My goal is to establish myself as an independent investigator in the area of right ventricular (RV) mechanics. Following the design of this award, two Phases are proposed. Phase I includes a laboratory project and a didactic program. During the laboratory project, we will investigate a unique aspect of heart-lung interaction, the effects of positive end-expiratory pressure (PEEP) on RV function. Specifically, we hypothesize that an improvement in RV maximal elastance (a leftward shift of the RV end-systolic pressure volume relation) during ventilation with PEEP is due to an asymmetric increase in surface pressure caused by PEEP and not to increased RV contractility. To test this, contractility will be assessed from RV maximal stress-strain relations. Biplane cineradiography will be performed on dogs with radiopaque markers surgically implanted in the RV. This technique measures exact spacial positions of markers at 60 Hz, from which volume of the RV chamber or lengths and curvatures in a small region of the RV free wall can be reconstructed. Assumptions about ventricular mechanics, including linear elasticity, isotropism, homogeneity of deformation, and lack of shear, will be accepted in Phase I for calculation of RV stress. The didactic program of Phase I has been designed by the primary sponsor, an established expert in the physiology of ventricular mechanics. The didactic program is focused to prepare the Candidate for investigations of RV wall stress without simplifying assumptions. These investigations require a knowledge of advanced engineering, mathematics, and computer concepts, and thus, a schedule of appropriate courses at a local college of engineering has been prepared by the primary sponsor. After completion of the mathematics, engineering, and computer training (14mo) the Candidate will begin a 12 month tutorial, Mechanical Principles in the Evaluation of Myocardial Function, with the primary sponsor. In Phase II, two research projects are proposed for the biplane cineradiography lab to test the assumptions: (1) that the RV myocardium deforms homogeneously in all regions; and (2) that the elastic stiffness of the RV free wall is equal in all directions. The effects of ventilation with PEEP on these properties will then be evaluated. The studies in Phases I and II will be of clinical value by adding new insight into management strategies for patients requiring mechanical ventilation. Also our understanding of RV function in conditions of altered lung mechanics will be enhanced.
| Schwiep, F; Cassidy, S S; Ramanathan, M et al. (1988) Rapid in vivo determinations of instantaneous right ventricular pressure and volume in dogs. Am J Physiol 254:H622-30 |
