. Anchor scores and variables at baseline that worsened Δ6MWD were higher SGRQ scores, lower FVC (% predicted), lower DL_CO (% predicted), higher Krebs von den Lungen-6, old age, and undergoing treatment at registration. Similarly, these clinical parameters and elevated CRP, excluding undergoing treatment at registration, worsened ΔFBS.

CONCLUSIONS

The decreased walking distance and exacerbation of dyspnea on exertion over time in patients with NTM-PD may reflect a deterioration of health-related quality of life and pulmonary function. Thus, the change in 6MWT over time can be used as an indicator to accurately assess the patient's condition and tailor their healthcare environment.

Three-axis accelerometer system for comparison of gait parameters in children with cystic fibrosis and healthy peers

BACKGROUND

Cystic Fibrosis (CF), affecting functional exercise capacity generally measured by submaximal exercise test such as 6min walk test, is a progressive, autosomal recessive and metabolic disorder. Three-axis accelerometers, which are used during gait, are an easy way to assess gait parameters in patients and healthy individuals. Gait parameters were significantly associated with clinical outcomes of COPD. However, the association between gait parameters and clinical outcomes in children with CF is unclear.

RESEARCH QUESTION

Do clinical outcomes in CF have an important role in determining gait parameters?.

METHODS

Twenty-one CF and 21 healthy subjects participated in this case-control study. Body composition was evaluated using Tanita-BC 418. Respiratory and knee extension muscle strengths were assessed. Functional exercise capacity was evaluated using the 6-min walk test (6MWT). Spatiotemporal gait parameters were evaluated using a validated wireless inertial sensing device (G-Sensor, BTS Bioengineering S.p.A., Italy) during the 6MWT and 7-meter gait test.

RESULTS

MIP, the distance of 6MWT, and stride length were significantly lower in the CF group compare to healthy children (p<0.05). Gait speed and functional exercise capacity, cadence and functional exercise capacity, quadriceps muscle strength, FEV1, fat-free mass were found to be correlated in CF patients (p<0.05).

SIGNIFICANCE

The aerobic capacity and gait parameters were affected in CF patients with mild disease severity in our study. Clinical outcomes were associated with gait parameters in CF patients. This is the first study to use the 3-axis accelerometer to evaluate functional exercise capacity and gait parameters of CF and healthy children. A three-axis accelerometer can be used to assess functional exercise capacity and gait parameters in CF patients at the clinics.

Gait characteristics and their associations with clinical outcomes in patients with chronic obstructive pulmonary disease

BACKGROUND

Abnormalities of spatiotemporal gait parameters are frequently observed in chronic obstructive pulmonary disease (COPD). However, associations of gait parameters with clinical outcomes and their implementation into clinical practice have not been established.

RESEARCH QUESTION

To investigate gait abnormalities and their association with clinical outcomes of COPD.

METHODS

This study included 34 male outpatients with COPD and 16 community-dwelling healthy men aged ≥65 years. The subjects underwent a ten-metre walk test wearing an accelerometer. Data on gait speed, step length, cadence, walk ratio, acceleration magnitude, and standard deviation of step time (step time SD) were collected. Forced expiratory volume in 1-second, modified Medical Research Council dyspnoea score, six-minute walk distance (6MWD), quadriceps muscle strength (QMVC), and physical activity (daily steps and time spent in moderate to vigorous physical activity per day) were measured in the COPD group as clinical outcomes of COPD. We tested group differences in gait parameters, associations between gait parameters and COPD clinical outcomes, and predictive capability of gait parameters for reductions in 6MWD, QMVC, and daily steps in COPD.

RESULTS

All gait parameters except walk ratio deteriorated in COPD. Step time SD and gait speed were significant independent predictors of 6MWD in COPD (B=-0.440, p = 0.001, B = 0.339, p = 0.007, respectively). Step length was a significant independent predictor of QMVC (B=-0.609, p < 0.001) and daily steps (B=-0.453, p = 0.006). Step length was a significant predictor of muscle weakness and physical inactivity, and step time SD was significant in predicting poor 6MWD in COPD.

SIGNIFICANCE

Significant associations between gait abnormalities measured by an accelerometer and deficits in extra-pulmonary features of COPD were observed. An accelerometer-based gait analysis could be an alternative approach to assessing gait abnormalities and screening of functional decline in COPD.

Changes in exercise capacity and anthropometric measures after Work It Out-a holistic chronic disease self-management program for urban Aboriginal and Torres Strait Islander people

OBJECTIVES

The Work It Out (WIO) program is a holistic chronic disease self-management and rehabilitation program in Queensland that is tailored for urban Aboriginal and Torres Strait Islander people with/at risk of chronic disease. This study aimed to examine the overall changes in participants' exercise capacity and anthropometric measurements and to explore the correlations between these changes.

STUDY DESIGN

Quasi-experimental prepost intervention study.

METHODS

A total of 406 participants self-identified as Aboriginal and Torres Strait Islander people, who had attended one or more cycles of the program from 2014 to 2017, were included. Health information from the last review assessment was compared with that of the initial assessment using paired t-tests. Multivariate regression models were applied to explore the associations between changes in 6-min walk distance (6MWD) and anthropometric measurements.

RESULTS

An increase in 6MWD (77 m, 95% confidence interval [CI]: 65, 90), as well as small reductions in waist circumference (WC) (-1.79 cm, 95% CI: -2.76 to -0.82) and hip circumference (-1.11 cm, 95% CI: -2.13 to -0.08) were identified. Statistically significant reductions were observed across all anthropometric measures in the respective highest tertiles (body mass index: -0.71, 95% CI: -1.35 to -0.07; weight: -2.59 kg, 95% CI: -4.84 to -0.34; WC: -5.09 cm, 95% CI: -6.99 to -3.20; waist to hip ratio: -0.033, 95% CI: -0.047 to -0.02). The increments of 6MWD in returning participants (92 m, 95% CI: 75 to 109) was found to be greater than those in one-off participants (59 m, 95% CI: 40-78). In particular, the percentage of 6MWD change from baseline was significantly correlated to the percentage of WC change after adjusting for age, gender, the number of pre-existing chronic conditions, and the number of cycles attended (coefficient: -1.33, 95% CI: -2.42 to -0.24).

CONCLUSION

Significant improvement in functional exercise capacity and modest changes in anthropometric measurements were identified in WIO participants. WC change could be used as an indicator of the change of participants' six-minute walk distance. Findings may be useful for promoting and guiding similar health programs for improving chronic disease management in Australian Indigenous communities.

Ambrisentan for treatment of inoperable chronic thromboembolic pulmonary hypertension (CTEPH)

This multicenter, randomized, double-blind, placebo-controlled study assessed ambrisentan or placebo in patients with inoperable chronic thromboembolic pulmonary hypertension. Futility of enrollment led to early termination. Trends of improvement in favor of ambrisentan versus placebo in the primary and some secondary endpoints were observed; adverse event profiles were similar between groups.

Effects of home-based exercise training on functional outcomes and quality of life in patients with pulmonary hypertension: A randomized clinical trial

Objectives

The objective of this study was to assess the effects of home-based exercise training (HBET) on function and quality of life (QoL) in patients with pulmonary hypertension (PH).

Methods

A prospective, nonblinded, randomized clinical trial was carried out on 84 medically stable patients with PH belonging to any functional class or etiology and of either sex. Patients were randomized to either standard care or HBET. Both groups also received education using the Pulmonary Hypertension Manual (PulHMan). Outcomes included functional capacity from 6-min walk distance (6MWD), QoL using the Medical Outcomes Survey Short Form – 36, functional class (FC), and right heart indices (right ventricular systolic pressure [RVSP] and tricuspid annular plane systolic excursion [TAPSE]) and were assessed at entry and after 12 weeks.

Results

HBET improved 6MWD by 48.5 m and 13 m in the experimental and control groups, respectively (p < 0.001). QoL showed statistical improvements after HBET between the groups for the physical and mental components and for the various subdomains (except body pain). Furthermore, FC improved by one grade with HBET (p < 0.001).

Conclusion

HBET program improved functional capacity, QoL, and FC in patients with PH.

A Contemporary Approach to Pulmonary Arterial Hypertension

In recent years, there have been major changes in the landscape of pulmonary arterial hypertension therapy with the introduction of novel agents and innovative treatment strategies for this progressive disease. The aim of this review is to discuss the evolution in trial design in this field and highlight the salient features of recently published studies. We also summarize our approach to therapy selection in this chronic disease and identify areas for future exploration. The therapeutic armamentarium now includes 13 approved therapies. While most of these agents have been studied in small, short-term trials using the 6-min walk distance as a primary endpoint, there has been a shift in recent years toward larger, long-term, event-driven trials that utilize combined morbidity and mortality endpoints. The SERAPHIN and GRIPHON trials were two such studies, which led to the approval of the dual endothelin-receptor antagonist macitentan and the selective prostacyclin receptor antagonist selexipag, respectively. Other event-driven trials, like AMBITION and COMPASS-2, have provided valuable insight into the use of combined oral therapies in symptomatic patients. In conclusion, despite being a more manageable disease in the modern treatment era, pulmonary hypertension is still associated with considerable morbidity and much more work remains to be done in this field. Important questions remain about the most optimal way to manage patients and conduct trials going forward.

Comparison between stair-climbing test and six-minute walk test after lung resection using video-assisted thoracoscopic surgery lobectomy

[Purpose] Currently, the six-minute walk distance (6MWD) is used to evaluate exercise capacity in people following lung resection for non-small cell lung cancer. However, it is unclear whether the 6MWD can detect changes in cardiorespiratory fitness induced by exercise training or lung resection. Conversely, the stair-climbing test is used frequently for the preoperative evaluation of lung resection candidates. It is considered a sensitive method for detecting changes associated with training, but is not used to evaluate exercise capacity after lung resection. The purpose of this study was to compare the stair-climbing test and the six-minute walk test (6MWT) after lung resection. [Subjects and Methods] Fourteen patients undergoing lung resection completed the stair-climbing test and the 6MWT preoperatively, and one month postoperatively. The postoperative values and the percentage change in the stair-climbing test and the 6MWT were evaluated. [Results] The stair-climbing test results showed a significant deterioration at one month after lung resection; however, a significant change in the 6MWD was not observed. [Conclusion] When compared with the 6MWT, the stair-climbing test was more sensitive in detecting lung resection-induced changes in cardiorespiratory fitness.

Early declines in physical function among aging adults with type 2 diabetes

AIMS

Type 2 diabetes (T2DM) is associated with reduced physical function and early disability. We hypothesized that changes in physical function occur early and differ by age. Our aims were to determine and compare differences in and predictors of physical function in older and younger adults with T2DM.

METHODS

Eighty adults completed six-minute walk distance (6MWD) tests, wore wrist actigraphy for 5days and completed diabetes health and symptom surveys. Comparative and bivariate analyses were completed to assess differences between age groups determined by serial Box's M-plot analyses.

RESULTS

6MWD was low (476.9±106.2m), and negatively associated with female gender, age, neuropathic pain, diabetes duration, BMI, poor sleep quality, and fatigue and positively with habitual activity and education (p<0.05). Covariance matrices changed at age 59. In subjects age <58, 6MWD was predicted by gender, sleep quality, and neuropathic pain (R²=0.593, p<0.001). In those age ≥59, 6MWD was predicted by diabetes duration, education, and habitual activity (R²=0.554, p<0.001). There were no shared predictors of 6MWD between groups.

CONCLUSIONS

T2DM is associated with early declines in physical function; the predictors of which change in midlife. Therapies to maintain or improve physical function should be tailored by age, pain symptoms, and habitual activity levels.

Changes in derived measures from six-minute walk distance following home-based exercise training in congestive heart failure: A preliminary report

The response of derived parameters from six-minute walk distance (6MWD), like 6MW work (6MWW), to exercise training and its correlation with quality of life (QoL) in congestive heart failure (CHF) is not known. A secondary analysis from a randomized controlled trial on 30 patients (23 males; mean age 57.7 ± 10.4 years; mean ejection fraction 31 ± 10%) with CHF in NYHA class I–IV who completed an eight-week home-based exercise training program found a significant improvement in 6MWW (p < 0.05), with similar correlations between 6MWD and 6MWW with QoL. 6MWW does not appear to provide additional benefit to 6MWD in cardiac rehabilitation for CHF.

Emphysema and DLCO predict a clinically important difference for 6MWD decline in COPD

BACKGROUND

Exercise impairment is a central feature of chronic obstructive pulmonary disease (COPD), and a minimal clinically important difference (MCID) for 6-min walk distance (6MWD) decline (>30 m) has been associated with increased mortality. The predictors of the MCID are not fully known. We hypothesize that physiological factors and radiographic measures predict the MCID.

METHODS

We assessed 121 COPD subjects during 2 years using clinical variables, computed tomographic (CT) measures of emphysema, and functional measures including diffusion lung capacity for carbon monoxide (DLCO). The association between an MCID for 6MWD and clinical, CT, and physiologic predictors was assessed using logistic analysis. The C-statistic was used to assess the predictive ability of the models.

RESULTS

Forty seven (39%) subjects had an MCID. In an imaging-based model, log emphysema and age were the best predictors of MCID (emphysema Odds Ratio [OR] 2.47 95%CI [1.28-4.76]). In a physiologic model, DLCO, age, and male gender were selected the best predictors (DLCO OR 1.19 [1.08-1.31]). The C-statistic for the ability of these models to predict an MCID was 0.71 and 0.75, respectively.

CONCLUSION

In COPD patients the burden of emphysema on CT scan and DLCO predict a clinically meaningful decline in exercise capacity.