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The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7)—as well as earlier reports—states that the proper position for the measurement of blood pressure (BP) is sitting.1 Two questions come to mind regarding this recommendation: Are there significant differences between BPs obtained in the supine and sitting positions? and What is the evidence that BP should be measured in the seated position?

There are conflicting data regarding the relationship between supine and sitting BPs in otherwise healthy (i.e., not hypovolemic) individuals. Although both the International Society of Hypertension of the World Health Organization2 and the Hypertension Task Force of the American Heart Association3 assert that the two approaches to BP measurement are equivalent (assuming all measurements are performed with the arm at the level of the right atrium), numerous prospective studies have challenged this notion. Whereas some authors have demonstrated that systolic BP is lower and diastolic BP higher in the sitting, compared with the supine position,4 others have shown that both the systolic and diastolic BP are lower in the sitting position.5,6 Conversely, another group has demonstrated that mean intra-arterial ambulatory systolic and diastolic BP were higher in the sitting position.7 It is noteworthy that the differences in BPs recorded in these studies were as high as 10 mm Hg. Some of the discrepancies between these studies can be explained by differences in technique (i.e., sphygmomanometric vs. oscillometric vs. intra-arterial) and research subject characteristics (i.e., hypertensive or diabetic status). Nevertheless, it is unclear if there is a consistent relationship between these two methods of BP measurement. Furthermore, it is unclear which method better approximates intra-aortic pressure and would thus be a better predictor of cardiovascular outcomes.

The strongest argument in favor of routinely measuring BP in the sitting position is that the overwhelming majority of data associating hypertension with poor cardiovascular outcomes and the treatment of hypertension with improved outcomes were derived from studies in which the BP was measured, by protocol, in the sitting position. Specifically, the Framingham study measured BPs in the sitting position.8 Furthermore, the large BP treatment trials of the 1960s and 1970s, namely the Veteran's Affairs Cooperative Study Group on Antihypertensive Agents9 and the trial of the Medical Research Council (MRC) Working Party on Mild to Moderate Hypertension10 both measured BPs, by protocol, in the sitting position. In addition, two large trials from the late 1980s and early 1990s, the Multiple Risk Factor Intervention Trial (MRFIT)11 and the Systolic Hypertension in the Elderly (SHEP) trial,12 also measured BP in the sitting position. Finally, the major trials of antihypertensive therapy over the past decade, namely the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT),13 the Second Australian National Blood Pressure Study (ANBP2),14 the Hypertension Optimal Treatment (HOT) trial,15 and the Losartan Intervention for Endpoint (LIFE) Reduction in Hypertension Study,16 all measured BPs in the sitting position only.

In conclusion, it is unclear if there are significant differences between BPs measured in the sitting vs. the supine position or which position best approximates intra-aortic pressure. It certainly is more convenient in most instances to take the BP when someone is sitting—and virtually all of the evidence linking hypertension with poor cardiovascular outcomes, as well as the data that support treating hypertension to improve these outcomes—were derived from studies that measured sitting BPs. The published guidelines recommending specific target BPs in certain populations were all based on measurement of BPs in the sitting position. Therefore, for the routine measurement of BP in the office setting, patients should be seated.

References

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  2. References
  • 1
    The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure: the JNC 7 report. JAMA. 2003;289:25602572.
  • 2
    1993 guidelines for the management of mild hypertension. Memorandum from a World Health Organization/International Society of Hypertension meeting. Guidelines Subcommittee of the WHO/ISH Mild Hypertension Liaison Committee. Hypertension. 1993;22(3):392403.
  • 3
    Recommendations for human blood pressure determination by sphygmomanometers. Circulation. 1988;77(2):501A514A.
  • 4
    Jamieson MJ, Webster J, Philips S, et al. The measurement of blood pressure: sitting or supine, once or twice? J Hypertens. 1990;8(7):635640.
  • 5
    Netea RT, Elving LD, Lutterman JA, et al. Body position and blood pressure measurement in patients with diabetes mellitus. J Intern Med. 2002;251(5):393399.
  • 6
    Netea RT, Lenders JW, Smits P, et al. Both body and arm position significantly influence blood pressure measurement. J Hum Hypertens. 2003;17(7):459462.
  • 7
    Cavelaars M, Tulen JH, van Bemmel JH, et al. Reproducibility of intra-arterial ambulatory blood pressure: effects of physical activity and posture. J Hypertens. 2004;22(6):11051112.
  • 8
    Kannel WB, Dawber TR, Sorlie P, et al. Components of blood pressure and risk of atherothrombotic brain infarction: the Framingham study. Stroke. 1976;7(4):327331.
  • 9
    Effects of treatment on morbidity in hypertension. Results in patients with diastolic blood pressures averaging 115 through 129 mm Hg. JAMA. 1967;202(11):10281034.
  • 10
    Randomised controlled trial of treatment for mild hypertension: design and pilot trial. Report of Medical Research Council Working Party on Mild to Moderate Hypertension. BMJ. 1977;1(6074):14371440.
  • 11
    Dischinger P, DuChene AG. Quality control aspects of blood pressure measurements in the Multiple Risk Factor Intervention Trial. Control Clin Trials. 1986;7(3 suppl):137S157S.
  • 12
    Labarthe DR, Blaufox MD, Smith WM, et al. Systolic Hypertension in the Elderly Program (SHEP). Part 5: baseline blood pressure and pulse rate measurements. Hypertension. 1991;17(3 suppl):II62II76.
  • 13
    Davis BR, Cutler JA, Gordon DJ, et al. Rationale and design for the Antihypertensive and Lipid Lowering Treatment to Prevent Heart Attack Trial (ALLHAT). ALLHAT Research Group. Am J Hypertens. 1996;9(4 pt 1):342360.
  • 14
    Australian comparative outcome trial of angiotensin-converting enzyme inhibitor-and diuretic-based treatment of hypertension in the elderly (ANBP2): objectives and protocol. Management Committee on behalf of the High Blood Pressure Research Council of Australia. Clin Exp Pharmacol Physiol. 1997;24(2):188192.
  • 15
    Hansson L, Zanchetti A, Carruthers SG, et al. Effects of intensive blood-pressure lowering and low-dose aspirin in patients with hypertension: principal results of the Hypertension Optimal Treatment (HOT) randomised trial. HOT Study Group. Lancet. 1998;351(9118):17551762.
  • 16
    Dahlof B, Devereux RB, Julius S, et al. Characteristics of 9194 patients with left ventricular hypertrophy: the LIFE study. Losartan Intervention for Endpoint Reduction in Hypertension. Hypertension. 1998;32(6):989997.