Determinants of 6-minute walk distance in patients with idiopathic pulmonary fibrosis undergoing lung transplant evaluation.
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ABSTRACT:
SUBMITTER: Porteous MK
PROVIDER: S-EPMC4809664 | biostudies-other | 2016 Mar
REPOSITORIES: biostudies-other
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Project description:RationaleFunctional studies may be useful to predict survival in idiopathic pulmonary fibrosis (IPF). Various cutoffs of 6-min-walk distance (6MWD) have been suggested to identify patients at a high risk of death.ObjectivesTo examine the association between 6MWD and survival in patients with IPF listed for lung transplantation, and to identify sensitive and specific cutoffs for predicting death at 6 mo.MethodsWe performed a retrospective cohort study of 454 patients classified as having IPF listed for lung transplantation with the United Network for Organ Sharing between June 30, 2004 and July 22, 2005.Measurements and main resultsLower 6MWD was associated with an increased mortality rate (p value for linear trend < 0.0001). Patients with a walk distance less than 207 m had a more than fourfold greater mortality rate than those with a walk distance of 207 m or more, despite adjustment for demographics, anthropomorphics, FVC % predicted, pulmonary hypertension, and medical comorbidities (adjusted rate ratio, 4.7; 95% confidence interval, 2.5-8.9; p < 0.0001). 6MWD was a significantly better predictor of 6-mo mortality than was FVC % predicted (c-statistic = 0.73 vs. 0.59, respectively; p = 0.02).ConclusionsLower 6MWD was strongly and independently associated with an increased mortality rate for wait-listed patients classified as having IPF. 6MWD was a better predictor of death at 6 mo than was FVC % predicted.
| S-EPMC2648057 | biostudies-literature
Project description:Pulmonary hypertension is a common finding in patients with idiopathic pulmonary fibrosis (IPF), and is associated with increased morbidity and mortality. Therapy with sildenafil has been shown to decrease pulmonary vascular resistance in patients with pulmonary fibrosis and may improve functional status. Patients with IPF and documented pulmonary hypertension were followed up in an open-label study of sildenafil. The 6-min walk test distance (6MWD) was obtained before and after 3 months of sildenafil therapy. Fourteen patients were followed up in the study; 11 patients completed both 6-min walk tests. The mean improvement in walk distance was 49.0 m (90% confidence interval, 17.5 to 84.0 m). When all 14 patients were dichotomized into groups of "responders" (ie, >/= 20% improvement in 6MWD) or "nonresponders" (ie, < 20% change or unable to complete), 57% were classified as responders. Sildenafil is a promising and well-tolerated therapeutic agent for use in patients with IPF and pulmonary hypertension, and should be studied in a large, well-controlled trial.
| S-EPMC2098039 | biostudies-literature
Project description:The six-minute walk test (6MWT) is a simple test that is widely used to assess functional exercise capacity in patients with idiopathic pulmonary fibrosis (IPF). Patients with IPF have reduced exercise capacity due to a number of factors, such as impaired respiratory mechanics and circulatory problems. As a self-paced and usually submaximal exercise test, the 6MWT reflects the exercise level of everyday activities. Variables measured during the 6MWT, such as six-minute walk distance (6MWD) and desaturation, are strong predictors of mortality in patients with IPF. However, the results of a 6MWT are affected by numerous factors, including age, body size, comorbidities and the use of supplemental oxygen during the test, and these need to be borne in mind when interpreting the results of individual and serial tests. Clinical studies, including trials of potential therapies for IPF, have differed in the methodology used to implement the 6MWT, hindering the comparison of results across studies. In this review, I describe the utility of the 6MWT in patients with IPF and provide recommendations for standardisation of the test for use both in clinical practice and research. A brief video on how to set up and administer the 6MWT is available at http://www.usscicomms.com/respiratory/lancaster/6mwt/.
| S-EPMC6291931 | biostudies-literature
Project description:Rationale and hypothesisIdiopathic pulmonary fibrosis is a fatal disease with a variable rate of progression. We hypothesized that changes in distance walked and quantity of desaturation during a six-minute-walk test (6MWT) would add prognostic information to changes in FVC or diffusing capacity for carbon monoxide.MethodsOne hundred ninety-seven patients with idiopathic pulmonary fibrosis were evaluated. Desaturation during the 6MWT was associated with increased mortality even if a threshold of 88% was not reached. Baseline walk distance predicted subsequent walk distance but was not a reliable predictor of subsequent mortality in multivariate survival models. The predictive ability of serial changes in physiology varied when patients were stratified by the presence/absence of desaturation < or = 88% during a baseline 6MWT. For patients with a baseline saturation < or = 88% during a 6MWT, the strongest observed predictor of mortality was serial change in diffusing capacity for carbon monoxide. For patients with saturation > 88% during their baseline walk test, serial decreases in FVC and increases in desaturation area significantly predicted subsequent mortality, whereas decreases in walk distance and in diffusing capacity for carbon monoxide displayed less consistent statistical evidence of increasing mortality in our patients.ConclusionThese data highlight the importance of stratifying patients by degree of desaturation during a 6MWT before attributing prognostic value to serial changes in other physiologic variables.
| S-EPMC2648064 | biostudies-literature
Project description:BackgroundFew studies have investigated the relationship between physiological outcomes and quality of life in patients with idiopathic pulmonary fibrosis (IPF). Health-related quality of life (HRQL) data may provide a valuable patient-centred outcome for the evaluation of interventions. Determination of which physiological and functional variables are associated with HRQL may facilitate interpretation of disease progression and impacts of therapy.ObjectivesTo determine whether an association between Medical Outcomes Short-Form 36 and St George's Respiratory Questionnaire scores and other markers of disease severity exist, and to identify which physiological and functional variables are independently associated with HRQL.MethodsIn a cross-sectional study, 137 patients with IPF completed HRQL surveys and underwent clinical assessment. Multiple linear regression analysis was used to determine the relationship between age, forced vital capacity, diffusing capacity of carbon monoxide, 6 min walk distance (6MWD) and oxygen requirement, and HRQL scores.Results6MWD was the only functional measure of disease severity significantly associated with all domain scores of the St George's Respiratory Questionnaire and the Medical Outcomes Short-Form 36 physical component summary score.Conclusions6MWD was associated with HRQL among patients with IPF. This highlights the importance of 6MWD not only as a prognostic indicator in IPF, but also a predictor of HRQL and a meaningful outcome for patients.
| S-EPMC3267607 | biostudies-literature
Project description:Background: To date, there is no reference for a 6-min walk test distance (6-MWD) immediately after cardiac surgery. Therefore, this study aimed to identify the determinants and to generate equations for prediction reference for 6-MWD in patients immediately after cardiac surgery. Methods: This is a cross-sectional study of the 6-min walk test (6-MWT) prior to participation in the cardiac rehabilitation (CR) program of patients after coronary artery bypass surgery (CABG) or valve surgery. The 6-MWT were carried out in a gymnasium prior to the CR program immediately after the cardiac surgery. Available demographic and clinical data of patients were analyzed to identify the clinical determinants of 6-MWD. Results: This study obtained and analyzed the data of 1,509 patients after CABG and 632 patients after valve surgery. The 6-MWD of all patients was 321.5 ± 73.2 m (60-577). The distance was longer in the valve surgery group than that of patients in the CABG group (327.75 ± 70.5 vs. 313.59 ± 75.8 m, p < 0.001). The determinants which significantly influence the 6-MWD in the CABG group were age, gender, diabetes, atrial fibrillation, and body height, whereas in the valve surgery group these were age, gender, and atrial fibrillation. The multivariable regression models generated two formulas using the identified clinical determinants for patients after CABG: 6-MWD (meter) = 212.57 + 30.47 (if male gender) - 1.62 (age in year) + 1.09 (body height in cm) - 12.68 (if with diabetes) - 28.36 (if with atrial fibrillation), and for patients after valve surgery with the formula: 6-MWD (meter) = 371.05 + 37.98 (if male gender) - 1.36 (age in years) - 10.61 (if atrial with fibrillation). Conclusion: This study identified several determinants for the 6-MWD and successively generated two reference equations for predicting 6-MWD in patients after CABG and valve surgery.
| S-EPMC8416754 | biostudies-literature
Project description:BackgroundThe 6-min walk test (6MWT) is a commonly used clinical assessment of exercise capacity in patients with cardiopulmonary or neuromuscular disease, but normal values are lacking for young adults, who are frequent subjects of testing.MethodsIn a two-center study, 272 young adults, ages 18-50, underwent American Thoracic Society protocolized 6-min walk testing, and 56 underwent repeat testing. A linear regression model was developed based on anthropomorphic data. This model was compared to existing prediction equations.ResultsMedian 6MWD for the cohort was 637 m (IQR 584-686 m) and was not significantly impacted by age. This is in contrast to existing equations extrapolated from older subjects that predict increasing 6MWD in younger subjects. We found weak correlation of 6MWD with height, weight, BMI, and resting heart rate. Heart rate at completion correlated most strongly with 6MWD (rho 0.53 p < 0.0001). Repeat 6MWD was surprisingly variable, with a median difference between tests of 32.5 ± 31.9 m. Established reference equations performed poorly in this population, largely because age has much less effect on 6MWD in this group than in older adults.ConclusionsEstablished reference equations should be reconfigured to include data from young adults, as age has minimal effect on 6MWD in this population. Heart rate response may be a valuable measure of effort in normal subjects. Six-minute walk distance, as with pulmonary function and exercise testing, should have predictive equations across the spectrum of age to allow for accurate assessment of exercise limitation.
| S-EPMC7174378 | biostudies-literature
Project description:BACKGROUND: Exercise tolerance can be assessed by the cycle endurance test (CET) and six-minute walk test (6MWT) in patients with Chronic Obstructive Pulmonary Disease (COPD). We sought to investigate the characteristics of functional exercise performance and determinants of the CET and 6MWT in a large clinical cohort of COPD patients. METHODS: A dataset of 2053 COPD patients (43% female, age: 66.9 ± 9.5 years, FEV1% predicted: 48.2 ± 23.2) was analyzed retrospectively. Patients underwent, amongst others, respiratory function evaluation; medical tests and questionnaires, one maximal incremental cycle test where peak work rate was determined and two functional exercise tests: a CET at 75% of peak work rate and 6MWT. A stepwise multiple linear regression was used to assess determinants. RESULTS: On average, patients had impaired exercise tolerance (peak work rate: 56 ± 27% predicted, 6MWT: 69 ± 17% predicted). A total of 2002 patients had CET time of duration (CET-Tend) less than 20 min while only 51 (2.5%) of the patients achieved 20 min of CET-Tend . In former patients, the percent of predicted peak work rate achieved differed significantly between men (48 ± 21% predicted) and women (67 ± 31% predicted). In contrast, CET-Tend was longer in men (286 ± 174 s vs 250 ± 153 s, p < 0.001). Also, six minute walking distance (6MWD) was higher in men compared to women, both in absolute terms as in percent of predicted (443 m, 67%predicted vs 431 m, 72%predicted, p < 0.05). Gender was associated with the CET-Tend but BMI, FEV1 and FRC were related to the 6MWD highlighting the different determinants of exercise performance between CET and 6MWT. CONCLUSIONS: CET-Tend is a valuable outcome of CET as it is related to multiple clinical aspects of disease severity in COPD. Gender difference should temper the interpretation of CET.
| S-EPMC4229855 | biostudies-other
Project description:Nearly all available treatments for pulmonary arterial hypertension have been approved based on change in 6-minute walk distance (?6MWD) as a clinically important end point, but its validity as a surrogate end point has never been shown. We aimed to validate the difference in ?6MWD against the probability of a clinical event in pulmonary arterial hypertension trials.First, to determine whether ?6MWD between baseline and 12 weeks mediated the relationship between treatment assignment and development of clinical events, we conducted a pooled analysis of patient-level data from the 10 randomized placebo-controlled trials previously submitted to the US Food and Drug Administration (n=2404 patients). Second, to identify a threshold effect for the ?6MWD that indicated a statistically significant reduction in clinical events, we conducted a meta-regression among 21 drug/dose-level combinations. ?6MWD accounted for 22.1% (95% confidence interval, 12.1%- 31.1%) of the treatment effect (P<0.001). The meta-analysis showed an average difference in ?6MWD of 22.4 m (95% confidence interval, 17.4-27.5 m), favoring active treatment over placebo. Active treatment decreased the probability of a clinical event (summary odds ratio, 0.44; 95% confidence interval, 0.33-0.57). The meta-regression revealed a significant threshold effect of 41.8 m.Our results suggest that ?6MWD does not explain a large proportion of the treatment effect, has only modest validity as a surrogate end point for clinical events, and may not be a sufficient surrogate end point. Further research is necessary to determine whether the threshold value of 41.8 m is valid for long-term outcomes or whether it differs among trials using background therapy or lacking placebo controls entirely.
| S-EPMC4237273 | biostudies-literature
Project description:Background and objectivesField exercise tests (eg, 6-minute walk test [6MWT]) are important measures of functional exercise capacity in people with COPD. Shorter tests such as the 2-minute walk test (2MWT) may offer advantages in some populations but lack information about responsiveness to change. This study examined responsiveness, minimal important difference (MID), test-retest reliability, and construct validity of the 2MWT in people with stable COPD attending outpatient pulmonary rehabilitation (PR).MethodsAt pre-PR assessment, study participants completed a 2MWT twice in addition to usual measures (6MWT and Chronic Respiratory Questionnaire). At post-PR assessment following a standard PR program, measures were repeated and global rating of change scores obtained (patient and therapist). Pre-post program change scores were examined for correlations with change in 2-minute walk distance (2MWD) and used (where r≥0.3) to estimate the MID through anchor-based methods. Distribution-based estimates based on standard error of measurement were examined. Test-retest reliability (intraclass correlation coefficient [ICC] and Bland-Altman agreement) and validity (Pearson correlation with 6-minute walk distance [6MWD]) were reported.ResultsFifty-nine people (28 men) with stable COPD, mean age 68 years (SD 10 years), and percentage predicted forced expiratory volume in 1 second 48% (SD 20%) attended pre-PR assessment. Test-retest ICC for same-session 2MWD was 0.985. A mean difference of 2.4 m (95% confidence interval [CI] 0.7-4.0 m, P=0.006) occurred between the first and second trials. 2MWD and 6MWD were highly correlated (r=0.87, P<0.001). Forty-one participants completed PR and were included in responsiveness and MID analysis. Mean 2MWD improved significantly post-PR (8.8 m, 95% CI 3.6-14 m, P=0.001). The MID in 2MWD, anchored against clinically meaningful change in 6MWD, was 5.5 m (area under curve =0.81, P=0.001). Distribution-based methods estimated an MID of 4 m.ConclusionChange in 2MWD of at least 5.5 m following a PR program corresponded to a clinically meaningful change. A practice test is recommended due to learning effects.
| S-EPMC5640407 | biostudies-literature