- Email: [email protected]
Effect of exercise on respiratory exchange in heart disease
115
ABSTRACTS Campbell, J. M. H., and Sale, F. J.: Effect of Exercise on Respiratory Heart Disease. Arch. Int. Med., 193T, xl, 237.
Exchange
in
A detailed investigation of the effect of exercise, roughly equivalent to slow and ordinary walking, has been made in three patients with heart disease. The metabolism relative to the subject’s weight did not vary greatly from the normal, which shows that the capacity for increasing ventilation and circulation, rather than any change in the metabolism or total ventilation required, limits exertion. Throughout the range examined, both of these increased regularly with the work done, so that their relationship could be shown graphically by a straight line. In these patients the extra oxygen intake as the result of work was only slightly As the exercise became harder the percentage of the extra higher than normal. oxygen required, which had to be obtained at the end of the exertion, increased more in the patients. Both these differences would tend to produce breathlessness, but the degree of change would not have been sufficient to do so in a normal subject. Greater differences were noted in the elimination of carbon dioxide. At the end of exercise it was retained more than normally, so that the output of this gas and the ventilation fell to their resting values more than usual at the beginning and rose considerably more than usual at the end. The percentage of carbon dioxide in the expired air tended to be low, probably because over-ventilation was needed to compensate for defective circulation. In one patient there was practically no rise in the percentage during exercise, so that the whole of the increased output of carbon dioxide had to be obtained by increased ventilation. The rate and depth of breathing varied in type. In a patient with mitral stenosis it was rapid and shallow. This has been found in several others with mitral stenosis, and is probably associated with the reduced vital capacity and congestion of the lungs to which these patients are liable. The rapid, shallow breathing is itself a further cause of breathlessness. In a patient with aortic disease the breathing was deep and of normal rate. This has been found frequently but not invariably in patients with sortie regurgitation. Clark-Kennedy, A. E., and Owen, Trevor. The Limitation of Muscular and Its Relation to Cardiac Failure; Quart. Jour. Med., 1927, xx, 383.
Effort
The limitation of voluntary effort is usually said to depend on failure of the cardiorespiratory system, more particularly the heart, to effect further oxygen supply to the working muscles. Failure to excrete carbon dioxide seems hardly to have been considered as a possible factor in the determination of the rate of work of which a man is capable. The symptomatology of extreme muscular exhaustion is not comparable with that of congestive heart failure. Congestive heart failure is characterized by accumulation of blood in the venous system, but this does not occur during severe muscular effort in the normal man. The normal heart is capable of dealing with the venous return of the most intense effort. In heart failure the diseased heart is unable to cope with the venous return under resting conditions. The respiratory exchange in normal men has been investigated at increasing rates of work over the same period of time breathing (a) air, (b) 26 per cent r.xygen, and (c) 16 per cent oxygen at prevailing barometric pressure. With increasing rate of work (increasing oxygen requirement) the volume of pulmonary ventilation required to effect the intake of unit quantity of oxygen and the excretion of unit quantity of carbon dioxide rises progressively. With increasing rate of work less and less oxygen is taken out of the same volume of inspired air, and less and less carbon dioxide added to it; the alveolar 0, tension rises, and the alveolar CO, tension fails. The percentage of oxygen requirement incurred as debt increases. During work of the same duration and oxygen requirement, when 26 per cent
ABSTRACTS Campbell, J. M. H., and Sale, F. J.: Effect of Exercise on Respiratory Heart Disease. Arch. Int. Med., 193T, xl, 237.
Exchange
in
A detailed investigation of the effect of exercise, roughly equivalent to slow and ordinary walking, has been made in three patients with heart disease. The metabolism relative to the subject’s weight did not vary greatly from the normal, which shows that the capacity for increasing ventilation and circulation, rather than any change in the metabolism or total ventilation required, limits exertion. Throughout the range examined, both of these increased regularly with the work done, so that their relationship could be shown graphically by a straight line. In these patients the extra oxygen intake as the result of work was only slightly As the exercise became harder the percentage of the extra higher than normal. oxygen required, which had to be obtained at the end of the exertion, increased more in the patients. Both these differences would tend to produce breathlessness, but the degree of change would not have been sufficient to do so in a normal subject. Greater differences were noted in the elimination of carbon dioxide. At the end of exercise it was retained more than normally, so that the output of this gas and the ventilation fell to their resting values more than usual at the beginning and rose considerably more than usual at the end. The percentage of carbon dioxide in the expired air tended to be low, probably because over-ventilation was needed to compensate for defective circulation. In one patient there was practically no rise in the percentage during exercise, so that the whole of the increased output of carbon dioxide had to be obtained by increased ventilation. The rate and depth of breathing varied in type. In a patient with mitral stenosis it was rapid and shallow. This has been found in several others with mitral stenosis, and is probably associated with the reduced vital capacity and congestion of the lungs to which these patients are liable. The rapid, shallow breathing is itself a further cause of breathlessness. In a patient with aortic disease the breathing was deep and of normal rate. This has been found frequently but not invariably in patients with sortie regurgitation. Clark-Kennedy, A. E., and Owen, Trevor. The Limitation of Muscular and Its Relation to Cardiac Failure; Quart. Jour. Med., 1927, xx, 383.
Effort
The limitation of voluntary effort is usually said to depend on failure of the cardiorespiratory system, more particularly the heart, to effect further oxygen supply to the working muscles. Failure to excrete carbon dioxide seems hardly to have been considered as a possible factor in the determination of the rate of work of which a man is capable. The symptomatology of extreme muscular exhaustion is not comparable with that of congestive heart failure. Congestive heart failure is characterized by accumulation of blood in the venous system, but this does not occur during severe muscular effort in the normal man. The normal heart is capable of dealing with the venous return of the most intense effort. In heart failure the diseased heart is unable to cope with the venous return under resting conditions. The respiratory exchange in normal men has been investigated at increasing rates of work over the same period of time breathing (a) air, (b) 26 per cent r.xygen, and (c) 16 per cent oxygen at prevailing barometric pressure. With increasing rate of work (increasing oxygen requirement) the volume of pulmonary ventilation required to effect the intake of unit quantity of oxygen and the excretion of unit quantity of carbon dioxide rises progressively. With increasing rate of work less and less oxygen is taken out of the same volume of inspired air, and less and less carbon dioxide added to it; the alveolar 0, tension rises, and the alveolar CO, tension fails. The percentage of oxygen requirement incurred as debt increases. During work of the same duration and oxygen requirement, when 26 per cent