The 6-min walking distance: long-term follow up in patients with COPD

Abstract

The 6-min walking distance (6MWD) test is used in clinical practice and research into patients with chronic obstructive pulmonary disease (COPD). However, little is known about natural long-term change in this parameter.The 6MWD was measured at baseline and then annually for 5 yrs in 294 patients with COPD and its annual rate of decline was determined. Forced expiratory volume in one second (FEV1) was also measured and the relationship between changes in both markers was explored.At baseline, the median 6MWD was 380 m (range 160-600 m). It declined by 19% (16 m?yr -1 ) over the 5 yrs compared with baseline in patients with American Thoracic Society/European Respiratory Society stage III COPD (FEV1 30-50% predicted) and by 26% (15 m?yr -1 ) in patients with stage IV COPD (FEV1 ,30% pred). Over the 5-yr follow-up, the proportion of patients with a minimal clinically significant decline of 54 m increased with the severity of the disease. It was 24% in stage II, 45% in stage III, and 63% in stage IV disease. In contrast, the rate of decline of FEV1 was greater in patients with milder airflow obstruction and lesser in patients with lower absolute FEV1 values.In conclusion, the 6-min walking distance test provides increasingly useful information as the severity of chronic obstructive pulmonary disease increases.KEYWORDS: Chronic obstructive pulmonary disease, 6-min walking distance T he 6-min walking distance (6MWD) test has gained importance in the assessment of functional exercise capacity in patients with chronic obstructive pulmonary disease (COPD) [1,2] Introduced in 1976 as a 12-min walk test to measure the exercise capacity of patients with COPD, the abbreviated 6MWD has proved to be reliable, inexpensive, safe and easy to apply [7][8][9][10]. Furthermore, it correlates well with other important outcomes in COPD patients such as dyspnoea, airway obstruction and lung hyperinflation [11]. The test has been shown to be an important prognostic factor for outcome independent of the forced expiratory volume in one second (FEV1) [12]. The 6MWD is a submaximal excercise test, but it correlates well with the maximal cardiopulmonary exercise test [13][14][15], and appears to be better tolerated and more reflective of the activities of daily living than other walk tests [16,17].While there is plenty of data concerning the natural history of FEV1 over time, little information has been published regarding the temporal behaviour of the 6MWD. This is a significant omission, as the 6MWD test is frequently used to evaluate the long-term impact of interventions. Changes in 6MWD over time have been addressed in one published study [12], but it was limited to patients with severe COPD, the follow-up time was relatively short (1 yr) and the decline trend was established with only two measurements.As part of the large body mass index, degree of obstruction, dyspnoea and exercise capacity (BODE) cohort, the present authors have evaluated the 6MWD systematically as one of several variables included in the evaluation of pati...

Three-year follow-up study of respiratory and systemic manifestations of chronic obstructive pulmonary disease

“…Another prospective study evaluated COPD patients with a wide range of airflow obstruction during a 5-year period. They also showed an annual decline of the 6MWD; however, in contrast to our findings, the 54-m decrease was really significant only in patients whose FEV 1 was less than 50% of predicted values (8).…”

“…The mean rate of decline in FEV 1 was 26 mL/year, and only 22 patients (23%) presented changes greater than 200 mL and 12% within a 3-year period. These results are consistent with those reported by Casanova et al (8), who showed that FEV 1 values, in liters, declined significantly over 5 s, with a 23 mL/year mean rate of decline.…”

“…Oga et al (7) showed deterioration of health status over 5 years, with changes being only weakly correlated with changes in FEV 1 (7). Another longitudinal study showed that exercise tolerance declined over time without correlation with the rate of decline in FEV 1 (8).…”

Systemic manifestations and comorbidities of COPD

“…Whether the result of systemic inflammation or disuse atrophy, or a combination of both, it is known that the exercise capacity as demonstrated by low peak exercise oxygen uptake during a cardiopulmonary exercise test or decreased 6MWD, are important factors predictive of poor outcome [68]. Interestingly, in patients with severe COPD who have little room to loose more lung function, the decline in FEV1 slows over time, whereas the decrease in 6MWD continues and may actually help assess the progression of disease [69]. Other factors contribute to decreased functional capacity, including anaemia, osteoporosis and cardiovascular compromise.…”

Prueba de caminata en seis minutos en sujetos chilenos sanos de 20 a 80 años

“…En los últimos años ha adquirido una importancia progresiva por su fácil implementación y reproducibilidad. Se ha utilizado ampliamente en pacientes con enfermedades respiratorias y cardiovasculares; para evaluar la capacidad de ejercicio de los pacientes [3][4][5][6][7][8] ; la respuesta a intervenciones terapeúticas 9,10 ; como factor pronóstico de sobrevida 6,7,11,12 ; y como índice de deterioro en la enfermedad pulmonar obstructiva crónica (EPOC) 13,14 .…”