Kazuya Yamamoto

Kitasato University, Tokyo, Tokyo-to, Japan

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Publications (6)10.16 Total impact

  • Article: Excessive fall of blood pressure during maintenance hemodialysis in patients with chronic renal failure is induced by vascular malfunction and imbalance of autonomic nervous activity.
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    ABSTRACT: Acute hypotension during maintenance hemodialysis (HD) is not only a critical complication, but also an independent risk factor for mortality in patients with chronic renal failure (CRF). This study was designed to clarify the mechanisms underlying excessive fall of blood pressure during HD. Fifty-six CRF patients with HD thrice a week were divided into two groups according to the intradialytic hypotension episodes after 4 weeks of the observation period; the hypotension group, showing four or more episodes of intradialytic hypotension, and the non-hypotension group, showing three episodes of intradialytic hypotension or less. The intradialytic hypotension was defined as a fall of ≥30 mm Hg in the systolic blood pressure during HD. The brachial-ankle pulse wave velocity (ba-PWV), serum high-sensitivity (hs)-CRP, reactive oxygen species (ROS) generation, and serum malondialdehyde-modified LDL (MDA-LDL) were measured before HD. The high- frequency (HF) and low-frequency components (LF) of the heart rate variability and entropy were analyzed by the maximal entropy method. The ba-PWV, hs-CRP, ROS generation, and MDA-LDL were significantly higher in the hypotension group than in the non-hypotension group. HF, LF/HF, and entropy during HD increased significantly in the non-hypotension group, while entropy during HD decreased significantly in the hypotension group as compared with the baseline. LF/HF and entropy during HD were significantly lower in the hypotension group than in the non-hypotension group. These findings suggest that the major factors causing excessive fall of blood pressure during HD in patients with CRF might be vascular malfunction and imbalance of autonomic nervous activity.
    Therapeutic apheresis and dialysis: official peer-reviewed journal of the International Society for Apheresis, the Japanese Society for Apheresis, the Japanese Society for Dialysis Therapy 06/2012; 16(3):219-25. · 1.39 Impact Factor
  • Article: Effects of prolonged expiration breathing on cardiopulmonary responses during incremental exercise.
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    ABSTRACT: This study was designed to clarify the effects of breathing with prolonged expiration on cardiopulmonary responses and autonomic nervous activity during incremental exercise. Eleven healthy men were randomly assigned to breathing mode: a prolonged expiration breathing with a 2-s inspired time and 4-s expired time and a spontaneous breathing without any constraints. Oxygen uptake (V(O2)), ventilation efficiency (V(E)/V(CO2)) and rate pressure product were measured. Low- (LF) and high-frequency (HF) components of blood pressure and heart rate variability were analyzed to assess sympathetic and parasympathetic nervous activities, respectively. V(E)/V(CO2), rate pressure product and LF were significantly lower, and [Formula: see text] and HF were significantly higher during exercise with prolonged expiration than with spontaneous breathing. Striking effects of prolonged expiration breathing included the improvement of ventilation efficiency, the suppression of sympathetic nervous activity and the activation of parasympathetic one during incremental exercise. Furthermore, prolonged expiration breathing may have suppressed the exercise-induced increase in myocardial V(O2).
    Respiratory Physiology & Neurobiology 07/2011; 178(2):275-82. · 2.24 Impact Factor
  • Article: Development of a novel questionnaire evaluating disability in activities of daily living in the upper extremities of patients undergoing maintenance hemodialysis.
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    ABSTRACT: The aim of the present study was to develop a novel questionnaire evaluating disability in the activities of daily living in the upper extremities of hemodialysis (HD) patients (QDUE-HD). We recruited 83 patients (40 males and 43 females) aged 66 ± 8 years, and measured their muscle strength and range of motion in the upper extremities. Moreover, 14 patients performed a six-week exercise training regimen (the exercise group) and were compared with 15 patients not performing such training (the control group). In an initial questionnaire consisting of 37 items, 30 were taken from the Disabilities of the Arm, Shoulder and Hand questionnaire and the Activities of Daily Living Test, and the remaining seven were selected from activities that HD patients perceived as impossible or extremely difficult to perform. The principal factor analysis focused on 11 items, as 26 showing floor and ceiling effects were excluded. These 11 items were divided into two categories consisting of six items termed "light work" and five termed "holding activities". The scores for light work and holding activities correlated significantly and positively with both muscle strength and range of motion in the upper extremities. These scores increased significantly after the six-week exercise training as compared with those before training in the exercise group. We conclude that the QDUE-HD is clinically useful for evaluating disability in activities of daily living in the upper extremities of HD patients because of its high reliability, validity and responsiveness.
    Therapeutic apheresis and dialysis: official peer-reviewed journal of the International Society for Apheresis, the Japanese Society for Apheresis, the Japanese Society for Dialysis Therapy 04/2011; 15(2):185-94. · 1.39 Impact Factor
  • Article: Physical activity is necessary to prevent deterioration of the walking ability of patients undergoing maintenance hemodialysis.
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    ABSTRACT: Maintenance of the walking ability is very important for smooth continuation of maintenance hemodialysis (HD). The aim of the present study was to clarify the physical activity level in daily living that HD patients should maintain to prevent deterioration of their walking ability. Outpatients undergoing maintenance HD, consisting of 65 males and 88 females with a mean age of 64 +/- 11 years, were recruited for the present study. Their physical activity level was recorded over a week with an accelerometer. The physical activity level in daily living was defined as the sum of the lengths of time for which the patients were engaged in physical activity of light or greater intensity during the day, and expressed as the average duration per day. The walking ability was assessed by the normal walking speed and maximum walking speed. Data were analyzed using the receiver operating characteristic (ROC) curve, and the cut-off point for the physical activity time was determined to predict deterioration of the walking ability. In the prediction of deterioration of the normal and maximum walking speeds, the areas under the ROC curve for the physical activity time were 0.78 (95% confidence interval, 0.69-0.87, P < 0.001) and 0.75 (95% confidence interval, 0.63-0.86, P < 0.001), respectively. Moreover, the ROC curve revealed that the cut-off point for the physical activity time to prevent deterioration of the normal and maximum walking speeds was 50 min/day. Thus, HD patients should engage in physical activity for at least 50 min/day to prevent deterioration of their walking ability.
    Therapeutic apheresis and dialysis: official peer-reviewed journal of the International Society for Apheresis, the Japanese Society for Apheresis, the Japanese Society for Dialysis Therapy 04/2010; 14(2):193-200. · 1.39 Impact Factor
  • Article: Effects of phase II cardiac rehabilitation on job stress and health-related quality of life after return to work in middle-aged patients with acute myocardial infarction.
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    ABSTRACT: The aim of the present study was to clarify the effects of phase II cardiac rehabilitation (CR) on job stress and health-related quality of life (HRQOL) after return to work in middle-aged patients with acute myocardial infarction (AMI). A total of 109 middle-aged outpatients (57 +/- 7 years) who completed a phase I CR program after AMI were enrolled, 72 of whom participated in a phase II CR program for 5 months after hospital discharge (CR group) and 37 who discontinued the phase II CR program after the discharge (non-CR group). Job stress was assessed at 6 months after the AMI using a brief job stress questionnaire containing questions related to job stressors, worksite support, level of satisfaction with work or daily life, and psychological distress. HRQOL was assessed using the short-form 36-item health survey (SF-36) at hospital discharge and at 3 and 6 months after the AMI. There were no significant differences in clinical and occupational characteristics between the CR and non-CR groups. The CR group patients exhibited significantly better results for job stressors and psychological distress and higher SF-36 scores at 6 months after the AMI, as compared with those in the non-CR group. These findings suggest that discontinuing a phase II CR program induced chronic psychosocial stress after return to work in these middle-aged post-AMI patients.
    International Heart Journal 06/2009; 50(3):279-90. · 1.16 Impact Factor
  • Article: Influence of nifedipine coat-core and amlodipine on systemic arterial stiffness modulated by sympathetic and parasympathetic activity in hypertensive patients.
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    ABSTRACT: The aim of this study was to compare the effects of nifedipine coat-core (once daily formulation) and amlodipine on systemic arterial stiffness in patients with hypertension. Study drugs were assigned by the randomized open-label crossover method. After the blood pressure was maintained below 130/85 mm Hg for 8 months by treatment with either drug in 48 hypertensive patients (aged 63.2+/-6.9 years; 64.5% men), they were switched to the other drug for another 8 months. The blood pressure, heart rate, plasma catecholamine level and brachial-ankle pulse wave velocity were measured before and after a bicycle ergometer testing. Heart rate recovery was calculated from the change of the heart rate after treadmill exercise testing. The high-frequency and low-frequency components of the heart rate variability spectrum were analyzed from 24-h Holter electrocardiograms. The change of blood pressure after exercise testing showed no significant difference between the two medications. However, the increases of heart rate, noradrenalin and branchial-ankle pulse wave velocity after exercise were significantly smaller with nifedipine treatment than with amlodipine (P=0.0472, P=0.006 and P=0.0472, respectively). Heart rate recovery was significantly faster with nifedipine treatment (P=0.0280). The nighttime high-frequency component of heart rate variability was significantly larger after nifedipine treatment than after amlodipine (P=0.0259), while the nighttime low/high-frequency ratio was significantly smaller with nifedipine (P=0.0429). Nifedipine reduced functional arterial stiffness and improved heart rate recovery by altering the autonomic activity balance in hypertensive patients.
    Hypertension Research 05/2009; 32(5):392-8. · 2.58 Impact Factor