Abstract
Background:
The 6-minute walk test (6MWT) and the Glittre ADL-test (GT) are used to assess functional capacity and exercise tolerance; however, the reproducibility of these tests needs further study in patients with acute lung diseases.
Objectives:
The aim of this study was to investigate the reproducibility of the 6MWT and GT performed in patients hospitalized for acute and exacerbated chronic lung diseases.
Method:
48 h after hospitalization, 81 patients (50 males, age: 52±18 years, FEV1: 58±20% of the predicted value) performed two 6MWTs and two GTs in random order on different days.
Results:
There was no difference between the first and second 6MWT (median 349 m [284-419] and 363 m [288-432], respectively) (ICC: 0.97; P<0.0001). A difference between the first and second tests was found in GT (median 286 s [220-378] and 244 s [197-323] respectively; P<0.001) (ICC: 0.91; P<0.0001).
Conclusion:
Although both the 6MWT and GT were reproducible, the best results occurred in the second test, demonstrating a learning effect. These results indicate that at least two tests are necessary to obtain reliable assessments.
physical therapy; reproducibility of results; exercise tolerance; exercise test; lung diseases
Introduction
Clinical field tests are used to assess the functional capacity (FC) and exercise
tolerance of patients with pulmonary diseases. It is important to know the
reproducibility of these tests to achieve an accurate assessment of the patient's FC
and responsiveness to treatment11 ERS Task Force, Palange P, Ward SA, Carlsen KH, Casaburi R,
Gallagher CG, et al. Recommendations on the use of exercise testing in clinical
practice. Eur Respir J. 2007;29(1):185-209.
http://dx.doi.org/10.1183/09031936.00046906 . PMid:17197484
http://dx.doi.org/10.1183/09031936.00046...
. The
variability of a test must also be known so that its results are reliable; this
ensures the differences are due to interventions or the evolution of the patient
rather than fluctuations inherent to the test.
The 6-minute walk test (6MWT) is a simple and low-cost field test that provides a
comprehensive and integrated measure of the patient's physical condition22 ATS Committee on Proficiency Standards for Clinical Pulmonary
Function Laboratories. ATS statement: guidelines for the six-minute walk test.
Am J Respir Crit Care Med. 2002;166(1):111-7.
http://dx.doi.org/10.1164/ajrccm.166.1.at1102 . PMid:12091180
http://dx.doi.org/10.1164/ajrccm.166.1.a...
. The reproducibility of the 6MWT has been
tested in patients with various lung diseases, particularly patients with chronic
obstructive pulmonary disease (COPD)3-5 mainly in the outpatient setting.
The variability found in these studies has been attributed to a learning effect. A
recent study found a difference of 27 m (7%) greater in the second test66 Hernandes NA, Wouters EFM, Meijer K, Annegarn J, Pitta F, Spruit MA.
Reproducibility of 6-minute walking test in patients with COPD. Eur Respir J.
2011;38(2):261-7. http://dx.doi.org/10.1183/09031936.00142010 .
PMid:21177838
http://dx.doi.org/10.1183/09031936.00142...
. Sciurba et al.77 Sciurba F, Criner GJ, Lee SM, Mohsenifar Z, Shade D, Slivka W, et
al. Six-minute walk distance in chronic obstructive pulmonary disease:
reproducibility and effect of walking course layout and length. Am J Respir Crit
Care Med. 2003;167(11):1522-7. http://dx.doi.org/10.1164/rccm.200203-166OC .
PMid:12615634
http://dx.doi.org/10.1164/rccm.200203-16...
found a difference of 20 m (7%), Chatterjee et al.88 Chatterjee AB, Rissmiller RW, Meade K, Paladenech C, Conforti J,
Adair NE, et al. Reproducibility of the 6-minute walk test for ambulatory oxygen
prescription. Respiration. 2010;79(2):121-7. http://dx.doi.org/10.1159/000220343
. PMid:19468196
http://dx.doi.org/10.1159/000220343...
found a 32-m difference (10%), Stevens et
al.99 Stevens D, Elpern E, Sharma K, Szidon P, Ankin M, Kesten S.
Comparison of hallway and treadmill six-minute walk tests. Am J Respir Crit Care
Med. 1999;160(5 Pt 1):1540-3. http://dx.doi.org/10.1164/ajrccm.160.5.9808139 .
PMid:10556117
http://dx.doi.org/10.1164/ajrccm.160.5.9...
found 42 m (13%), and Jenkins and
Cecins1010 Jenkins S, Cecins NM. Six-minute walk test in pulmonary
rehabilitation: do all patients need a practice test?. Respirology.
2010;15(8):1192-6. http://dx.doi.org/10.1111/j.1440-1843.2010.01841.x .
PMid:20920121
http://dx.doi.org/10.1111/j.1440-1843.20...
identified a 37-m difference
(11%).
The reproducibility of the 6MWT has also been studied in patients with idiopathic
interstitial pneumonia (ICC: 0.98, standard deviation/mean: 4.2%)1111 Eaton T, Young P, Milne D, Wells AU. Six-minute walk, maximal
exercise tests: reproducibility in fibrotic interstitial pneumonia. Am J Respir
Crit Care Med. 2005;171(10):1150-7. http://dx.doi.org/10.1164/rccm.200405-578OC
. PMid:15640367
http://dx.doi.org/10.1164/rccm.200405-57...
, cystic fibrosis (6.5 m or 4.3%)1212 Ziegler B, Rovedder PME, Oliveira CL, Abreu e Silva F, Tarso Roth
Dalcin P. Repeatability of the 6-minute walk test in adolescents and adults with
cystic fibrosis. Respir Care. 2010;55(8):1020-5. PMid:20667149
., interstitial lung disease (41 m, 10%)1010 Jenkins S, Cecins NM. Six-minute walk test in pulmonary
rehabilitation: do all patients need a practice test?. Respirology.
2010;15(8):1192-6. http://dx.doi.org/10.1111/j.1440-1843.2010.01841.x .
PMid:20920121
http://dx.doi.org/10.1111/j.1440-1843.20...
, bronchiectasis (22 m, 4%)1010 Jenkins S, Cecins NM. Six-minute walk test in pulmonary
rehabilitation: do all patients need a practice test?. Respirology.
2010;15(8):1192-6. http://dx.doi.org/10.1111/j.1440-1843.2010.01841.x .
PMid:20920121
http://dx.doi.org/10.1111/j.1440-1843.20...
, and asthma (19 m, 4%)1010 Jenkins S, Cecins NM. Six-minute walk test in pulmonary
rehabilitation: do all patients need a practice test?. Respirology.
2010;15(8):1192-6. http://dx.doi.org/10.1111/j.1440-1843.2010.01841.x .
PMid:20920121
http://dx.doi.org/10.1111/j.1440-1843.20...
.
The Glittre ADL-test (GT) is another field test developed to evaluate the capacity to
perform activities of daily living (ADL). Its reproducibility was tested in patients
with COPD, showing a decrease of 22 s in the time to completion in the second test,
which was attributed to a learning effect1313 Skumlien S, Hagelund T, Bjørtuft O, Ryg MS. A field test of
functional status as performance of activities of daily living in COPD patients.
Respir Med. 2006;100(2):316-23. http://dx.doi.org/10.1016/j.rmed.2005.04.022 .
PMid:15941658
http://dx.doi.org/10.1016/j.rmed.2005.04...
.
Considering the importance of field-testing in clinical practice, its reproducibility
should also be solidly studied in hospitalized patients not only with exacerbation
of COPD but also with acute lung conditions, such as community-acquired pneumonia
(CAP). To our knowledge, there is no study testing the reproducibility of the 6MWT
and GT in hospitalized patients. The ability of the GT to detect exercise-induced
desaturation, as previously demonstrated with the 6MWT in COPD1414 Poulain M, Durand F, Palomba B, Ceugniet F, Desplan J, Varray A, et
al. 6-minute walk testing is more sensitive than maximal incremental cycle
testing for detecting oxygen desaturation in patients with COPD. Chest.
2003;123(5):1401-7. http://dx.doi.org/10.1378/chest.123.5.1401 .
PMid:12740254
http://dx.doi.org/10.1378/chest.123.5.14...
, should be assessed so that it can be used to identify
patients with hypoxemia during ADL. The aim of this study was to investigate the
reproducibility of the 6MWT and GT in patients hospitalized for acute and
exacerbated chronic lung diseases and to compare the desaturation induced by both
tests.
Method
Participants
The sample from a cross-sectional study previously published by our group1515 José A, Corso SD. Patients hospitalized for community-acquired
pneumonia present reduced functional performance. Braz J Phys Ther.
2013;17(4):351-8. http://dx.doi.org/10.1590/S1413-35552013005000098 .
PMid:24072224
http://dx.doi.org/10.1590/S1413-35552013...
was used for this current work. The
sample included 103 adult patients hospitalized for less than 48 h for acute or
exacerbated chronic lung diseases, with or without oxygen supplementation and
without comorbidities that might limit their performances on the tests. For
better characterization of the sample, patients were divided into three groups
according to the most prevalent diseases of hospitalization in our hospital:
CAP, COPD, and Others (other lung diseases). This study was approved by the
Research Ethics Committee of Universidade Nove de Julho, São Paulo, Brazil
(protocol no. 273811/2009). All patients signed an informed consent form.
Design
The study was conducted in two visits on consecutive days. On the first visit, spirometry was performed, the body mass index (BMI) was calculated, and dyspnea was assessed according to the Medical Research Council (MRC) scale. The randomization was performed using sealed and opaque envelopes that each contained a card indicating the 6MWT or GT. A person uninvolved in the research selected one of these envelopes, which determined which test would be performed first (6MWT or GT).
An hour of rest was allowed between testing and retesting. On the second visit (24 h apart), the other test was performed. The total period of hospitalization was recorded.
Assessments
Spirometry
Spirometry was performed with the Pony portable spirometer (COSMED, Italy). The acceptability and reproducibility criteria adopted for the technical procedures were those recommended by the Brazilian guidelines for the testing of lung function1616 Sociedade Brasileira de Pneumologia e Tisiologia. Diretrizes para testes de função pulmonar. J Bras Pneumol. 2002;28(S3):S44-58.. The values of forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), and the FEV1/FVC ratio were expressed in absolute values and as percentage of the predicted value for the Brazilian population1717 Pereira CAC, Barreto SP, Simões JG, Pereira FWL, Gerstler JG, Nakatani J. Valores de referência para espirometria em uma amostra da população brasileira adulta. J Bras Pneumol. 1992;18(1):10-22..
Body mass index
BMI was calculated by dividing the body weight of the patient in kilograms (kg) by the square of the height in square meters (m2), and the result was expressed in kg/m2 1818 World Health Organization - WHO. The world health report 2002: reducing risks, promoting health life. Geneva: WHO; 2002.. The patient was classified as underweight if BMI<18.5 kg/m2, normal weight if 18.5-24.9 kg/m2, overweight if 25-29.9 kg/m2, and obese if BMI>30 kg/m2 1919 Associação Brasileira para o Estudo da Obesidade e da Síndrome Metabólica - ABESO. Sobrepeso e obesidade: diagnóstico. 3a ed. Itapevi, SP: AC Farmacêutica; 2009..
Medical Research Council's dyspnea scale
The Medical Research Council's (MRC) scale of dyspnea includes five items. The
patient chooses which of the items corresponds to the perceived limitations of
dyspnea on his/her ADLs. The patient selects a value from 1-5; the higher the
score the greater the limitations dyspnea imposes on the patient's ADL2020 Kovelis D, Segretti NO, Probst VS, Lareau SC, Brunetto AF, Pitta F.
Validação do Modified Pulmonary Functional Status and Dyspnea Questionnaire e da
escala do Medical Research Council para o uso em pacientes com doença pulmonar
obstrutiva crônica no Brasil. J Bras Pneumol. 2008;34(12):1008-18.
http://dx.doi.org/10.1590/S1806-37132008001200005 .
PMid:19180335
http://dx.doi.org/10.1590/S1806-37132008...
.
Six-minute walk test (6MWT)
The 6MWT was performed on a 20-meter-long flat corridor. Two tests with 1-h rest
times were performed on the same day. Other procedures and standardizations were
performed according to the American Thoracic Society recommendations22 ATS Committee on Proficiency Standards for Clinical Pulmonary
Function Laboratories. ATS statement: guidelines for the six-minute walk test.
Am J Respir Crit Care Med. 2002;166(1):111-7.
http://dx.doi.org/10.1164/ajrccm.166.1.at1102 . PMid:12091180
http://dx.doi.org/10.1164/ajrccm.166.1.a...
. The test with the longest distance
walked was selected for analysis, and the distance walked was expressed in m and
predicted values2121 Enright PL, Sherrill DL. Reference equations for the six-minute walk
in healthy adults. Am J Respir Crit Care Med. 1998;158(5 Pt 1):1384-7.
http://dx.doi.org/10.1164/ajrccm.158.5.9710086 . PMid:9817683
http://dx.doi.org/10.1164/ajrccm.158.5.9...
. Heart rate (HR) and
oxyhemoglobin saturation (SpO2) were measured at rest, at 3 min, and
at the end of the test using a pulse oximeter (Nonin 9500 model, Minnesota,
United States). The scores for sensation of dyspnea (Borg D) and lower limb
fatigue (Borg LL) were measured at rest and at the end of the test according to
the modified Borg scale2222 Wilson RC, Jones PW. A comparison of the visual analogue scale and
modified Borg scale for the measurement of dyspnoea during exercise. Clin Sci
(Lond). 1989;76(3):277-82. PMid:2924519 ..
Evaluation of oxygen desaturation was also obtained from the longest test
considering the lowest SpO2 recorded. Oxygen supplementation, when
necessary, was maintained in accordance with the prescription of the medical
team. A covered distance <82% of the predicted value was considered below
normal2323 Troosters T, Gosselink R, Decramer M. Six minute walking distance in
healthy elderly subjects. Eur Respir J. 1999;14(2):270-4.
http://dx.doi.org/10.1034/j.1399-3003.1999.14b06.x .
PMid:10515400
http://dx.doi.org/10.1034/j.1399-3003.19...
.
Glittre ADL-test (GT)
The GT comprises a circuit of functional activities the patient must cover 5
times in the shortest time possible. The patient performs activities such as
walking, using stairs, sitting on a chair and standing up, and handling 1-kg
weights to simulate moving objects from one shelf to another and then to the
floor. Throughout the test, the patient wears a weighted backpack1313 Skumlien S, Hagelund T, Bjørtuft O, Ryg MS. A field test of
functional status as performance of activities of daily living in COPD patients.
Respir Med. 2006;100(2):316-23. http://dx.doi.org/10.1016/j.rmed.2005.04.022 .
PMid:15941658
http://dx.doi.org/10.1016/j.rmed.2005.04...
.
Two tests were performed on the same day, with a 1-h rest interval between them. HR, SpO2, and time to completion were measured at rest and at the end of each completed lap. The Borg D and Borg LL2222 Wilson RC, Jones PW. A comparison of the visual analogue scale and modified Borg scale for the measurement of dyspnoea during exercise. Clin Sci (Lond). 1989;76(3):277-82. PMid:2924519 .scores were also evaluated at rest and at the end of the test. The test's total time to completion was recorded at the end.
Evaluation of oxygen desaturation was obtained from the test with the shorter duration considering the lowest SpO2 recorded. As described for 6MWT, oxygen supplementation, when necessary, was maintained in accordance with the prescription of the medical team.
Statistical analysis
The data analysis was performed using SPSS for Windows version 20.0 (SPSS, Chicago, Illinois, USA). The Shapiro-Wilk test was used to verify the compliance of the data distribution with the normality curve. Parametric data were express ed as mean and SD. Non-parametric data were expressed as median and interquartile intervals. In the sample characterization, comparisons between groups were performed by one-way analysis of variance (ANOVA) with post-hoc Tukey's analysis. Interclass correlation coefficient and Bland-Altman analysis were used for test-retest reproducibility. Intragroup comparisons for parametric data were performed by paired t-tests for dependent samples, and by the Wilcoxon test for the non-parametric data. P<0.05 was considered statistically significant.
Results
Sample
Of the 103 patients enrolled in the study, 10 were excluded for failure to perform the 6MWT and 12 for failure to perform the GT because of hospital discharge. At the end of the study, 81 subjects (50 men) were surveyed.
Fifty-one patients (63%) had a diagnosis of CAP, 16 patients (20%) were diagnosed with exacerbated COPD, and 14 (17%) were diagnosed with other diseases (lung cancer = 7, asthma = 4, and tuberculosis = 3). According to BMI, 3 patients (4%) were classified as underweight, 39 (48%) as normal weight, 19 (23%) as overweight, and 20 (25%) as obese.
The patients with CAP were younger than those in the COPD group (P<0.0001). Additionally, BMI and dyspnea were higher in the COPD group compared with patients in the CAP group (all P<0.05). The hospitalization period did not differ between groups. Spirometry differed among groups (Table 1).
Reproducibility
No significant difference was found in the distance covered between the two 6MWTs, with a 14-m increase in the second test (4% increase). 49 patients (61%) covered a greater distance in the second test and 50 patients (62%) had a difference of <27 m between the two tests. HR, SpO2 and dyspnea, and lower limb fatigue scales were equivalent (Table 2).
In the GT, a 42-s difference was found in the second test (17% increase, P<0.001), and 71 patients (88%) performed the second test in less time than the first. As in the 6MWT, the HR, SpO2 and dyspnea, and lower limb fatigue scales were equivalent in both tests (Table 3).
The Bland-Altman analysis reveals that the patients improved the distances covered in the second test of the 6MWT (Figure 1) and the GT (Figure 2), showing a narrow mean difference. However, the confidence interval of the means of the differences was wide, showing great variability of results between testing and retesting.
Bland-Altman of the average distance covered in the 6MWT and the difference between the distances in the two tests. The solid horizontal line represents the average polarization. The dashed horizontal lines represent the upper and lower limits of agreement.
Bland-Altman of the average of time of completion of GT and the difference between the times of completion of the two tests. The dashed horizontal lines represent the upper and lower limits of agreement.
The distance covered in the best 6MWT was greater than 82% of the predicted value in 15 patients (19%) (CAP: 60%, COPD: 27%, Others: 13%) and smaller than 82% of the predicted value in 66 patients (81%) (CAP: 64%, COPD: 18%, Others: 18%). A comparison of these groups, respectively, showed that the older individuals (61±16 and 50±17 years, P<0.05) had higher BMIs (28±4 and 25±5 kg/m2, P<0.05) and walked 453±83 and 353±98 m in the 6MWT (P<0.0001) (96±17 and 61±13% of the predicted value, P<0.0001). However, no differences were found in lung function, period of hospitalization, dyspnea scale or GT (240±69 s and 282±126 s, P=0.08).
There were no significant differences between the 6MWTs in HR and
SpO2. The mean biases (95% CI of the differences) were 0 (-23-23
beats/min-
11 ERS Task Force, Palange P, Ward SA, Carlsen KH, Casaburi R,
Gallagher CG, et al. Recommendations on the use of exercise testing in clinical
practice. Eur Respir J. 2007;29(1):185-209.
http://dx.doi.org/10.1183/09031936.00046906 . PMid:17197484
http://dx.doi.org/10.1183/09031936.00046...
) and 1 (-5-6%) respectively; for the GT
they were -1 (-19-18 beats/min-
11 ERS Task Force, Palange P, Ward SA, Carlsen KH, Casaburi R,
Gallagher CG, et al. Recommendations on the use of exercise testing in clinical
practice. Eur Respir J. 2007;29(1):185-209.
http://dx.doi.org/10.1183/09031936.00046906 . PMid:17197484
http://dx.doi.org/10.1183/09031936.00046...
) and 0 (-6-5%) respectively.
In the separate evaluations of the reproducibility of the 6MWT in COPD and CAP patients, the results were as follows: COPD: 318±81 and 328±84 m, in the first and second test, respectively (P=0.18), mean bias 10 m (-44-64); ICC: 0.97 (0.91-0.99), P<0.0001; CAP: 368±103 and 366±113 m, in the first and second tests respectively (P=0.84), mean bias 1 s (-78-80); ICC: 0.97 (0.94-0.98), P<0.0001. In relation to the reproducibility of the GT in COPD and CAP patients, the results were as follows: COPD: 378±136 and 302±115 s in the first and second tests respectively (P=0.006), mean bias 77 s (-113-267); ICC: 0.75 (0.15-0.92), P=0.01; CAP: 301±125 and 264±110 s in the first and second tests respectively (P<0.0001), mean bias 37 s (-82-155); ICC: 0.91 (0.76-0.97), P<0.0001.
Comparison of oxyhemoglobin desaturation between the two test types
The comparison between the lowest saturation on the best 6MWT and GT showed no significant differences (P=0.37) and were reproducible (ICC=0.69 (95% CI: 0.51-0.80), P<0.0001). The mean bias (95% CI) of the desaturation between 6MWT and GT was -0.4 (-9-8%).
Discussion
This study examined the reproducibility of the 6MWT and GT in a sample of patients
with acute and exacerbated chronic lung diseases. Both tests were reproducible. In
the 6MWT, most patients increased the distance covered in the second test (median
variation: 14 m, 4% improvement); this was also found in GT, as most patients
reduced the time to completion in the second test (median variation: 42 s, 17%
lower), suggesting the presence of a learning effect. For both cases, the
Bland-Altman analysis confirmed that the second test was better than the first, and
the detected limits of agreement were higher than the upper limits of a clinically
significant change; that is, changes of 26 m in the 6MWT2424 Puhan MA, Chandra D, Mosenifar Z, Ries A, Make B, Hansel NN, et al.
The minimal important difference of exercise tests in severe COPD. Eur Respir J.
2011;37(4):784-90. http://dx.doi.org/10.1183/09031936.00063810 .
PMid:20693247
http://dx.doi.org/10.1183/09031936.00063...
and 53 s in the GT1313 Skumlien S, Hagelund T, Bjørtuft O, Ryg MS. A field test of
functional status as performance of activities of daily living in COPD patients.
Respir Med. 2006;100(2):316-23. http://dx.doi.org/10.1016/j.rmed.2005.04.022 .
PMid:15941658
http://dx.doi.org/10.1016/j.rmed.2005.04...
.
While there is interest in the early rehabilitation of patients hospitalized for
acute and chronic lung diseases, we were interested in investigating the
reproducibility of the 6MWT and the GT since there are no studies on this group. Our
results demonstrate that the variability in these conditions is similar to that
observed in non-hospitalized patients with chronic lung conditions66 Hernandes NA, Wouters EFM, Meijer K, Annegarn J, Pitta F, Spruit MA.
Reproducibility of 6-minute walking test in patients with COPD. Eur Respir J.
2011;38(2):261-7. http://dx.doi.org/10.1183/09031936.00142010 .
PMid:21177838
http://dx.doi.org/10.1183/09031936.00142...
.
It is common to find a large variability in field tests, which has been credited to
the learning effect. In our study, this effect can be identified in the difference
in time to perform the GT and the high variability observed by the large limits of
agreement in both tests. However, the analysis of this effect is compromised because
most studies commonly express the data as mean and SD, showing no variability
between tests. In the present study, we employed the Bland-Altman method2525 Bland JM, Altman DG. Statistical methods for assessing agreement
between two methods of clinical measurement. Lancet. 1986;1(8476):307-10.
http://dx.doi.org/10.1016/S0140-6736(86)90837-8 . PMid:2868172
http://dx.doi.org/10.1016/S0140-6736(86)...
, which is considered a better analysis to
compare the agreement of two measurements.
Six-minute Walk Test (6MWT)
In the first 6MWT, our patients walked a distance of 349 m (285-419). In the
second test, the patients walked 363 m (288-432), representing a 14-m increase
in the second test (4% increase). This was less than the difference found in
other studies66 Hernandes NA, Wouters EFM, Meijer K, Annegarn J, Pitta F, Spruit MA.
Reproducibility of 6-minute walking test in patients with COPD. Eur Respir J.
2011;38(2):261-7. http://dx.doi.org/10.1183/09031936.00142010 .
PMid:21177838
http://dx.doi.org/10.1183/09031936.00142...
7 Sciurba F, Criner GJ, Lee SM, Mohsenifar Z, Shade D, Slivka W, et
al. Six-minute walk distance in chronic obstructive pulmonary disease:
reproducibility and effect of walking course layout and length. Am J Respir Crit
Care Med. 2003;167(11):1522-7. http://dx.doi.org/10.1164/rccm.200203-166OC .
PMid:12615634
http://dx.doi.org/10.1164/rccm.200203-16...
8 Chatterjee AB, Rissmiller RW, Meade K, Paladenech C, Conforti J,
Adair NE, et al. Reproducibility of the 6-minute walk test for ambulatory oxygen
prescription. Respiration. 2010;79(2):121-7. http://dx.doi.org/10.1159/000220343
. PMid:19468196
http://dx.doi.org/10.1159/000220343...
9 Stevens D, Elpern E, Sharma K, Szidon P, Ankin M, Kesten S.
Comparison of hallway and treadmill six-minute walk tests. Am J Respir Crit Care
Med. 1999;160(5 Pt 1):1540-3. http://dx.doi.org/10.1164/ajrccm.160.5.9808139 .
PMid:10556117
http://dx.doi.org/10.1164/ajrccm.160.5.9...
10 Jenkins S, Cecins NM. Six-minute walk test in pulmonary
rehabilitation: do all patients need a practice test?. Respirology.
2010;15(8):1192-6. http://dx.doi.org/10.1111/j.1440-1843.2010.01841.x .
PMid:20920121
http://dx.doi.org/10.1111/j.1440-1843.20...
11 Eaton T, Young P, Milne D, Wells AU. Six-minute walk, maximal
exercise tests: reproducibility in fibrotic interstitial pneumonia. Am J Respir
Crit Care Med. 2005;171(10):1150-7. http://dx.doi.org/10.1164/rccm.200405-578OC
. PMid:15640367
http://dx.doi.org/10.1164/rccm.200405-57...
-
1212 Ziegler B, Rovedder PME, Oliveira CL, Abreu e Silva F, Tarso Roth
Dalcin P. Repeatability of the 6-minute walk test in adolescents and adults with
cystic fibrosis. Respir Care. 2010;55(8):1020-5. PMid:20667149
., resulting in an excellent correlation
coefficient (ICC=0.97-95%, CI 0.95-0.98; P<0.001). The difference found in
our study was lower than that suggested by Puhan et al.2424 Puhan MA, Chandra D, Mosenifar Z, Ries A, Make B, Hansel NN, et al.
The minimal important difference of exercise tests in severe COPD. Eur Respir J.
2011;37(4):784-90. http://dx.doi.org/10.1183/09031936.00063810 .
PMid:20693247
http://dx.doi.org/10.1183/09031936.00063...
, whose study was conducted among patients with stable
COPD, suggesting a minimal clinically significant difference of 26 m. The
difference in our work was also lower than that suggested by Hernandes et
al.66 Hernandes NA, Wouters EFM, Meijer K, Annegarn J, Pitta F, Spruit MA.
Reproducibility of 6-minute walking test in patients with COPD. Eur Respir J.
2011;38(2):261-7. http://dx.doi.org/10.1183/09031936.00142010 .
PMid:21177838
http://dx.doi.org/10.1183/09031936.00142...
, whose study was also conducted
among patients with stable COPD (difference of 27 m). We found a difference of
<27 m between tests in 50 patients (62%), which was reported as a clinically
important difference by these researchers.
Despite the high test-retest variability by the Bland-Altman analysis (Figure 1), our data showed lower limits of
agreement than those previously described using the same method of analysis
(-67-120 m in the study by Hernandes et al.66 Hernandes NA, Wouters EFM, Meijer K, Annegarn J, Pitta F, Spruit MA.
Reproducibility of 6-minute walking test in patients with COPD. Eur Respir J.
2011;38(2):261-7. http://dx.doi.org/10.1183/09031936.00142010 .
PMid:21177838
http://dx.doi.org/10.1183/09031936.00142...
and -77-70 m in our study). The high variability, which was also
found in our study, was attributed to the learning effect, and supports the need
to perform two 6MWTs. However, the extent to which the test-retest variability
is representative of the learning effect remains unclear33 Spruit MA, Watkins ML, Edwards LD, Vestbo J, Calverley PM,
Pinto-Plata V, et al. Determinants of poor 6-min walking distance in patients
with COPD: the ECLIPSE cohort. Respir Med. 2010;104(6):849-57.
http://dx.doi.org/10.1016/j.rmed.2009.12.007 . PMid:20471236
http://dx.doi.org/10.1016/j.rmed.2009.12...
4 Puhan MA, Mador MJ, Held U, Goldstein R, Guyatt GH, Schünemann HJ.
Interpretation of treatment changes in 6-minute walk distance in patients with
COPD. Eur Respir J. 2008;32(3):637-43.
http://dx.doi.org/10.1183/09031936.00140507 . PMid:18550610
http://dx.doi.org/10.1183/09031936.00140...
5 Pinto-Plata VM, Cote C, Cabral H, Taylor J, Celli BR. The 6-min walk
distance: change over time and value as a predictor of survival in severe COPD.
Eur Respir J. 2004;23(1):28-33. http://dx.doi.org/10.1183/09031936.03.00034603 .
PMid:14738227
http://dx.doi.org/10.1183/09031936.03.00...
6 Hernandes NA, Wouters EFM, Meijer K, Annegarn J, Pitta F, Spruit MA.
Reproducibility of 6-minute walking test in patients with COPD. Eur Respir J.
2011;38(2):261-7. http://dx.doi.org/10.1183/09031936.00142010 .
PMid:21177838
http://dx.doi.org/10.1183/09031936.00142...
7 Sciurba F, Criner GJ, Lee SM, Mohsenifar Z, Shade D, Slivka W, et
al. Six-minute walk distance in chronic obstructive pulmonary disease:
reproducibility and effect of walking course layout and length. Am J Respir Crit
Care Med. 2003;167(11):1522-7. http://dx.doi.org/10.1164/rccm.200203-166OC .
PMid:12615634
http://dx.doi.org/10.1164/rccm.200203-16...
8 Chatterjee AB, Rissmiller RW, Meade K, Paladenech C, Conforti J,
Adair NE, et al. Reproducibility of the 6-minute walk test for ambulatory oxygen
prescription. Respiration. 2010;79(2):121-7. http://dx.doi.org/10.1159/000220343
. PMid:19468196
http://dx.doi.org/10.1159/000220343...
9 Stevens D, Elpern E, Sharma K, Szidon P, Ankin M, Kesten S.
Comparison of hallway and treadmill six-minute walk tests. Am J Respir Crit Care
Med. 1999;160(5 Pt 1):1540-3. http://dx.doi.org/10.1164/ajrccm.160.5.9808139 .
PMid:10556117
http://dx.doi.org/10.1164/ajrccm.160.5.9...
10 Jenkins S, Cecins NM. Six-minute walk test in pulmonary
rehabilitation: do all patients need a practice test?. Respirology.
2010;15(8):1192-6. http://dx.doi.org/10.1111/j.1440-1843.2010.01841.x .
PMid:20920121
http://dx.doi.org/10.1111/j.1440-1843.20...
11 Eaton T, Young P, Milne D, Wells AU. Six-minute walk, maximal
exercise tests: reproducibility in fibrotic interstitial pneumonia. Am J Respir
Crit Care Med. 2005;171(10):1150-7. http://dx.doi.org/10.1164/rccm.200405-578OC
. PMid:15640367
http://dx.doi.org/10.1164/rccm.200405-57...
-
1212 Ziegler B, Rovedder PME, Oliveira CL, Abreu e Silva F, Tarso Roth
Dalcin P. Repeatability of the 6-minute walk test in adolescents and adults with
cystic fibrosis. Respir Care. 2010;55(8):1020-5. PMid:20667149
.. To illustrate the magnitude of the
variability between the two walking tests carried out on the same day, we also
cite a study from Puhan et al.2424 Puhan MA, Chandra D, Mosenifar Z, Ries A, Make B, Hansel NN, et al.
The minimal important difference of exercise tests in severe COPD. Eur Respir J.
2011;37(4):784-90. http://dx.doi.org/10.1183/09031936.00063810 .
PMid:20693247
http://dx.doi.org/10.1183/09031936.00063...
, which
found a mean difference of 20±45 m pre-rehabilitation, which is higher than
ours.
In addition to the learning effect already mentioned, we credit the variability found in our study to the heterogeneity of our sample, which comprised patients with several lung diseases. Additionally, there were also acute clinical situations among our patients that could predispose this population to clinical conditions, such as hyperthermia, active infection, cough, chest pain, dyspnea, muscle fatigue, tachycardia, myalgia, sweating, malnutrition, hypoxemia, and adynamia. The patient with chronic lung disease may also present some of these signs and symptoms. However, the patient with acute pulmonary disease presents with this clinical situation without the body, organic, and metabolic adaptations that develop in a patient with chronic disease over his or her lifetime, thereby making this clinical condition quite debilitating with respect to FC and exercise tolerance.
Hernandes et al.66 Hernandes NA, Wouters EFM, Meijer K, Annegarn J, Pitta F, Spruit MA.
Reproducibility of 6-minute walking test in patients with COPD. Eur Respir J.
2011;38(2):261-7. http://dx.doi.org/10.1183/09031936.00142010 .
PMid:21177838
http://dx.doi.org/10.1183/09031936.00142...
also investigated the
determinants for a >42 m distance covered in the second 6MWT. They concluded
that a poor first 6MWT (<350 m), Charlson index <2 points, or a BMI<30
kg/m2 were determinants. Sciurba et al.77 Sciurba F, Criner GJ, Lee SM, Mohsenifar Z, Shade D, Slivka W, et
al. Six-minute walk distance in chronic obstructive pulmonary disease:
reproducibility and effect of walking course layout and length. Am J Respir Crit
Care Med. 2003;167(11):1522-7. http://dx.doi.org/10.1164/rccm.200203-166OC .
PMid:12615634
http://dx.doi.org/10.1164/rccm.200203-16...
found that participants with higher maximal inspiratory
pressures showed more marked improvements in the second walk.
Glittre ADL-test (GT)
Patients performed the first GT in a median of 286 s (220-378) and the second
test in a median of 244 s (197-323), with a time difference of 42 s (17%
decrease) and a good correlation (ICC=0.91-95%, CI: 0.75-0.96; P<0.001). The
time to completion of the second test was closest to the time found in the study
by Skumlien et al.1313 Skumlien S, Hagelund T, Bjørtuft O, Ryg MS. A field test of
functional status as performance of activities of daily living in COPD patients.
Respir Med. 2006;100(2):316-23. http://dx.doi.org/10.1016/j.rmed.2005.04.022 .
PMid:15941658
http://dx.doi.org/10.1016/j.rmed.2005.04...
conducted in
patients with stable COPD (median 250 s). In this study, 52 patients underwent
two GTs to test its reproducibility. The test-retest difference was 22 s (7%
decrease), which was attributed to the learning effect. As observed in our
study, there were no differences in dyspnea and SpO2. It was not
possible to compare our limits of agreement with this study because this type of
analysis was not performed. It is interesting to note that, in another group of
COPD patients that performed a pulmonary rehabilitation program, there was an
improvement of 53 s in the test duration1313 Skumlien S, Hagelund T, Bjørtuft O, Ryg MS. A field test of
functional status as performance of activities of daily living in COPD patients.
Respir Med. 2006;100(2):316-23. http://dx.doi.org/10.1016/j.rmed.2005.04.022 .
PMid:15941658
http://dx.doi.org/10.1016/j.rmed.2005.04...
, a post-treatment difference higher than ours (42 s).
Few studies beyond the original1313 Skumlien S, Hagelund T, Bjørtuft O, Ryg MS. A field test of
functional status as performance of activities of daily living in COPD patients.
Respir Med. 2006;100(2):316-23. http://dx.doi.org/10.1016/j.rmed.2005.04.022 .
PMid:15941658
http://dx.doi.org/10.1016/j.rmed.2005.04...
have
used the GT as a field test. However, none of these studies provided test-retest
measurements, therefore this test's reproducibility and variability was not
established2626 Karloh M, Karsten M, Pissaia FV, Araujo CL, Mayer AF. Physiological
responses to the Glittre-ADL test in patients with chronic obstructive pulmonary
disease. J Rehabil Med. 2014;46(1):88-94.
http://dx.doi.org/10.2340/16501977-1217 . PMid:24104462
http://dx.doi.org/10.2340/16501977-1217...
27 Valadares YD, Corrêa KS, Silva BO, Araujo CLP, Karloh M, Mayer AF.
Applicability of activities of daily living tests in individuals with heart
failure. Rev Bras Med Esporte. 2011;17(5):310-4.
http://dx.doi.org/10.1590/S1517-86922011000500003 .
http://dx.doi.org/10.1590/S1517-86922011...
-
2828 Corrêa KS, Karloh M, Martins LQ, Santos K, Mayer AF. Can the Glittre
ADL test differentiate the functional capacity of COPD patients from that of
healthy subjects?. Rev Bras Fisioter. 2011;15(6):467-73.
http://dx.doi.org/10.1590/S1413-35552011005000034 .
PMid:22094546
http://dx.doi.org/10.1590/S1413-35552011...
.
We can raise the hypothesis of the learning effect to explain the great
variability found in our study in addition to what has been previously described
with the heterogeneity and the acute clinical condition of our sample. Just as
it is common to find differences between the 6MWT that can be credited to the
learning effect, the GT may also be influenced by this effect, as considered in
another study1313 Skumlien S, Hagelund T, Bjørtuft O, Ryg MS. A field test of
functional status as performance of activities of daily living in COPD patients.
Respir Med. 2006;100(2):316-23. http://dx.doi.org/10.1016/j.rmed.2005.04.022 .
PMid:15941658
http://dx.doi.org/10.1016/j.rmed.2005.04...
. This effect can be
greater when compared with the effect shown in the 6MWT because this test has
additional and more complex activities.
Oxyhemoglobin desaturation between the two test types
We also found that the changes in oxygen saturation measured by pulse oximeter were reproducible in both the 6MWT and GT. When comparing the lowest pulse oximetric saturation in the best 6MWT and best GT, we also found good equivalence; however, although the analysis using the Bland-Altman method showed a small mean of the differences, we observed large limits of agreement (-9-8%). This wide dispersion of results can be credited to the heterogeneity of the studied sample, whose physiopathological changes may limit the individual's activities in different ways. For example, some patients may experience great difficulty in exercising the upper limbs, bending down and carrying weights (COPD), whereas others do not have much difficulty performing these activities (CAP and other diseases).
Potential and implications of the study
Although the reproducibility of the 6MWT has already been widely studied in the literature and the GT has already been described in COPD, our study was the first to assess the reproducibility of these tests in patients hospitalized for acute lung diseases, which are routinely found in hospital wards. Our study also showed a statistical analysis that yielded results of clinical importance, and it constituted not only the data of averages and differences but also the limits of agreement between the assessments.
The clinical implications of the findings in this study relate to the fact that
the differences found in the clinical field tests may lead to erroneous
interpretations of the FC examination of these patients. Our findings
demonstrate that the results were better in the second test of both examinations
surveyed, meaning that interpretations based on a first test would be inaccurate
for the patient assessment, prescription, or responsiveness of a training
program. Therefore, we recommend that at least two 6MWTs, as recommended by
American Thoracic Society (ATS)22 ATS Committee on Proficiency Standards for Clinical Pulmonary
Function Laboratories. ATS statement: guidelines for the six-minute walk test.
Am J Respir Crit Care Med. 2002;166(1):111-7.
http://dx.doi.org/10.1164/ajrccm.166.1.at1102 . PMid:12091180
http://dx.doi.org/10.1164/ajrccm.166.1.a...
, and two
GTs should be performed in patients hospitalized for acute or exacerbated
chronic lung diseases.
Limitations of the study
This study has some limitations. First, the tests were not always performed by
the same examiner; however, the testing was standardized22 ATS Committee on Proficiency Standards for Clinical Pulmonary
Function Laboratories. ATS statement: guidelines for the six-minute walk test.
Am J Respir Crit Care Med. 2002;166(1):111-7.
http://dx.doi.org/10.1164/ajrccm.166.1.at1102 . PMid:12091180
http://dx.doi.org/10.1164/ajrccm.166.1.a...
,
1313 Skumlien S, Hagelund T, Bjørtuft O, Ryg MS. A field test of
functional status as performance of activities of daily living in COPD patients.
Respir Med. 2006;100(2):316-23. http://dx.doi.org/10.1016/j.rmed.2005.04.022 .
PMid:15941658
http://dx.doi.org/10.1016/j.rmed.2005.04...
and these examiners were trained.
Moreover, to represent an acute pulmonary situation, the results are applicable
to patients who were hospitalized at up to 48 h. Nevertheless, we know that a
patient can seek hospital care at the first symptoms of the disease while others
wait until they have a significant worsening of symptoms, which could lead to a
variability in clinical conditions among the sample population. Finally, we had
to adjust the distance of the 6MWT for 20 m due to space constraints in the
hospital environment.
Conclusions
The 6MWT and GT were reproducible in patients hospitalized for acute lung diseases, and most patients improved their scores on the second test. The detected variability was large and the limits of agreement exceeded the minimal clinically significant difference. Desaturation was similar between 6MWT and GT; therefore, the GT can be used to detect exercise-induced desaturation, and we speculate that the GT could also be used to identify patients who would present desaturation during ADL.
Our study showed that, in the evaluation of the FC of this group of patients, at least two tests of each examination are needed to obtain reliable and valid assessments.
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» http://dx.doi.org/10.2340/16501977-1217 -
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» http://dx.doi.org/10.1590/S1517-86922011000500003 -
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» http://dx.doi.org/10.1590/S1413-35552011005000034
Publication Dates
-
Publication in this collection
29 May 2015 -
Date of issue
May-Jun 2015
History
-
Received
22 July 2014 -
Reviewed
08 Nov 2014 -
Accepted
16 Dec 2014