Bruceのプロトコルを用いた多相トレッドミル負荷試験による酸素輸送系の機能評価—とくに，心脈管反応の人種差について

Functional Evaluation of the Oxygen Transport System with Multiphasic Treadmill Stress Testing after Bruce's Protocol:Racial Difference in Cardiovascular Response to Exercise

　近年，運動負荷試験は潜在性虚血の診断，胸痛の鑑別診断，心機能の評価，治療効果の判定，身体適性の評価，そして予後の判定など多くの目的について行なわれるようになり，従来のMasterの2階段法ではこれらの目的を十分に達成することができなくなった。1954年，AstrandとRhymingが亜最大運動において心拍数と酸素摂取量が比例することを示し^1），このことを受けてBruceは身体適性の評価の方法としてトレッドミルによる運動負荷のプロトコルを示し^2），これによって運動負荷試験は新たな時代を迎えることになった。わが国の臨床でトレッドミルが用いられるようになったのはごく最近のことで，その方法や評価について意見の一致がみられない点も多い。今回は健常成人にBruceのプロトコルによる多相トレッドミル負荷試験を行なった際の心脈管反応を欧米人のそれを比較し，本邦人の最大運動負荷における循環反応の特徴，身体適性の評価，そして運動処方上の問題点について検討した。

Multiphasic treadmill stress testing has been widely used as one of the most useful non-invasive techniqus to assess the functional state of the oxygen transport system. It has long been demonstrated that the maximal heart rate and maximal oxygen intake are inversely related to the age and therefore, the age adjusted maximal heart rate has been accepted in clinical use to determine the arbitrary end-point of exercise stress testing or to prescribe exercise training with target heart rate method. The present studydemonstrated the racial difference in the maximal heart rate and total oxygen intake based on the results obtained from normal healthy 198 male and 103 female subjects with the age range from 20 to 75. Original Bruce's protocol was used in the test.

There was no significant difference in the maximal heart rate observed between male and female subjects. As a whole, however, the total oxygen intake was higher in male than in female subjects. The maximal heart rate in each age category obtained from Japanese male subjects was found to be lower than those shown in American (Sheffield et al., 1965) or Swedish population (Astrand and Christensen, 1964). Total oxygen intake was also higher in Swedish male than in Japanese male subjects. On the contrary, however, the weight adjusted oxygen intake was found to be identical both in Japanese and American male subjects (Dehn & Bruce, 1973). Since anthropometric differences were clearly demonstrated between Japanese and Americanpopulations (Pollock et al., 1976), racial difference in the maximal heart rate seems to be related to the oxygen intake which is primarily deter-mined by tissue weight demanding oxygen during exercise. Several autopsy studies also demonstrated racial differance in the heart-body weight ratio which is higher in Japanese than in American populations. Our present study concerning the cardiac volume obtained from biplane chest x-ray films also comfirmed the racial difference when the data was compared to that shown by Chikos et al. (1977).