Poster Asaio 2007 Conf A Modified Elastance Model To Control Mock Ventricles In Real Time

UNIVERSITÀ DELLACALABRIA

A Modified Elastance Model to Control Mock Ventricles in Real-Time

Dipartimento di MECCANICA

1 Colacino ,

2 Piedimonte ,

1 Moscato ,

1 Arabia ,

1 Danieli ,

2 Nicosia

Francesco M. Fabio Francesco Maurizio Guido Salvatore 1 Mechanical Engineering Department, University of Calabria – Italy; 2 Dipartimento di Informatica Sistemi e Produzione, University of Rome “Tor Vergata” – Italy

NUMERICAL VALIDATION

AIM

EXPERIMENTAL VALIDATION Continuous run experiments based on variations of:



To build a mock ventricle able to reproduce the correct ventricular pressure/volume relationship in order to obtain the correct interaction between the mock ventricle and the environment connected to it.

Systemic arterial resistance: Ras Mean circulatory pressure: Pmc 

For Physiologic Cases:





A control condition has been reached (HR = 60 bpm) Afterload Increase – Preload Constant: MPao ↑ - Ved ↔ Preload Increase – Afterload Constant: Ved ↑ - MPao ↔

For Pathologic Cases:





A control condition has been reached (HR = 100 bpm) Afterload Decrease: MPao ↓ Preload Decrease: Ved ↓

IMPEDANCE MODEL Based on stress/speed measurements of the cardiac sarcomere, and on energetic considerations, resistive and inductive terms (R(t) and L(t) respectively) are added to the classical Suga-Sagawa elastance model throughout the whole cardiac cycle. PLV t   P0   VLV t , t   Ri t  VLV t   Li t   VLV t  where :

 VLV t , t    p VLV t    a VLV t    p VLV t  f iso t  and



Ri t   sat Ri MIN  K Ri f iso t , Ri MAX



 1 1 1  sat  K Li f iso t , L Li t  Li MIN  i MAX

   

with :  x t  x t   y sat x t , y    x t   y y

EXPERIMENTAL SETUP Mock Ventricle Rcs, Lcs

Cas

Rla, Lla

NUMERICAL VALIDATION

Ras, Las

The LV volumes (VLV) calculated from both Cla the classical model and the modified Cvs elastance model, in presence of a Rvs, Lvs sinusoidal pressure disturbance of amplitude 1 mmHg, are shown below (solid lines). Dotted lines are for the case CONTROL STRATEGY with no disturbance. VLV calculated from The pressure measured into the mock ventricle (P ) is feed back LV the classical model is very sensitive to the CONCLUSIONS into the mathematical model and the calculated reference V is LV pressure disturbance, especially during The presented model is suitable to control mock ventricles in real-time where acoustic-type used to drive the piston by means of a PI controller. the filling phase. The modified model filters vibrations are responsible for sudden pressure disturbances, which on the contrary make the  17.57 s  46 C s   out the disturbance effects. classical elastance model unsuited unless using mechanical filters. s

Advantages:

Device conceived to study the correct ventricle-environment interaction Mock ventricle working according to the elastance mechanism Correct sensitivity to Preload and Afterload Pathologic and physiologic working conditions can be mimicked To be solved: High pressure drop across the mitral valve (negative pressure during filling) Better shaping of ventricular pressure waveform (low frequency oscillations) General improvements of hydraulic components (Ras) Closed loop with both systemic and pulmonary circulations