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Therapeutic Apheresis and Dialysis 2014; ••(••):••–•• doi: 10.1111/1744-9987.12177 © 2014 The Authors Therapeutic Apheresis and Dialysis © 2014 International Society for Apheresis
Investigation of Factors Affecting the Six-Minute Walk Test Results in Hemodialysis Patients Kenichi Kono,1 Yusuke Nishida,2 Yoshihumi Moriyama,3 Hiroki Yabe,4 Masahiro Taoka,5 and Takashi Sato5 1
Department of Rehabilitation, Aichi Medical College, Kiyosu, Aichi, 2Department of Rehabilitation, Seirei Christopher University, Hamamatsu, Shizuoka, 3Wellness Center, 4Department of Rehabilitation, Nagoya Kyoritsu Hospital, and 5Hemodialysis Center, Meiko Kyoritsu Clinic, Nagoya, Aichi, Japan
Abstract: Renal anemia, uremic myopathy, and malnutrition are some of the factors that affect the results of the 6-minute walk test (6MWT) in hemodialysis patients. We hypothesized that skeletal muscle dysfunction caused by skeletal myolysis, protein hypercatabolism, and mitochondrial deficiency are strongly related factors. The purpose of this study was to clarify the factors that affect the 6MWT results in hemodialysis patients to assess their exercise tolerance. The study included 43 outpatients from the hemodialysis unit. The 6MWT was performed, and knee extension strength, 1-leg standing time, and grip were measured. In addition, the subjects’ characteristics such as age, preexisting coronary artery disease, hemoglobin level, total iron binding capacity, serum albumin level, creatinine generation rate, and normalized protein catabolic rate
were investigated. A stepwise multiple regression model was used to examine the factors affecting the 6MWT results. Multiple regression analysis revealed that knee extension strength (β = 0.446, P = 0.001), total iron binding capacity (β = −0.299, P = 0.021), and preexisting coronary artery disease (β = −0.272, P = 0.035) significantly affected the 6MWT results (R = 0.66, R2 = 0.44). The 6MWT in hemodialysis patients was strongly affected by muscle strength, iron deficiency anemia, and preexisting coronary artery disease, suggesting that resistance training is important for improving 6MWT results. Our findings indicate that iron deficiency and cardiac function should be assessed before exercising or undergoing an exercise tolerance test. Key Words: Hemodialysis, Iron-deficiency, Muscle, Physical endurance, Walking.
According to the statistical survey from the Japanese Society for Dialysis Therapy, there are approximately 300 000 dialysis patients in Japan (1). The exercise capacity of hemodialysis (HD) patients is about 50−60% of that in normal subjects (2,3), and HD patients show impairments in activities of daily living and quality of life, and decreased survival (4). Peak oxygen consumption (peak VO2) is the most accurate parameter for assessing exercise capacity. Particularly in HD patients, exercise capacity is affected by multiple factors such as renal anemia, uremic myopathy, and reduction of energetic substrate (3). Recently, renal anemia has been treated with erythropoiesis-stimulating agents. Therefore, we
hypothesized that decreased exercise capacity is caused by muscle dysfunction, such as reduction of muscle mass, muscle strength, and muscle energy metabolism, resulting from skeletal myolysis, protein hypercatabolism, and mitochondrial deficiency. Consequently, we examined the factors affecting the results of the 6-minute walk test (6MWT), which is a method for assessing exercise capacity that is easier to use than peak VO2 measurement. The 6MWT has been used as an assessment tool for exercise capacity since it was performed for patients with chronic obstructive pulmonary disease (COPD) for the first time in 1982 (5). The 6MWT results correlated strongly with peak VO2 (correlation coefficient, 0.68−0.88) (6−9). Additionally, the results of the 6MWT can predict a decrease in peak VO2 to < 14 mL·min·kg with a high sensitivity and specificity (10). Furthermore, in a previous systematic review (11), predicting the peak VO2 value from the 6MWT results was reportedly suitable for a test with
Received July 2013; revised October 2013. Address correspondence and reprint requests to Mr Kenichi Kono, Assistant Professor, Department of Rehabilitation, Aichi Medical College, 519 Ichiba, Kiyosu, Aichi Pref 452-1931, Japan. Email: [email protected]
1
2
K Kono et al.
a distance of < 490 m. In many HD patients that meet this criterion, the 6MWT is a valid assessment tool for testing exercise capacity. The objective of this study was to identify factors affecting the results of the 6MWT among the characteristics of HD patients, including physical function, nutritional state, and anemic state. PATIENTS AND METHODS The study included 43 outpatients from the HD unit. Exclusion criteria were heart failure (New York Heart Association stage 3 or 4), chronic respiratory failure, post-stroke patients, peripheral artery disease (Fontaine stage > 2), and inadequate Kt/V (
Therapeutic Apheresis and Dialysis 2014; ••(••):••–•• doi: 10.1111/1744-9987.12177 © 2014 The Authors Therapeutic Apheresis and Dialysis © 2014 International Society for Apheresis
Investigation of Factors Affecting the Six-Minute Walk Test Results in Hemodialysis Patients Kenichi Kono,1 Yusuke Nishida,2 Yoshihumi Moriyama,3 Hiroki Yabe,4 Masahiro Taoka,5 and Takashi Sato5 1
Department of Rehabilitation, Aichi Medical College, Kiyosu, Aichi, 2Department of Rehabilitation, Seirei Christopher University, Hamamatsu, Shizuoka, 3Wellness Center, 4Department of Rehabilitation, Nagoya Kyoritsu Hospital, and 5Hemodialysis Center, Meiko Kyoritsu Clinic, Nagoya, Aichi, Japan
Abstract: Renal anemia, uremic myopathy, and malnutrition are some of the factors that affect the results of the 6-minute walk test (6MWT) in hemodialysis patients. We hypothesized that skeletal muscle dysfunction caused by skeletal myolysis, protein hypercatabolism, and mitochondrial deficiency are strongly related factors. The purpose of this study was to clarify the factors that affect the 6MWT results in hemodialysis patients to assess their exercise tolerance. The study included 43 outpatients from the hemodialysis unit. The 6MWT was performed, and knee extension strength, 1-leg standing time, and grip were measured. In addition, the subjects’ characteristics such as age, preexisting coronary artery disease, hemoglobin level, total iron binding capacity, serum albumin level, creatinine generation rate, and normalized protein catabolic rate
were investigated. A stepwise multiple regression model was used to examine the factors affecting the 6MWT results. Multiple regression analysis revealed that knee extension strength (β = 0.446, P = 0.001), total iron binding capacity (β = −0.299, P = 0.021), and preexisting coronary artery disease (β = −0.272, P = 0.035) significantly affected the 6MWT results (R = 0.66, R2 = 0.44). The 6MWT in hemodialysis patients was strongly affected by muscle strength, iron deficiency anemia, and preexisting coronary artery disease, suggesting that resistance training is important for improving 6MWT results. Our findings indicate that iron deficiency and cardiac function should be assessed before exercising or undergoing an exercise tolerance test. Key Words: Hemodialysis, Iron-deficiency, Muscle, Physical endurance, Walking.
According to the statistical survey from the Japanese Society for Dialysis Therapy, there are approximately 300 000 dialysis patients in Japan (1). The exercise capacity of hemodialysis (HD) patients is about 50−60% of that in normal subjects (2,3), and HD patients show impairments in activities of daily living and quality of life, and decreased survival (4). Peak oxygen consumption (peak VO2) is the most accurate parameter for assessing exercise capacity. Particularly in HD patients, exercise capacity is affected by multiple factors such as renal anemia, uremic myopathy, and reduction of energetic substrate (3). Recently, renal anemia has been treated with erythropoiesis-stimulating agents. Therefore, we
hypothesized that decreased exercise capacity is caused by muscle dysfunction, such as reduction of muscle mass, muscle strength, and muscle energy metabolism, resulting from skeletal myolysis, protein hypercatabolism, and mitochondrial deficiency. Consequently, we examined the factors affecting the results of the 6-minute walk test (6MWT), which is a method for assessing exercise capacity that is easier to use than peak VO2 measurement. The 6MWT has been used as an assessment tool for exercise capacity since it was performed for patients with chronic obstructive pulmonary disease (COPD) for the first time in 1982 (5). The 6MWT results correlated strongly with peak VO2 (correlation coefficient, 0.68−0.88) (6−9). Additionally, the results of the 6MWT can predict a decrease in peak VO2 to < 14 mL·min·kg with a high sensitivity and specificity (10). Furthermore, in a previous systematic review (11), predicting the peak VO2 value from the 6MWT results was reportedly suitable for a test with
Received July 2013; revised October 2013. Address correspondence and reprint requests to Mr Kenichi Kono, Assistant Professor, Department of Rehabilitation, Aichi Medical College, 519 Ichiba, Kiyosu, Aichi Pref 452-1931, Japan. Email: [email protected]
1
2
K Kono et al.
a distance of < 490 m. In many HD patients that meet this criterion, the 6MWT is a valid assessment tool for testing exercise capacity. The objective of this study was to identify factors affecting the results of the 6MWT among the characteristics of HD patients, including physical function, nutritional state, and anemic state. PATIENTS AND METHODS The study included 43 outpatients from the HD unit. Exclusion criteria were heart failure (New York Heart Association stage 3 or 4), chronic respiratory failure, post-stroke patients, peripheral artery disease (Fontaine stage > 2), and inadequate Kt/V (
