title: Non-invasive measurement of aortic pressure in patients: Comparing pulse wave analysis and applanation tonometry.
abstract: OBJECTIVE
  The aim of the present study was to validate and compare novel methods to determine aortic blood pressure non-invasively based on Oscillometric Pulse Wave Velocity (PWV) measurement using four limb-cuff pressure waveforms and two lead Electrocardiogram (ECG) with a validated tonometric pulse wave analysis system in patients.
  
  
  METHODS
  After receiving the consent, in 49 patients with hypertension, coronary artery disease, diabetes mellitus, PWV, and central blood pressures were recorded in a randomised manner using both the oscillometric and tonometric devices. All recordings were performed 10 minutes after the patient lying comfortably in a noise-free temperature-controlled room. The test was performed between 09 am and 10 am after overnight fast. A minimum of three measurements were performed by the same skilled and trained operator. From the raw data obtained with two devices, software calculated the final vascular parameters.
  
  
  RESULTS
  A total of 49 patients (8 women and 41 men), of mean age 40.5 years (range: 19-81 years) participated in the present study. After transforming the brachial pressures into aortic pressures, the correlation coefficient between the Aortic Systolic Pressure (ASP) values obtained with two methods was 0.9796 (P<0.0001). The mean difference between ASP with two methods was 0.3 mm Hg. Similarly, Aortic Diastolic Pressure (ADP) values obtained with two methods also correlated significantly with correlation coefficient of 0.9769 (P<0.0001). The mean difference of ADP was 0.2 mm Hg. In case of Aortic Pulse Pressure (APP), the mean difference was 0.1 mm Hg. All parameters of central aortic pressures obtained with two methods correlated significantly.
  
  
  CONCLUSIONS
  The new method of transforming the Carotid Femoral PWV (cfPWV) and brachial blood pressure values into aortic blood pressure values seems to be reasonably good. The significant correlation between the values obtained by tonometric device and oscillometric PWV method shows that the latter can be used non-invasively in patients to find the aortic pressure.
authors.affiliation: Department of Clinical Pharmacology and Therapeutics, Nizam's Institute of Medical Sciences, Hyderabad, India.
authors.forename: M U R
authors.initials: MU
authors.lastname: Naidu
authors.forename: C Prabhakar
authors.initials: CP
authors.lastname: Reddy