Brian J. Sproule

CARDIOPULMONARY PHYSIOLOGICAL RESPONSES TO HEAVY EXERCISE IN PATIENTS WITH ANEMIA

The hemodynamic adaptation of the human body to acute and chronic anemia has been extensively studied. There are few reports, however, of investigations of the response of anemic individuals to exercise. The most exhaustive study to date is that of Bishop, Donald and Wade (1), who evaluated 11 patients with anemia at moderate levels of exercise, performed in a supine position at minute ventilations up to 20 L. Preliminary observations in our laboratory indicated that subjects suffering from moderately severe anemia are capable of exerting themselves on a treadmill at levels of exercise approaching or exceeding those producing maximal oxygen intake in normal subjects. This led us to investigate the response of anemic subjects to very severe exertion.

Behavior of stroke volume at rest and during exercise in human beings.

The implications of Starlings law of the heart, as stated in the Linacre Lecture (1), miiake it clear that physical exercise brings about increased venous return and increased diastolic filling of the heart. This, in terms of the Starling concept, induces sufficient increase in the energy of contraction to drive increased volumes of blood into the aorta with each stroke. While Starling was aware that the heart is subject to the control of the central nervous system by means of its inhibitor and augmentor nerves . . . he undoubtedly placed the emphasis, insofar as cardiac adaptation to stress is concerned, on intrinsic response of the miiyocardium to change in end-diastolic fiber length. It follows, if Starlings Linacre Lecture is credited, that the heart must meet the demiiands imiiposed by physical exertion, in part at least, by increasing its stroke volume. This was indeed found to be the case in older studies on the effect of exercise on human circulatory function (2-4) ; these studies served further to establish the view that increase in both stroke volume and pulse rate are utilized by the organism during exercise. A different view has been gradually formulated by Rushmer who, using continuous measurements of internal left ventricular diameters (5) and circumference (6) in unanesthetized dogs exercising on a treadmill, was not convinced that response to such stress was entirely in accord with Starlings law. These results, and an examination of other workers data on human subjects, ultimately led him to a radical revision of the older view concerning the interdependence of increase in stroke volume, pulse rate and arteriovenous oxygen difference in adaptation to exercise. In his words (7): Evidence that the stroke volume need not change significantly during exercise which in-

A STUDY OF CARDIOPULMONARY ALTERATIONS IN PATIENTS WITH SICKLE CELL DISEASE AND ITS VARIANTS

It has recently become apparent that a high proportion of individuals who possess S type hemoglobin exhibit significant desaturation of the arterial blood. In 1942 Klinefelter (1) found arterial oxygen saturations of 89 and 91 per cent in two patients, and in 1943 Reinhard, Moore, Dubach, and Wade (2) found values ranging from 74.2 to 90.8 per cent saturation in one patient with sickle cell disease. Leight, Snider, Clifford, and Hellems (3) studied 13 patients with sickle cell disease in 1954, 10 of whom had arterial 02 desaturation. Within the past year reports from this laboratory (4, 5) and from Jensen, Rucknagel, and Taylor (6) indicate that desaturation of arterial blood exists in most people who possess S type hemoglobin. The exact mechanism responsible for this phenomenon has not been elucidated. The various possibilities may be distinguished with fair accuracy by determining alveolar and arterial oxygen tensions and calculating A-a oxygen tension gradients at three levels of oxygenation. If desaturation is due to hypoventilation, no appreciable gradient exists at any level of oxygenation and CO2 retention is usually evident. Any increase in A-a gradient must, therefore, be due to some other mechanism. Lilienthal, Riley, Proemmel, and Franke (7) suggested that one might distinguish between a diffusion defect and veno-arterial admixture by measurement of the effective alveolar-arterial gradient at two levels of oxygenation, one of which produces significant desaturation of arterial blood. Low levels of inspired 02 (12 to 14 per cent) exaggerate the effects of impaired diffusion and minimize the effects of veno-arterial admixture. Veno-arterial admixture, thus delineated, may be either through actual anatomical communications, or the result of reduction in the ventilation-perfusion ratios.

The maximal oxygen intake test in patients with predominant mitral stenosis. A preoperative and postoperative study.

I N FUNCTIONALLY significant mitral stenosis the value of surgical reduction of the block to left atrial outflow is not firmly established. Methods for objective measurement of the degree of functional impairment before and after operation have been slow in development. The critical use of symptoms, physical signs, x-ray films, and electrocardiograms is undoubtedly the first resort for this purpose, and in many cases it is sufficient. In some instances, however, these technics leave important questions unanswered; symptoms do not always fit signs and, most important, subjective improvement after operation is almost the rule even when the usual methods of clinical examination disclose little or no innprovement. Attempts to use quantitative hemodynamic and respiratory methods for evaluation have often been disappointing in that they frequently throw very little light on subjective improvement induced by operation.1 It may indeed be held that, in the selection of patients for surgery, the superiority of such sophisticated methods over the astute use of ordinary clinical tools has not been demonstrated. It was inherent in the work by Hickam and Cargill2 over a decade ago, and in subsequent studies by Gorlin and co-workers,3 that resting hemodynamie and respiratory studies might be of limited value in the functional evaluation of patients with mitral stenosis unless combined with exercise studies. More re-

Venous-Arterial Admixture in the Lungs in Primary and Secondary Polycythemia

By use of a polarographic technic for measuring arterial oxygen tension, venous-arterial shunting in the lungs was investigated in patients with primary and secondary polycythemia before and after treatment and in nonpolycythemic normal and emphysematous subjects.

Rapid onset of emphysema associated with diffuse parenchymal disease

In experimental models pulmonary emphysema may be produced in hours to days; however, in human subjects emphysema commonly develops over a period of many years. In this report we document a case of severe emphysema which developed in less than six months in association with an unexplained illness characterized by dyspnea, hypoxemia and bilateral lung parenchymal disease. There was no hereditary predisposition. The diffuse alveolar injury syndrome must be considered as a potential cause of alveolar disruption.