Dr. H. C. Mann says: “That as compensation fails, the diastolic pressure begins to fall, and the systolic becomes irregular.” It must seem very difficult for a beginner, or even for an experienced busy practitioner, to find his way through all these devious by-paths, which must look to him often to be blind alleys and to lead nowhere, but out of the welter a few good and sound working principles emerge.
“Firstly, that at middle age and afterwards the knowledge of an habitual systolic pressure is of first-rate importance.
“Secondly, that this knowledge can be confirmed and sometimes rectified by knowledge of the diastolic pressure (manifest valvular diseases of the heart, especially aortic regurgitation, are excluded); and that a continuous rise of systolic and diastolic pressure point conclusively to threatening or confirmed arterio-sclerosis.
“Thirdly, that a steady ratio between the two pressures, even when much above normal, is a sign that the heart is doing its work well; and conversely, a falling diastolic ratio is a sign of failing compensation.”
Dr. Louis M. Warfield, in his work on Arterio-Sclerosis, says: “It is most important to estimate accurately the diastolic pressure as well as the systolic, for only in this way can we obtain any data of value regarding the driving power of the heart and the condition of the vaso-motor. A high systolic pressure does not necessarily mean that a great deal of blood is forced into the capillaries. Actually it may mean that very little blood enters the periphery. The heart wastes its strength in dilating constricted vessels without carrying on the circulation adequately. The pulse pressure is the difference between the systolic and diastolic pressure, and practically represents the heart lode.”
All these considerations demonstrate the importance of watching closely the pump as well as the pipes.
In the above figures I am presuming that the auscultatory method of determining pressure has been used. It must also be manifest that, the earlier treatment begins, the more sure will be the success. It may be that all our theories will meet the ultimate fate of so many others and be abandoned, or partially disproved, but the practical therapeutic results will remain—an increased capacity for work and considerable prolongation of the later years of life.
For a short and graphic description of the two methods of estimating pressures I am poaching from an excellent book called Blood-pressure Technique Simplified, by Dr. W. H. Cowing, of America (pp. 12–15):—
“There are two methods of determining blood pressure, that by oscillation, and that by auscultation.
“We will first describe the method by oscillation.