BME 9502/ECE 4455/MEDBIO 4455
MATLAB Investigation 2
Due November 9, 2022 at 11:55 pm

Assignments must be submitted electronically in Word or PDF format YLD WKH ³0$7/$%
Investigation 6XEPLVVLRQ´OLQNRQWKH(&(2:/VLWH A single submission from each group
of investigators is sufficient. Remember to identify all of your group members on your
submission.

All questions in this assignment are relevant to the required journal article, M. Mansouri,
R.F. Salamonsen, et al.³Preload-based Starling-like control for rotary blood pumps: Numerical
comparison with pulsatility control and constant speed operation´PLoS One, vol. 10, article
e0121413, 2015, which can be downloaded from the Required Resources list in the Unit 3 Course
Content section on the OWL site.

The questions require the MATLAB scripts LVAD_batch.m and LVAD_model.m as well as the
scripts they call (init_vectors.m and LVAD_model2.m), which can also be downloaded from the
Required Resources list in the Unit 3 Course Content section on the OWL site.


Run LVAD_batch.m. Keep both output figures open while working on Questions 1-4.


1. Consider Figure 1 output by LVAD_batch.m. Suggest a policy to select a constant LVAD flow
rate, Qlvad, that will provide some support for heart failure patients both at rest and during
exercise. Based on your policy, what value of Qlvad do you recommend? Using that value of
Qlvad, how completely does the LVAD compensate for heart failure at both activity levels?
[4 marks]


2. Observe in Figure 1 from LVAD_batch.m that when the LVAD is disabled (Qlvad = 0), the
failing heart produces a modest cardiac output. However, the plots for both the resting and
exercising SDWLHQWVH[KLELWD³NQHH´VXGGHQFKDQJHLQVlope) where the total output converges to
Qlvad, which implies that the outflow produced by the left ventricle, Qc, decreases to zero (i.e., the
LVAD overrides the heart). For a heart failure patient at rest, choose a Qlvad setting to the right
of the knee and use LVAD_model.m to obtain pressure, flow, and volume waveforms for this case.
Run LVAD_model.m a second time to simulate a resting heart failure patient with no LVAD. Use
the results to explain why the LVAD overrides the heart at higher settings of Qlvad. Illustrate your
response with any waveform plots needed to support your explanation. (Hint: Inspect the arterial
pressure waveform, Pa, and the left ventricular pressure waveform, Plv.)
[5 marks]


3. Observe in Figure 2 output by LVAD_batch.m that our model produces a knee in the plot of
Qlvad vs. left ventricular end-diastolic pressure for a resting heart failure patient that corresponds
(albeit at a different location in the plot) to the knee highlighted in Fig. 2 of the Mansouri et al.
paper. Mansouri et al. propose setting the value of K, the scaling factor for the Starling law
supervisory controller, such that the controller curve intersects the plot of Qlvad vs. left ventricular
end-diastolic pressure at the knee. Describe the interaction between the LVAD and a resting
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your conclusion.
[4 marks]


4. Referring to Figure 2 output by LVAD_batch.m, specify the value of K for the Starling law
controller that would provide complete support to an exercising heart failure patient. With this
choice of K, where should the knee of the Qlvad vs. Plved curve for a resting patient be located for
the Starling law controller to also provide appropriate support when the patient is resting? A
complete answer will include an annotated copy of LVAD_batch Fig. 2 showing the operating
point on the Starling law controller curve during exercise and the most desirable location of the
knee in the resting subject curve.
[4 marks]


5. A serious risk to the patient arises when the LVAD flow rate is much higher than necessary for
WKHSDWLHQW¶VFXUUHQWDFWLYLW\OHYHO8VHLVAD_model.m to simulate a heart failure patient at rest
with Qlvad /PLQ:KDWULVNWRWKHSDWLHQW¶VKHDUWFDQ\RXLQIHUIURPWKHUHVXOWV",OOXVWUDWH
your response with any waveform plots needed to support your explanation. (Hint: Inspect the left
ventricular pressure, Plv, and volume, Vlv, waveforms.)
[4 marks]