Minimal clinically important differences in the six-minute walk test and the incremental shuttle walking test

Simple walking tests are widely used for the assessment of functional status in patients with cardiorespiratory disorders. These tests require far less instrumentation than formal cardiopulmonary exercise tests, but they do require standardization of procedures to achieve reproducible results. The most widely used tests for patients with COPD are the 6-minute walking test (6MWT) and the incremental shuttle walking test (SWT). The 6MWT has been characterized in COPD patients with respect to reproducibility and responsivity to change in health status. The 6MWT results are correlated with pulmonary function, health-related quality of life, maximum exercise capacity, and mortality. The minimal clinically important difference (MCID) for the 6MWT is conservatively estimated to be 54-80 meters using both distributional and discriminative methods. For an individual patient, the 6MWT would need to change by about 86 meters to be statistically confident that there has been a change. The SWT has been less extensively validated than the 6MWT, but has similar reproducibility in COPD (CV = approximately 20%). The SWT results improve with pulmonary rehabilitation and bronchodilation, and are highly correlated with maximum oxygen consumption. There are no studies that address the issue of MCID for the SWT. In addition to the MCID, the design and interpretation of COPD clinical trials should take into account the severity of initial impairment, the asymmetry between positive and negative changes, the proportion of patients who show substantial improvement, and the costs and risks of the treatment.     

Shuttle walking test and 6-minute walking test induce a similar cardiorespiratory performance in patients recovering from an acute exacerbation of chronic obstructive pulmonary disease

BACKGROUND: The incremental shuttle walking test (SWT) has recently been proposed as a more valid and reproducible alternative to the conventional 6-min walking test (6MWT) in the evaluation of exercise tolerance in patients with chronic obstructive pulmonary disease (COPD). OBJECTIVE: To compare the cardiorespiratory performance obtained during two sessions of SWT with that obtained during two sessions of 6MWT. METHODS: We examined 18 patients (forced expiratory volume in 1 s: 48 +/- 14%) recovering from an acute exacerbation of COPD that had required hospitalization. In the same afternoon, each patient performed two SWT and two 6MWT, with an interval of at least 30 min between each test; the sequence of the tests was randomized. RESULTS: Mean walking distance was greater in the second SWT test than in the first SWT. The changes from baseline in systolic blood pressure, heart rate, respiratory rate, oxygen saturation and dyspnea Borg index at the end of the test were similar between the two 6MWT and the two SWT. There was a highly significant correlation between walking distances measured during SWT and during 6MWT (rho: 0.85, p < 0.0005). Neither SWT nor 6MWT correlated with functional data of COPD. CONCLUSIONS: SWT, though being considered to be closer to a submaximal exercise test than 6MWT, does not induce a greater cardiorespiratory performance than 6MWT in patients recovering from acute exacerbation of COPD.     

Minimal Clinically Important Differences in 6-Minute Walk Test in Patients With HFrEF and Iron Deficiency

BackgroundThe 6-minute walk test (6MWT) is widely used to measure exercise capacity; however, the magnitude of change that is clinically meaningful for individuals is not well established in heart failure with reduced ejection fraction (HFrEF).ObjectiveTo calculate the minimal clinically important difference (MCID) for change in exercise capacity in the 6MWT in iron-deficient populations with HFrEF.MethodsIn this pooled secondary analysis of the FAIR-HF and CONFIRM-HF trials, mean changes in the 6MWT from baseline to weeks 12 and 24 were calculated and calibrated against the Patient Global Assessment (PGA) tool (clinical anchor) to derive MCIDs in improvement and deterioration.ResultsOf 760 patients included in the 2 trials, 6MWT and PGA data were available for 680 (89%) and 656 (86%) patients at weeks 12 and 24, respectively. The mean 6MWT distance at baseline was 281 ± 103 meters. There was a modest correlation between changes in 6MWT and PGA from baseline to week 12 (r = 0.31; P < 0.0001) and week 24 (r = 0.43; P < 0.0001). Respective estimates (95% confidence intervals) of MCID in 6MWT at weeks 12 and 24 were 14 meters (5;23) and 15 meters (3;27) for a “little improvement” (vs no change), 20 meters (10;30) and 24 meters (12;36) for moderate improvement vs a “little improvement,”, -11 meters (-32;9.2) and -31 meters (-53;-8) for a “little deterioration” (vs no change), and -84 meters (-144;-24) and -69 meters (-118;-20) for “moderate deterioration” vs a “little deterioration”.ConclusionsThe MCID for improvement in exercise capacity in the 6MWT was 14 meters–15 meters in patients with HFrEF and iron deficiency. These MCIDs can aid clinical interpretation of study data.     

Six‐minute walk test: observed adverse events and oxygen desaturation in a large cohort of patients with chronic lung disease

Background: The 6‐min walk test (6MWT) is widely used to assess patients with chronic lung disease (CLD). Anecdotal reports and studies in small numbers of patients with CLD suggest that complications associated with the 6MWT are rare. This study reports the incidence of observed adverse events during the 6MWT in patients referred to an outpatient pulmonary rehabilitation service. Methods: Seven hundred and forty‐one patients with stable CLD (chronic obstructive pulmonary disease (COPD), n= 572) completed the 6MWT in accordance with a standardized protocol that included continuous monitoring of oxygen saturation (SpO₂) and heart rate (Polar). Results: Adverse events occurred in 43 tests (6%). One 6MWT was terminated by the tester because of chest pain and one patient developed persistent tachycardia and irregular pulse immediately following the test. In 35 tests, the tester instructed the patient to stop walking because of profound oxygen desaturation (SpO₂ < 80%). Six patients prematurely terminated the 6MWT because of symptoms. Forty‐seven per cent (n= 345) of patients exhibited significant oxygen desaturation (≥4% fall in SpO₂ to <90%). Pre‐exercise SpO₂ was a significant predictor of desaturation in the COPD (1.79, 1.54–2.08, adjusted odds ratio (OR), 95% confidence intervals) and ILD (OR 1.40, 1.11–1.77) cohorts with FEV₁ (forced expiratory volume in 1 s) also a predictor in COPD (OR 3.02, 1.77–5.15). Conclusion: Profound oxygen desaturation is the most common adverse event observed during the 6MWT in patients with stable ILD and COPD. We propose that the American Thoracic Society 6MWT guidelines are revised to recommend continuous monitoring of SpO₂ during the 6MWT in patients with ILD and COPD.     

Effects of high-flow nasal cannula with oxygen on self-paced exercise performance in COPD: A randomized cross-over trial

Introduction:Studies have demonstrated that noninvasive ventilation improves exercise intolerance in patients with chronic obstructive pulmonary disease (COPD). The role of heated humidified high-flow nasal cannula (HFNC) therapy in patients with COPD on self-paced exercise performance remains unclear. Therefore, the purpose of the present study was to determine whether HFNC-aided supplemental oxygen during a 6-minute walk test (6MWT) would change self-paced exercise performance and cardiopulmonary outcomes in patients with stable COPD.Methods:A single-site, cross-over trial was conducted in a pulmonary rehabilitation outpatient department. This study enrolled 30 stable COPD patients without disability. The participants with and without HFNC performed 6MWTs on 2 consecutive days. Outcomes were the distance walked in the 6MWT, physiological, and cardiopulmonary parameters.Results:Those performing HFNC-aided walking exhibited a longer walking distance than those performing unaided walking. The mean difference in meters walked between the HFNC-aided and unaided walking scenarios was 27.3 ± 35.6 m (95% CI: 14.4–40.5 m). The energy expenditure index was significantly lower when walking was aided by HHHNFC rather than unaided (median: 1.21 beats/m walked vs median: 1.37 beats/m walked, P < .001). However, there were no differences in transcutaneous carbon dioxide tension between HHHNFC and non-HHHNFC patients.Conclusion:Walking distance and arterial oxygen saturation improved in stable COPD patients receiving HFNC with additional oxygen support. However, HFNC did not affect transcutaneous carbon dioxide tension and the self-reported dyspnea score during the walking test. The present study demonstrated the feasibility and safety of using HFNC in self-paced exercise.Trial registration:NCT03863821     

Multivariable assessment of the 6-min walking test in patients with chronic obstructive pulmonary disease

Functional exercise tolerance in patients with chronic obstructive pulmonary disease (COPD) is often assessed by the 6-min walking test (6MWT). To assess if the use of multiple factors adds to walking distance in describing performance in the 6MWT, an exploratory factor analysis was performed on physiological measurements and dyspnea ratings recorded during testing. Eighty-three patients with mild to severe COPD performed repeated 6MWTs before inpatient pulmonary rehabilitation. Factor analysis on 15 variables yielded a stable four-factor structure explaining 78.4% of the total variance. Recorded heart rate variables contributed to factor 1 (heart rate pattern), walking distance, heart rate increase, and decrease contributed to factor 2 (endurance capacity), oxygen desaturation variables contributed to factor 3 (impairment of oxygen transport), and dyspnea and effort variables contributed to factor 4 (perceived symptoms). Walking distance decreased in half of the 53 patients measured posttreatment, but self-perceived change in exercise tolerance improved in 84% and was explained by change in walking distance, by less desaturation, and by less dyspnea (R(2) = 0.55, p = 0.005). Qualitative analysis showed that 29 of 53 patients improved in three or four factors. Performance in the 6MWT can be described with four statistically independent and clinically interpretable factors. Because clinically relevant changes consist of more than only walking distance, assessment of functional exercise tolerance in patients with COPD improves by reporting multiple variables.     

6-minute walk testing is more sensitive than maximal incremental cycle testing for detecting oxygen desaturation in patients with COPD

STUDY OBJECTIVES: Some respiratory patients exhibit oxygen desaturation during rehabilitative walking but not during maximal cardiopulmonary exercise testing (CPET). We evaluated exercise-induced desaturation during 6-min walk testing (6MWT) in comparison with CPET in patients with COPD and determined the reproducibility of the phenomenon. PATIENTS: We tested 80 consecutive patients with COPD (FEV(1), 62.4 +/- 2% predicted) and 10 patients with supplementary COPD (FEV(1), 59.1 +/- 5% predicted) [mean +/- SEM] to determine the reproducibility. MEASUREMENTS AND RESULTS: First, patients with COPD performed cycle CPET (first CPET [CPET-1]). Three days later, they performed two 6MWTs (first 6MWT [6MWT-1] and second 6MWT [6MWT-2]). Pulse oximetric saturation (SpO(2)) was recorded every minute in both tests. Three groups emerged: desaturation at 6MWT not observed at CPET (DND) [n = 23], desaturation in both tests (n = 16), and no desaturation in either test (n = 41). Second, to evaluate reproducibility, 10 additional subjects with COPD who exhibited desaturation during two successive 6MWTs but not in CPET performed a second CPET (CPET-2) and a single-bout 6MWT (6MWT-3) in a supplementary trial. When two CPETs were performed, lack of O(2) desaturation was noted in both. O(2) desaturation was confirmed in 6MWT-2 and 6MWT-3 (7.4 +/- 1% and 7.4 +/- 1.5%, respectively). CONCLUSION: Twenty-eight percent of patients with COPD presented DND. The phenomenon was reproducible and not protocol dependent, emphasizing the clinical interest of the 6MWT.     

Different COPD Disease Characteristics are Related to Different Outcomes in the 6-minute Walk Test

Abstract

Background: Chronic obstructive pulmonary disease (COPD) can lead to severe disability as the disease advances. The 6-minute walk test (6MWT) is commonly used to measure functional capacity in COPD patients and has three potential outcomes; walking distance, oxygen desaturation, and self-perceived dyspnea assessed by the Borg scale, all reflecting different aspects of COPD. The aim of this study was to identify predictors of all 3 outcomes of 6MWT in patients with COPD. Methods: 370 COPD patients, aged 40–75 yrs, were included from the first phase of the Bergen COPD cohort study. They were examined with spirometry, bioelectrical impedance measurements, 6MWT, Center for Epidemiologic Studies of Depression (CES-D) Scale, Medical Research Council (MRC) dyspnea scale, Charlson index for co-morbidities, self-reported physical activity questionnaire, plasma levels of C-reactive protein (CRP) and arterial blood gases. Results: Significant predictors in the multivariate analyses were sex, age, FEV₁ in% predicted, symptoms of dyspnea (MRC), co-morbidities (Charlson Index) and self-reported physical activity for walking distance, FEV₁ in% predicted and PaO₂ for oxygen desaturation, and body composition, smoking and co-morbidities for self-perceived dyspnea assessed by the Borg scale. Conclusion: Several COPD characteristics have predictive value for the 6MWT, and some COPD characteristics are more strongly related to specific 6MWT outcomes than others.     

Comparison of the Sit-to-Stand Test with 6 min walk test in patients with chronic obstructive pulmonary disease

OBJECTIVE: To discuss the utility of Sit-to-Stand Test (STST) compared to the 6min walking test (6MWT) for the evaluation of functional status in patients with chronic obstructive pulmonary disease (COPD). MATERIAL-METHOD: SUBJECTS: Fifty-three patients with stable COPD (mean forced expiratory volume in 1s (FEV(1)) 46+/-9% predicted, mean age 71+/-12 year) and 15 healthy individuals (mean FEV(1) 101+/-13% predicted and mean age 63+/-8) were included. INTERVENTIONS: Functional performance was evaluated by STST and 6MWT. During the tests, severity of dyspnea (by Modified Borg Scale), heart rate, pulsed oxygen saturation (SpO(2), by Modified Borg Scale) (by pulse oxymeter), blood pressure were measured. The pulmonary function (by spirometry), quadriceps femoris muscle strength (by manual muscle test) and quality of life (by Nottingham Health Profile Survey) were evaluated. RESULTS: The STST and 6MWT results were lower in COPD group than the healthy group (P<0.05). During the 6MWT the rise in the heart rate, systolic blood pressure and the decrease in SpO(2) were statistically significant according to STST in COPD groups (P<0.05). The STST and 6MWT were strongly correlated with each other in both groups (P<0.05). Similarly, they were correlated with age, quality of life, peripheral muscle strength and dyspnea severity in COPD groups (P<0.05). CONCLUSION: Similar to 6MWT, STST is also able to determine the functional state correctly. Additionally, it produces less hemodynamical stress compared to the 6MWT. In conclusion, STST can be used as an alternative of the 6MWT in patients with COPD.     

两种运动试验对慢性阻塞性肺疾病患者运动低氧的比较

目的:对比6min步行试验(6MWT)与心肺运动试验(CPET)对慢性阻塞性肺疾病(COPD)患者运动低氧敏感性的差别。方法:选择30例稳定期COPD患者,分别行6MWT与CPET,两个试验的先后顺序随机,比较两种运动试验中运动低氧发生情况的差异。结果:6MWT中运动低氧发生率为46.6%(14/30),CPET中发生运动低氧发生率为50.0%(15/30),两种试验运动低氧的发生率,差异无统计学意义(P=0.796)。运动开始第2min至第6min,6MWT每分钟末脉搏血氧饱和度(SpO2)值低于心肺运动试验(P均0.05)。运动低氧发生时间6MWT(M=2)秒,明显早于CPET(M=8)秒(P=0.01)。结论:6MWT与CPET在COPD患者运动低氧发生率差异无统计学意义,运动低氧发生时间6MWT早于CPET。6MWT是一个简单、可行的COPD患者运动低氧的评价方案。     

肺康复治疗对稳定期慢性阻塞性肺疾病病人的疗效分析

目的观察肺康复治疗对稳定期慢性阻塞性肺疾病(Chronic obstructive pulmonary disease,COPD)患者的效果。方法测定以下肢训练为主的社区康复治疗前后患者的FEV1(第一秒用力呼气量占预计值百分比)、6 min步行距离、呼吸困难评分(Borg评分)、年人均急性发作次数、年人均住院次数。结果肺康复治疗前后的FEV1、6 min步行距离、Borg评分明显好于治疗前(P0.05),年COPD急性发作次数及住院次数治疗前后有统计学意义。结论肺康复治疗可改善COPD患者的呼吸功能,减少年均急性发作次数及住院次数。     

Effects of Pulmonary Hypertension on Exercise Capacity in Patients With Chronic Obstructive Pulmonary Disease

IntroductionThe impact of pulmonary hypertension (PH) on exercise tolerance in chronic obstructive pulmonary disease (COPD) has not been fully elucidated. It is necessary to characterize pulmonary hemodynamics in patients with moderate to severe COPD in order to improve their management. The aim of the study was to determine whether in COPD the presence of PH is associated with reduced exercise tolerance in a cohort of stable COPD patients.MethodsCross-sectional analysis of 174 COPD patients clinically stable: 109 without PH and 65 with PH (COPD-PH). We assessed socio-demographic data, lung function, quality of life, dyspnea, cardiopulmonary exercise testing (CPET), constant workload endurance time (CWET), and six-minute walk test (6MWT). We elaborated a logistic regression model to explore the impact of PH on exercise capacity in COPD patients.ResultsCOPD-PH patients showed lower exercise capacity both at maximal (CPET) (43(20) versus 68(27) Watts and 50(19)% versus 71(18)% predicted peak oxygen consumption (VO₂peak), COPD-PH and COPD, respectively), and at submaximal tests (6MWT) (382(94) versus 486(95) m). In addition, the COPD-PH group had lower endurance time than the non-PH COPD group (265(113) s and 295(164) s, respectively).ConclusionsThe presence of PH is an independent factor that impairs exercise capacity in COPD.     

Heart rate recovery after the 6‐min walk test is related to 6‐min walk distance and percutaneous oxygen saturation recovery in patients with COPD

Heart rate recovery (HRR) after maximal load exercise affects mortality in chronic obstructive pulmonary disease (COPD). However, the associations of clinical characteristics with HRR after the 6‐min walk test (6MWT), which is defined as a submaximal load test, remain unclear. We showed that HRR in patients with COPD after 6MWT was related to 6‐min walk distance and percutaneous oxygen saturation recovery. HRR after the 6MWT may be useful to assess exercise capacity in COPD.     

Encouraged 6-min walking test indicates maximum sustainable exercise in COPD patients

STUDY OBJECTIVES: In patients with moderate-to-severe COPD, an encouraged 6-min walking test (6MWT) is a high-intensity submaximal exercise protocol that shows an oxygen uptake (Vo(2)) plateau after the third minute of the test. This last feature prompted the hypothesis that self-paced walking speed is set to achieve "maximal" sustainable Vo(2), namely "critical power" or "critical speed." PATIENTS AND METHODS: Eight patients with moderate-to-severe COPD (mean age, 68 +/- 7 years [+/- SD]; FEV(1), 50 +/- 13% predicted; Pao(2), 69 +/- 8 mm Hg) underwent the following tests on different days in order: (1) encouraged 6MWT; (2) standard incremental shuttle test to identify peak walking speed; (3) four different high-intensity, constant walking speed tests to exhaustion to calculate critical walking speed; and (4) timed walking test at critical walking speed (CWS) to examine sustainability of the exercise. RESULTS: 6MWT and CWS showed similar results (mean of last 3 min): Vo(2) (1,605 +/- 304 mL/min vs 1,584 +/- 319 mL/min), minute ventilation (47 +/- 12 L/min vs 48 +/- 11 L/min), respiratory exchange ratio (0.89 +/- 0.1 vs 0.90 +/- 0.1), heart rate (130 +/- 18 beats/min vs 131 +/- 16 beats/min), Borg dyspnea score (5.4 +/- 1.3 vs 5.5 +/- 2.4), and walking speed (1.49 +/- 0.1 m/s vs 1.44 +/- 0.1 m/s, respectively). CONCLUSION: This study supports that 6MWT indicates maximum sustainable exercise that might be related with its predictive value in COPD patients.     

Relationship between field walking tests and incremental cycle ergometry in COPD

Background and objective: Cycle ergometer training is an important component of pulmonary rehabilitation for patients with COPD. However, incremental cycle tests from which individualized cycle training intensity can be prescribed may not be readily available to clinicians. The aims of the study were to (i) investigate the physiological and psychophysical responses to the 6‐min walk test (6MWT), incremental shuttle walk test (ISWT) and cycle ergometer test (CET); and (ii) determine whether the distance walked in either the 6MWT or the ISWT could be used to estimate peak work rate on a cycle ergometer. Methods: A repeated measures study was undertaken in COPD patients in a stable condition. The 6MWT, ISWT and CET were performed in random order, and physiological responses, rate of perceived exertion and dyspnoea were measured. Results: Twenty‐two patients with COPD completed the study. There was no significant difference in peak oxygen uptake between the 6MWT, ISWT and CET. The significant correlation between the 6MWD and incremental shuttle walk distance with peak watts on the CET (r = 0.63, P = 0.002 and r = 0.75, P < 0.001, respectively) was strengthened by the inclusion of weight, age and gender (r = 0.89 P = 0.001 and r = 0.91, P < 0.001). Bland–Altman analysis demonstrated a strong agreement between peak work rate measured on the CET and that estimated from either the 6MWT or the ISWT. Conclusions: The significant relationships found between the three exercise tests, and the regression equations predicting peak work rate on the CET from the 6MWT or the ISWT, may allow for the estimation of intensity of cycle exercise training from walk tests in COPD patients.     

Physiologic responses to incremental and self-paced exercise in COPD: a comparison of three tests

OBJECTIVES: To investigate cardiorespiratory and dyspnea responses to incremental and self-paced exercise tests in patients with COPD. DESIGN: A prospective within-subject design was used. PATIENTS: Twenty stable subjects (15 men), with a mean (+/- SD) age of 64.0 +/- 7.5 years and moderate-to-severe COPD (ie, mean FEV(1), 0.8 +/- 0.3 L and 28.9 +/- 7.9% predicted) were studied. METHODS: Each subject completed a 6-min walk test (6MWT), an incremental shuttle walking test (ISWT), and a cycle ergometer test (CET), within a 2-week period. The tests were performed at least 24 h apart. Standardized encouragement was utilized in each test with the aim of maximizing performance. Heart rate (HR) and dyspnea were measured each minute throughout the tests, and pulse oximetric saturation (Spo(2)) was measured before and immediately after each test. The distances walked in the 6MWT and ISWT were compared to peak oxygen uptake (Vo(2)) values from the CET. RESULTS: HR increased linearly with increasing workload during the CET and ISWT, but increased alinearly with a disproportionate increase early in the 6MWT. In contrast, dyspnea scores increased linearly during the 6MWT, but increased alinearly with a disproportionate increase late during the CET and ISWT. Peak HR and dyspnea were not significantly different between tests. Spo(2) was significantly lower at the end of both walking tests compared to that at the end of the CET (p < 0.001). The distance walked in both the ISWT and 6MWT were related to peak Vo(2) values on the CET (for both tests, r = 0.73; p < 0.001). CONCLUSIONS: The patterns of response in HR and dyspnea seen during the 6MWT suggest that patients with COPD titrate exertion against dyspnea to achieve a peak tolerable intensity. This strategy is not possible in an externally paced ISWT or CET. However, it is a limited strategy, with performance converging at higher workloads. Similar peak exercise responses were achieved in the 6MWT, ISWT, and CET. Greater oxygen desaturation was observed during the field walking tests, suggesting that both the ISWT and 6MWT are more sensitive than the CET in detecting exercise-induced hypoxemia and in assessing ambulatory oxygen therapy needs.     

The six-minute walk test: a useful metric for the cardiopulmonary patient

Measurement of exercise capacity is an integral element in assessment of patients with cardiopulmonary disease. The 6-min walk test (6MWT) provides information regarding functional capacity, response to therapy and prognosis across a range of chronic cardiopulmonary conditions. A distance less than 350 m is associated with increased mortality in chronic obstructive pulmonary disease, chronic heart failure and pulmonary arterial hypertension. Desaturation during a 6MWT is an important prognostic indicator for patients with interstitial lung disease. The 6MWT is sensitive to commonly used therapies in chronic obstructive pulmonary disease such as pulmonary rehabilitation, oxygen, long-term use of inhaled corticosteroids and lung volume reduction surgery. However, it appears less reliable to detect changes in clinical status associated with medical therapies for heart failure. A change in walking distance of more than 50 m is clinically significant in most disease states. When interpreting the results of a 6MWT, consideration should be given to choice of predictive values and the methods by which the test was carried out.     

Walking with Non-Invasive Ventilation Does Not Prevent Exercise-Induced Hypoxaemia in Stable Hypercapnic COPD Patients

Background: Non-invasive positive pressure ventilation (NPPV) in addition to supplemental oxygen improves arterial oxygenation, walking distance and dyspnea when applied during exercise in stable hypercapnic COPD patients. The aim of the current study was to investigate whether NPPV without supplemental oxygen is capable of preventing severe exercise-induced hypoxemia in these patients when applied during walking. Methods and Results: 15 stable hypercapnic COPD patients (FEV1 29.9 ± 15.9%) performed two 6-minute walk tests (6MWT) with a rollator in a randomized cross-over design: using either supplemental oxygen

(2.4 ± 0.7 L/min) or NPPV (inspiratory/expiratory positive airway pressure of 28.2 ± 2.8 / 5.5 ± 1.5 mbar) without supplemental oxygen. Results: 10 patients were able to complete both 6MWT. 6MWT with supplemental oxygen resulted in no changes for PO2 (pre: 67.3 ± 11.2 mmHg vs. post: 65.6 ± 12.0 mmHg, p = 0.72) whereas PCO2 increased (pre: 50.9 ± 8.1 mmHg vs. post: 54.3 ± 10.0 mmHg (p < 0.03). During 6MWT with NPPV PO2 significantly decreased from 66.8 ± 7.2 mmHg to 55.5 ± 10.6 mmHg (p < 0.02) whereas no changes occurred in PCO2 (pre: 50.6 ± 7.5 mmHg vs. post: 53.0 ± 7.1 mmHg; p = 0.17). Walking distance tended to be lower in 6MWT with NPPV compared to 6MWT with supplemental oxygen alone (318 ± 160 m vs. 377 ± 108 m; p = 0.08). Conclusion: The use of NPPV during walking without the application of supplemental oxygen does not prevent exercise-induced hypoxemia in patients with stable hypercapnic COPD.     

Six-minute walking-induced systemic inflammation and oxidative stress in muscle-wasted COPD patients

BACKGROUND: Systemic inflammation and oxidative stress are potential mechanisms for muscle wasting in COPD patients. Six-minute walking testing (6MWT) has been suggested as simple and valid exercise test in COPD that is well tolerated, and reflective of activities of daily living. The present study investigated physiologic and systemic immunologic responses to a 6MWT in muscle-wasted patients with COPD and compared them with maximal cardiopulmonary exercise testing (CPET). METHODS: Ten patients with muscle-wasted COPD were included (fat-free mass index [FFMI]: men, < 16 kg/m2; women, < 15 kg/m2). 6MWT and CPET were performed in random order. The physiologic response was followed by a mobile oxycon. Arterial blood was obtained at rest and after exercise to measure blood gases and markers of systemic inflammation and oxidative stress. RESULTS: In these patients (FEV1 55 +/- 4% of predicted [mean +/- SE]), the 6MWT was a submaximal, albeit intense, exercise as reflected by oxygen uptake (VO2), minute ventilation, heart rate, and lactate values. Leukocytosis was less intense after 6MWT compared to CPET. Contrary, the increase in interleukin-6, free radical release by neutrophils, oxidation of proteins and lipids, and the reduction in antioxidant capacity were similar after both exercises. FFMI was inversely related to 6MWT-induced increases in protein and lipid peroxidation. CONCLUSIONS: This study shows that a 6MWT induces a systemic immunologic response in muscle-wasted patients with COPD, which is comparable to CPET-induced responses. The correlation between systemic oxidative stress and the degree of muscle wasting supports a possible causal relation between systemic inflammation, oxidative stress, and muscle wasting.     

The effect of body mass index on functional parameters and quality of life in COPD patients

Malnutrition increases dyspnea and exercise intolerance in chronic obstructive pulmonary disease (COPD) patients by effecting respiratory muscle strength (RMS) and thereby decreasing quality of life (QoL). This is a prospective study conducted to find out the differences due to pulmonary function tests (PFT), arterial blood gases (ABG), RMS, exercise capacity (EC) and QoL in COPD patients having low and normal body mass index (BMI). The study was carried out between April 2003-June 2004 and included 65 male COPD patients with a mean age of 63.4 +/- 9.6. The patients were grouped into 2: Low BMI group (BMI < 21) and normal BMI group (BMI= 21-28). All patients were investigated with PFT (spirometry, maximal inspiratory and expiratory pressures, diffusion capacity), ABG analyses, Modified Medical Research Council (MMRC) dyspnea scale, determination of EC by 6 minutes walking test (6 MWT) and determination of QoL by Turkish version of St. George Respiratory Questionnaire (SGRQ). Of these cases, 29 (44.6%) had low and 36 (55.4%) had normal BMI; MMRC was higher in the first group without statistical significance (p= 0.074). The first group demonstrated significantly lower diffusion capacity (DLco) and DLco%, PEmax, PEmax%, RMS and RMS% (p< 0.05). ABG analyses, 6 MWT results and SGRQ symptom scores revealed no significant difference. As a conclusion, BMI is closely related to dyspnea score, RMS and QoL in COPD patients, therefore in patients with low BMI pulmonary rehabilitation programs including nutritional support should accompany medical treatment.