Midterm 2 Flashcards
(38 cards)
Mechanical properties of muscles depend on
fiber orientation and muscle size (cross sectional area)
hierarchy of muscle
start with a single fiber, then you have many fibers that are bundled together and then you have all those bundles bundled together to provide a failsafe measure in our system in our tissues (same thing is true for tendons and ligaments)
-If you break a muscle fiber, you don’t have catastrophic failure; the fibers around that fiber will take on higher stresses, but when you have a lot of those muscle fibers start to fail then you start to get into phase that catastrophic failure is possible
Orientation of the fibers
tell us the primary loading direction for those fibers, so if you look at muscle itself you can see what direction the muscle needs to pull in order to generate forces - fiber orientation tells you a lot of the muscle function itself, similar to anisotropic orientation
-If they have fanning fibers/two different directions of fiber orientation, they are strong in multiple directions
Force of muscle contraction:
rate of electrical signal and number of myosin bridges
- contracts - as it gets shorter, force goes up which is opposite of metal and polymers
- Think about how the material works and how it is different than other materials
Describe how muscles contract at a sub-tissue level (interaction between myosin and actin filaments)
Electrical signal sent from brain to arm (no muscles in fingers)
muscles have relationship between myosin bridges and actin filaments, when signal comes to the muscle, the myosin filaments will attach to actin and bring the muscle in closer
Myosin bridges only move muscles in one direction - can only contract
-to lengthen it / get it back in original state due to passive movement of opposite muscle that is pulling
Muscle groups work together to create movement
EMG
electromyography, used to measure electrical output from muscle by creating a circuit with your muscle; can be surface EMGs or Internal EMG (close to muscle to get better data, needles inserted in the muscle)
- Strength of signal on surface EMG depend on thickness of body which varies as the signal must travel through multiple layers
- can measure if it is close enough to the sensor
- Distance the electrical activity needs to travel to be picked up by the sensor - creates a lot of noise
- varies from person to person and depends on location on the body as different areas have different layers of fat
- creating circuit with body so need to have both electrodes on same muscle
- hydration can also change the output and results
Understand what factors affect muscle force output and how muscles function to provide force
Force of muscle contraction: rate of electrical signal and number of myosin bridges
Muscle force output depends on muscle length before electrical stimulus
Passive force: due to inherent material properties (muscle as a rope-like material)
Active force: due to electrical stimulus
Biological tissues behave like nonlinear springs
Have on-off response
To support movement, the force needs to be transferred to the skeleton
How quickly to provide a force - depends on actin/myosin bridge, and the electrical rate that is sent from the brain to the muscle will depend on how quickly and how strong the muscle will contract
-if you apply electrical stimulus to muscle, do you want constant or pulse stimulus - stimulus
Non polymer based materials are linear elastic (spring) - pull on it, it has linear displacement behavior
-biological tissues do not behave like that - can pull on it awhile and it doesn’t really care but then eventually it does start to stiffen up - nonlinear response if pulling passively
-but pulling actively due to electrical stimulus - pull and zap would give total force is passive and active force from contraction; will give you total force
-depends on resting length of muscle; when muscles are tense, the muscles get shorter over time and resting length decreases - not going to have the best performance/not going to be able to contract muscle that much
-if muscle is too long also not good, cannot perform at peak value due to lengthening behavior, there is an optimization of resting length that muscles want to be at
Electrical signal sent from brain - sending series of electrical impulses not constant, frequency is as signals get closer and closer together, you go from pusles to a fused form of pulse and allows for active and continuous muscle contraction (like step input but only addition of multiple impulses)
Not all muscle fibers are the same - slow twitch versus fast twitch - react very different
Slow Twitch Muscle: Uses oxygen for fuel, provides continuous energy, Offers extended muscle contraction, Fires slowly, Has high endurance, Great for marathons
Fast twitch muscle: uses anaerobic metabolism for fuel, provides short bursts of speed, fires rapidly, fatigues more quickly, great for sprinters
Explain how myoelectric prosthetics work to use existing muscles in amputees
Bio-mech-atronics: science of fusing mechanical devices with human muscle, skeleton, and nervous system to assist or enhance motor control - central nervous system and peripheral nervous system
Electric connected to limb - sending info into control pack, reliably get signal to move the hand - close or open hand depending on how you program it when signal occurs, learning by patient
Myoelectric limbs: send signals - registers muscle activity to move the prosthetic but very expensive
Electrodes are connected to a control unit and a battery pack and send signals to an electric hand after reading the signals from the arm
Devices aim to fulfill Maslow’s Hierarchy of Needs
Want communication in both ways - for stroke recovery where you read signals and send signals
Factors to consider in stimulating someone’s muscles - similar issues during reading and stimulation
-Size of muscle and person
-Activity desired
-Hydration
Myoelectric limbs - sensing
-Pre-programmed for grip strength relative to muscle activation
-Think about how you grab an object (grip strength applied to hold an egg, baseball, vs unknown object)
-Additional sensors - soft material at fingertips to act as strain sensors
Myoelectric limbs - receiving signals (signal goes from electric hand to socket)
-Registers sensation and translate it to the arm
Muscles get fatigued - can try and alternate where the muscle gets stimulated to limit the fatigue
Devices aim to fulfill Maslow’s Hierarchy of Needs
- Basic needs (safety and physiological needs)
- Psychological needs (belongingness and love needs, esteem needs)
- Self-fulfillment needs (self-actualization)
Explain potential uses, advantages, and limitations of myoelectric devices
Fusing medical devices with skeleton/muscles - prosthetic hand (high end)
Very expensive ($100k)
Battery and controller are heavy (heavier than forearm) - changes behavior because there are higher loads on biceps to move/hold arm (FBD - center of gravity will change, magnitude of force/weight will change (heavier)) - ex increasing weight by 2.5lbs force applied by bicep will be 3x more
Apply more load, start to degrade tissues faster
Can do computational analysis to change material/design
EMG sensor - needs to be placed in spot where the electrical activity can be read easy
Electrical activity moves through different material differently - density/water content will affect signal - change what muscles you use in design depending on best position
Trying to adjust when amount of force to grip is difficult
Infection from inside the body to outside
Surgeries to implant devices could go wrong
Time between surgery and time to control device is a long time
Examples and differences between active and passive devices
Passive devices: only collect information, most devices are passive (fitbits/wearable technology)
-current wearable technology can measure movement (monitor sleep and activity), measure heart rate, and energy consumption (math and averages)
Active devices: examples pacemakers and insulin monitors where it senses and transmits
Accuracy vs precision - accuracy is how close you are to the bullseye; precision is how close all of your shots are together
Example: pacemaker - used to just stimulate constantly; now tracks heartbeat and stimulates when needed
Automatic defibrillator
Describe types and purpose of prototypes–Communication, learning, or integration
Initial sketches/CAD - fast and allow for easy communication before creating time consuming CAD models
CAD can be time consuming and is more restrictive than sketching in making design changes, but can allow you to visualize how multiple components will fit together
Physical “looks like” prototypes - not functional but provides information about the feel and integration with existing products/ecosystems (making a clay car)
Make a “works like” prototype from computational model - functional but not pretty, more restrictive than analytical prototypes, how you use materials may weaken them so may need to test design mechanics in addition to material property
-allows for testing/performance; can test components separately
-test in position (plan for alpha/beta testing when setting milestones)
Wide range of prototypes - each to serve as a different purpose (physical, comprehensive, analytical, focused)
Benefit of prototypes - increased probability of success during production (constant iterations increase success rate) and can decrease total time from concept to production, can prevent unanticipated phenomena
Without proper testing could end up with unintended consequences (street lights not light enough) - want to take big problems and break it down into smaller components
FEA models are good but not always completely accurate so the truest way to test is to experimentally create it and then try to break it so means you need a works like prototype
Design a less invasive solution using a combination of existing technology
Future of wearable devices: smaller sensors allow for more sensors on same size device
New sensors to measure other bodily functions (ex. Caloric intake, measuring markers through sweat)
Personalized health care - current healthcare based on averages and trends, but everyone has a different baseline of normal - aim to make passive devices to active in order to adjust for everyone’s normal/make more personalized
Ex: Glucose monitoring device - helps patients manage glucose-insulin balance, patients must tell device how much insulin to inject
Using big data/using computers to see patterns with collection of information
Moving healthcare back home - using fitbits/devices out of clinics
Devices for heart health
-Response and repair (pacemaker, external defibrillator)
-Education/Entertainment (Current wearables, PPG)
-Monitoring (Pulse oximetry, EKG, heart rate)
-Prevention - needed
Biomimicry
-Look to nature for design ideas - how do different creatures move from point A to B (horizontally, vertically, aerially); ex: gecko movement
Understand the limitations/additional requirements needed for designing devices that may be considered medical devices
Most things are built based on an average so hard to design personalized devices
Want to move towards prevention
Have to think of FDA/HIPPA issues when thinking about biotech companies
Make assumptions but not always as accurate (pressure at lung might not be the same pressure at the alveoli)
Difference between 3 classes
Based on intended use, indications for use, and level of risk
Class I: low risk, general controls (good manufacturing, labeling, etc.) alone are sufficient to provide assurance of safety and efficacy
-ex: surgical tools, bandaids, stethoscope, floss, bone cement
Class II: medium risk, general controls alone are insufficient to provide assurance and safety, subject to mandatory performance standards and post-market surveillance
-ex: breast pump, condoms, motorized wheelchairs, hospital beds, hip implants
Class III: high risk, life sustaining or have the potential to lead to serious injury, subject to pre-market approval
-ex: IUD birth control, cardiovascular stents, breast implants
Understanding of approval process for Class I/II and Class III
Current process of getting device to market
- Me Too Devices (510K Submission): device is substantially equivalent to existing device, costs $2600-$5000
- Pre-market approval device (PMA submission): novel, class III, costs $66k-$260k
Ability to explain the importance and limitations of FDA process
Medical device approval is overseen by the Center for Devices and Radiological Health (CDRH) under the Food and Drug Administration (FDA)
-System is patterned off of the pharmaceutical approval process, system is complex and evolving
-Due to misleading claims and impurity and demand for safer food and drugs - need to show proof if health claims made and scientifically assess purity
FDA: 1. Test drug safety before it goes to market, 2. Brought medical devices and cosmetics under FDA control, 3. Prohibited false claims, 4. Food: addressed packaging, quality and inspections
Must show efficacy and safety
Today’s FDA: established 3 classes of medical devices, required pre-market approval, required safety and efficacy for all devices, required manufacturers to register with FDA and follow quality control procedures (required to report if there is a complication due to the drug or use of device)
Labels required on safe proper use but people can use products off label
Approval under 510k based on previous implant success - so only laboratory tests needed
-Problem with hip replacements that have different materials - metal on metal, caused hip replacements to become Class III device
The debate between what a me too device is and why or why not
Unintended consequence of FDA - sold in Europe first; but starting to combine processes
FDA Safety and Innovation Act 2012
Promote innovation
Drugs: expedited process for drugs that help patients with serious/life threatening disease
Medical devices - FDA provided guidelines to direct clinical trials
Increase stakeholder (patient engagement)
Life/death, quality of life
Enhance safety of drug supply chain
Understand the difference between the 510K and PMA submission process
510k submission (FDA 2012 Act: Time went from ~6 months in 2014 to ~3 months in 2019)
Medical device concept
Establishment registration and device listing
Compliance with Quality Systems Regulation (QSR)
510(k) notification or 510(k) exempt (majority of exempt devices are class I)
If 510(k) notification: 510(k) review
Labeling Requirements
Legally market device
Note: user fees - large business ~$5000, small business ~$2,000
PMA submission (FDA 2012 Act went from ~9 months in 2013 to ~4 months in 2016 and approval went from 70% to 98%)
Medical device concept
Establishment registration and device listing
Preclinical and biocompatibility testing
Significant risk study protocol
Note: both steps 4, 5, 6, and 7 studies must show safety and efficacy, lab and animal studies
Investigational device exemption (IDE) submission
Investigational review board (IRB) review
Clinical Trial
PMA application
Labeling requirements
Legally marketed device
Note: user fees - large business $260k, small business $66k
Purpose and function of the cardiovascular system
Arteries sends oxygen rich blood (nutrients) from the heart to rest of body/muscles (including heart)
Veins transport oxygen-depleted blood (waste) from body to the heart (which is then sent to the lungs)
Purpose: Transport of nutrients, oxygen, and hormones to cells throughout the body and removal of metabolic wastes (carbon dioxide, nitrogenous wastes)
Heart is a muscle - contraction causes increase pressure in order to send blood
-Systolic: pressure during heart beat
-Diastolic: pressure between heart beat
-Normal ~120/80 mmHg
Pressure is testing by applying pressure above systolic pressure until blood flow stops, pressure is released below diastolic and when pressure equals the systolic pressure, blood will resume flow
Heart is a machine - a muscle that feeds itself
Failure of heart: loss of blood supply/fluid flow (atherosclerosis/hardening of vessel wall due to plaque buildup causing heart attack or embolism or aneurysm) - increased flow velocity and decrease in pressure at location of clot; inconsistent signals to muscle/electrical - bradycardia (slower heart beat due to weakened heart after heart attack), not enough blood to body if too slow, but too fast the heart needs to work harder
How the cardiovascular system interacts with the musculoskeletal system and the lungs
Cardiovascular transports nutrients/oxygen to muscles and then transports the depleted blood from the muscles to the lungs to become deoxygenated
When going for a run: oxygen uptake by muscles so decrease in oxygen in blood; to increase/adjust for lack of oxygen - can increase blood pressure (amount of blood pumped) and increase the frequency of heart beat
By having your heart work harder during certain times such as exercise, your heart becomes healthier/resting heart rate is lowered
Range of heartbeats makes monitoring and therefore prevention more challenging (healthy resting heartbeat = 60-100 bpm)
Identify differences between muscle types
Skeletal muscle - voluntary muscle activity, increase in muscle force and muscle length decreases by myosin/actin control
Smooth muscle and Cardiac muscle - involuntary muscle activity
Explain how PPG sensors work and differences between various types of PPGs
Measuring quality of blood circulation - can measure oxygen concentration and heart beat/electrical behavior
PPG - photoplethysmography - method to optically obtain volumetric changes in a an organ/tissue
-have optical emitter and a detector (photodiode): change in output voltage is representative of change in light intensity
-Blood absorbs green light and reflects red light: tradeoffs - greed LEDs provide more reliable and consistent data but red LEDs are more efficient
Pulse Oximetry - red LED
-measures oxygen levels in blood
-normal = 95-100% saturation, below 90% means low blood oxygen (hypoxemia)
-low oxygen levels a problem if chronic (anemia, sleep apnea, emphysema), at high elevation acute problems
Electrocardiography (EKG) - process of recording electrical activity of the heart
-PPG can detect heart beat but not as accurate as EKG → limitations if attached sensor too loosely/lightly as can have light refraction/noise before hitting skin
Describe how the respiratory system functions normally
Lung anatomy - spongy elastic material, 300 million alveoli, total lung capacity=6L, tidal volume 500mL; alveoli is where gas exchange occurs
1. Trachea
2. Left main stem bronchus
3. bronchi
4. bronchioles
5. alveoli
Other parts: right/left lobes, pleura, pleural fluid, diaphram
Left side is smaller than right side due to heat
Work: contraction of diaphragm, mechanical function with negative pressure
Diaphram contracts - it becomes straightens so it allows for more area for lung to expand and when it relaxes it’s curved
Boyle’s Law: P1V1=P2V2
-Volume increases and pressure decreases w.r.t. atm pressure
Measure normal air function - incentive spriometer (measuring output force by lung), oximetry (measuring lung efficiency (red LED, absorption differences between infrared and red LED gives oxygen levels)
Change in pressure is 0.015 atm for change in volume of 5 L
12-20 breaths per minute (babies breathe faster than that)
