title: Peripheral blood pressure measurement is as good as applanation tonometry at predicting ascending aortic blood pressure.
abstract: BACKGROUND
  The Sphygmocor system purports to be able to assess ascending aortic blood pressure using a transfer function. It has been shown to be accurate when data obtained invasively are used, but has not been tested prospectively using data obtained non-invasively.
  
  
  OBJECTIVE
  To investigate the accuracy of this equipment when measurements are obtained non-invasively, as would normally be the case in the clinic setting.
  
  
  METHODS
  The study was observational. Ascending aortic pressure measurements were taken simultaneously with radial artery pressure wave recordings for estimation of ascending aortic blood pressure, in 28 patients undergoing diagnostic cardiac catheterization.
  
  
  RESULTS
  The transfer function in the Sphygmocor system significantly underestimated invasively measured systolic blood pressure [mean -7.23 +/- 10.07 mmHg; 95% confidence interval (CI) -3.3 to -11.14 mmHg, P = 0.001] and significantly overestimated invasively measured diastolic blood pressure (mean 12.20 +/- 7.14 mmHg; 95% CI 9.43 to 14.97 mmHg, P <0.001). Oscillometrically measured brachial systolic blood pressure was not significantly different from that measured invasively in the ascending aorta (mean 3.36 +/- 10.47 mmHg; 95% CI -0.69 to 7.43 mmHg, P = 0.1), but oscillometric measurement of brachial diastolic blood pressure gave a significant overestimation of that measured invasively (mean 11.70 +/- 7.18 mmHg; 95% CI 8.91 to 14.49 mmHg, P <0.001). CONCLUSIONS The transfer function in the Sphygmocor system is no better at estimating ascending aortic blood pressure than are standard peripheral blood pressure measurements. It may be necessary to derive a new transfer system that is based on data that are acquired entirely non-invasively.
authors.affiliation: Department of Clinical Pharmacology, Department of Cardiology and Department of Epidemiology and Public Health, Ninewells Hospital and Medical School, Dundee DD1 9SY, Scotland, UK. j.i.davies@dundee.ac.uk
authors.forename: Justine I
authors.initials: JI
authors.lastname: Davies
authors.forename: Margaret M
authors.initials: MM
authors.lastname: Band
authors.forename: Stuart
authors.initials: S
authors.lastname: Pringle
authors.forename: Simon
authors.initials: S
authors.lastname: Ogston
authors.forename: Allan D
authors.initials: AD
authors.lastname: Struthers
mesh_terms: D000368:Aged; D001011:Aorta / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D001795:Blood Pressure Determination / Q000295:instrumentation / Q000379:methods* / Q000706:statistics & numerical data; D001916:Brachial Artery / Q000502:physiology; D005260:Female; D006801:Humans; D006973:Hypertension / Q000175:diagnosis / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D017534:Radial Artery / Q000502:physiology; D019722:Sphygmomanometers / Q000706:statistics & numerical data