Ferguson, Connor R.

Laurie, Steven S.

Stenger, Michael B.

NASA Technical Reports Server

Model Flow Determination of Stroke 
Volume
Connor R Ferguson
University of Kentucky
Steven S Laurie PhD, Michael B Stenger PhD
Wyle Science, Technology, and Engineering Group
Cardiovascular Laboratory
National Aeronautics and Space Administration
www.nasa.gov 
https://ntrs.nasa.gov/search.jsp?R=20140010655 2019-08-31T20:08:50+00:00Z
National Aeronautics and Space Administration Modelflow Determination of Stroke Volume 2
Introduction
  Education: Mechanical Engineering (BS, 2015) - University of Kentucky
  Research and Career Interests: Biomedical Engineering, Bioengineering, Aerospace 
Engineering 
  Experience with NASA JSC CVL + UKY BME to evaluate countermeasures to cardiovascular 
deconditioning induced by prolonged exposure to spaceflight: 
(1) AlterG
(2) Ames Human Performance Centrifuge
National Aeronautics and Space Administration Modelflow Determination of Stroke Volume 3
Orthostatic Intolerance
Inability to maintain blood pressure during upright posture
Stroke Volume Heart Rate
Blood Pressure
Cardiac Output TPR
  20% of Crewmembers on Short Duration Flights 8
  60% to 80% of Crewmembers on Long Duration Flights 8
Earth’s Gravity (1G)
Normal Volume
Microgravity
Volume Shifts
to Chest and Head
Return to Earth’s Gravity
Volume is Low and Now
Shifts from Head to Legs
Possibility of Fainting!
Adaptation
to Microgravity
Adaptation to Microgravity
Volume is Low
and Still Shifted 
to Chest and Head
National Aeronautics and Space Administration Modelflow Determination of Stroke Volume 4
TILT STAND
Arm Position
Orthostatic Tolerance Test
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Doppler ultrasound
  Measures aortic blood flow velocity and diameter of the aorta to calculate stroke 
volume
Drawbacks:
  Requires a trained operator and expensive specialized equipment
  Each measurement typically incorporates a small sample of beats
  Difficulty in imaging certain subjects
Modelflow Determination of Stroke Volume 5
U
parabolic 
velocity profile
pulsed Doppler
Stroke 
Volume
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BeatScope Modelflow
  Continuous blood pressure waveform acquired using a finger cuff (finger 
plethysmography)
  Computes aortic flow pulsations from arterial pressure waveforms by simulating a 
model that incorporates assumptions of human morphology
Modelflow Determination of Stroke Volume 6
Pressure Flow
Stroke 
Volume
Three‐element model used to compute aortic flow as proposed by Wesseling et 
al.  Zo, characteristic impedance of proximal aorta; Cw, windkessel compliance of 
arterial system; Rp, total systemic peripheral resistance; Q(t), blood flow; P(t) 
arterial pressure waveform; Pw(t), windkessel pressure
FINOMETER
PORTAPRES
National Aeronautics and Space Administration
Objectives of Internship
  To conceive, develop, and conduct a human subject research protocol to evaluate the 
use of Modelflow estimation of stroke volume during a stand or tilt test
  Retrospective analysis to determine if Modelflow can be applied to previously 
collected data
  Determine the possibility of analyzing future data in situations in which ultrasound 
measurements of stroke volume may not be possible, such as field testing
Modelflow Determination of Stroke Volume 7
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Protocol
Modelflow Determination of Stroke Volume 8
B Dinamap
US Ultrasound
FM Right Arm Extended At Heart Level
PP Left Arm Extended At Heart Level
Supine Stand
Baseline B Baseline B PP B FM B
US US US US US US US US
1 2 3 4 5 6 7 8 9 10 11 12 13
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Results
Modelflow Determination of Stroke Volume 9
StandSupine
Finometer
Portapres
Ultrasound
National Aeronautics and Space Administration Modelflow Determination of Stroke Volume 10
Results
Finometer
Portapres
Ultrasound
Rebreathe
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‐30
‐20
‐10
0
C
h
a
n
g
e
 
i
n
 
S
V
 
F
r
o
m
 
H
a
n
d
 
D
o
w
n
 
(
m
l
)
Modelflow Determination of Stroke Volume 11
Raise 
PP
Raise 
FM
Results
Finometer
Portapres
Ultrasound
PORTAPRES
FINOMETER
National Aeronautics and Space Administration
0
20
40
60
80
100
S
t
r
o
k
e
 
V
o
l
u
m
e
 
(
m
l
)
Retrospective Analysis
Modelflow Determination of Stroke Volume 12
TiltSupine
Finometer
Ultrasound
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Individual Data
Modelflow Determination of Stroke Volume 13
Finometer
Ultrasound
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Discussion
Modelflow Determination of Stroke Volume 14
Drawbacks and Limitations
  Modelflow may not accurately report absolute values of stroke volume
  Modelflow may not accurately report changes in stroke volume between postures
  The algorithm used by Modelflow estimates body surface area and aortic diameter
  Reliability of Modelflow computation of SV is dependent on its ability to track 
arterial pressure
Future Direction
  Identifying factors that contribute to differences between modelflow and ultrasound 
estimates
  Evaluate alternative inputs to the modelflow algorithm
  Investigate positional changes in finger cuff blood pressure acquisition
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Acknowledgements
Modelflow Determination of Stroke Volume 15
Cardiovascular Lab
Steven Laurie, PhD
Michael Stenger, PhD
Steven Platts, PhD
Stuart Lee, MS
David Martin, MS
Tim Caine
Tim Matz, BA
Sondra Perez, MS
Chris Ribeiro, MS
Tiffany Phillips, MS
Space Life Sciences Summer Institute
Lauren Merkel, PhD
NASA Internship Coordinators
Missy Mathias
Diego Rodriguez
National Aeronautics and Space Administration
Citations
1. Bogert, Lysander W. J., and Johannes J. van Lieshout. “Non-Invasive Pulsatile Arterial Pressure and Stroke Volume Changes from the Human Finger.” Experimental 
Physiology 90, no. 4 (July 2005): 437–46. doi:10.1113/expphysiol.2005.030262.
2. Buckey, J. C., L. D. Lane, B. D. Levine, D. E. Watenpaugh, S. J. Wright, W. E. Moore, F. A. Gaffney, and C. G. Blomqvist. “Orthostatic Intolerance after Spaceflight.” Journal 
of Applied Physiology (Bethesda, Md.: 1985) 81, no. 1 (July 1996): 7–18.
2. Dyson, Kenneth S., J. Kevin Shoemaker, Philippe Arbeille, and Richard L. Hughson. “Modelflow Estimates of Cardiac Output Compared with Doppler Ultrasound during Acute 
Changes in Vascular Resistance in Women.” Experimental Physiology 95, no. 4 (April 2010): 561–68. doi:10.1113/expphysiol.2009.050815.
4. Gizdulich, P., A. Prentza, and K. H. Wesseling. “Models of Brachial to Finger Pulse Wave Distortion and Pressure Decrement.” Cardiovascular Research 33, no. 3 (March 
1997): 698–705.
5. Kostas, Vladimir. “EFFECT OF LOWER BODY POSITIVE PRESSURE ON CARDIOVASCULAR RESPONSE AT VARIOUS DEGREES OF HEAD UP TILT.” Theses and 
Dissertations--Kinesiology and Health Promotion, January 1, 2012. http://uknowledge.uky.edu/khp_etds/3.
6. Kostas, Vladimir I., Michael B. Stenger, Charles F. Knapp, Robert Shapiro, Siqi Wang, André Diedrich, and Joyce M. Evans. “Cardiovascular Models of Simulated Moon and 
Mars Gravities: Head-up Tilt vs. Lower Body Unweighting.” Aviation, Space, and Environmental Medicine 85, no. 4 (April 2014): 414–19.
7. Langewouters, G. J., K. H. Wesseling, and W. J. Goedhard. “The Static Elastic Properties of 45 Human Thoracic and 20 Abdominal Aortas in Vitro and the Parameters of a 
New Model.” Journal of Biomechanics 17, no. 6 (1984): 425–35.
8. Meck, J. V., C. J. Reyes, S. A. Perez, A. L. Goldberger, and M. G. Ziegler. “Marked Exacerbation of Orthostatic Intolerance after Long- vs. Short-Duration Spaceflight in 
Veteran Astronauts.” Psychosomatic Medicine 63, no. 6 (December 2001): 865–73.
9. Sprangers, R. L., K. H. Wesseling, A. L. Imholz, B. P. Imholz, and W. Wieling. “Initial Blood Pressure Fall on Stand up and Exercise Explained by Changes in Total Peripheral 
Resistance.” Journal of Applied Physiology 70, no. 2 (February 1, 1991): 523–30.
10. Van Lieshout, Johannes J., Karin Toska, Erik Jan van Lieshout, Morten Eriksen, Lars Walløe, and Karel H. Wesseling. “Beat-to-Beat Noninvasive Stroke Volume from 
Arterial Pressure and Doppler Ultrasound.” European Journal of Applied Physiology 90, no. 1–2 (September 2003): 131–37. doi:10.1007/s00421-003-0901-8.
11. Wesseling, K. H., J. R. Jansen, J. J. Settels, and J. J. Schreuder. “Computation of Aortic Flow from Pressure in Humans Using a Nonlinear, Three-Element Model.” Journal 
of Applied Physiology (Bethesda, Md.: 1985) 74, no. 5 (May 1993): 2566–73.
12. Zhang, Qingguang, Charles F. Knapp, Michael B. Stenger, Abhijit R. Patwardhan, Samy C. Elayi, Siqi Wang, Vladimir I. Kostas, and Joyce M. Evans. “Simulations of 
Gravitational Stress on Normovolemic and Hypovolemic Men and Women.” Aviation, Space, and Environmental Medicine 85, no. 4 (April 2014): 407–13.
Modelflow Determination of Stroke Volume 16
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Model Flow Determination of Stroke Volume

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