ASEE New England Section 2006 Annual Conference, March 17-18, 2006

A Modular Approach to Teaching the Engineering Challenges of Physiology

Gregory J. SonekDept. of Electrical and Computer Engineering

Merrimack CollegeNorth Andover, MA

ASEE New England Section 2006 Annual Conference, March 17-18, 2006

• Background and Introduction

• Course Structure and Development

• Examples of Themes and Projects

• Results and Conclusions

ASEE New England Section 2006 Annual Conference, March 17-18, 2006

Background and Introduction

“Engineering Challenges in Physiology” is a course offered as part of a biomedical engineering curriculum with the following goals and objectives:

• To provide students with literacy and fluency in basic physiological processes and systems

• To enable students to identify, through an understanding of universal concepts and themes, engineering challenges i.e. needs and opportunities for new techniques, devices, and systems at the molecular, cellular, tissue, and whole body scales

• To provide an opportunity for application of course concepts through self study and exploration

ASEE New England Section 2006 Annual Conference, March 17-18, 2006

Course Challenges

Physiology is a highly interdisciplinary subject that crosses the boundaries of science and engineering. Both the audience and course content present significant challenges:

• Course offered to undergraduates and graduates who are pursuing• BSBME degree, second major, and minor• ME, MS, and Ph.D. degrees• Certificate degree in bioengineering

• Draws students that have diverse educational backgrounds and varying degrees of industrial and professional training. Backgrounds include

• Engineering (electrical, mechanical, chemical, biological)• Life sciences (biology, premedicine)• Physics

• Students are motivated to leverage existing or prior experiences with new coursework that will facilitate their involvement in the biomedical field

ASEE New England Section 2006 Annual Conference, March 17-18, 2006

Course Challenges

• The subject of physiology is vast and diverse

• Engineering concepts and themes must be reviewed and applied

• Engineering challenges must be identified

ASEE New England Section 2006 Annual Conference, March 17-18, 2006

Course Structure and Development

A modular approach was adopted to address course challenges:

• Present select topics in physiology in 2 – 3 week intensive modules for in depth study

• Develop common themes and concepts that bridge all systems

• Use a combination of lectures, text readings, homework, and weekly review of current events to engage all students

• Draw upon expertise from faculty and researchers in specific areas of physiology e.g. respiratory, neuro, cardiovascular, renal

• Focus on problem solving, identification of problems, and challenges

• Use a final project to integrate course concepts and provide an opportunity for research and self exploration

ASEE New England Section 2006 Annual Conference, March 17-18, 2006

• Introduction to Engineering in Physiology Human body as a complex system; sensing, feedback, and control

Physiological parameters, transport, fluid/gas mechanics, chemistry, electrical processes

• Cellular Physiology Cell structure, cell transport, ion channels

Potentials (membrane, action), intracellular signaling, neurotransmission

• Neurophysiology

Central and peripheral nervous systems, autonomic and sympathetic processes

Receptors, neural pathways, sensory (auditory, visual) systems

Interfacing with the nervous system, neuro-prosthetics, bionic devices

• Respiratory Physiology

Functional anatomy and control of breathing

Mechanics of breathing, gas exchange (diffusion), ventilation/perfusion matching

• Cardiovascular Physiology

Basic hemodynamics, electrophysiology, electrocardiography

Mechanical events of the cardiac cycle, peripheral circulation regulation

Cardiac muscle mechanics, molecular cardiology

• Renal Physiology

Quantitation of renal transport processes, renal tubular function

Acid/base balance, blood pressure and volume control

• Special Topics

Temperature regulation. exercise, high-altitude, and hyperbaric physiologies

• Final Projects Student chosen projects in select areas of physiology

ASEE New England Section 2006 Annual Conference, March 17-18, 2006

Basic Principles and Common Themes

The course emphasizes many basic principles and themes common across allphysiological systems, including:

• Energy Electrochemical potential, metabolism (ATP, glucose, FFA)

• Communications Signaling, receptors, integrated pathways

• Information Audition, vision, tactile sensing, neural processing

• Feedback & Open/closed loop, negative/positive feedback, sensor Control integration with chemical and neural systems

• Transport Drift, diffusion, passive and active transport, fluids, gases, ions, solutes

• Processes Chemical, mechanical, and electrical processes

ASEE New England Section 2006 Annual Conference, March 17-18, 2006

An example of two principles that applies to many different systems are those of Ohm’s Law , where resistance represents opposition to flow ( = x R) andPotential Energy (storage) represents the capacity for accumulation (= 1/C dt)

OHM’S LAW CAPACITY

Electrical V = IR q = C V

Mechanical F = v Rm x = F Cm

Fluidic P = Q Rf V = P Cf

Thermal = Q Rt Q = Ct

Chemical = Q Rc M = V Cc

I

F

v

Q

P = P1 – P2

1 2

Q

1 2

= 1 - 2

xF

PV

12

Basic Principles and Common Themes

ASEE New England Section 2006 Annual Conference, March 17-18, 2006

Universal Concepts and ThemesBASIC CONTROL SYSTEM WITH NEGATIVE FEEDBACK

CONTROL SYSTEM WITH NEGATIVE AND POSTIVE FEEDBACK

ASEE New England Section 2006 Annual Conference, March 17-18, 2006

1-adrenergicreceptor activation

Force of ContractionSystemic vascularresistance

-adrenergicreceptor activation

Stroke Volume

Cardiac Output

Sympathetic Activity

Parasympathetic Activity

INTERVENTION

Arterial Pressure Increase Decrease

Baroreceptor stretch

Baroreceptorfiring rate

Heart Rate

Muscarinicreceptor activation

Cardiovascular Feedback and Control

ASEE New England Section 2006 Annual Conference, March 17-18, 2006

Application of Engineering Principles

STEP CHEMICAL & PHYSICAL PRINCIPLES

Alveolar Ventilation Fluid mechanics of laminar and turbulent flows

Pulmonary Gas Diffusion; Henry’s Law; Law of Mass ActionExchange Allosteric conformational effects on hemoglobin

Oxygenated Blood Fluid mechanics; Physical chemistry ofCirculation hemoglobin

Extravascular Oxygen DiffusionDistribution

Oxygen Transport into Diffusion; Henry’s Law; Mass ActionCells & Mitochrondria

Cell Respiration Kinetics of electron transport chains

EXAMPLE: OXYGEN CONSUMPTION

ASEE New England Section 2006 Annual Conference, March 17-18, 2006

Analysis of Engineering and Clinical DataOBJECTIVE: To apply course engineering and physiological concepts to thesolution of problems derived from real clinical or experimental data.

EXAMPLE: To investigate the mechanics of breathing through the concepts of flow and pressure-flow relationships. Data is derived from spirometer and pneuno-tachograph measurements

• FIND RESISTANCE BY THE ISOVOLUME METHOD • IDENTIFY PATIENT P - V CURVES

ASEE New England Section 2006 Annual Conference, March 17-18, 2006

Analysis of Physiological DataEXAMPLE: To explore the role that the kidneys and lungs play in acid/base balanceand identification of various acid/base disorders, including metabolic andrespiratory acidosis and alkalosis

• Henderson – Hasselbalch Eqn.

pH = pK + log [HCO3-]

0.03 x PCO2

pH = Kidneys Lungs

• Sample Conditions A = Uncompensated metabolic acidosis

B = Metabolic alkalosis and respiratory acidosis

• Davenport Diagram

A

B

ASEE New England Section 2006 Annual Conference, March 17-18, 2006

Engineering Concepts and Challenges

To further develop the theme of engineering challenges, modules usetake home assignments that pose open ended questions or problems forwhich there are no current solutions. Some examples include:

• Continuous Measurement of Airway Obstruction during Sleep Requires a method for analyzing nasal flow and chest/abdomen movement to diagnose hypopnea (reduction of airflow) in patients with obstructive sleep apnea (OSA)

• Implantable Gas Exchanger (Artificial Lung) as Lung Transplantation Alternative Considers the design of an artificial gas exchanger as an alternative to extra- corporeal oxygen devices for patients with advanced lung disease

• Changes in Fluid Volumes and Osmolarities Considers the changes to intracellular and extracellular fluid volumes and osmolarities in marathon runners who compete on a hot day, rehydrate only with pure water, and suffer muscle cramping near the end of a race

ASEE New England Section 2006 Annual Conference, March 17-18, 2006

SUGGESTED TOPIC STUDENT PROJECTS

Space Physiology “Physiological effects of fluid shifts on the cardiovascular system during space travel”

Neonatal Physiology “Neurology and the human auditory system”

“Effects of neutropenia in the neonate”

“Respiratory physiology of preterm births”

Sports Medicine Physiology “Turning Michael Johnson into a marathon runner”

“Performance monitoring in cyclists: VO2

max, lactate threshold, nutrition, muscle function, and power training”

High-Altitude Physiology “Engineering challenges in high-altitude physiology”

Hyperbaric Medicine “Physiology under hyperbaric conditions”

Final Projects

ASEE New England Section 2006 Annual Conference, March 17-18, 2006

Examples“Performance Monitoring in Cyclists: VO2 max, lactate threshold, nutrition, muscle function, and power training”

OBJECTIVE: To understand VO2 max and the factors that affect it, from basicmetabolic processes and barriers, to muscle types, nutrition, training regimens,and devices used to monitor performance

ASEE New England Section 2006 Annual Conference, March 17-18, 2006

Examples “Physiology under Hyperbaric Conditions”

OBJECTIVE: To understand the effects of pressure on the human body, includingDalton’s Law, tissue saturation, nitrogen narcosis, and the neurological effects ofgas partial pressures (lipid bilayer alteration, modified neuronal firing rates)

ASEE New England Section 2006 Annual Conference, March 17-18, 2006

Results and Conclusions

• A modular approach to the study of engineering and its challenges in physiology has proven to be a successful course model

• The course focuses on concepts and themes that are common to different physiological systems (cellular, neuro, respiratory, CV, renal)

• It has the goal of helping students identify engineering challenges (needs and opportunities) for new techniques, devices, and systems from the molecular to whole body scales

• The strength of the course lies in its breadth, interdisciplinary nature, and expertise brought by a diverse group of faculty and lecturers with backgrounds in engineering, medicine, R&D, and clinical applications

ASEE New England Section 2006 Annual Conference, March 17-18, 2006

Acknowledgments

We are grateful to all the participating faculty, researchers, and students at Tufts University who made this work possible:

Prof. David Kaplan Dept. of Biomedical Engineering

Prof. Andrew Hoffman School of Veterinary Medicine andLung Function Testing Laboratory

Prof. Larry Engelking Dept. of Biomedical Sciences andSchool of Veterinary Medicine

Prof. Eunice Bloomquist Dept. of Physiology and School of Medicine

Dr. Michael Mendelsohn Molecular Cardiology Institute and NEMC

Dr. Ron Risso Inner Sea Tech

BME Students Brian Orrick, Jason Waterman, Clemens Alt, Leonardo Angelone