PHLT 432 Exam 2 STUDY GUIDE

Based on Review Slideshow ONLY

List the hierarchy of controls and examples of each.

From most effective to least effective…

• Elimination: Physically removing the hazard

  • Removing a toxic chemical from the facility

• Substitution: Replacing the hazard

  • Exchanging the toxic chemical for a less-toxic chemical

• Engineering Controls: Isolating people from the hazard

  • Designing exhaust hoods to prevent workers from inhaling toxic fumes

• Administrative Controls: Changing the way people work

  • Changing a worker’s schedule to eliminate the amount of time they are in contact with the hazard

• PPE: Protect the worker with personal protective equipment

  • Requiring the worker to wear a hard hat, safety goggles, and a mask

List the definitions and characteristics of anatomy-specific diagnoses and conditions

• Cervical syndrome: painful cramps in the shoulder muscle; can’t move head right/left

  • Pain and reduced mobility in the cervical (neck) spine

  • Can cause painful radiation in the arms

• Chronic low back pain

  • Can be caused by an intervertebral disc rupture or deterioration; nerve will be pressed by bulging disks/pinched or pressed against adjacent vertebra

  • Back pain can also be caused by compression fractures of vertebrae, muscle spasms, scoliosis, kyphosis, and lordosis

• Tendinitis

  • Inflammation of the tendon

  • CAUSED BY arthritis or injury. Common in neck, wrists, lower extremities

• Tenosynovitis

  • Inflammation of the tendon’s synovial sheath (connective tissue around the tendon)

  • Common in wrists and lower extremities

• Bursitis

  • Inflammation of bursa (small connective-tissue sacs to cushion the friction between tissue and bone)

  • Common in lower extremities and shoulders (ex: baseball players get shoulder bursitis commonly)

• Carpal tunnel syndrome: Impairs sensory and motor function of the hand

  • The carpal tunnel is between the forearm and the wrist It has 8 carpal bones and ligaments

  • 9 tendons and a median nerve pass through the tunnel from forearm and hand. When the wrist tendons become irritated and swollen, it compresses the median nerve. You will start to lose feeling in the palm, and then radiating pain

    • Common for people who type a lot

      • Ways to reduce: Don’t type on surfaces with a fixed edge, float wrists away from surface, maintain neutral position of wrist reduce compression of median nerve

What are the CTD (cumulative trauma disorder) risk factors?

There are occupational and biological risk factors. Of course, the big 3 are…

• Force, repetition, and posture

  • 1/3 = Higher probability of CTD

  • 2/3 = Exponential increase in CTD

  • 3/3 = Almost guaranteed likelihood of a CTD

• Most CTDs are caused by repetition. However, most jobs are repetitive in nature, causing a clash in productivity and ergonomics.

  • Ex: Typing → carpal tunnel syndrome

    • Try to reduce repetition or spread pressure

Other risk factors:

• Pregnancy and menopause: Changes in estrogen and hormones

• Diabetes, hypertension, arthritis (causes tendonitis and tenosynovitis)

• Temperature: Cold temperatures are associated with more CTDs

• Vibration: Hand tool vibration causes vibration syndrome (Raynaud’s disease)

• Repeated exposure without adequate rest

  • People who work for long periods of time w/o rest usually have more CTDs

Countermeasures?

• Hierarchy of controls

1991 NIOSH Lifting Guide: Assumptions, Definitions, & Limitations

Assumptions:

• Overexertion is the result of job demands that exceed a worker’s capacity

• These injuries result by direct trauma, overexertion, or repetitive trauma

• Assumes that the L5/S1 vertebral join is the site of the greatest stress during lifting

  • The at risk level for compressive force at this joint is 3400 N.

• Also assumes favorable environment temperatures, assumes predictable situations (no shifting loads), assumes work activities other than lifting are minimal

Applications/Limitations:

• Lifting and lowering tasks are assumed to pose the same risk of injury

• DOES NOT ADDRESS:

  • One handed lifts

  • Lifts while seated or kneeling

  • Lifting in a constrained work area

Multipliers/Starting Points:

• Load constant is always 23 kg or 51 pounds

• *For all 6 factors, always measure at the origin and destination of lift

• You will calculate RWL beginning and RWL end in kg. You will lose the LOWEST value when calculating LI. Remember that LI = LC (the actual weight of whatever object) / RWL.

How do you interpret results for RWL/LI?

• The LI (lifting index) should always be less than 1.0 to prevent lower back injury. So if you get a LI of 1.3, you are 30% over where you should be, and will need to adjust the limiting factor from the RWL.

Limiting Factors:

• The smallest multiplier inflicts the biggest mathematical penalty on the RWL, dropping the allowable weight limit lower and lower. This is important for ergonomists because it tells you exactly what to fix first. If HM is the lowest, you’d bring the object closer to the body because it would yield the biggest improvement.

RULA

What are the groupings?

• Group A: Upper arm, lower arm, wrist, wrist twist

• Group B: Neck, trunk, legs

• Postural scores are ordered from 1 for good to 4 for very bad

How do you score?

• There is a table and you assign values and then you use like a Sudoko type table to decide a score. YOU NEVER ADD THEM. You also assign values for muscle use and force/load. This will give you Score C (for Group A) and Score C (for Group B). You use another table to get the grand score which is your “Action Level.”

What is your outcome and how do you interpret the outcome?

• Action Levels

  • Action Level 1: A grand score of 1 or 2 indicates that the posture is acceptable (as long as it’s not maintained for long periods)

  • Action Level 2: A grand score of 3 or 4 indicates that further investigation is needed, changes may be required

  • Action Level 3: A grand score of 5 or 6 indicates that investigation and changes are required soon

  • Action Level 4: A grand score of 7+ indicates that investigation and changes are required immediately.

• Limiting factors

  • The group with the highest score (upper arm, lower arm, wrist, wrist twist, etc.) drives the score to be higher. This leads to negative outcomes like CTDs. Therefore, we should focus efforts and resources here (hierarchy of controls)

Training

• Hawthorne Effect

  • Short-term improvements that results from a trainer/supervisor watching the trainee; causes people to act differently (and usually better)

• Potentially useful content areas (training value is questionable)

  • Specific lifting techniques, like skill improvement

  • Training in biomechanics, awareness, and self-responsibility for back injuries → attitude change

  • Training body via physical fitness so that it’s less susceptible to injury

• Best practices for lifting

  • “Lift with your legs, not your back” is generally not useful

  • Design manual lifting and lowering to prevent human error and injury

  • Think before acting, have handling aids, do not twist or bend sideways, do not lift or lower, push or pull awkwardly, do not hesitate to get help (mechanical or coworker help), do not lift or lower with arms extended, do not continue heaving when the load is too heavy

  • Use carts or conveyor belts

How do the 3 different components of decision-making effect choices?

Task, person, context

• Task

  • Goals, frequency, hazards, steps

  • Ex: Let’s say your task is to write an essay. You do this frequently (monthly) and there are very few hazards

• Person

  • Cognitive processes, demographics, physical attributes

  • You use your long-term working memory and upper extremities to type. Your motivations could be to just finish or to get a good grade.

• Context

  • Environment, psychosocial, tools/artifacts

  • You are writing the essay inside, have pressure from your psychosocial environment (grades matter), and use a typewriter or computer as your tool

What are the 3 classes of decisions?

• Rational/normative

  • How people “should” make decisions. Focuses on pros and cons.

  • Studies how far people have departed from the normative (optimal) choice

  • Ex: Making a spreadsheet to decide on the most optimal product.

• Naturalistic

  • When you have to make a decision in a real-world environment with complexity, time contraints (usually experts use this one)

  • Ex: Experienced firefighter relies on pattern recognition to tell everyone to run out of a burning building

• Cognitive/information processing

  • Heuristics: Mental shortcuts when there are contraints, “this is good enough,” rule of thumb

  • Focuses on how people made that decision and the biases that led to it (how the mind works through

What role do the different issues with cues have on decisions?

• Salience: How physically noticeable or prominent a cue is (flashing red light vs. quiet gauge)

  • A low-value cue with high salience (something loud but unimportant) can steal your attention away from critical, subtle data which leads to poor choices

• Modulation: How much weight your brain assigns to each cue when multiple sources are present

  • If multiple cues are given equal weight, there is generally no effect on decision-making, but if one improperly over-weights, the decision breaks down.

• Missing or Unexpected Cues: Cues are not present or different than expected

  • Causes expert intuition (RPD) to fail. 3 Mile Island - key cues were misleading and operators failed to recognize a coolant loss scenario.

• Cue Diagnosticity and Human Perceptual Limits: How accurately a cue diagnoses the true state of the system

  • Humans are bad at estimating certain types of cues such as rare events, non-linear trends, and small differences a thigh simulation (Weber’s Law)

What is salience and why do you care about it?

Salience is the rate at which a cue stands out to you.

• How physically prominent or noticeable it is with you.

• Something with high salience but low importance (like a red flashing light or an alarm) could take your attention away from things that actually matter.

• So, if you were designing an important Stop button, ergonomists should make sure it has enough salience to ensure that a worker’s attention is drawn to it.

What are the differences between serial and parallel decision making?

Serial search: Looking through a cluttered environment and you must check them all individually (all blue shapes, “find the one diamond”)

Parallel search: Ability to analyze multiple streams of information at the same time. Your brain splits into separate components (Shape, color) so the “pop-out” effect occurs. (Ex: All blue shapes, one red shape, “Find the red shape”)

What effect do different information differences have on decisions?

Complexity, uncertainty, expertise, time

• Time pressure

  • Forces people towards heuristics (rapid intuitive decision making) and RPD

  • Low time pressure allows people to switch to systematic problem diagnosis

  • Also Single-time choices (one decision based on fixed info; immediately determined and unchangeable) vs. Evolving decision (continuous process where choices are made sequentially, allows you to adapt)

• Expertise

  • Can make rapid choices with very little deliberation (RPD)

    • RPD is not advisable without time pressure, with missing cues, or with unexpected cue deviations

  • Novices are more susceptible to information overload

• Complexity

  • Requires brain to modulate and weigh many different cues. Prone to weighing some more than others which would cause a negative outcome

• Uncertainty

  • Causes negative outcomes, prone to bias

  • Uncertainty causes people to think about the consequences; the weight of consequences are different for certain decisions (Buying a car vs, deciding whether to fly a plane), forces people to either use expert testimony or bias like overconfidence

Explain the different biases

• Overconfidence: Prematurely stop seeking new information because they are confident in their own understanding of memory

  • RPD = Recognition primed decision making

• Anchoring: Giving unequal weight to another hypothesis by overvaluing your original hypothesis or “initial impression”

  • “Going with your gut”

• Confirmation bias: Decision-maker actively searches for information that confirms their pre-existing hypothesis.

  • Ignores or discounts evidence supporting alternative explanations

Describe the 2 case studies in the decision-making powerpoint

Three Mile Island: Nuclear Accident in Pennsylvania

• Failure in main feedwater pump stopped water from reaching steam generators, and a pressurizer valve opened. But, the instruments falsely indicated that it was closed because the light was on. Since there were no checks inside the gauges to make sure the reactor was filled with water (people assume that it was always filled with water), there was an exponential loss of coolant. Caused a nuclear meltdown, released chemicals into the air.

• Bias present:

  • Missing and misleading cues: lack of water gauge and false valve indicator light

  • Anchoring and confirmation bias: Operators focused on cues that supported their original hypothesis, ignored signs pointing to severe loss of coolant

  • Evolving decision crisis: Misdiagnoses compounded over time

Morton-Thiokol Inc: NASA Space Shuttle Disaster

• Morton-Thiokol manufactured rocket boosters for NASA. Normal risk failure was low, but data showed a clear relationship between failure and temperature (selective data bias)

• Leading up to the launch, NASA faced a lot of organizational pressure (previous launch failures, funding issues, goals, etc.)

• Bias present:

  • Confirmation bias and selective data filtering: Relationship between temperature and failure was clear but not analyzed because decision-makers just wanted to data to confirm their desire to launch

  • Overconfidence: NASA exhibited overconfidence in past flight success and stopped their search for deeper evaluation too quickly

  • This was a single time event: Fly/no fly

What makes an ideal gas exchange, how do the lungs fulfill this model, and why are these characteristics important to work physiology?

• ALVEOLI: Large contact area and very thin membrane separating blood and air, maximizes diffusion speed

• NASAL CAVITY: Air conditioning with heat and moisture (humidity) - air is cooled to body temperature (around 37 degrees C) and saturated with moisture by nose and mouth membranes. This protects delicate lung tissues

• PULMONARY ARTERIOLES AND BRONCHIOLES: Even blood and gas distribution (minimize variation in blood levels of oxygen and carbon dioxide leaving the lungs)

• CARDIAC AND RESPIRATORY SYSTEM: Metabolic adaptability: System should adjust ventilation rates to adjust to the carbon dioxide and oxygen needs of the body

***Always moves from an area of high concentration to low concentration (down the gradient)

Allows us to match a worker’s gas physical work capacity to the demands of the job

What are the pathways for gas exchange and blood throughout the combined systems?

1. Venous (deoxygenated blood) goes into the right atrium via the vena cava.

2. From right atrium, it moves into the right ventricle (through the tricuspid valve)

3. From the tricuspid valve, it moves into the pulmonary artery through the pulmonary valve

4. Moves into the lungs where gas exchange occurs. In the lungs, gas exchange occurs across the thin alveolar-capillary membrane via passive diffusion. Oxygen diffuses into red blood cells and binds to hemoglobin, while carbon dioxide diffuses out into the alveoli for exhalation

5. Oxygenated blood comes back into the left atrium through the pulmonary vein. Enters the left ventricle through the mitral valve.

6. Then from left ventricle moves into the aorta to distribute oxygenated blood to the whole body

What are the mechanisms for gas exchange and what effects do the passive and active breathing mechanics play in gas exchange?

Mechanisms for gas exchange:

• Oxygen diffusion: Inhaled air reaches the alveoli. Because partial pressure here is high, around 100 torr, oxygen diffuses across the capillaries into the blood. Oxygen binds to the hemoglobin on red blood cells at a 98% saturation rate, pH is 7.4. Blood reaches muscle tissue where O2 partial pressure is low (only 20 torr) and pH is lower due to CO2 and metabolic waste. Oxygen unbinds from hemoglobin and diffuses into muscle tissue cells.

• CO2 elimination: Once hemoglobin drops off its oxygen, it binds to CO2 waste from the muscle and carries it back through the venous system to the lungs to be exhaled and starts the process over again.

Pressure Mechanics:

• Negative pressure = INHALATION

  • Diaphragm contracts and moves down, intercostal muscles lift and expand the ribcage

  • Diaphragm and intercostal muscles expand the volume of the pleural cavity, and the air inside the lungs is below the atmospheric pressure (creates NEGATIVE PRESSURE)

    • Air naturally flows from high atmospheric pressure outside the body to lower pressure in the alveoli. This supplies fresh oxygen for gas exchange

  • Positive pressure = EXHALATION

    • When you exhale, you have a higher pressure inside your lungs because the volume of the thoracic pleural cavity smaller.

    • This is exactly why CO2 air is released; because it moves from higher pressure inside the lungs to the lower pressure outside of it

Passive and Active Breathing:

• Passive breathing = resting respiration

  • Exhalation is passive, it relies mostly on natural recoil of lungs

  • Creates gentle positive pressure without extra energy expenditure

• Active breathing = forced respiration during work

  • When work demands increase, respiration transitions into active breathing

  • Exhalation is much more forceful and inhalation is too, to sustain dynamic metabolic capacity

    • Also needs to release more CO2 to prevent acidosis and get more oxygen in

What does oxygen consumption look like as it relates to changes in job demands, intermittent work, and prolonged work?

Oxygen debt will become too large if job demands exceed physical work capacity and max oxygen intake

• In LISS (low intensity steady state), it levels out after 3-5 minutes. Uses carbs and fats for energy

• In HIIT (high intensity training intervals), it bounces up and down and until your body becomes exhausted. No steady state. Uses carbs because its mainly anaerobic work

What are the components of blood and cells? What are their roles?

• Red blood cells: Function primarily to transport oxygen from the lungs to active tissues, and CO2 waste back to the lungs

  • Formed in the bone marrow, lifespan around 120 days

• Hemoglobin: Found within red blood cells

  • Heme: Red-pigmented, iron containing protein (grabs onto oxygen)

  • Globin: Large polypeptide protein (holds heme together)

  • Hemoglobin exhibits a loose, reversible binding affinity for oxygen and CO2. Purpose is to allow loading and unloading across pressure gradients (easily takes in oxygen and releases it in the muscles, and picks up CO2 to take it back to the vena cava)

• White blood cells: Function is to destroy and remove foreign materials from the body; part of the IMMUNE SYSTEM

  • There are around 5000 WBCs per cubic millimeter of blood

• Platelets: Assist in blood clotting (coagulation) to stop bleeding when blood vessels are injured

  • Form scabs!

  • There are around 250,000 platelets per cubic milimeter of blood

What are the inputs and outputs of the metabolic processes for both anaerobic and aerobic capacities?

ANAEROBIC (no oxygen)

• Input is 1 glucose molecule (usually from carbs you eat or stored in glycogen)

• Output is 4 gross ATP, 2 net ATP, 2 pyruvic acid (which becomes lactic acid when there is no oxygen), and heat which is evaporated

AEROBIC (WITH OXYGEN)

• Inputs are 2 Pyruvic acid, 6 O2, 6 H2O

• Outputs are 36 ATP (net and gross), 6 CO2, 12 H20 (6 net H2O)

What are the differences between maximal and submaximal stress tests?

Maximal: Very fatiguing and dangerous (high injury rate)

• Work output is increased to identify the point at which oxygen uptake stabilizes

• Measures oxygen uptake

Submaximal: Less fatiguing and less dangerous, but much less accurate

• Assumes linear relationship between heart rate and oxygen consumption

• Max heart rates are only estimated based on age

You need to go through and practice all of the calculations

I did it and did practice examples from gemini

• Energy estimation

• BMR

• Astrand nomogram

• PWC predictive calculations

• Step test

• TLV for whole body vibration (just look up in table) and segmental (x, y, z axis)

• Grip force calculation

Explain the difference between resonance and attenuation.

Resonance: Excitation matches natural frequency, causing motion amplification

• Ex: Tacoma Narrows Bridge collapse (winds matched the bridge’s natural frequency, causing energy to build up and amplitudes to grow uncontrollably)

Attenuation: Isolation/reduction in the value of the vibration

• Ex: A technician wearing a lead apron during an X-Ray; dense lead absorbs and scatters the rays

Explain spectral analysis

Using 1/3 octave frequency analysis to decompose complex multi-frequency vibration into bands matching human psychological sensitivity

Piezoresistive acceleromters vs. piezoelectric acceleromters

Piezoresistive: Substance sits under. amass. As the sensory moves, the mess presses on the substrate. An external power source sends currents through the substrate and the sensor measures how much resistance changes. BEST FOR LOW FREQUENCY VIBRATIONS like WHOLE BODY VIBRATION

Piezoelectric: Crystal sits next to the mass. When a tool vibrates, it shakes and creates an electrical signal and produces voltage. BEST USED FOR HIGH FREQUENCY VIBRATIONS like SEGMENTAL HAVS

Physical effects of whole body vibration vs segmental/HAVS (hand arm) vibration

WBV:

• Spinal and muscoskeletal damage (increases risk of chronic low back disorders and spinal strain)

• Motion sickness

• Elevated cardiac and pulmonary responses, increased metabolic demand, and involuntary contractions

• At each frequency something new happens to your body. Ex: 4-8 hz is spine resonance but 30-60 hz is eye resonance and impaired visual acuity

HAVS:

• Raynaud’s syndrome and vibration white finger

  • Causes spasms in the blood vessels of the fingers

  • Leads to blanching (fingers turning pale/white), severe cold sensitivity, reduced blood flow

  • Categorized by Stockholm Workshop Scale (stage 1 is mild blanching to Stage 4 is severe blanching with skin changes)

• Numbness and tingling in hands

• Muscle fatigue, decreased grip strength, and loss of motor control. Which would force workers to apply higher grip forces (poor coupling) when operating tools