- Email: [email protected]
What is the accuracy of clinic blood pressure measurement?
AJH
2005; 18:244 –248
What Is the Accuracy of Clinic Blood Pressure Measurement? Carla Sala, Erika Santin, Marta Rescaldani, Cesare Cuspidi, and Fabio Magrini Background: In clinical practice, blood pressure (BP) is frequently measured at the end of the visit in patients sitting on one side of the bed and not on a chair according to guidelines. Methods: In 540 consecutive subjects with essential hypertension (EH) attending a hospital outpatient clinic, BP was measured in the following sequence: 1) patient seated on chair for at least 5 min, 2) patient supine, 3) patient seated on bed, and 4) patient standing for a few minutes.
chair-seated position) in only 6% and 2% of patients, respectively. Overall, SBP and DBP increments from the chair- to the bed-seated position were inversely related to the baseline chair-seated values; systolic increments were directly related to age, in particular in the subgroup of untreated EH (n ⫽ 70), and to body mass index. A genderrelated difference was apparent, as female subjects had more pronounced increments in SBP (⫹7.4 ⫾ 0.8 v ⫹3.5 ⫾ 0.7 mm Hg) and DBP (⫹4.4 ⫾ 0.5 v 2.9 ⫾ 0.4 mm Hg) than did male subjects (P ⬍ .05 for both).
Results: We found that mean (⫾SEM) BP was 143.5/ 87.2 ⫾ 0.9/0.5, 153.4/89.7 ⫾ 1.0/0.5, 148.9/90.9 ⫾ 1.0/ 0.5, and 144.8/91.7 ⫾ 1.0/0.6 mm Hg, respectively (P ⬍ .05 v position 1 for all). In 14% of patients, either systolic BP (SBP) or diastolic BP (DBP) was above the conventional upper limits of normality in the seated-on-bed but not in the recommended seated-on-chair position (“false” high clinic BP), whereas SBP and DBP were “false” normal (below limit for bed-seated and above limit for
Conclusions: Clinic SBP and DBP are overestimated in the bed-seated position at the end of the visit compared with the recommended chair-seated position in treated and untreated patients with EH, in particular in elderly obese women with mild hypertension. Am J Hypertens 2005;18: 244 –248 © 2005 American Journal of Hypertension, Ltd.
iagnostic and therapeutic decisions in hypertensive patients are largely based on blood pressure (BP) measurements made by a sphygmomanometer device in the clinic or doctor’s office.1 The accuracy of this method is affected by multiple factors related to instrumentation, observer, and patient.2 A common source of patient-related error is body posture and the length of time at rest before BP measurement.3 The sitting body position, with the subject comfortably seated on a chair for at least 5 min, the back supported, the arm passively supported at the mid-sternum level, and the feet on the floor is recommended as a standard for routine indirect BP measurement.4,5 A survey of leading medical journals shows that details of BP measuring methodology are omitted in a substantial number of papers6,7 and that the results of some epidemiologic studies and intervention trials in hypertension are based on BP measurements either in the supine or standing position.8,9
D
In clinical practice, guidelines indications for BP measurement are frequently disregarded because of either time restraint10 or unproven assumptions. In particular, because the defensive reaction causing an increase in BP tends to subside once the patient is accustomed to the observer,11 BP is frequently measured at the end of physical examination with the patient sitting on the visiting bed site. To evaluate the influence of body posture and time of the visit on BP values, during a routine visit BP was sequentially measured in subjects with essential hypertension (EH) in the following four ways: after sitting on a chair for at least 5 min, supine, sitting on a bed, and after standing up for a few minutes.
Received July 8, 2004. First decision September 8, 2004. Accepted September 8, 2004. From the Istituto Medicina Cardiovascolare and Centro Fisiologia Clinica e Ipertensione, Università di Milano and Ospedale Maggiore
IRCCS, Milano, Italy. Address correspondence and reprint requests to Dr. Carla Sala, Centro Fisiologia Clinica e Ipertensione, Policlinico–Via F. Sforza 35, 20122 Milano, Italy; e-mail: [email protected]
0895-7061/05/$30.00 doi:10.1016/j.amjhyper.2004.09.006
Key Words: Clinic blood pressure, body posture, blood pressure measurement, essential hypertension.
Methods Patients and Protocol In 540 consecutive patients with EH (266 male and 274 female, age 59.4 ⫾ 0.6 years, range 19 to 90 years, 470
© 2005 by the American Journal of Hypertension, Ltd. Published by Elsevier Inc.
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Table 1. Antihypertensive treatment in patients with essential hypertension (n ⫽ 470) Type of drug
Patients (%)
No. of drugs
Patients (%)
Diuretic Angiotensin converting enzyme inhibitor Angiotensin II receptor antagonist Calcium channel blocker -Blocker ␣-Blocker
55 43 19 30 34 19
1 2 3 ⬎3
32 32 24 12
treated patients) attending our hospital clinic on a weekday from 8 AM to 1 PM for a routine visit, BP and pulse rate were sequentially measured in the following positions: 1) patient seated on a chair for 5 to 10 min during the history taking, with the back comfortably supported, the arm supported on the desk at the mid-sternum level, and the feet placed on the floor; 2) patient supine for 5 min, at the end of physical examination; 3) patient seated on the side of the bed for 3 to 5 min with the back unsupported, the arm supported by the operator at the mid-sternum level and the feet placed on a foot stool; and 4) after patient had been standing for 3 to 5 min. The BP was measured in duplicate on the same arm with a mercury sphygmomanometer, taking the first Korotkoff sound as systolic and the fifth phase as diastolic pressure, and with an adequate cuff size used according to arm size. To minimize observer bias, BP in positions 1 and 2, 3, and 4 were alternatively measured by two trained physicians blinded to each other’s measurements. Antihypertensive regimens used in treated EH subjects are listed in Table 1. Statistical Analysis Results are reported as mean ⫾ SEM. The Student paired t test was used for comparisons. The correlation coefficient was calculated by the Pearson test, and frequency distribution was tested by contingency tables. A P value of ⬍ .05 was set for statistical significance.
Results In subjects with EH, SBP and DBP were lower at the first measurement in the chair-seated position compared with
subsequent measurements in the supine, bed-seated, and standing positions (Table 2). This was also the case in the smaller group of untreated EH subjects (n ⫽ 70), in whom BP was 144.6/93.0 ⫾ 3.1/1.5 mm Hg, 150.6/93.1 ⫾ 3.3/ 1.4, 148.8/97.3 ⫾ 3.3/1.4, 145.2/99.1 ⫾ 3.2/1.5, respectively. In particular, SBP and DBP was higher in the bed-seated compared with the chair-seated position. Heart rates were similar in the two seated positions. Figure 1 shows BP values measured in the chair-seated (x axis) and those in the bed-seated position (y axis) in the whole group: it is apparent that in 14% of patients, SBP or DBP values were above the normal upper cut-off line for hypertension or for goal BP (⬍140 or ⬍90 mm Hg) in the bed-seated position but not in the recommended chairseated position (false-high clinic BP). In contrast, SBP and DBP were below the cut-off in the bed-seated and above the cut-off in the chair-seated position in 6% and 2% of patients, respectively (false-normal clinic BP). The increments of BP from the chair- to the bed-seated position were more pronounced in female subjects than in male, in particular SBP increments in treated hypertensive subjects and DBP increments in the untreated subjects (Table 3). Overall, systolic increments from the chair- to the bedseated position were directly related to age (r ⫽ 0.11, P ⬍ .05), particularly in the subgroup of untreated patients (r ⫽ 0.35, P ⬍ .01), and to body mass index (r ⫽ 0.14, P ⬍ .01); moreover, an inverse relationship between SBP and DBP increments and the corresponding chair-seated values was present (r ⫽ ⫺0.12 and ⫺0.32, respectively, P ⬍ .01 for both) (Fig. 2).
Table 2. Clinic blood pressure (BP) and heart rate in patients with essential hypertension (n ⫽ 540) at subsequent measurements in different postures during a routine visit Position Sitting on chair Supine Sitting on bed Standing
SBP (mm Hg) 143.5 153.4 148.9 144.8
⫾ ⫾ ⫾ ⫾
0.9 1.0* 1.0* 1.0†
DBP ⫽ diastolic blood pressure; SBP ⫽ systolic blood pressure. Data are means ⫾ SEM. * P ⬍ .01, † P ⬍ .05, vs position 1 (sitting on chair).
DBP (mm Hg) 87.2 89.7 90.9 91.7
⫾ ⫾ ⫾ ⫾
0.5 0.5* 0.5* 0.6*
Heart rate (beats/min) 72.9 70.5 73.1 76.8
⫾ ⫾ ⫾ ⫾
0.5 0.5* 0.5 0.5*
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FIG. 1 Systolic blood pressure (SBP) (upper panel) and diastolic blood pressure (DBP) (lower panel) measured in the chair-seated (x axis) and subsequently in the bed-seated (y axis) position in patients with essential hypertension (EH) (n ⫽ 540). The identity line for the two measurements (dotted line) and the percentage of “false” and “true” high (H) and normal (N) clinic blood pressure, according to conventional limits of 140 mm Hg for SBP and 90 mm Hg for DBP, are shown.
Discussion In this study, during a routine clinic visit, arterial pressure was lower at the first measurement in subjects with EH comfortably seated on a chair for at least 5 min than at subsequent readings with the patient supine, seated on the bed, and standing. In particular, SBP and DBP were higher when the patient was sitting on the side of the bed at the end of the visit compared with the previous position seated on a chair (Table 2); this was the case both in the larger group of treated patients and in the subgroup of untreated subjects. Differences in classes of antihypertensive drugs used do not seem to affect our results, at least in the subgroup of patients on monotherapy (n ⫽ 151).
AJH–February 2005–VOL. 18, NO. 2, Part 1
Differences in BP between the two seated positions was not related to a hydrostatic effect, as the arm was passively supported at the heart level in both positions.12 Although hemodynamic data are not available in the present study, the increase in SBP in the bed-seated position may be related to an increased stroke volume carried over from the previous supine position, whereas this phenomenon does not occur when the behavioral sequence is from standing to sitting on a chair.3 On the other hand, the increase in DBP from the chair-seated to the bed-seated position may result from the isometric stress performed by the patient to maintain body posture, in particular, to support the back: indeed, the isometric stress of squeezing a tennis ball has been shown to increase DBP by 7 mm Hg in normotensive subjects.13 Individual differences in the hemodynamic adjustments to the bed-seated position may cause significant errors in clinic BP determination; some categories of patients are more prone to this error. First, elderly subjects with hypertension had their arterial pressure overestimated to a greater extent than the younger ones, as SBP increments from the chair- to the bed-seated position were directly related to age, particularly in untreated patients. Stiffening of the large arteries may contribute to the exaggerated systolic response in elderly individuals.14 Second, obese hypertensive subjects had more pronounced SBP increments from the chair- to the bed-seated position compared with lean hypertensive subjects, probably as a consequence of a larger increase in stroke volume in obese subjects characterized by an expanded intravascular volume.15 Third, a gender-related difference was apparent, as SBP increments from the chair- to the bed-seated position were almost double in women than in men, in particular in the older group of treated patients (Table 3). A genderdependent interaction between patient and observer can be excluded, as only female physicians were participating in the study.16 It is also unlikely that the higher systolic values in women in the chair-seated position were responsible for the larger increments, inasmuch as in both sexes the two parameters were inversely related. Moreover, in treated hypertensive subjects, who represented the majority of our patients, sexes were matched for body mass index and for number and class of antihypertensive agents used, with the sole exception of ␣-blockers in a small group of patients (n ⫽ 52 male versus 36 female patients, P ⬍.05). The shorter stature of women, and therefore an increased contribution of wave reflection, may possibly explain the enhanced SBP increments in hypertensive women.17,18 The larger DBP increments, on the other hand, may indicate that women exert greater isometric stress to maintain body posture in the bed-seated position. Finally, subjects with mild hypertension had their BP more easily overestimated when sitting on the bed, as systolic and diastolic increments from the chair- to the bed-seated position were inversely related to the baseline chair-seated values (Fig. 2). When BP measurement was not standardized to the guidelines recommendations in the
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Table 3. Clinical data, systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) in the seated-on-chair position and their changes in the subsequent seated-on-bed position in patients with essential hypertension (EH) according to treatment and gender Treated EH Patients Men (230) Sex (n) Age (yr) Height (cm) Weight (kg) BMI (kg/m2) SBP (mm Hg) DBP (mm Hg) HR (beats/min) ⌬ SBP (mm Hg) ⌬ DBP (mm Hg) ⌬ HR (beats/min)
60.4 171 81.6 27.9 140.3 86.8 70.6 ⫹3.5 ⫹3.1 ⫹0.7
⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾
0.8 0.5* 0.8* 0.2 1.3* 0.8 0.7† 0.8* 0.5 0.4
Untreated EH Patients
Women (240) 61.9 157 68.3 27.7 146.1 86.0 73.1 ⫹7.7 ⫹3.9 ⫹0.5
⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾
0.8 0.4 0.8 0.3 1.4 0.7 0.8 0.8 0.5 0.4
Men (36) 45.4 174 86.6 28.7 141.0 94.0 80.7 ⫹3.4 ⫹1.9 ⫺1.7
⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾
2.1 1.2* 2.8* 0.9* 2.4 1.6 2.3 1.9 1.2* 0.9
Women (34) 49.3 159 63.9 25.0 148.3 92.0 79.4 ⫹5.1 ⫹6.9 ⫹0.1
⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾
2.4 1.2 2.5 0.9 5.8 2.6 2.1 1.7 1.2 1.0
BMI ⫽ body mass index. Data are means ⫾ SEM. * P ⬍ .01, † P ⬍ .05, men v women.
chair-seated position but was performed in subjects seated on the bed, up to 20% SBP and approximately 16% DBP values were incorrectly classified (Fig. 1): the amount of false high clinic BP, 14% for SBP and DBP, far exceeded that of false-normal clinic BP, as both pressures were overestimated in the bed-seated compared with the standard chair-seated position. A limitation of the study is that BP measurements were not randomized; in particular, we did not test whether clinic BP in the chair-seated position could have been even lower if measured at the end of the visit, when the increase of BP due to the alarm reaction tends to subside,11 because the inverse sequence of measurements in the seated position, first on the bed and then on the chair, would be impractical and time consuming in a routine clinical setting. In the evaluation of the postural effects of drugs, it should be noted that both SBP and DBP values in patients treated for EH who were seated on a chair were lower than in any other position tested in this fixed sequence of measurements: in particular, SBP was even lower than on standing, and DBP was lower than in the supine position, in accordance with observations in normotensive subjects.19 Our results also confirm that SBP is lower in the chair-seated than in the supine position, provided that the hydrostatic effect is abolished by having the arm supported on the desk at the mid-sternum level.19,20 In conclusion, clinic SBP and DBP pressure tended to be overestimated in subjects with EH when measured with the subject seated on a bed at the end of the visit, compared with previous measurements with the subject seated on a chair, as recommended by the guidelines.4,5 In the whole group of treated and untreated patients, the error was more pronounced in older subjects than in younger ones, in obese subjects than in leaner ones, in female subjects than in male subjects, and in mildly hypertensive
FIG. 2 Relationship between SBP (upper panel) and DBP values (lower panel) in the chair-seated position (x axis) and their changes in the subsequent bed-seated position (y axis) in treated and untreated patients with essential hypertension. Abbreviations as in Fig. 1.
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subjects than in those with severe hypertension. This methodologic error in clinic BP measurement may lead to inappropriate diagnosis and over-treatment of hypertension in a significant numer of patients.
AJH–February 2005–VOL. 18, NO. 2, Part 1
9.
10.
References 1. 2.
3.
4.
5.
6.
7.
8.
Petrie JC, O’Brien ET, Littler WA, De Swiet M: Recommendations on blood pressure measurement. Br Med J 1986;293:611– 613. Bailey RH, Bauer JH: A review of common errors in the indirect measurement of blood pressure. Arch Intern Med 1993;153:2741– 2748. Netea RT, Lenders JWM, Smits P, Thien T: Influence of body and arm position on blood pressure readings: an overview. J Hypertens 2003;21:237–241. Chobanian AV, Bakris GL, Black HR, Cushman WC, Green LA, Izzo JL Jr, Jones DW, Materson BJ, Oparil S, Wright JT Jr, Roccella EJ: The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. J Am Med Assoc 2003;289:2560 –2572. Guidelines Committee: 2003 European Society of Hypertension– European Society of Cardiology guidelines for the management of arterial hypertension. J Hypertens 2003;21:1011–1053. Roche V, O’Malley K, O’Brien E: How scientific is blood pressure measurement in leading medical journals? J Hypertens 1990;8: 1167–1168. Brown MJ, Palmer CR, Castaigne A, De Leeuw PW, Mancia G, Rosenthal T, Ruilope LM: Morbidity and mortality in patients randomised to double-blind treatment with a long-acting calcium channel blocker or diuretic in the international Nifedipine GITS study: Intervention as a Goal in Hypertension Treatment (INSIGHT). Lancet 2000;356:366 –372. Benetos A, Thomas F, Bean K, Gautier S, Smulyan H, Guize L:
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Prognostic value of systolic and diastolic blood pressure in treated hypertensive men. Arch Intern Med 2002;162:577–581. Dahlöf B, Lindholm LH, Hansson L, Schertsen B, Ekbom T, Wester PO: Morbidity and mortality in the Swedish Trial in Old Patients with Hypertension (STOP-Hypertension). Lancet 1991;338:1281– 1285. Ambrosioni E, Leonetti G, Pessina AC, Rappelli A, Trimarco B, Zanchetti A: Patterns of hypertension management in Italy: results of a pharmacoepidemiological survey on antihypertensive therapy. J Hypertens 2000;18:1691–1699. Mancia G, Parati G, Pomidossi G, Grassi G, Casadei R, Zanchetti A: Alerting reaction and rise in blood pressure during measurement by physician and nurse. Hypertension 1987;9:209 –215. Webster J, Newnhan D, Petrie JC, Lovell HG: Influence of arm position on blood pressure. Br Med J 1984;288:1574 –1575. Webb G: Pitfalls in the measurement of blood pressure. Am J Hypertens 1992;5:859. O’Rourke MF: Arterial stiffness, systolic blood pressure and logical treatment of arterial hypertension. Hypertension 1990;15:339 –347. Redon J: Hypertension in obesity. Nutr Metab Cardiovasc Dis 2001;11:344 –353. Millar JA, Accioly JM: Measurement of blood pressure may be affected by an interaction between subject and observer based on gender. J Hum Hypertens 1996;10:449 – 453. Heyward CS, Kelly RP: Gender-related differences in the central pressure waveform. J Am Coll Cardiol 1997;30:1863–1871. Mitchell GF, Lacourcière Y, Ouellet JP, Izzo JL, Neutel J, Kerwin LJ, Block AJ, Pfeffer MA: Determinants of elevated pulse pressure in middle-aged and older subjects with uncomplicated systolic hypertension. Circulation 2003;108:1592–1598. Terent A, Breig-Asberg E: Epidemiological perspective of body position and arm level in blood pressure measurement. Blood Press 1994;3:156 –163. Jamieson JM, Webster J, Philips S, Jeffers AT, Scott AK, Robb OJ, Lovell HG, Petrie JC: The measurement of blood pressure sitting or supine, once or twice? J Hypertens 1990;8:653-640.
2005; 18:244 –248
What Is the Accuracy of Clinic Blood Pressure Measurement? Carla Sala, Erika Santin, Marta Rescaldani, Cesare Cuspidi, and Fabio Magrini Background: In clinical practice, blood pressure (BP) is frequently measured at the end of the visit in patients sitting on one side of the bed and not on a chair according to guidelines. Methods: In 540 consecutive subjects with essential hypertension (EH) attending a hospital outpatient clinic, BP was measured in the following sequence: 1) patient seated on chair for at least 5 min, 2) patient supine, 3) patient seated on bed, and 4) patient standing for a few minutes.
chair-seated position) in only 6% and 2% of patients, respectively. Overall, SBP and DBP increments from the chair- to the bed-seated position were inversely related to the baseline chair-seated values; systolic increments were directly related to age, in particular in the subgroup of untreated EH (n ⫽ 70), and to body mass index. A genderrelated difference was apparent, as female subjects had more pronounced increments in SBP (⫹7.4 ⫾ 0.8 v ⫹3.5 ⫾ 0.7 mm Hg) and DBP (⫹4.4 ⫾ 0.5 v 2.9 ⫾ 0.4 mm Hg) than did male subjects (P ⬍ .05 for both).
Results: We found that mean (⫾SEM) BP was 143.5/ 87.2 ⫾ 0.9/0.5, 153.4/89.7 ⫾ 1.0/0.5, 148.9/90.9 ⫾ 1.0/ 0.5, and 144.8/91.7 ⫾ 1.0/0.6 mm Hg, respectively (P ⬍ .05 v position 1 for all). In 14% of patients, either systolic BP (SBP) or diastolic BP (DBP) was above the conventional upper limits of normality in the seated-on-bed but not in the recommended seated-on-chair position (“false” high clinic BP), whereas SBP and DBP were “false” normal (below limit for bed-seated and above limit for
Conclusions: Clinic SBP and DBP are overestimated in the bed-seated position at the end of the visit compared with the recommended chair-seated position in treated and untreated patients with EH, in particular in elderly obese women with mild hypertension. Am J Hypertens 2005;18: 244 –248 © 2005 American Journal of Hypertension, Ltd.
iagnostic and therapeutic decisions in hypertensive patients are largely based on blood pressure (BP) measurements made by a sphygmomanometer device in the clinic or doctor’s office.1 The accuracy of this method is affected by multiple factors related to instrumentation, observer, and patient.2 A common source of patient-related error is body posture and the length of time at rest before BP measurement.3 The sitting body position, with the subject comfortably seated on a chair for at least 5 min, the back supported, the arm passively supported at the mid-sternum level, and the feet on the floor is recommended as a standard for routine indirect BP measurement.4,5 A survey of leading medical journals shows that details of BP measuring methodology are omitted in a substantial number of papers6,7 and that the results of some epidemiologic studies and intervention trials in hypertension are based on BP measurements either in the supine or standing position.8,9
D
In clinical practice, guidelines indications for BP measurement are frequently disregarded because of either time restraint10 or unproven assumptions. In particular, because the defensive reaction causing an increase in BP tends to subside once the patient is accustomed to the observer,11 BP is frequently measured at the end of physical examination with the patient sitting on the visiting bed site. To evaluate the influence of body posture and time of the visit on BP values, during a routine visit BP was sequentially measured in subjects with essential hypertension (EH) in the following four ways: after sitting on a chair for at least 5 min, supine, sitting on a bed, and after standing up for a few minutes.
Received July 8, 2004. First decision September 8, 2004. Accepted September 8, 2004. From the Istituto Medicina Cardiovascolare and Centro Fisiologia Clinica e Ipertensione, Università di Milano and Ospedale Maggiore
IRCCS, Milano, Italy. Address correspondence and reprint requests to Dr. Carla Sala, Centro Fisiologia Clinica e Ipertensione, Policlinico–Via F. Sforza 35, 20122 Milano, Italy; e-mail: [email protected]
0895-7061/05/$30.00 doi:10.1016/j.amjhyper.2004.09.006
Key Words: Clinic blood pressure, body posture, blood pressure measurement, essential hypertension.
Methods Patients and Protocol In 540 consecutive patients with EH (266 male and 274 female, age 59.4 ⫾ 0.6 years, range 19 to 90 years, 470
© 2005 by the American Journal of Hypertension, Ltd. Published by Elsevier Inc.
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Table 1. Antihypertensive treatment in patients with essential hypertension (n ⫽ 470) Type of drug
Patients (%)
No. of drugs
Patients (%)
Diuretic Angiotensin converting enzyme inhibitor Angiotensin II receptor antagonist Calcium channel blocker -Blocker ␣-Blocker
55 43 19 30 34 19
1 2 3 ⬎3
32 32 24 12
treated patients) attending our hospital clinic on a weekday from 8 AM to 1 PM for a routine visit, BP and pulse rate were sequentially measured in the following positions: 1) patient seated on a chair for 5 to 10 min during the history taking, with the back comfortably supported, the arm supported on the desk at the mid-sternum level, and the feet placed on the floor; 2) patient supine for 5 min, at the end of physical examination; 3) patient seated on the side of the bed for 3 to 5 min with the back unsupported, the arm supported by the operator at the mid-sternum level and the feet placed on a foot stool; and 4) after patient had been standing for 3 to 5 min. The BP was measured in duplicate on the same arm with a mercury sphygmomanometer, taking the first Korotkoff sound as systolic and the fifth phase as diastolic pressure, and with an adequate cuff size used according to arm size. To minimize observer bias, BP in positions 1 and 2, 3, and 4 were alternatively measured by two trained physicians blinded to each other’s measurements. Antihypertensive regimens used in treated EH subjects are listed in Table 1. Statistical Analysis Results are reported as mean ⫾ SEM. The Student paired t test was used for comparisons. The correlation coefficient was calculated by the Pearson test, and frequency distribution was tested by contingency tables. A P value of ⬍ .05 was set for statistical significance.
Results In subjects with EH, SBP and DBP were lower at the first measurement in the chair-seated position compared with
subsequent measurements in the supine, bed-seated, and standing positions (Table 2). This was also the case in the smaller group of untreated EH subjects (n ⫽ 70), in whom BP was 144.6/93.0 ⫾ 3.1/1.5 mm Hg, 150.6/93.1 ⫾ 3.3/ 1.4, 148.8/97.3 ⫾ 3.3/1.4, 145.2/99.1 ⫾ 3.2/1.5, respectively. In particular, SBP and DBP was higher in the bed-seated compared with the chair-seated position. Heart rates were similar in the two seated positions. Figure 1 shows BP values measured in the chair-seated (x axis) and those in the bed-seated position (y axis) in the whole group: it is apparent that in 14% of patients, SBP or DBP values were above the normal upper cut-off line for hypertension or for goal BP (⬍140 or ⬍90 mm Hg) in the bed-seated position but not in the recommended chairseated position (false-high clinic BP). In contrast, SBP and DBP were below the cut-off in the bed-seated and above the cut-off in the chair-seated position in 6% and 2% of patients, respectively (false-normal clinic BP). The increments of BP from the chair- to the bed-seated position were more pronounced in female subjects than in male, in particular SBP increments in treated hypertensive subjects and DBP increments in the untreated subjects (Table 3). Overall, systolic increments from the chair- to the bedseated position were directly related to age (r ⫽ 0.11, P ⬍ .05), particularly in the subgroup of untreated patients (r ⫽ 0.35, P ⬍ .01), and to body mass index (r ⫽ 0.14, P ⬍ .01); moreover, an inverse relationship between SBP and DBP increments and the corresponding chair-seated values was present (r ⫽ ⫺0.12 and ⫺0.32, respectively, P ⬍ .01 for both) (Fig. 2).
Table 2. Clinic blood pressure (BP) and heart rate in patients with essential hypertension (n ⫽ 540) at subsequent measurements in different postures during a routine visit Position Sitting on chair Supine Sitting on bed Standing
SBP (mm Hg) 143.5 153.4 148.9 144.8
⫾ ⫾ ⫾ ⫾
0.9 1.0* 1.0* 1.0†
DBP ⫽ diastolic blood pressure; SBP ⫽ systolic blood pressure. Data are means ⫾ SEM. * P ⬍ .01, † P ⬍ .05, vs position 1 (sitting on chair).
DBP (mm Hg) 87.2 89.7 90.9 91.7
⫾ ⫾ ⫾ ⫾
0.5 0.5* 0.5* 0.6*
Heart rate (beats/min) 72.9 70.5 73.1 76.8
⫾ ⫾ ⫾ ⫾
0.5 0.5* 0.5 0.5*
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FIG. 1 Systolic blood pressure (SBP) (upper panel) and diastolic blood pressure (DBP) (lower panel) measured in the chair-seated (x axis) and subsequently in the bed-seated (y axis) position in patients with essential hypertension (EH) (n ⫽ 540). The identity line for the two measurements (dotted line) and the percentage of “false” and “true” high (H) and normal (N) clinic blood pressure, according to conventional limits of 140 mm Hg for SBP and 90 mm Hg for DBP, are shown.
Discussion In this study, during a routine clinic visit, arterial pressure was lower at the first measurement in subjects with EH comfortably seated on a chair for at least 5 min than at subsequent readings with the patient supine, seated on the bed, and standing. In particular, SBP and DBP were higher when the patient was sitting on the side of the bed at the end of the visit compared with the previous position seated on a chair (Table 2); this was the case both in the larger group of treated patients and in the subgroup of untreated subjects. Differences in classes of antihypertensive drugs used do not seem to affect our results, at least in the subgroup of patients on monotherapy (n ⫽ 151).
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Differences in BP between the two seated positions was not related to a hydrostatic effect, as the arm was passively supported at the heart level in both positions.12 Although hemodynamic data are not available in the present study, the increase in SBP in the bed-seated position may be related to an increased stroke volume carried over from the previous supine position, whereas this phenomenon does not occur when the behavioral sequence is from standing to sitting on a chair.3 On the other hand, the increase in DBP from the chair-seated to the bed-seated position may result from the isometric stress performed by the patient to maintain body posture, in particular, to support the back: indeed, the isometric stress of squeezing a tennis ball has been shown to increase DBP by 7 mm Hg in normotensive subjects.13 Individual differences in the hemodynamic adjustments to the bed-seated position may cause significant errors in clinic BP determination; some categories of patients are more prone to this error. First, elderly subjects with hypertension had their arterial pressure overestimated to a greater extent than the younger ones, as SBP increments from the chair- to the bed-seated position were directly related to age, particularly in untreated patients. Stiffening of the large arteries may contribute to the exaggerated systolic response in elderly individuals.14 Second, obese hypertensive subjects had more pronounced SBP increments from the chair- to the bed-seated position compared with lean hypertensive subjects, probably as a consequence of a larger increase in stroke volume in obese subjects characterized by an expanded intravascular volume.15 Third, a gender-related difference was apparent, as SBP increments from the chair- to the bed-seated position were almost double in women than in men, in particular in the older group of treated patients (Table 3). A genderdependent interaction between patient and observer can be excluded, as only female physicians were participating in the study.16 It is also unlikely that the higher systolic values in women in the chair-seated position were responsible for the larger increments, inasmuch as in both sexes the two parameters were inversely related. Moreover, in treated hypertensive subjects, who represented the majority of our patients, sexes were matched for body mass index and for number and class of antihypertensive agents used, with the sole exception of ␣-blockers in a small group of patients (n ⫽ 52 male versus 36 female patients, P ⬍.05). The shorter stature of women, and therefore an increased contribution of wave reflection, may possibly explain the enhanced SBP increments in hypertensive women.17,18 The larger DBP increments, on the other hand, may indicate that women exert greater isometric stress to maintain body posture in the bed-seated position. Finally, subjects with mild hypertension had their BP more easily overestimated when sitting on the bed, as systolic and diastolic increments from the chair- to the bed-seated position were inversely related to the baseline chair-seated values (Fig. 2). When BP measurement was not standardized to the guidelines recommendations in the
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Table 3. Clinical data, systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) in the seated-on-chair position and their changes in the subsequent seated-on-bed position in patients with essential hypertension (EH) according to treatment and gender Treated EH Patients Men (230) Sex (n) Age (yr) Height (cm) Weight (kg) BMI (kg/m2) SBP (mm Hg) DBP (mm Hg) HR (beats/min) ⌬ SBP (mm Hg) ⌬ DBP (mm Hg) ⌬ HR (beats/min)
60.4 171 81.6 27.9 140.3 86.8 70.6 ⫹3.5 ⫹3.1 ⫹0.7
⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾
0.8 0.5* 0.8* 0.2 1.3* 0.8 0.7† 0.8* 0.5 0.4
Untreated EH Patients
Women (240) 61.9 157 68.3 27.7 146.1 86.0 73.1 ⫹7.7 ⫹3.9 ⫹0.5
⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾
0.8 0.4 0.8 0.3 1.4 0.7 0.8 0.8 0.5 0.4
Men (36) 45.4 174 86.6 28.7 141.0 94.0 80.7 ⫹3.4 ⫹1.9 ⫺1.7
⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾
2.1 1.2* 2.8* 0.9* 2.4 1.6 2.3 1.9 1.2* 0.9
Women (34) 49.3 159 63.9 25.0 148.3 92.0 79.4 ⫹5.1 ⫹6.9 ⫹0.1
⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾ ⫾
2.4 1.2 2.5 0.9 5.8 2.6 2.1 1.7 1.2 1.0
BMI ⫽ body mass index. Data are means ⫾ SEM. * P ⬍ .01, † P ⬍ .05, men v women.
chair-seated position but was performed in subjects seated on the bed, up to 20% SBP and approximately 16% DBP values were incorrectly classified (Fig. 1): the amount of false high clinic BP, 14% for SBP and DBP, far exceeded that of false-normal clinic BP, as both pressures were overestimated in the bed-seated compared with the standard chair-seated position. A limitation of the study is that BP measurements were not randomized; in particular, we did not test whether clinic BP in the chair-seated position could have been even lower if measured at the end of the visit, when the increase of BP due to the alarm reaction tends to subside,11 because the inverse sequence of measurements in the seated position, first on the bed and then on the chair, would be impractical and time consuming in a routine clinical setting. In the evaluation of the postural effects of drugs, it should be noted that both SBP and DBP values in patients treated for EH who were seated on a chair were lower than in any other position tested in this fixed sequence of measurements: in particular, SBP was even lower than on standing, and DBP was lower than in the supine position, in accordance with observations in normotensive subjects.19 Our results also confirm that SBP is lower in the chair-seated than in the supine position, provided that the hydrostatic effect is abolished by having the arm supported on the desk at the mid-sternum level.19,20 In conclusion, clinic SBP and DBP pressure tended to be overestimated in subjects with EH when measured with the subject seated on a bed at the end of the visit, compared with previous measurements with the subject seated on a chair, as recommended by the guidelines.4,5 In the whole group of treated and untreated patients, the error was more pronounced in older subjects than in younger ones, in obese subjects than in leaner ones, in female subjects than in male subjects, and in mildly hypertensive
FIG. 2 Relationship between SBP (upper panel) and DBP values (lower panel) in the chair-seated position (x axis) and their changes in the subsequent bed-seated position (y axis) in treated and untreated patients with essential hypertension. Abbreviations as in Fig. 1.
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subjects than in those with severe hypertension. This methodologic error in clinic BP measurement may lead to inappropriate diagnosis and over-treatment of hypertension in a significant numer of patients.
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