title: Assessment of central blood pressure in patients with type 2 diabetes: a comparison between SphygmoCor and invasively measured values.
abstract: BACKGROUND
  The SphygmoCor is used for noninvasive assessment of ascending aortic blood pressure (BP). However, the validity of the SphygmoCor transfer function has not been tested in an exclusively type 2 diabetic patient sample. Calibration with systolic (SBP) and diastolic (DBP) brachial BP has previously been associated with substantial imprecision of central BP estimates. We hypothesized that different noninvasive calibration strategies might improve the accuracy of the estimated ascending aortic BPs.
  
  
  METHODS
  In 34 patients with type 2 diabetes we estimated ascending aortic SBP and DBP using the SphygmoCor device and compared these data with invasively recorded data. The validity of the transfer function was assessed by calibrating with invasively recorded DBP and mean BP (MBP). The influence of noninvasive calibration strategies was assessed by calibrating with brachial oscillometric SBP+DBP vs. DBP+MBP using a form factor (ff) of 0.33 and 0.40, respectively.
  
  
  RESULTS
  When calibrating with invasive BP, the difference between estimated and invasively measured ascending aortic SBP and DBP was -2.3±5.6/1.0±0.9 mm Hg. When calibrating with oscillometric brachial BPs, the differences were -9.6±8.1/14.1±6.2 mm Hg (calibration with SBP and DBP), -8.3±11.7/13.9±6.1 mm Hg (DBP and MBP; ff = 0.33), and 1.9±12.2/14.1±6.2 mm Hg (DBP and MBP; ff = 0.40), respectively. Calibration with the average of 3 brachial BPs did not improve accuracy.
  
  
  CONCLUSIONS
  The SphygmoCor transfer function seems valid in patients with type 2 diabetes. Noninvasive calibration with DBP and MBP (ff = 0.40) enables accurate estimation of mean ascending aortic SBP at the group level. However, the wide limits of agreement indicate limited accuracy in the individual patient.
  
  
  BACKGROUND
  Clinical Trials No. NCT01538290.
authors.affiliation: Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Esben
authors.initials: E
authors.lastname: Laugesen
authors.forename: Niklas B
authors.initials: NB
authors.lastname: Rossen
authors.forename: Christian D
authors.initials: CD
authors.lastname: Peters
authors.forename: Michael
authors.initials: M
authors.lastname: Mæng
authors.forename: Eva
authors.initials: E
authors.lastname: Ebbehøj
authors.forename: Søren T
authors.initials: ST
authors.lastname: Knudsen
authors.forename: Klavs W
authors.initials: KW
authors.lastname: Hansen
authors.forename: Hans E
authors.initials: HE
authors.lastname: Bøtker
authors.forename: Per L
authors.initials: PL
authors.lastname: Poulsen
mesh_terms: D000368:Aged; D062186:Arterial Pressure / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D001795:Blood Pressure Determination / Q000295:instrumentation*; D002138:Calibration; D003924:Diabetes Mellitus, Type 2 / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D063177:Pulse Wave Analysis
keywords: applanation tonometry; blood pressure; blood pressure monitoring; central blood pressure; hypertension; invasive blood pressure monitoring; transfer function; type 2 diabetes; validation.