- Email: [email protected]
Availability of the 6-Min Walk Test in Coal Workers' Pneumoconiosis Evaluations
4. Akinbami L. Asthma Prevalence, Health Care Use and Mortality: United States, 2003-2005. Hyattsville, MD: National Center for Health Statistics; 2006. 5. Schober SE, Carroll MD, Lacher DA, Hirsch R. High Serum Total Cholesterol–An Indicator for Monitoring Cholesterol Lowering Efforts: U.S. Adults, 2005-2006. NCHS Data Brief. No.2. Hyattsville, MD: National Center for Health Statistics; 2007.
Availability of the 6-Min Walk Test in Coal Workers’ Pneumoconiosis Evaluations To the Editor: Not only is coal workers’ pneumoconiosis (CWP) still one of the most predominant occupational diseases, even now rates of CWP are increasing, based on the compensation records from the Industrial Accident Compensation Insurance that is operated by the Korea Labor Welfare Corporation. In this manner, it is important to accurately estimate malfunction-induced disorders. The current CWP diagnosis system is generally based on history, examination, radiology, and lung function tests; however, those methods are not sufficient to confirm or refute CWP, and, therefore, it is important to develop complementary methods.1 We
recommend the 6-min walk test (6MWT) as a complementary diagnosis method for CWP. The 6MWT, developed by Balke in 1963,2 is one of the tests widely used to assess functional exercise capacity evaluated by measuring the distance walked during 6 min. The merits of this test are that it is easy to administer and it is better tolerated and more reflective of the activities of daily living than other walk tests.3-5 Most activities of daily life usually are performed at a submaximal level of exertion, so the 6MWT seems to better reflect the functional exercise level for daily physical activities. Accordingly, the 6MWT would be a good estimation tool for objective health and assessment in CWP. In our study, when we compared the 6-min walk distance (6MWD) to other common diagnostic inspections, such as respiratory symptoms, chest radiographs, and pulmonary function tests, we found that the 6MWD was significantly related to coughs, Medical Research Council dyspnea (MRC dyspnea), FVC, maximal voluntary ventilation (MVV), and breathing reserve · e) divided by index (BRI) measured using minute ventilation (V · MVV [(VeⲐMVV)100] during maximum exercise estimated by the Master two-step exercise test. Moreover, the 6MWD decreased linearly in phases for each variable (dyspnea, cough, FVC, MVV, or BRI) that was statistically significant (Table 1). The study by Villalba et al (January 2007)3 compared the 6MWD to other clinical variables in patients with scleroderma, and the results indicated that 6MWD was associated with age, dyspnea index, fibrosis on chest radiography, FVC , 80% of predicted, pulmonary arterial systolic BP ⱖ 30 mm Hg, and
Table 1—6-Minute Walk Distance in Objective and Subjective Variables of Coal Workers’ Pneumoconiosis Measurements Cough Yes (ⱖ 3 moⲐy) Yes (, 3 moⲐy) No Sputum Yes (ⱖ 3 moⲐy) Yes (, 3 moⲐy) No MRC dyspnea 0 1 2 3 4 Chest roentgenogram stage Category 0 Category 1 Category 2 Category 3 Category 4 FVC (% predicted) ⱖ 80% , 80% FEV1ⲐFVC (% predicted) ⱖ 70% , 70% MVV Normal Impaired BRI Normal Impaired
No. (%)
Mean 6MWD (SD), m
Estimatea
Standard Errora
P Valuea
64 (77.1) 8 (9.6) 11 (13.3)
457.9 (84.1) 504.2 (46.8) 506.8 (71.7)
257.7782 28.0411 0.0000
26.9596 36.6250 …
.0367 … …
64 (77.1) 9 (10.8) 10 (12.1)
463.4 (84.6) 514.3 (36.6) 462.3 (84.0)
4.7349 64.2936 0.0000
26.3023 35.1535 …
.0900 … …
3 (3.6) 26 (31.3) 37 (44.6) 17 (20.5) 0 (0.0)
533.7 (58.6) 497.7 (58.2) 467.7 (85.2) 415.6 (83.0) …
106.7932 70.4065 51.6293 0.0000 …
47.2045 23.7117 21.7235 … …
.0151 … … … …
39 (45.4) 24 (27.9) 14 (16.3) 3 (3.5) 6 (7.0)
472.3 (76.6) 466.1 (86.3) 467.8 (93.4) 495.0 (36.3) 445.3 (77.6)
40.5762 23.9579 17.1546 48.1228 0.0000
34.2606 35.2540 37.5861 55.0803 …
.7062 … … … …
74 (87.1) 11 (12.9)
476.9 (73.6) 423.7 (106.1)
51.9352 0.0000
23.9904 …
.0334 …
51 (60.0) 34 (40.0)
474.8 (74.1) 462.7 (88.4)
21.6238 0.0000
17.6555 …
.9270 …
77 (89.5) 9 (10.5)
477.3 (75.3) 395.6 (88.2)
78.3486 0.0000
25.8052 …
.0032 …
27 (33.3) 54 (66.7)
490.5 (74.4) 466.8 (75.7)
39.6420 0.0000
17.4591 …
.0260 …
6MWD 5 6-min walk distance; BRI 5 breathing reserve index; MRC 5 Medical Research Council; MVV 5 maximal voluntary ventilation. a All variables were adjusted for age, sex, height, and weight when entered into the models. 1492
Correspondence
Downloaded from chestjournal.chestpubs.org by Kimberly Henricks on June 7, 2010 © 2010 American College of Chest Physicians
desaturation (DSat, resting oxygen saturation 2 oxygen saturation after the 6-min period), defined as a decline of end-of-test saturation ⱖ 4%. Baughman et al6,7 applied the 6MWD to assess patients with sarcoidosis and showed that the 6MWD is a useful test, whereas lung function tests and chest roentgenogram are not correlated well in sarcoidosis. The 6MWD was associated with the variables, FVC, lowest oxygen saturation, St. George Respiratory Questionnaire, fatigue assessment score, final Borg score, and MRC dyspnea. Guyatt et al8 showed that the 6MWD for patients with chronic airflow limitation correlated with dyspnea measured by chronic respiratory questionnaire and might reflect functional status of patients in their daily living. CWP is still a major occupational disease, and new cases are still occurring among miners who have worked exclusively under current dust exposure limits.9 In addition, it takes a long time until the onset of the disease occurs, and many coal mining workers show considerable respiratory symptoms and decreased quality of life even in the absence of chest radiograph observations.10 Because of these points, a more rational system to help diagnose impairment and disability should be developed and should complement the CWP diagnosis system. The 6MWT has been used as an objective functional status assessment tool for patients in many clinical research studies, because it is a practical and simple test to perform and does not require highly technical equipment or advanced technical training.3-5 According to the results of the current research studies, the 6MWT is extremely sensitive and appropriate for assessing exercise capacity among 2-, 6-, and 12-min walking tests.11 In addition, the 6MWD appears to have better reproducibility than the 1-s forced expiratory volume in patients with COPD.8,11 In conclusion, the 6MWT would be a valuable supplementation method for the quantification of the associated pneumoconiosis and could be gaining popularity as a way to diagnose CWP, complementing chest radiographs and pulmonary function tests. Su Ryeon Noh, MPH Seoul, Republic of Korea Affiliations: From the Department of Occupational and Environmental Medicine, School of Public Health and Institute of Health and Environment, Seoul National University. FinancialⲐnonfinancial disclosures: The author has reported to CHEST that no potential conflicts of interest exist with any companiesⲐorganizations whose products or services may be discussed in this article.
www.chestpubs.org
Correspondence to: Su Ryeon Noh, MPH, Department of Occupational and Environmental Medicine, School of Public Health and Institute of Health and Environment, Seoul National University, 28 Yeongeon-Dong, Chongro-Gu, Seoul, 110-799, Republic of Korea; e-mail: [email protected] © 2010 American College of Chest Physicians. Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestpubs.orgⲐ siteⲐmiscⲐreprints.xhtml). DOI: 10.1378Ⲑchest.10-0070
References 1. Wang ML, Petsonk EL, Beeckman LA, Wagner GR. Clinically important FEV1 declines among coal miners: an exploration of previously unrecognised determinants. Occup Environ Med. 1999;56(12):837-844. 2. Balke B. A Simple Field Test for the Assessment of Physical Fitness. CARI Report 63-6. Oklahoma City, OK: Civil Aeromedical Research Institute; 1963. 3. Villalba WO, Sampaio-Barros PD, Pereira MC, et al. Six-minute walk test for the evaluation of pulmonary disease severity in scleroderma patients. Chest. 2007;131(1):217-222. 4. Salzman SH. The 6-min walk test: clinical and research role, technique, coding, and reimbursement. Chest. 2009;135(5): 1345-1352. 5. Cardoso F, Tufanin AT, Colucci M, Nascimento O, Jardim JR. Replacement of the 6-min walk test with maximal oxygen consumption in the BODE Index applied to patients with COPD: an equivalency study. Chest. 2007;132(2):477-482. 6. Baughman RP, Lower EE. Six-minute walk test in managing and monitoring sarcoidosis patients. Curr Opin Pulm Med. 2007;13(5):439-444. 7. Baughman RP, Sparkman BK, Lower EE. Six-minute walk test and health status assessment in sarcoidosis. Chest. 2007;132(1):207-213. 8. Guyatt GH, Townsend M, Keller J, et al. Measuring functional status in chronic lung disease: conclusions from a randomized control trial. Respir Med. 1991;85(suppl B):17-21. 9. Carta P, Aru G, Barbieri MT, Avataneo G, Casula D. Dust exposure, respiratory symptoms, and longitudinal decline of lung function in young coal miners. Occup Environ Med. 1996;53(5):312-319. 10. Vallyathan V, Brower PS, Green FH, Attfield MD. Radiographic and pathologic correlation of coal workers’ pneumoconiosis. Am J Respir Crit Care Med. 1996;154(3 pt 1):741-748. 11. Butland RJ, Pang J, Gross ER, Woodcock AA, Geddes DM. Two-, six-, and 12-minute walking tests in respiratory disease. Br Med J (Clin Res Ed). 1982;284(6329):1607-1608.
CHEST / 137 / 6 / JUNE, 2010
Downloaded from chestjournal.chestpubs.org by Kimberly Henricks on June 7, 2010 © 2010 American College of Chest Physicians
1493
Availability of the 6-Min Walk Test in Coal Workers’ Pneumoconiosis Evaluations To the Editor: Not only is coal workers’ pneumoconiosis (CWP) still one of the most predominant occupational diseases, even now rates of CWP are increasing, based on the compensation records from the Industrial Accident Compensation Insurance that is operated by the Korea Labor Welfare Corporation. In this manner, it is important to accurately estimate malfunction-induced disorders. The current CWP diagnosis system is generally based on history, examination, radiology, and lung function tests; however, those methods are not sufficient to confirm or refute CWP, and, therefore, it is important to develop complementary methods.1 We
recommend the 6-min walk test (6MWT) as a complementary diagnosis method for CWP. The 6MWT, developed by Balke in 1963,2 is one of the tests widely used to assess functional exercise capacity evaluated by measuring the distance walked during 6 min. The merits of this test are that it is easy to administer and it is better tolerated and more reflective of the activities of daily living than other walk tests.3-5 Most activities of daily life usually are performed at a submaximal level of exertion, so the 6MWT seems to better reflect the functional exercise level for daily physical activities. Accordingly, the 6MWT would be a good estimation tool for objective health and assessment in CWP. In our study, when we compared the 6-min walk distance (6MWD) to other common diagnostic inspections, such as respiratory symptoms, chest radiographs, and pulmonary function tests, we found that the 6MWD was significantly related to coughs, Medical Research Council dyspnea (MRC dyspnea), FVC, maximal voluntary ventilation (MVV), and breathing reserve · e) divided by index (BRI) measured using minute ventilation (V · MVV [(VeⲐMVV)100] during maximum exercise estimated by the Master two-step exercise test. Moreover, the 6MWD decreased linearly in phases for each variable (dyspnea, cough, FVC, MVV, or BRI) that was statistically significant (Table 1). The study by Villalba et al (January 2007)3 compared the 6MWD to other clinical variables in patients with scleroderma, and the results indicated that 6MWD was associated with age, dyspnea index, fibrosis on chest radiography, FVC , 80% of predicted, pulmonary arterial systolic BP ⱖ 30 mm Hg, and
Table 1—6-Minute Walk Distance in Objective and Subjective Variables of Coal Workers’ Pneumoconiosis Measurements Cough Yes (ⱖ 3 moⲐy) Yes (, 3 moⲐy) No Sputum Yes (ⱖ 3 moⲐy) Yes (, 3 moⲐy) No MRC dyspnea 0 1 2 3 4 Chest roentgenogram stage Category 0 Category 1 Category 2 Category 3 Category 4 FVC (% predicted) ⱖ 80% , 80% FEV1ⲐFVC (% predicted) ⱖ 70% , 70% MVV Normal Impaired BRI Normal Impaired
No. (%)
Mean 6MWD (SD), m
Estimatea
Standard Errora
P Valuea
64 (77.1) 8 (9.6) 11 (13.3)
457.9 (84.1) 504.2 (46.8) 506.8 (71.7)
257.7782 28.0411 0.0000
26.9596 36.6250 …
.0367 … …
64 (77.1) 9 (10.8) 10 (12.1)
463.4 (84.6) 514.3 (36.6) 462.3 (84.0)
4.7349 64.2936 0.0000
26.3023 35.1535 …
.0900 … …
3 (3.6) 26 (31.3) 37 (44.6) 17 (20.5) 0 (0.0)
533.7 (58.6) 497.7 (58.2) 467.7 (85.2) 415.6 (83.0) …
106.7932 70.4065 51.6293 0.0000 …
47.2045 23.7117 21.7235 … …
.0151 … … … …
39 (45.4) 24 (27.9) 14 (16.3) 3 (3.5) 6 (7.0)
472.3 (76.6) 466.1 (86.3) 467.8 (93.4) 495.0 (36.3) 445.3 (77.6)
40.5762 23.9579 17.1546 48.1228 0.0000
34.2606 35.2540 37.5861 55.0803 …
.7062 … … … …
74 (87.1) 11 (12.9)
476.9 (73.6) 423.7 (106.1)
51.9352 0.0000
23.9904 …
.0334 …
51 (60.0) 34 (40.0)
474.8 (74.1) 462.7 (88.4)
21.6238 0.0000
17.6555 …
.9270 …
77 (89.5) 9 (10.5)
477.3 (75.3) 395.6 (88.2)
78.3486 0.0000
25.8052 …
.0032 …
27 (33.3) 54 (66.7)
490.5 (74.4) 466.8 (75.7)
39.6420 0.0000
17.4591 …
.0260 …
6MWD 5 6-min walk distance; BRI 5 breathing reserve index; MRC 5 Medical Research Council; MVV 5 maximal voluntary ventilation. a All variables were adjusted for age, sex, height, and weight when entered into the models. 1492
Correspondence
Downloaded from chestjournal.chestpubs.org by Kimberly Henricks on June 7, 2010 © 2010 American College of Chest Physicians
desaturation (DSat, resting oxygen saturation 2 oxygen saturation after the 6-min period), defined as a decline of end-of-test saturation ⱖ 4%. Baughman et al6,7 applied the 6MWD to assess patients with sarcoidosis and showed that the 6MWD is a useful test, whereas lung function tests and chest roentgenogram are not correlated well in sarcoidosis. The 6MWD was associated with the variables, FVC, lowest oxygen saturation, St. George Respiratory Questionnaire, fatigue assessment score, final Borg score, and MRC dyspnea. Guyatt et al8 showed that the 6MWD for patients with chronic airflow limitation correlated with dyspnea measured by chronic respiratory questionnaire and might reflect functional status of patients in their daily living. CWP is still a major occupational disease, and new cases are still occurring among miners who have worked exclusively under current dust exposure limits.9 In addition, it takes a long time until the onset of the disease occurs, and many coal mining workers show considerable respiratory symptoms and decreased quality of life even in the absence of chest radiograph observations.10 Because of these points, a more rational system to help diagnose impairment and disability should be developed and should complement the CWP diagnosis system. The 6MWT has been used as an objective functional status assessment tool for patients in many clinical research studies, because it is a practical and simple test to perform and does not require highly technical equipment or advanced technical training.3-5 According to the results of the current research studies, the 6MWT is extremely sensitive and appropriate for assessing exercise capacity among 2-, 6-, and 12-min walking tests.11 In addition, the 6MWD appears to have better reproducibility than the 1-s forced expiratory volume in patients with COPD.8,11 In conclusion, the 6MWT would be a valuable supplementation method for the quantification of the associated pneumoconiosis and could be gaining popularity as a way to diagnose CWP, complementing chest radiographs and pulmonary function tests. Su Ryeon Noh, MPH Seoul, Republic of Korea Affiliations: From the Department of Occupational and Environmental Medicine, School of Public Health and Institute of Health and Environment, Seoul National University. FinancialⲐnonfinancial disclosures: The author has reported to CHEST that no potential conflicts of interest exist with any companiesⲐorganizations whose products or services may be discussed in this article.
www.chestpubs.org
Correspondence to: Su Ryeon Noh, MPH, Department of Occupational and Environmental Medicine, School of Public Health and Institute of Health and Environment, Seoul National University, 28 Yeongeon-Dong, Chongro-Gu, Seoul, 110-799, Republic of Korea; e-mail: [email protected] © 2010 American College of Chest Physicians. Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestpubs.orgⲐ siteⲐmiscⲐreprints.xhtml). DOI: 10.1378Ⲑchest.10-0070
References 1. Wang ML, Petsonk EL, Beeckman LA, Wagner GR. Clinically important FEV1 declines among coal miners: an exploration of previously unrecognised determinants. Occup Environ Med. 1999;56(12):837-844. 2. Balke B. A Simple Field Test for the Assessment of Physical Fitness. CARI Report 63-6. Oklahoma City, OK: Civil Aeromedical Research Institute; 1963. 3. Villalba WO, Sampaio-Barros PD, Pereira MC, et al. Six-minute walk test for the evaluation of pulmonary disease severity in scleroderma patients. Chest. 2007;131(1):217-222. 4. Salzman SH. The 6-min walk test: clinical and research role, technique, coding, and reimbursement. Chest. 2009;135(5): 1345-1352. 5. Cardoso F, Tufanin AT, Colucci M, Nascimento O, Jardim JR. Replacement of the 6-min walk test with maximal oxygen consumption in the BODE Index applied to patients with COPD: an equivalency study. Chest. 2007;132(2):477-482. 6. Baughman RP, Lower EE. Six-minute walk test in managing and monitoring sarcoidosis patients. Curr Opin Pulm Med. 2007;13(5):439-444. 7. Baughman RP, Sparkman BK, Lower EE. Six-minute walk test and health status assessment in sarcoidosis. Chest. 2007;132(1):207-213. 8. Guyatt GH, Townsend M, Keller J, et al. Measuring functional status in chronic lung disease: conclusions from a randomized control trial. Respir Med. 1991;85(suppl B):17-21. 9. Carta P, Aru G, Barbieri MT, Avataneo G, Casula D. Dust exposure, respiratory symptoms, and longitudinal decline of lung function in young coal miners. Occup Environ Med. 1996;53(5):312-319. 10. Vallyathan V, Brower PS, Green FH, Attfield MD. Radiographic and pathologic correlation of coal workers’ pneumoconiosis. Am J Respir Crit Care Med. 1996;154(3 pt 1):741-748. 11. Butland RJ, Pang J, Gross ER, Woodcock AA, Geddes DM. Two-, six-, and 12-minute walking tests in respiratory disease. Br Med J (Clin Res Ed). 1982;284(6329):1607-1608.
CHEST / 137 / 6 / JUNE, 2010
Downloaded from chestjournal.chestpubs.org by Kimberly Henricks on June 7, 2010 © 2010 American College of Chest Physicians
1493