HLTH 640 Physio.docx.pdf

Introduction and Atmosphere

Human factor – how you interact with the aircraf

The atmosphere

o60 miles tall

o5 layers

oComposition

Nitrogen 78%

Oxygen 21%

Argon 1%

Co2 1%

Etc 1%

oAtmospheric pressure

Basis for most physiological problems in aviation

Pressure change per 1000 feet is greater at lower altitude

oMeasuring pressure

Atmospheres (atm)

1atm

Psi

14.7 at sea level

mmHg

29.92 inches

oMSL

True altitude (how high you are in atmosphere

oAGL

Above ground level (how high you are above the ground)

oFL180 (18k feet)

Pressure altitude

Used above 25k feet

oTemperature change

2 degrees C or 3.5 F per 1k feet climb

oTroposphere

FL300-600

oStratosphere

30 miles

oPhysiological Dvisions

Physiological Zone

10k feet

Physiological Deficient Zone

10k-50k

522mmHg

Required to have supplemental oxygen on board

Space Equivalent Zone

50k+

87mmHg

Gas Laws

oDalton’s Law

The total pressure of a mixture of gasses is equal to the sum of the partial

pressures of each gas in the mix

oBoyle’s Law

At constant temperature, the volume of gas varies inversely to its pressure

Gas expansion

Wet gases expand more rapidly than dry

You’re made of liquid gas

Fart in the tank, don’t hurt yourself

oHenry’s Law: Dissolved Gases

The amount of gas in a solution varies directly with the partial pressure of that

gas over the solution

Affected by

Solubility of gas

Temperature of liquid

Partial pressure of gas

Significance

Evolved gas disorder

Causes decompression sickness

oGaseous Diffusion

Gases move from area of high to low concentration

Significance

Movement across alveolar-capillary membrane

Respiration and Circulation

Respiratory System

oRespiration

Ventilation, diffusion, transportation, utilization of gases between a living

organism and its environment

oFunctions

Condition air

Warm

Humidify

Filter

Gas exchange

Temperature regulation

Metabolic function

Maintain acid-base balance (pH) of blood

oRespiration control

Subconscious 12-16 breaths per minute at rest

oVentilation Phase

Breathing in is active

Breathing out is passive

oDiffusion

Oxygen exchange in blood

oComposition of Inspired air

Sea level - 98

10k ft – 87

FL340 with 100% oxygen

98

FL400 with 100% oxygen

87

Factors in Oxygen Delivery

oAltitude

oG Force

oToxic Gas

oDehydration

Altitude Threats

Hypoxia

oState of oxygen deficiency

oTypes:

Hypoxic (Alt)

Most dangerous

Reduced oxygen

Recognize teammate Symptoms:

oCyanosis (blue lips/fingernails)

oDecreased reaction time

oEuphoria

oBelligerence

oImpaired judgment

oIncreased respiration

oMental confusion

oMuscle incoordination

oUnconsciousness

oDysphoria (state of unease or generalized dissatisfaction)

Recognize subjective symptoms

oAir hunger

oApprehension

oDizzy

oFatigue

oHeadache

oHot/cold flash

oNausea

oNumbness

oTingling

oTunnel Vision

oVisual Impairment

oEuphoria

oDysphoria

Time of useful consciousness (TUC)

oAbility to think and act

oFactors

Altitude

Rate of ascent

Duration at altitude

oFL180

20-30 min

oFL250

3-5 min

oFL350

30-60 seconds

oFL400

15-30 seconds

Proactive

oPRICE Check

Corrective procedures

oOn 100% O2 emergency pressure

Slam all three up

oMask on

oCheck regulator & connections

oControl breathing

Pressure breathing

oInhale slowly… pause…. Exhale forcefully…. Pause

Oxygen paradox

Symptoms

oConfusion

oWorsened Vision

oLoss of consciousness

May occur upon reoxygenation afer severe or prolonged hypoxia

Hypemic (blood)

Reeducation in O2 carrying capacity

Stagnant (no-flow)

Restricted circulation

Histotoxic

Inability of the tissues to accept or utilize O2 due to poisoning of the

cells

oAlcohol & smoke

Hypocapnia

oVentilation > Metabolic need to eliminate CO2

oDon’t panic, control breathing

oSame correction as hypoxia

Trapped gas disorders

oEar block

Mostly a problem when descending

Valsalva on decent only

Keep Afrin on person

Delayed blocks afer breathing 100% O2

oSinus block

Air bubble trapped in sinus

Severe sudden pain

Only upper teeth

Ground aircrew

Don’t fly while sick

oGI pain

Limit high fiber food

Usually starts above FL180

oTeeth

Gas pocket in tooth

Any tooth

oLunges

Breath normal when decompression occurs

Decompression sickness (DCS)

oHenry’s Law

Nitrogen in blood settles in various parts of body

Can push on nerves and blood vessels

oTypes

Musculoskeletal (Bends)

Joint and or muscle pain

Skin (Creeps)

Tingling, hot and/or cold sensation, numbness, pins and needles

Respiratory (Chokes)

Deep sharp pain under sternum

Dry, progressive cough

Neurological manifestations (CNS)

Severe headache and visual disturbance

Most severe, life threatening

Permanent damage

oOnset of DCS

Immediate

Symptoms may resolve upon return to ground level

Delayed

50% of cases develop within 1 hour of exposure

Up to 24hrs afer

oPrevention

Pre-oxygenation (chamber)

In flight below FL180

oDenitrogenation

30 min – 33%

oDCS treatment

Immediately

Notify aircraf commander or declare IFE

Descend < FL180

100% O2 via tight fitting mask

Immobilize affected area

Seek qualified medical personnel

72-hr DNIF minimum

Review Questions

oLand as soon as practical, not as soon as possible

oDuring ascent gases trapped in body will expand

o4 area of the body influenced by

oDCS nitrogen comes out

Situational Awareness

A continuous perception of self and aircraf in relation to the dynamic environment of flight,

threats, and mission, and the ability to forecast, then execute tasks based on that perception

Mechanisms

oVisual

Primary

oAuditory

oVestibular System

oSomatosensory System

Conscious processing

oSlow, limited storage

oAccurate, high reliability

Subconscious

oFast, multitasking

oUnreliable in “vision limited” environments

Primary components of SA

oGeographical

Location of own/other aircraf, terrain

oSpatial/Temporal

Altitude

Levels of SA

oLevel 1 (Basic)

Perception of environmental elements

oLevel 2 (Intermediate)

Comprehension of current situation

oLevel 3 (Advanced)

Predication of future

Attention Management Threats (AMT)

oThe most predominant attention management threats are captured in the person-level

factors section and categorized physical and mental state

Cabin Pressurization

Isobaric Schedule

oEnsures multi-place aircraf cabin altitude remains below 10k f with an 8 to 9 psi

differential

Isobaric differential

o5 psi differential

Advantages

oDecreased risk of hypoxia

oMobility

oTemperature regulation

oImproved comms

Disadvantages

oCabin decompression risk

oNeed to minimize cabin contaminants

oImpact on aircraf performance

oIncreased maintenance costs

Cabin Decompression

Slow

Rapid

o0.5 to 15 seconds

Explosive

o0.2-0.5 seconds

Rapid Decompression

Factors

Cabin volume

Size of opening

Pressure differential

Cabin altitude

Spatial Disorientation

Orientation is the interpretation of one’s linear and angular position and motion relative to the

plane of the Earth’s surface.

SD Classification

oUnrecognized

Most dangerous

oRecognized

oIncapacitating

Vestibular System

oSemicircular Canals

Detect rotation

Threshold of 2 degrees per second

Adaption <30 sec to constant angular motion

oOtoliths

Linear acceleration detection

oVestibular system is designed to work in a 1G environment

Vestibular illusion

oFalse pitch up/down

Somatotropic illusion

oG-Excess Effect

Happens in turn

oThe Leans/Graveyard Spiral

Incorrect feeling of bank

Enter a sub-threshold bank – unrecognized

Enter a supra-threshold bank – recognized

oCoriolis Illusion

Multiple planes of rotation

oNystagmus

Repetitive eye reflex that affects vision

Can lead to significant disorientation

Potential SD Inducers

oLack of visual reference

oConflicting orientation cue

oAcceleration

oRotation in multiple planes

oSelf and mission-imposed stress



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