THE IMPORTANCE OF A TIGHT BLOOD PRESSURE CUFF

WILLIAM F. NUESSLE, M.D.*

MINNEAPOLIS, MINN.

W HEN taking blood pressure, The American Heart Association recommends that the deflated bag and cuff should be applied evenly and snugly around

the arm.’ Casual application of a loose cuff is a common error in blood pressure determination, especially with the newer clip-on cuffs. A study was under- taken to determine what differences arose when cuffs were applied loosely.

METHODS

Blood pressure determinations were made on one hundred individuals during examinations for employment and insurance. Pressures were obtained with a clip-on cuff applied tightly, and then redetermined with the cuff loosened so that its circumference was extended 3.1 cm.

RESULTS

There was a general increase in systolic and diastolic levels using the loosened cuff. Higher readings were found in ninety-four instances. The mean sys- tolic increase was 8.1 mm. Hg and diastolic 9.3 mm. The degree of change was approximately the same in the forty-three men and fifty-seven women. The change was greater in persons of average or heavy build. This may be illustrated by grouping the individuals in categories varying by Z-pound incre- ments from ideal weight (Table I), The mean change for the sixty average and heavy individuals was 9.8 mm. Hg systolic and 11.5 diastolic. The change in the forty lean persons was 5.4 mm. Hg systolic and 6.5 diastolic.

DISCUSSION

The principle employed in the indirect measurement of blood pressure con- sists of balancing air pressure against the pressure of the blood in the brachial artery and then estimating the former by means of a manometer.2 The inflatable bag should be 20 per cent wider than the diameter of the arm or thigh on which it is to be used.’ In the conventional arm cuff the bag measures 12 by 23 cm. Narrower arm cuffs such as the Riva-Rocci band give “high” reading.3 Pedi- atric cuffs applied to the adult arm and arm cuffs applied to the leg give similar findings.4l5 Cuffs which are relatively too broad give “low” readings6v7 ---__

Received for publication March 19, 1956. *Assistant Medical Director. Prudential Insurance Company of America.

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TABLE I. BLOOD PRESSCRI' INCREASE I:slNc LOOSE CWF IN IXDIVID(-ALS C;ROUPI<L) :~COKI,IS~; TO IDEAL \I~EIGHT FOR THEIR HEIGHT

_ --_-- I I

MIiAN SYSTOLIC 1 MEAN DIASTOLIC CATEC~RY NUMBER OF CHANGE

! INDIVIDUALS (MM. HG.)

I

More than 30 pounds overweight 6 ( 12.3 / 11 .?I 16 to 30 pounds overweight 10.0 8.8 Ideal weight to 1.5 pounds overweight :i 10.2 11.9 Ideal weight to 15 pounds underweight ’ 25 8.6 I 12.3 16 to 30 pounds underweight 26 5.0 6.1 More than 30 pounds underweight I 14 6.3 j 7.1

Thomson and Doupe8 measured tissue pressures under inflated cuffs. They found pressures equal to the manometric only near the center of the cuff. The tissue pressure in the lateral margins of the cuff was less than that recorded in the manometer. The zone of effective pressure narrowed at greater depths in the tissues. At the depth of bone the margin of ineffective pressure extended 6 cm. from the edge of the cuff. It may be assumed that if the brachial artery is being compressed by this margin because of a rotated or narrow cuff, greater manometric pressures will be necessary to occlude the vessel, and “high” read- ings will result.

Bazett and Laplace emphasized the importance of a tight cuff. The? indicated that “high” readings will otherwise be obtained because of pressure wasted in distention of the rubber. This reasoning can be disputed by placing the cuff on a table and inflating the bag to a volume exceeding that under a loose cuff. No pressure is recorded.

It is suggested that a loose cuff gives high readings because of the central ballooning of the bag, which exerts the pressure-effect of a narrow cuff with effective longitudinal axis shortened as well. This can be exemplified by re- cording pressures during rotation of the cuff in the four quarters of the arm. Little change occurs in the small arm. In the large arm, “high” levels are ob-

tained when the bag is opposite the brachial artery. This effect can be magni- fied by using a loose cuff. Another illustration is that of placing a cuff around a limb and partially inflating. If a second cuff is wrapped tightly and then loosely over the first cuff, air pressure introduced in the second will have a greater effect on the first when tight than when loose.

It is sometimes difficult to apply clip-type cuffs on heavy arms so that the inflatable bag compresses the brachial artery directly. However, it is in these individuals where direct pressure with a tightly-wrapped bag is most important, for in the deeper tissues there is a diminished zone of pressure equal to the mano- metric air pressure.

SUMMARY

Loosely applied blood pressure cuffs gave high readings with a mean in- crease of 8.1 mm. systolic and 9.3 mm. diastolic. This effect was augmented in people with large arms. Care should be taken to apply cuffs so the brachial artery is directly compressed by the mid-portion of the tightly-bound inflatable bag.

“N;Llr “6” IMPORTANCE OF TIGHT BLOOD PRESSURE CUFF 907

REFERENCES

1. Bordley, James, Connor, C. A. R., Hamilton, W. F., Kerr, W. J., and Wiggers, C. J.: Cir- culation 4503, 1951.

2. Best, C. H., and Taylor, N. B.: The Physiological Basis of Medical Practice, Baltimore,

3. 195?, Williams & Wilkins Company, p. 152.

van Reckhnghausen, Heinrich: Arch. exper. Path. u. Pharmakol. 46:78, 1901. 4. Kotte, J, H., Iglauer, A., McQuire, J.: AM. HEART J. 28:476, 1944. 5. Sapp, 0. L., Arney, G. K., and Mattingly, T. W.: J.A.M.A. X9:1727, 1956. 6. Woodbury, R. A., Robinow, M., and Hamilton, W. F.: Am. J. Physiol. 122:472, 1938. 7. Ragan, Charles, and Bordley, James: Bull. Johns Hopkins Hosp. 69:504, 1941. 8. Thomson, A. E., and Doupe, J.: Canad. J. Res. 27:72, 1949. 9. Bazett, H. C., and Laplace, L. B.: Am. J. Physiol. 103:48, 1933.