This psychic influence on blood pressure is stated by Maloney and Sorapure [Footnote: Maloney and Sorapure: New York Med. Jour., May 23, 1914, p. 1021.] "to be greater than that from posture, than that arising from carbonic acid gas control of the blood, than that arising from mechanical action of deep breathing upon the circulation, and than that arising from removal of spasm from the musculature."
Weysse and Lutz [Footnote: Weysse and Lutz: Am. Jour. Physiol., May, 1915.] find that the systolic pressure varies during the day in normal persons, and is increased by the taking of food, on an average of 8 mm. The diastolic pressure is not much affected by food. This increased systolic pressure is the greatest about half an hour after a meal, and then gradually declines until the next meal.
Any active, hustling man, or a man under strain, has a rise of blood pressure during that strain, especially notable with surgeons during operation, or with brokers or persons under high nervous tension. Daland [Footnote: Daland: Pennsylvania Med Jour., July, 1913.] states that a man driving an automobile through a crowded street may have an increase of systolic pressure of 30 mm., and an increase of 15 mm. in his diastolic pressure, while the same man driving through the country where there is little traffic will increase but 10 mm. systolic and 5 mm. diastolic. Fear always increases the blood pressure. This is probably largely due to the peripheral contractions of the blood vessels and nervous chilling of the body.
VENOUS PRESSURE
The venous pressure, after a long neglect, is now again being studied, and its determination is urged as of diagnostic and prognostic significance.
Hooker [Footnote: Hooker: Am. Jour. Physiol., March, 1916.] says there is a progressive rise of venous pressure from youth to old age. He has described an apparatus [Footnote: Hooker: Am. Jour. Physiol., 1914, xxxv, 73.] which allows of the reading of the blood pressure in a vein of the hand when the arm is at absolute rest, and best with the patient in bed and reclining at an angle of 45 degrees. He finds that just before death there is a rapid rise in venous pressure, or a continuously high pressure above the 20 cm. of water level, and he believes that a venous pressure continuously above this 20 cm. of water limit which is not lowered by digitalis or other means is serious; and that the heart cannot long stand such a condition. These dangerous rises in venous pressure are generally coincident with a fall of systolic arterial pressure, although there may be no constant relation between the two. He also finds that with an increase of venous pressure the urinary output decreases. This, of course, shows venous stasis in the kidneys as well as a probable lowering of arterial pressure.
Clark [Footnote: Clark, A. D.: A Study of the Diagnostic and Prognostic Significance of Venous Pressure Observations in Cardiac Disease, Arch. Int. Med., October, 1915, p. 587.] did not find that venesection prevented a subsequent rapid rise in venous pressure in dire cases. From his investigations he concludes that a venous pressure of 20 cm. of water is a danger limit between compensation and decompensation of the heart, and a rise above this point will precede the clinical signs of decompensation.
Hooker also found that there are daily variations of venous pressure from 10 to 20 cm. of water, with an average of 15 cm., while in sleep it falls 7 or 8 cm.
It seems probable that there may be a special nervous mechanism of the veins which may increase the blood pressure in them as epinephrin solution may cause some constriction.
Wiggers [Footnote: Wiggers C. J.: The Supravascular Venous Pulse in Man, THE JOURNAL. A.M.A., May 1, 1915, p. 1485.] describes a method of taking and interpreting the supraclavicular venous pulse. He also [Footnote: Wiggers C. J.: The Contour of the Normal Arterial Pulse, THE JOURNAL. A.M.A., April 24, 1915, p. 1380.] carefully describes the readings and the different phases of normal arterial pulse, and urges that it should be remembered that "the pulse as palpated or recorded from any artery is the variation in the arterial volume produced by the intra-arterial pressure change at that point."