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Other factors enter here, praticularly the previous history and personal habits of the case, especially addiction to alcohol.1

Gibson's Rule. So called because first formulated by Gibson’ in 1908. This blood-pressure pulse ratio has been

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Fig. 37.—Showing close relation between pulse rate and blood-pressure and application of Gibson's rule. Symptoms of collapse developed after crisis and continued until normal relation was reëstablished during convalescence.

the subject of much controversy and an occasional frank attack Newburgh and Minot, 3 nevertheless the bulk of clinicians adhere to it and find value in its application (see Fig. 37). This so-called rule as originally stated by Gibson 1L. H. Newburgh and G. R. Minot, Arch. Int. Med., July, 1914, xiv, No. 1.

Edinburgh Med. Jour., January, 1908. Loc. cit.

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is as follows: “When arterial (systolic) pressure expressed in millimeters of mercury does not fall below the pulse rate expressed in beats per minute, the fact may be taken as of excellent augury while the converse is equally true.” No one should accept this statement unconditionally, for there are many exceptions. In applying the rule the physician will avoid being led into the error of relying entirely on it, by giving due weight to such other factors, as the violence of infection, an alcoholic history or not, the presence of chronic disease, etc. Also the mere disturbance of this ratio for a short period is of little significance, becoming important only when the ratio persists for some time in the face of stimulating measures.

Concerning the practical value of this test, G. A. Gordon? states that in a recent series of cases studied by him there were no fatalities among those whose quotient remained B.P.>P.R.

Alex. Lambert? studied forty-eight cases; of these twenty failed to maintain B.P.P.R. and of them six or 42 per cent. died, while the twenty-eight in whom B.P.>P.R., five or 17.09 per cent. died. Gundrum and Johnson3 report observations on thirty institutional cases between the ages of eighteen and sixty, twenty of whom were alcoholic. They had nine deaths (mortality 30 per cent.) among those whose systolic blood-pressure on admission ranged between 65 and 122 mm. Hg. with a pulse of 68 to 148.

Eighteen cases maintained B.P.>P.R. and seventeen 1 Edinburgh Med. Jour., January, 1910. * Jour. A. M. A., Dec. 2, 1911, lvii, 23, p. 1827.

: F. F. Gundrum and E. E. Johnson, Calif. State Jour. of Med., May, 1912, x, 5.

or 94 per cent. recovered while of the twelve who showed B.P.<P.R., nine or 75 per cent. died. These observers feel that they are greatly aided in treatment by following the rise and fall of pulse pressure and systolic pressure.

Auscultatory Sounds as Aids to Prognosis.—The second and third phases when good and clear are considered favorable signs in pneumonia as they indicate heart strength (see page 99). The second phase is the one most quickly lost, from heart weakening in pneumonia, and its presence throughout the disease is therefore a good sign.

The muffling or weakening of any of the sounds should be looked upon with suspicion as such changes indicate a relaxation of peripheral resistance and a failing heart; the addition of arrhythmia to these variations is a further indication of the same adverse change.

Newburgh and Minot noted among other findings that the blood-pressure curve in pneumonia did not suggest a failure of the vasomotor center, which conclusion has been amply confirmed experimentally by W. T. Porter. Both were able to demonstrate that it was not the vasomotor center but the myocardium itself that failed in fatal pneumonia. Even more convincing are the microscopic findings of Willson who in every instance was able to detect myocardial changes due either to a toxemia or to a local infection.

F. Tice? found Gibson's ratio to hold good in 88 per cent. of cases and considers it of value not only in prognosis but also of much assistance in treatment, where it is a valuable guide to the administration of stimulants.

1 A. A. Howell, Jour. A. M. A., Ixii, 16, Apr. 18, 1914. 2 Jour. A. M. A., Mar. 27, 1915, lxiv, 13.

Normal Pressure Level in Pneumonia.-G. M. Piersol followed ten cases, three of whom ran an average pressure above normal throughout the disease, four maintained a pressure that was normal for the age of the individual, three fell below during the active stage but quickly rose after the crisis to an approximately normal level.

Relation of Pressure to Crisis.-Piersol has seen a rise, in a woman aged fifty, amounting to 40 mm. systolic and 30 diastolic in less than twenty-four hours after crisis.

In mild cases there is not much change at the crisis, especially in young adults, although pressure will usually be lower after crisis and during convalescence than during the height of the disease. A. Lambert? has not noted any sudden fall at crisis, but a gradual return to normal in the cases that recover, the pulse usually diminishing in frequency before the blood-pressure rises, though occasionally the reverse may be true.

In cases where neither pulse nor fever is high, but the blood-pressure very low, below 100, with BP > P R the cases recover, but in these cases the pressure is very slow in rising and these hearts should be carefully watched and guarded.

In cases with chronic nephritis, though the pressure may remain between 170 and 220 yet the patients may die.

The reading of blood-pressure in arteriosclerosis and nephritis does not give a clue to the cardiac conditions and in these cases Gibson's ratio does not hold. Dyspnea may cause rise in blood-pressure, the pressure level is also influenced by the day of the disease.

1 Loc. cit.
2 Jour. A. M. A., Dec. 2, 1911, lvii, 23, p. 1829.

TYPHOID FEVER All authorities agree that typhoid fever is a disease of hypotension, and that the depression in systolic pressure appears early, and is progressive (unless interrupted by complications) throughout the active progress of the disease; further, the depression of pressure persists for a relatively long time, even after the temperature has returned to normal and the patient is well established in convalescence. The preëxistence of cardiovascular or renal lesions will modify the pressure readings and when variations from the usual course are met such complications should be suspected. Even in these cases a hypotension (but with readings above the patient's normal age level) may be demonstrated, if we were able to obtain a knowledge of the patient's pressure before the onset of the disease.

Vasomotor weakness of the splanchnics caused by the toxins of the disease is usually considered to be the cause of the pressure depression.

The pressure during the first week, when cases are rarely seen by the physician, may not be sufficiently modified to be noticeable.

Blood-pressure Readings.—The systolic pressure in typhoid fever, after the first week in young adults, will usually register below 100, progressively falling until the fourth week, when it usually begins to ascend. Pressures of 85 and 90 systolic are not uncommon, while a systolic pressure of 74 mm. has been recorded (Crile). The author as a matter of convenience, and as an aid to comparison, considers that the pressure in typhoid fever averages about

Geo. W. Crile, Jour. A. M. A., xl, 1903.

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