Special Issue - Review

Medical & Biological Engineering & Computing

, Volume 47, Issue 2, pp 221-232

First online:

Wave intensity analysis and the development of the reservoir–wave approach

  • John V. TybergAffiliated withDepartments of Cardiac Sciences and Physiology & Pharmacology, University of Calgary Email author 
  • , Justin E. DaviesAffiliated withImperial College Healthcare NHS Trust, International Centre for Circulatory Health, St Mary’s Hospital Campus
  • , Zhibin WangAffiliated withQingdao University Medical College Hospital
  • , William A. WhitelawAffiliated withDepartment of Medicine (Emeritus Professor), University of Calgary
  • , Jacqueline A. FlewittAffiliated withStephanson Cardiovascular MR Centre, University of Calgary
  • , Nigel G. ShriveAffiliated withDepartment of Civil Engineering, University of Calgary
  • , Darryl P. FrancisAffiliated withImperial College Healthcare NHS Trust, International Centre for Circulatory Health, St Mary’s Hospital Campus
  • , Alun D. HughesAffiliated withImperial College Healthcare NHS Trust, International Centre for Circulatory Health, St Mary’s Hospital Campus
  • , Kim H. ParkerAffiliated withPhysiological Flow Unit, Department of Bioengineering, Imperial College
    • , Jiun-Jr WangAffiliated withDepartments of Cardiac Sciences and Physiology & Pharmacology, University of Calgary

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Abstract

The parameters of wave intensity analysis are calculated from incremental changes in pressure and velocity. While it is clear that forward- and backward-traveling waves induce incremental changes in pressure, not all incremental changes in pressure are due to waves; changes in pressure may also be due to changes in the volume of a compliant structure. When the left ventricular ejects blood rapidly into the aorta, aortic pressure increases, in part, because of the increase in aortic volume: aortic inflow is momentarily greater than aortic outflow. Therefore, to properly quantify the effects of forward or backward waves on arterial pressure and velocity (flow), the component of the incremental change in arterial pressure that is due only to this increase in arterial volume—and not, fundamentally, due to waves—first must be excluded. This component is the pressure generated by the filling and emptying of the reservoir, Otto Frank’s Windkessel.

Keywords

Pressure Windkessel Aorta Wave intensity analysis Frank Reservoir Wave