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The error in indirect blood pressure measurement with the incorrect size of cuff
Clinical
communications
The error in indirect blood pressure measurement with the incorrect size of cuff
L. A. Geddes, M.E., S. J. Whistler, B.S. West Lafayette,
Ph.D.
Ind.
When the auscultatory (Korotkoff) method is used to measure blood pressure indirectly, the accuracy is dependent on many factors, the most important of which is the relationship of the width of the bladder in the cuff to the size of the member to which it is applied. Cuff width is that dimension measured along the member; Fig. 1 illustrates the terminology applied to blood pressure cuffs and presents a listing of the sizes presently available. The aspect ratio (length-towidth) of most of these cuffs is about two-to-one. The cuff width for human application has been specified by several cardiology groups.1-‘3 The most recent of these reports specified the correct cuff width as “20 per cent wider than the diameter of the arm.” Because arm diameter is difficult to measure accurately, this recommendation can be restated in terms of the arm circumference as follows: cuff width should be 1.2/a = 0.382, or about 40 per cent of the arm circumference. This means that for a typical adult subject with a 30 cm. arm, the cuff width should be 12 cm. In the most recent3 recommendations for cuff width it is stated that a cuff of 12 to 14 cm. is adequate for the 30 cm. adult arm. The length of the bladder is such that it should half encircle the arm. It is well known by pediatricians that the measurement of blood pressure in children”-” requires that special attention be given to use of From the Lafayette, Supported Institute,
Biomedical Ind. by grant Bethesda,
Engineering HL-18947-01, Md.
Center,
Purdue
National
Heart,
Received
for publication
Apr.
26, 1977.
Accepted
for publication
Dec.
19, 1977.
Reprint requests: L. A. Geddes, ing Center, Purdue University, neering Studies, West Lafayette,
4
July,
2978,
Vol.
Ph.D., Director, Institute for Ind. 47907.
96, No.
1
University, Lung
Biomedical Interdisciplinary
West
and
Blood
EngineerEngi-
the correct cuff width in relation to the size of the member to which it is applied. The use of a cuff that is too narrow provides falsely high, and the use of a cuff that is too wide provides falsely low values for indirect blood pressure. Similarly in adult subjects, it has been foundg-16 that the standard 12 cm. wide cuff gives falsely high values for pressure when applied to large arms. In fact, Orma and associates13 described the situation as It has been shown by Trout “cuff hypertension.” and colleagues12 and by King and co-workersi that by increasing the arm circumference by wrapping with cotton or sponge rubber, falsely high values for indirect pressure are obtained. Moreover, Neussel and co11aborators’7 have shown that the loose application of a standard cuff to the adult arm provides a falsely high value for indirect blood pressure. To reduce the error encountered when a standard cuff is applied to a large arm, several investigationsl3, 15,18-20have advocated the use of a longer, rather than a wider bladder in the cuff. They reasoned that a long bladder would allow better transmission of the pressure in the bladder to the underlying artery. However, widespread support for this suggestion has not been forthcoming. At present the length of the bladder is such that it encompasses about one half of the member circumference. From all of these reports, it is clear that the width of the cuff, in relation to the circumference of the member to which it is applied, importantly affects the values obtained for indirect blood pressure. However, there are few reports which specify the magnitude of the error to be expected when the incorrect cuff size is used, either because the correct size is unavailable or because of a lack of knowledge of the correct size. This paper
0002-8703/78/0196-0004$00.50/00
1978
The C.V.Mosby
Co.
resents data which ilk&rates the amount of error to be expected when the cuff width departs from the opeimum which is recommended to be 40 per cent of the circumference of the member to which it is applied. tkods
an
QXit?lS
To illustrate the order of error to be expected with cuffs which are too small and too large, blood pressure was measured indirectly in a group of 52 healthy adult subjects using three standard cuffs (9,12, and 18 cm. wide), applied to the upper arm. The arms ranged from 21.5 to 36 cm. in circumference. Resting blood pressure was measured with each of the three cuffs using the auscultatory method. During deflation of the cuff (at the rate of about 3 mm. Hg per heart beat), the first sound (Phase I) beard with a stethoscope placed at the antecubital fossa indicated systolic pressure. The cessation of sound (Phase V) signaled diastolic pressure. In order to illustrate the effect of cuff width on indirect blood pressure readings, the systolic and diastolic pressures obtained on each subject with the 12 cm. cuff ressures. In almost all were taken as referent casesit was found that width was very nearly 40 per cent of the arm circumference. The systolic and diastolic pressures obtained with the 9 and 18 cm. cuffs were expressed as ratios of the systolic and diastolic reference pressures. These ratios were then plotted versus the ratio of arm circumference to cuff width A linear regression line was determined for the data points for systolic, diastolic and the combined pressures. A previous study”’ showed that there exists a hyperbolic ectly measured prescorrelation betwee th to arm circumfersure and the ratio ence. A consequence of this fact is that there is a linear relationship between indirect pressure and the ratio of arm circumference to cuff width. Rssults Fig. 2 presents the values for the ratio of measured pressure to the reference pressure (12 cm. cuff) versus the ratio of arm circumference to cuff width for systolic and diastolic pressures. Fig. 3 presents the distribution of ratios for arm circumference to cuff width for the three cuff widths applied to the 52 subjects. Note that for both systolic and diastolic pressures the use of eufff t.hat is too narrow (i.e., arm-to-cuff ratio greater than 2.48) resulted in a higher indirect
Mewborn
Inrent
4.5 5.6
il.6
Child
8.3 9.4
35.7 21.3
Adult
!I.9 12.4
La rgs Adu i t Thigh
lie5
2: *g
15.2 15.5
25.9 52.1 31.3
18.0
56.0
18.6
110.2
Fig. 1. The meaning of cuff width and length, acd the cuff sizes presently available.
pressure. Similarly, with a cuff that ws LOOwi ratio less &an 2.48) the (i.e., arm-to-cuff measured pressure was lower. As^;arm -cErcumference-to-c~~~-~id~~ ratio of 2.48 is the same as a cuff width to arm circumference ratio of 0.483,
considerable importance ID interpretirg the is Fig. 3, which shows the histograms for the ratio of arm circumference to euB width among the 52 subjects. the 12 cm. cuff, the mean rence to cuff width was 2.3Ca. ratio of arm circ The reciprocal of this value is 0.435, which is very close to the 0.4 value recommended as optimum blood pressure for obtaining accurate indire at this group of values. It is not coincidental rovided this subjects possessed arms whiek value. For the 9 cm. cuff, the ‘mean va!ue for the ratio of arm circumference to cuff width was 3.02, which corresponds to a cuff width to arm circumference ratio of 0.33, This CUR is th.erefore too narrow for these subjects and provided a combined indirect pressure reading of k7 per cent above the reference value obtained iyith the 12
Geddes and Whistler
o-SYSTOLIC x-DIASTOLIC
.
l 3.5 4.0 x ARM CIRCUMFERENCE
CUFF WIDTH
D - DIASTOLIC S - SYSTOLIC C - COMBINED
Fig. 2. The circumference
ratio of measured indirect pressure to cuff width for the 52 subjects.
to reference
(12 cm.
cuff)
pressure
versus
the
ratio
of arm
/::or1yI;GTFFT; 4;4; L/O, ~jp$i~, 3;3;4’4; 0
0,s
1.0
la5
2,o
2.5
W&
3.5
4.0
4#5
ARM CIRCUMFERENCE DIVIDED BY CUFF Fig.
3. Distribution
of the ratio
of arm
cm. cuff. Likewise, the mean ratio of arm circumference to cuff width for the 18 cm. cuff applied to the subject was 1.54. The reciprocal of this figure is 0.67, i.e., the cuff width was 67 per cent of the arm circumference. This cuff was therefore too wide and provided combined indirect pressure readings which were 10 per cent below the reference values obtained with the 12 cm. cuff. The American Heart Association recommends that the cuff width should be 1.2 times the arm
6
circumference
to cuff width
for the 52 subjects.
diameter, i.e., 40 per cent of the arm circumference. However, it is not always possible to select a cuff width which is exactly 40 per cent of the arm circumference. In practice, the cuff is usually narrower or wider than this optimum value. The magnitude of error to be expected with a cuff width that is not optimal can be estimated from the type of relationship presented in Fig. 2. In addition, in the published literature there are several reports in which a range of cuff widths
July, 1978, Vol. 96, No. I
2.5
4*5c CUFF UIDTI(S KM)
685 1 9.0 12.0'1 15.0 1-1 18.Oc.
r 0
I 5
I 10
8 15
Fig. %. This illustration shows the error value which is 40 per cent of the member -5 per cent (left) error in indirect blood
I
I
-52 L
I
20 25 30 MENDER CIRCUMFERENCEKM:5
1 40
+5x 1
i li5
;Ll
55
expected for indirect blood pressure when the CUE width d&a-x3 40n~ a circumference. The ends of each bar represent a + 5 per cent (r@&) and a pressure measurement.
was applied to the arms of human subjects and the readings obtained were compared either with direct arterial pressure, or with the values obtained relative to one size of cuff. Accordingly the data presented in the papers by Erlanger,$ Robinow and colleagues,j DayP6 Ragan and Bordlt?y, I0 Trout and associates,12 Simpson and coworkers,19 Ming,‘” Kvols and collaborators,16 and Burch and Shewey”” were plotted in the manner shown in Fig. 2, to represent the ratio of indirect to direct (or reference 12 cm. cuff) pressure versus the ratio of arm circumference to cuff width. Linear, least-squares lines were obtained for each set of data. From the slope of this relationship is revealed the percentage error expected when the cuff width deviates from 48 per cent of the arm circumference. In those papers where the leastsquares line did not pass through the ratio of cuff width to arm circumference equal to 0.4, a proportional adjustment was made without altering the slope of the regression line. Thus the data from all of these reports were represented by straight lines passing through the 0.4 point on the axis representing arm circumference to cuff width ratio. Then the values for the ratio of cuff width to arm circumference corresponding to a plus five and minus five per cent error were identified for each subject. Using these minimum and maximum cuff-to-arm ratios, the ranges of member circumference for a t5 per cent error in indirect blood pressure measurement (with respect to the AHA recommended cuff size) were calculated for the .5, 6.5, 9, 12, 15, and 18 em. cuffs. Fig. 4 presents the result of this analysis and shows the cuff widths that are appropriate for members ranging from 5 to 55 cm. The cuff widths chosen
represent those that ave been describad in she literature or sizes that are presently available, The illustration points out that use of a cuff that is narrower than the recommended width results in an overestimation of pressure and the use of a cuff that is wider than that rec~rn~~e~d~d results in an underestimation of pressure. Cuff widths corresponding to the centers of the black bars in Fig. 4 represent a cuff width-to-arm of the circumference ratio of 0.4. T e extremities bars represent the extreme value of member circumference which will pro uce a 25 per cent error in measured pressure for a given cu In order to relate the information obtained in this study to present practice, we calculated the range of arm circumference for each of &be cu.&3 by the two largest rn~~~~fa,~~u~~rs of anometers. The limits of arm cireumference were based on obtaining a k 5 per cent error in blood pressure measurement. It was found that one manufacturer provides cuffs that are based on the American Heart Association criterion, i.e., optimum cuff width equals 40 per cent of the member circumference. The limit marks on the CUE provided by this manufacturer are in good agreement with the +5 per cent error in blood pressure found in this study, with the exception of the tlrtigh cuff which indicates that it is applicable to larger noembers than we would recommend. It was found that the other manufacturer provided cuffs which were centered about a rati3 for cuff width-to-member circumference eqt;al to 0.345, i.e., slightly less than that recommended by the AHA. However, hr all cuffs, the range of ar-m the circumference limits coincide very we%i%iikh +5 per cent criterion presented in. this paper.
Geddes
and
Whistler
Conclusion
The data in this report, and those presented in the published literature, show that the use of a cuff that is too narrow overestimates and one that is too wide underestimates indirect blood pressure. A cuff width-to-arm circumference ratio of 0.34 overestimates blood pressure by about 5 per cent; a cuff width-to-arm circumference ratio of 0.50 underestimates blood pressure by 5 per cent. For the same degree of mismatch, the error is greater when the cuff width is narrower rather than larger.
6. 7.
8.
9.
10.
11.
Summary
This paper shows the error to be expected when blood pressure is measured indirectly with a cuff that is too wide or too narrow for the member to which it is applied. A cuff that is too narrow overestimates and a cuff that is too wide underestimates blood pressure.
12.
13. 14. 15. 16.
REFERENCES 1.
2.
3.
4.
5.
Barker, M. H. (and committee): Standardization of blood pressure readings. Joint recommendations of the American Heart Association and the Cardiac Society of Great Britian and Ireland, AM. HEARTJ. 18:95,1939. Bordley J., Connor, C. A. R., Hamilton, W. F., Kerr, W. J., and Wiggers, C. J.: Recommendations for human blood pressure determination by sphygmomanmeters, Circulation 4:503, 1951. Kirkendall, W. M., Burton, A. C., Epstein, F. H., and Freis, E. D.: Recommendations for human blood pressure determinations by sphygmomanometer, Circulation 36:980, 1967. Woodbury, R. A., Robinow M., and Hamilton, W. F.: Blood pressure studies on infants, Am. J. Physiol. 122:472, 1938. Robinow, M., Hamilton, W. F., Woodbury, R. A., and Volpitto, P. P.: Accuracy of clinical determinations of blood pressure in children, Am. J. Dis. Child. 58:102, 1939.
17. 18.
19.
20. 21.
22.
Day, R.: Blood pressure determinations in children, J. Pediatr. 14:148, 1939. Moss, A. J., and Adams, F. H.: Auscultatory and intraarterial pressure. A comparison in children with special reference to cuff width, J. Pediatr. 66:1094, 1967. Hansen, R. L., and Stuckler, C. G.: The “non-hyperten”, sion” or “small-cuff” syndrome, Clin. Pediatr. 5:579, 1966. Erlanger, J.: A new instrument for determining the minimum and maximum blood pressure in man, Johns Hopkins Hosp. Rep. 12:53, 1904. Ragan, C., and Bordley, J. The accuracy of clinical measurements of arterial blood pressure, Bull. Johns Hopkins Hosp. 69:504, 1941. Pickering, G. W., Roberts, J. A., and Sowry, G. S. C.: The aetiology of essential hypertension. The effect of correcting for arm circumference on the growth rate of arterial pressure with age, Clin. Sci. 13:267, 1954. Trout, K. W., Bertrand, C. A., and Williams, M. II.: Measurement of blood pressure in obese persons, J.A.M.A. 162:970, 1956. Orma, E., Karvonen, M. H., and Keys, A.: Cuff hypertension, Lancet 2:51, 1960. Berliner. K. et al.: Blood pressure measurements in obese persons,‘Am. J. Cardiol. s:lO, 1901. King, G. E.: Errors in clinical measurement of blood pressure in obesity, Clin. Sci. 32:223, 1967. Kvols, L. K., Rohlfing, B. M., and Alexander, J. K.: A comparison of intra-arterial and cuff blood pressure measurements in very obese subjects, Cardiovasc. Res. Cent. Bull. 7:118, 1969, and Personal communication, 1975. Nuessel, W. F.: The importance of a tight blood pressure cuff, AM. HEARTJ. 61:905, 1956. Karvonen, M. H.: Effect of sphygmomanometer cuff size on blood pressure measurement, Bull WHO 27:805, 1962. Simpson, J. A., Jamieson, G., Dickhaus, D. W., and Grover, R. F.: Effect of cuff bladder on accuracy of measurement of indirect blood pressure, AM. HEARTJ. 70:208, 1965. Steinfeld, L., Alexander, H., and Cohen, M. L.: Updating sphygmomanometry, Am. J. Cardiol. 33:107, 1974. Geddes, L. A. and Tivey, R.: The importance of cuff width in the measurement of blood pressure indirectly, Cardiovasc. Res. Cent. Bull. 14:69, 1976. Burch, G. E., and Shewey, L.: Sphygmomanometric cuff size and blood pressure recordings, J.A.M.A. 225:1215, 1973.
July,
1978,
Vol.
96, No.
1
communications
The error in indirect blood pressure measurement with the incorrect size of cuff
L. A. Geddes, M.E., S. J. Whistler, B.S. West Lafayette,
Ph.D.
Ind.
When the auscultatory (Korotkoff) method is used to measure blood pressure indirectly, the accuracy is dependent on many factors, the most important of which is the relationship of the width of the bladder in the cuff to the size of the member to which it is applied. Cuff width is that dimension measured along the member; Fig. 1 illustrates the terminology applied to blood pressure cuffs and presents a listing of the sizes presently available. The aspect ratio (length-towidth) of most of these cuffs is about two-to-one. The cuff width for human application has been specified by several cardiology groups.1-‘3 The most recent of these reports specified the correct cuff width as “20 per cent wider than the diameter of the arm.” Because arm diameter is difficult to measure accurately, this recommendation can be restated in terms of the arm circumference as follows: cuff width should be 1.2/a = 0.382, or about 40 per cent of the arm circumference. This means that for a typical adult subject with a 30 cm. arm, the cuff width should be 12 cm. In the most recent3 recommendations for cuff width it is stated that a cuff of 12 to 14 cm. is adequate for the 30 cm. adult arm. The length of the bladder is such that it should half encircle the arm. It is well known by pediatricians that the measurement of blood pressure in children”-” requires that special attention be given to use of From the Lafayette, Supported Institute,
Biomedical Ind. by grant Bethesda,
Engineering HL-18947-01, Md.
Center,
Purdue
National
Heart,
Received
for publication
Apr.
26, 1977.
Accepted
for publication
Dec.
19, 1977.
Reprint requests: L. A. Geddes, ing Center, Purdue University, neering Studies, West Lafayette,
4
July,
2978,
Vol.
Ph.D., Director, Institute for Ind. 47907.
96, No.
1
University, Lung
Biomedical Interdisciplinary
West
and
Blood
EngineerEngi-
the correct cuff width in relation to the size of the member to which it is applied. The use of a cuff that is too narrow provides falsely high, and the use of a cuff that is too wide provides falsely low values for indirect blood pressure. Similarly in adult subjects, it has been foundg-16 that the standard 12 cm. wide cuff gives falsely high values for pressure when applied to large arms. In fact, Orma and associates13 described the situation as It has been shown by Trout “cuff hypertension.” and colleagues12 and by King and co-workersi that by increasing the arm circumference by wrapping with cotton or sponge rubber, falsely high values for indirect pressure are obtained. Moreover, Neussel and co11aborators’7 have shown that the loose application of a standard cuff to the adult arm provides a falsely high value for indirect blood pressure. To reduce the error encountered when a standard cuff is applied to a large arm, several investigationsl3, 15,18-20have advocated the use of a longer, rather than a wider bladder in the cuff. They reasoned that a long bladder would allow better transmission of the pressure in the bladder to the underlying artery. However, widespread support for this suggestion has not been forthcoming. At present the length of the bladder is such that it encompasses about one half of the member circumference. From all of these reports, it is clear that the width of the cuff, in relation to the circumference of the member to which it is applied, importantly affects the values obtained for indirect blood pressure. However, there are few reports which specify the magnitude of the error to be expected when the incorrect cuff size is used, either because the correct size is unavailable or because of a lack of knowledge of the correct size. This paper
0002-8703/78/0196-0004$00.50/00
1978
The C.V.Mosby
Co.
resents data which ilk&rates the amount of error to be expected when the cuff width departs from the opeimum which is recommended to be 40 per cent of the circumference of the member to which it is applied. tkods
an
QXit?lS
To illustrate the order of error to be expected with cuffs which are too small and too large, blood pressure was measured indirectly in a group of 52 healthy adult subjects using three standard cuffs (9,12, and 18 cm. wide), applied to the upper arm. The arms ranged from 21.5 to 36 cm. in circumference. Resting blood pressure was measured with each of the three cuffs using the auscultatory method. During deflation of the cuff (at the rate of about 3 mm. Hg per heart beat), the first sound (Phase I) beard with a stethoscope placed at the antecubital fossa indicated systolic pressure. The cessation of sound (Phase V) signaled diastolic pressure. In order to illustrate the effect of cuff width on indirect blood pressure readings, the systolic and diastolic pressures obtained on each subject with the 12 cm. cuff ressures. In almost all were taken as referent casesit was found that width was very nearly 40 per cent of the arm circumference. The systolic and diastolic pressures obtained with the 9 and 18 cm. cuffs were expressed as ratios of the systolic and diastolic reference pressures. These ratios were then plotted versus the ratio of arm circumference to cuff width A linear regression line was determined for the data points for systolic, diastolic and the combined pressures. A previous study”’ showed that there exists a hyperbolic ectly measured prescorrelation betwee th to arm circumfersure and the ratio ence. A consequence of this fact is that there is a linear relationship between indirect pressure and the ratio of arm circumference to cuff width. Rssults Fig. 2 presents the values for the ratio of measured pressure to the reference pressure (12 cm. cuff) versus the ratio of arm circumference to cuff width for systolic and diastolic pressures. Fig. 3 presents the distribution of ratios for arm circumference to cuff width for the three cuff widths applied to the 52 subjects. Note that for both systolic and diastolic pressures the use of eufff t.hat is too narrow (i.e., arm-to-cuff ratio greater than 2.48) resulted in a higher indirect
Mewborn
Inrent
4.5 5.6
il.6
Child
8.3 9.4
35.7 21.3
Adult
!I.9 12.4
La rgs Adu i t Thigh
lie5
2: *g
15.2 15.5
25.9 52.1 31.3
18.0
56.0
18.6
110.2
Fig. 1. The meaning of cuff width and length, acd the cuff sizes presently available.
pressure. Similarly, with a cuff that ws LOOwi ratio less &an 2.48) the (i.e., arm-to-cuff measured pressure was lower. As^;arm -cErcumference-to-c~~~-~id~~ ratio of 2.48 is the same as a cuff width to arm circumference ratio of 0.483,
considerable importance ID interpretirg the is Fig. 3, which shows the histograms for the ratio of arm circumference to euB width among the 52 subjects. the 12 cm. cuff, the mean rence to cuff width was 2.3Ca. ratio of arm circ The reciprocal of this value is 0.435, which is very close to the 0.4 value recommended as optimum blood pressure for obtaining accurate indire at this group of values. It is not coincidental rovided this subjects possessed arms whiek value. For the 9 cm. cuff, the ‘mean va!ue for the ratio of arm circumference to cuff width was 3.02, which corresponds to a cuff width to arm circumference ratio of 0.33, This CUR is th.erefore too narrow for these subjects and provided a combined indirect pressure reading of k7 per cent above the reference value obtained iyith the 12
Geddes and Whistler
o-SYSTOLIC x-DIASTOLIC
.
l 3.5 4.0 x ARM CIRCUMFERENCE
CUFF WIDTH
D - DIASTOLIC S - SYSTOLIC C - COMBINED
Fig. 2. The circumference
ratio of measured indirect pressure to cuff width for the 52 subjects.
to reference
(12 cm.
cuff)
pressure
versus
the
ratio
of arm
/::or1yI;GTFFT; 4;4; L/O, ~jp$i~, 3;3;4’4; 0
0,s
1.0
la5
2,o
2.5
W&
3.5
4.0
4#5
ARM CIRCUMFERENCE DIVIDED BY CUFF Fig.
3. Distribution
of the ratio
of arm
cm. cuff. Likewise, the mean ratio of arm circumference to cuff width for the 18 cm. cuff applied to the subject was 1.54. The reciprocal of this figure is 0.67, i.e., the cuff width was 67 per cent of the arm circumference. This cuff was therefore too wide and provided combined indirect pressure readings which were 10 per cent below the reference values obtained with the 12 cm. cuff. The American Heart Association recommends that the cuff width should be 1.2 times the arm
6
circumference
to cuff width
for the 52 subjects.
diameter, i.e., 40 per cent of the arm circumference. However, it is not always possible to select a cuff width which is exactly 40 per cent of the arm circumference. In practice, the cuff is usually narrower or wider than this optimum value. The magnitude of error to be expected with a cuff width that is not optimal can be estimated from the type of relationship presented in Fig. 2. In addition, in the published literature there are several reports in which a range of cuff widths
July, 1978, Vol. 96, No. I
2.5
4*5c CUFF UIDTI(S KM)
685 1 9.0 12.0'1 15.0 1-1 18.Oc.
r 0
I 5
I 10
8 15
Fig. %. This illustration shows the error value which is 40 per cent of the member -5 per cent (left) error in indirect blood
I
I
-52 L
I
20 25 30 MENDER CIRCUMFERENCEKM:5
1 40
+5x 1
i li5
;Ll
55
expected for indirect blood pressure when the CUE width d&a-x3 40n~ a circumference. The ends of each bar represent a + 5 per cent (r@&) and a pressure measurement.
was applied to the arms of human subjects and the readings obtained were compared either with direct arterial pressure, or with the values obtained relative to one size of cuff. Accordingly the data presented in the papers by Erlanger,$ Robinow and colleagues,j DayP6 Ragan and Bordlt?y, I0 Trout and associates,12 Simpson and coworkers,19 Ming,‘” Kvols and collaborators,16 and Burch and Shewey”” were plotted in the manner shown in Fig. 2, to represent the ratio of indirect to direct (or reference 12 cm. cuff) pressure versus the ratio of arm circumference to cuff width. Linear, least-squares lines were obtained for each set of data. From the slope of this relationship is revealed the percentage error expected when the cuff width deviates from 48 per cent of the arm circumference. In those papers where the leastsquares line did not pass through the ratio of cuff width to arm circumference equal to 0.4, a proportional adjustment was made without altering the slope of the regression line. Thus the data from all of these reports were represented by straight lines passing through the 0.4 point on the axis representing arm circumference to cuff width ratio. Then the values for the ratio of cuff width to arm circumference corresponding to a plus five and minus five per cent error were identified for each subject. Using these minimum and maximum cuff-to-arm ratios, the ranges of member circumference for a t5 per cent error in indirect blood pressure measurement (with respect to the AHA recommended cuff size) were calculated for the .5, 6.5, 9, 12, 15, and 18 em. cuffs. Fig. 4 presents the result of this analysis and shows the cuff widths that are appropriate for members ranging from 5 to 55 cm. The cuff widths chosen
represent those that ave been describad in she literature or sizes that are presently available, The illustration points out that use of a cuff that is narrower than the recommended width results in an overestimation of pressure and the use of a cuff that is wider than that rec~rn~~e~d~d results in an underestimation of pressure. Cuff widths corresponding to the centers of the black bars in Fig. 4 represent a cuff width-to-arm of the circumference ratio of 0.4. T e extremities bars represent the extreme value of member circumference which will pro uce a 25 per cent error in measured pressure for a given cu In order to relate the information obtained in this study to present practice, we calculated the range of arm circumference for each of &be cu.&3 by the two largest rn~~~~fa,~~u~~rs of anometers. The limits of arm cireumference were based on obtaining a k 5 per cent error in blood pressure measurement. It was found that one manufacturer provides cuffs that are based on the American Heart Association criterion, i.e., optimum cuff width equals 40 per cent of the member circumference. The limit marks on the CUE provided by this manufacturer are in good agreement with the +5 per cent error in blood pressure found in this study, with the exception of the tlrtigh cuff which indicates that it is applicable to larger noembers than we would recommend. It was found that the other manufacturer provided cuffs which were centered about a rati3 for cuff width-to-member circumference eqt;al to 0.345, i.e., slightly less than that recommended by the AHA. However, hr all cuffs, the range of ar-m the circumference limits coincide very we%i%iikh +5 per cent criterion presented in. this paper.
Geddes
and
Whistler
Conclusion
The data in this report, and those presented in the published literature, show that the use of a cuff that is too narrow overestimates and one that is too wide underestimates indirect blood pressure. A cuff width-to-arm circumference ratio of 0.34 overestimates blood pressure by about 5 per cent; a cuff width-to-arm circumference ratio of 0.50 underestimates blood pressure by 5 per cent. For the same degree of mismatch, the error is greater when the cuff width is narrower rather than larger.
6. 7.
8.
9.
10.
11.
Summary
This paper shows the error to be expected when blood pressure is measured indirectly with a cuff that is too wide or too narrow for the member to which it is applied. A cuff that is too narrow overestimates and a cuff that is too wide underestimates blood pressure.
12.
13. 14. 15. 16.
REFERENCES 1.
2.
3.
4.
5.
Barker, M. H. (and committee): Standardization of blood pressure readings. Joint recommendations of the American Heart Association and the Cardiac Society of Great Britian and Ireland, AM. HEARTJ. 18:95,1939. Bordley J., Connor, C. A. R., Hamilton, W. F., Kerr, W. J., and Wiggers, C. J.: Recommendations for human blood pressure determination by sphygmomanmeters, Circulation 4:503, 1951. Kirkendall, W. M., Burton, A. C., Epstein, F. H., and Freis, E. D.: Recommendations for human blood pressure determinations by sphygmomanometer, Circulation 36:980, 1967. Woodbury, R. A., Robinow M., and Hamilton, W. F.: Blood pressure studies on infants, Am. J. Physiol. 122:472, 1938. Robinow, M., Hamilton, W. F., Woodbury, R. A., and Volpitto, P. P.: Accuracy of clinical determinations of blood pressure in children, Am. J. Dis. Child. 58:102, 1939.
17. 18.
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1978,
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96, No.
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