Flight Physiology 101

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Flight Physiology 101

• Jeremy Maddux, NREMTP

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Functions of the Atmosphere

• Source of oxygen and carbon dioxide
• Shield against cosmic and solar radiation
• Protective layer that consumes debris from space
• Source of rain
• Maintains the temperature and climate that
  sustain life on earth

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Components of the Atmosphere

• Gas percentages REMAIN THE SAME with changes in
  altitude the NUMBER of molecules in a given
  area decrease with altitude increases
• Gases are compressible therefore pressures vary
  with altitude

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Atmospheric Pressure

• Atmospheric (barometric) pressure is the combined
  weight of all the atmospheric gases, creating a
  force upon the surface of the earth the cause
  of this force is gravity
• The pressure of a column of the atmosphere can be
  measured in force / unit area
• Pounds per square inch
• Millimeters of mercury
• Inches of mercury (Hg)

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Average Barometric Pressures
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Measures of Altitude

• True Altitude
• Altitude above mean sea level
• Absolute or Tapeline Altitude
• Altitude of aircraft above the surface
• Pressure Altitude
• Flown over the continental US above 18,000 feet
  and are referred to as flight levels
• i.e., 18,000 feet FL 180

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Measures of Altitude

• An Altitude Reference standard day conditions
• When the pressure is 29.92 inches of Hg (760 mm
  Hg) and the temperature is 59º F ( 15º C) a
  standard day exists
• As barometric pressure changes locally, this
  altitude changes
• Reflects standard conditions at sea level

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Physiologic Divisions of the Atmosphere

• Physiologic Zone
• Physiologically Deficient Zone
• Partial Space Equivalent Zone
• Space Equivalent Zone

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Physiologic Zone

• Sea level to approximately 10,000 feet
• Some references state 12,000 feet
• The human body is adapted in this zone
• Barometric pressure drops from approximately 760
  mm Hg to 485 mm Hg in this zone
• Zone where non-pressurized aircraft operate safely

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Physiologic Zone

• Problems may develop in individuals who are
  exposed to higher altitudes than they are
  normally exposed if they
• Remain at the altitude for prolonged periods
• Exert themselves

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Physiologic Zone

• Symptoms of Prolonged Exposure
• Shortness of breath
• Dizziness
• Headache
• Sleepiness
• Sinus and ear disturbances

• Treatment
• Supplemental oxygen
• Descent

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Physiologically Deficient Zone

• 10,000 to 50,000 feet (or FL 500)
• Most commercial aviation occurs in this zone
• Human survival in this zone depends on
  pressurized cabins and/or supplemental oxygen
• Barometric pressure drops to 87 mm Hg in this
  zone
• Because of the reducing atmospheric pressure,
  hypoxia is a problem during ascent without
  artificial atmosphere

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Partial Space Equivalent Zone

• 50,000 feet to 120 miles
• Similar to space
• Pressurized suits required
• Changes in gravity affect the body

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Space Equivalent Zone

• Above 120 miles
• Artificial atmosphere/pressure suits mandatory
  for life
• Weightlessness effects
• Outer space

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Gas Laws

• The body responds to barometric pressure changes
  in temperature, pressure, and volume.
• Boyles Law
• Henrys Law
• Charles Law
• Daltons Law
• Grahams Law

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Boyles Law

• At a constant temperature, a given volume of gas
  is inversely proportional to the pressure
  surrounding the gas
• A volume of gas expands as the pressure
  surrounding the gas is reduced
• As altitude increases / gas expands and as
  altitude decreases / gas compresses

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Boyles Law

• Boyles Law Formula
• P1 x P2 P2 x V2 or V2 (P1V1) P2
• Where
• P1 initial volume (original altitude)
• P2 final pressure (maximum altitude enroute)
• V1 initial volume (volume of gas at original
  altitude)
• V2 final volume (volume of gas at maximum
  altitude)

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Boyles Law

• Example
• A patient with a pneumothorax (without
  intervention) has 500cc of trapped gas within the
  lung at liftoff from sea level (760 mm Hg). The
  flight travels up to 6,000 ft where barometric
  pressure is 609 mm Hg.
• P1 760 V2 (760 x 500) 609
• P2 609 V2 623cc
• V1 500 V2 final volume of trapped air

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Boyles Law

• Clinical Significance
• The amount of volume expansion is limited by the
  pliability of the structure or membrane which
  encloses the gas
• PASG or Air Splints
• Respiratory Rate and Depth changes
• Flow rates of IV sets
• ETT or Tracheal cuff pressures
• Trapped gas effects within the body

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Henrys Law

• The amount of gas in solution is proportional to
  the partial pressure of that gas over the
  solution
• As the pressure of the gas above a solution
  increases, the amount of that gas dissolved in
  the solution increases
• Reverse is also true, as the pressure of the gas
  above a solution decreases, the amount of gas
  dissolved in the solution decreases and forms a
  bubble of gas within the solution

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Henrys Law

• In normal physiologic function, this law can be
  seen in the transfer of gas between the alveoli
  and the blood
• This is significant physiologically for the
  occurrence of evolved gas disorder, aka
  decompression sickness
• Explains the hypoxia experienced with increasing
  altitude as the pressure of gases is reduced
  with ascent, the amount of gases dissolved in
  solution decreases and this leads to hypoxia and
  may lead to nitrogen bubble formation

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Henrys Law

• Henrys Law Formula
• P1 A1 P2 A2
• Where
• P1 original pressure of the gas above the
  solution
• P2 final gas pressure above the solution
• A1 amount of gas dissolved in solution at the
  original pressure
• A2 amount of gas dissolved in solution at the
  final pressure

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Henrys Law

• Example
• Bottle of soda
• With the cap on, the gas within the solution is
  at equilibrium
• With the cap removed, the gas pressure decreases
  and bubbles are released into the solution

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Charles Law

• The pressure of a gas is directly proportional to
  its temperature with the volume remaining
  constant
• Temperature increases make gas molecules move
  faster, and greater force is exerted and volume
  expands
• The law explains the temperature changes
  associated with rapid decompression, and pressure
  changes inducing temperature changes with an
  oxygen cylinder

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Charles Law

• Charles Law Formula
• V1 T1 V2 T2
• Where
• V1 initial gas volume
• V2 final gas volume
• T1 initial absolute temperature
• T2 final absolute temperature
• Example
• Shaving cream can placed into fire

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Daltons Law

• Describes the pressure exerted by a gas at
  various altitudes (pressures)
• Each gas present in the atmosphere contributes to
  the total
• The sum of the partial pressures is equal to the
  total atmospheric pressure

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Daltons Law

• As altitude increases gases exert less pressure
• Explains the hypoxia that occurs with flight to
  higher altitudes
• Example
• Oxygen at sea level
• O2 21 and PO2 21 x 760 mm Hg 159.22 mm Hg
• Oxygen at 8,000 feet
• O2 21 and PO2 21 x 565 mm Hg 118.65 mm Hg
• THE PECENTAGE OF OXYGEN REMAINS THE SAME with
  changes in altitude

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Daltons Law

• Daltons Law Formula
• Where
• Pt P1 P2 P3Pn
• Pt total pressure
• P1Pn partial pressures of constituent gases of
  the mixture

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Daltons Law

• Air sample at seal level
• pO2 160 mm Hg 21
• pN2 593 mm Hg 78
• other 7 mm Hg 1
• 760 mm Hg 100

• Air sample at 18,000 feet
• pO2 80 mm Hg 21
• pN2 296 mm Hg 78
• other 4 mm Hg 1
• 380 mm Hg 100

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Grahams Law

• Law of gaseous diffusion
• Gases diffuse or migrate from a region of higher
  concentration (or pressure) to a region of lower
  concentration (or pressure) until equilibrium is
  reached
• The physiological significance is in the
  explanation of gas exchange
• Oxygen moves from the alveoli into the blood and
  from the blood into the tissues due to this
  phenomenon

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The Stresses of Flight

• Areas or methods in which persons involved in
  flight (patients and crew members) may be
  physiologically affected by the flight
  environment
• Stress is anything that places a strain on the
  ability of a human to perform at optimum level

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Types of Stresses

• Physical
• Size
• Shape
• Build
• Physiological
• Sleep State
• Fatigue
• Alcohol

• Psychological
• Mental State
• Psychosocial
• Motivation
• Goal Direction
• Money
• Family
• Pathological
• Health / Wellness

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The 9 Stresses of Flight

• Hypoxia
• Barometric Pressure
• Thermal
• Gravitational Forces
• Noise

• Vibration
• Third-Spacing
• Decreased Humidity
• Fatigue

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Hypoxia

• A state of oxygen deficiency sufficient to impair
  function
• There are four types
• Hypoxic hypoxia
• Hypemic hypoxia
• Stagnant hypoxia
• Histotoxic hypoxia

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Hypoxic Hypoxia

• AKA Altitude Hypoxia
• Due to a lack of oxygen available for gas
  exchange within the alveoli
• Causes
• Decreased partial pressure of oxygen in inspired
  air
• Airway obstruction
• Ventilation / Perfusion defects

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Hypoxic Hypoxia

• Occurrences
• Improper function of oxygen delivery equipment
• Loss of cabin pressurization
• No use of supplemental oxygen with sustained
  cabin altitudes above 10,000 feet
• Also seen in drowning victims or strangulation
  victims

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Hypoxic Hypoxia

• As altitude increases the partial pressure (PaO2)
  decreases (Daltons Law)
• As the PaO2 falls in the alveoli, the amount of
  O2 which diffuses into the blood decreases
  (Henrys Law)
• Results in a decrease in oxygen available to the
  tissues

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Changes in Oxygen Saturation in the Blood with
Altitude Increases
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Hypemic Hypoxia (Anemic)

• The inability of blood to accept sufficient
  oxygen
• A reduction in the oxygen-carrying capacity of
  the hemoglobin (Hgb)

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Hypemic Hypoxia (Anemic)

• Causes
• Anemia
• Blood Loss / Donation
• Carbon Monoxide (CO) Poisoning
• Sickle Cell Disease
• Sulfa Drugs
• Excessive Smoking (related to CO levels)

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Stagnant Hypoxia

• Pooling of blood causes insufficient flow of
  oxygenated blood to tissues
• Oxygen deficiency due to lack of movement of
  blood within the body

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Stagnant Hypoxia

• Causes
• Gravitational Forces
• Temperature Extremes
• Prolonged Positive Pressure Breathing
• Hyperventilation
• Regional Vasoconstriction (e.g., tourniquets)
• Heart Failure
• Compromised Cardiac Output States

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Histotoxic Hypoxia

• Inability of tissue cells to accept and utilize
  oxygen
• Metabolic disorder of the cytochrome oxidase
  enzyme system

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Histotoxic Hypoxia

• Causes
• Cyanide Poisoning
• Phosgene Gas
• Carbon Monoxide (CO) Poisoning
• Alcohol Ingestion
• Narcotics

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General Causes of Hypoxia

• All hypoxias are additive
• All hypoxias are insidious in presentation
• All hypoxias cause intellectual impairment
• All hypoxias occur between 15,000 and 35,000 feet
• REMEMBER AT 18,000 FEET
• YOU ARE AT ½ ATMOSPHERE

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Signs / Symptoms of Hypoxia

• Symptoms are the same regardless of the nature of
  the hypoxia
• Early symptoms mimic alcohol intoxication or
  extreme fatigue
• Each persons symptomology will vary as
  tolerances to hypoxic states vary
• Each crew member must be familiar with their own
  symptoms and must observe their coworkers for
  presentation symptomology

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Subjective (felt by you)Signs / Symptoms of
Hypoxia

• Apprehension
• Blurred or double vision
• Night vision decrements
• Dizziness
• Fatigue
• Headache

• Hot / Cold flashes
• Nausea
• Numbness
• Tingling
• Euphoria
• belligerence

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Signs / Symptoms of Hypoxia

• Night vision decrements
• Night vision is very subjective to hypoxia
• Night vision is reduced by 25 at 8,000 feet
• Cabin altitudes of 5,000 feet can alter night
  vision
• Night vision adaptation requires 30 minutes
• Looking at bright or white light erases
  adaptation and requires a re-adaptation period

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Objective (noticed by others)Signs / Symptoms of
Hypoxia

• Increased rate of breathing
• Cyanosis (late sign)
• Impaired task performance
• Loss of muscle coordination
• Mental confusion
• Unconsciousness

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Symptomology Altitude Frequency of Occurrence
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Stages of Hypoxia

• There are 4 general stages
• Indifferent Stage
• Compensatory Stage
• Disturbance Stage
• Critical Stage

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Indifferent Stage

• Sea Level to 10,000 feet
• O2 saturation 90 to 98
• Stage of normal operations
• Symptomology may appear with higher altitudes of
  this range
• Most persons unaware of symptoms
• Most common symptoms are increases in respiratory
  rate and decreases in night vision

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Compensatory Stage

• 10,000 to 15,000 feet
• O2 saturation 80 to 90
• Symptoms advance from previous stage
• Efficiency is impaired
• Night vision decreases 50

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Compensatory Stage

• Respiratory rate and depth increase related to
  air hunger
• Blood pressure and heart rate increase
• Nausea and vomiting (more pronounced in
  pediatrics)

• CNS Symptoms
• Headache
• Amnesia
• Decreased LOC
• Belligerence
• Fatigue
• Apprehension
• Evidenced by
• Poor judgment
• Impaired coordination
• irritability

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Disturbance Stage

• 15,000 to 20,000 feet
• O2 saturation 70 to 80
• Stage when definitely aware of symptoms
• Previous symptoms increase in intensity

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Disturbance Stage (Symptoms)

• CNS
• Slowed thinking
• Impaired mental functioning
• Impaired short-term memory
• Dizziness
• Sleepiness
• Loss of muscle coordination

• Sensory
• Increase in visual disturbances
• Mainly peripheral
• Tunnel vision
• Numbness
• Decreased awareness of pain
• Decreased sense of touch

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Disturbance Stage (Symptoms)

• Personality
• Euphoria
• Aggressive or belligerent
• Depression
• Over confident

• Performance
• Decreased coordination
• Slowed speech
• Impaired handwriting
• Cyanosis

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Critical Stage

• 20,000 to 30,000 feet
• O2 saturation 60 to 70
• Symptomology
• Mental confusion
• Incapacitation
• Unconsciousness
• Seizures
• Inability to remain upright
• Coma and death
• Ignored signs and symptoms of hypoxia can result
  in death

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Time of Useful Consciousness (TUC)

• The interval of time from interruption of an
  adequate oxygen supply to the tissues to the loss
  of the ability to help yourself
• The TUC is the time that the crew member has
  before LOSING CONSCIOUSNESS from hypoxia!
• This is the amount of time the crew member has to
  self-administer oxygen in order to maintain
  consciousness at higher altitudes
• DO NOT CONFUSE WITH EFFECTIVE PERFORMANCE TIME
  (EPT)

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Effective Performance Time (EPT)

• The amount of time a crew member can effectively
  function with an insufficient supply of oxygen
• NOT TIME OF USEFUL CONSCIOUSNESS (TUC)

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Time of Useful Consciousness (TUC)

• Explained by the gas laws
• Henrys Law
• O2 levels in the blood decrease in response to
  lower PaO2
• Law of Gaseous Diffusion
• Diffusion of gas from an area of higher
  concentration to an area of lower concentration
• The greater the gradient the faster the rate of
  diffusion and thus a rapid drop in TUC with
  increases in altitude

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Time of UsefulConsciousness (TUC)
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Time of UsefulConsciousness (TUC)

• A rapid decompression can reduce the TUC by 50
• Flight team members must be aware of their status
• Those who become incapacitated are a risk not
  only to themselves but to their patients and
  partners as well

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Factors Involved in Hypoxia

• Altitude
• Rate of ascent
• Duration of exposure
• Individual tolerance

• Physical fitness
• Physical activity
• Environmental temperatures
• Self-imposed stresses

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Prevention of Hypoxia

• Cabin pressurization (discussed later)
• Supplemental oxygen
• Ensures adequate oxygen deliver to lungs
• Oxygen adjustment calculation
• Used to calculate increase in oxygen delivery to
  compensate for decreases in PaO2 associated with
  altitude

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Oxygen Adjustment Calculation

• IO2 x BP1
• BP2
• Where
• BP1 barometric pressure prior to ascent
• BP2 barometric pressure at altitude
• IO2 inspired O2

IO2 required at altitude
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Oxygen Adjustment Calculation

• Example
• A patient is flown from seal level (760 mm Hg) to
  5,000 feet (632 mm Hg)
• 21 x 760
• 632
• Example
• A patient on .50 IO2 is flown from sea level (760
  mm Hg) to 5,000 feet (632 mm Hg)
• 50 x 760
• 632

.25 IO2 required
.60 IO2 required
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Oxygen Delivery / Adjustment Altitude Chart
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Positive Pressure Breathing

• Method of maintaining an adequate alveolar pO2 at
  high cabin altitudes (above 40,000 feet)
• Positive pressure drives the O2 to diffuse
• Causes a reversal of the breathing cycle to
  passive inspiration and very active expiration

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Positive Pressure Breathing

• Tendency to hyperventilate must be monitored, and
  controlled with training
• Use is limited in duration due to physiological
  effects of decreased venous return to the heart
  (stagnant hypoxia)
• Other limitations include very difficult speech
  over forced airflow, poor communication, and a
  feeling of claustrophobia in some individuals

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Treatment of Hypoxia

• Prevention
• Recognition of symptoms
• Monitor patient for symptoms / response
• Supplemental oxygen
• Oxygen cylinder capabilities

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Oxygen Concentration Available with Common
Adjuncts at Sea Level
73
Oxygen Cylinder Capabilities

• 1 cubic foot of gas 28.3 liters of oxygen
• Various cylinder sizes and capabilities
• D cylinder 12.7 cu.ft. 359.4 liters
• E cylinder 22 cu.ft 622.6 liters
• F cylinder 55 cu.ft. 1,556.5 liters
• G cylinder 187 cu.ft. 5,292 liters
• H/K cylinder 244 cu.ft. 6905.2 liters

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Calculation of Duration of Oxygen Availability

• cu.ft. x 28.3 x (PSI 2200)
• liter flow
• Where
• cu.ft. capacity of tank in cubic feet
• 28.3 liters of oxygen per cu.ft. of gas
• PSI Psi reading on gauge of cylinder
• 2200 a constant (maximum psi when full)

duration in minutes
75
Calculation of Duration of Oxygen Availability

• Example
• D cylinder
• 12.7 cu.ft. x 28.3 x (1,500 2,200) 245.05
• 10 liters per minute 10 lpm
• 24.5 minutes of available oxygen

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Liquid Oxygen (LOX)

• Each liquid liter 860.3 gaseous liters
• 860.3 gaseous liters 30.38 cu.ft.
• System capacity varies with size of container
• Common size for HEMS is 25 liquid liters
• 25 liquid liters 21,507.5 gaseous liters
• 21,507.5 gaseous liters 759.5 cu.ft.

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Barometric Pressure(Boyles Law)

• Gases within the body are influenced by pressure
  changes outside the body
• Ascent pressure is decreased and gases expand
• Descent pressure is increased and gases
  contract
• The body can withstand changes in total
  barometric pressure as long as the air pressure
  within the body cavities is equalized to ambient
  pressure

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Barometric Pressure

• Body cavities most often affected
• Gastrointestinal tract
• Middle ear
• Paranasal sinuses
• Teeth
• Respiratory tract

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Gastrointestinal Tract

• Most frequently experienced with a rapid ascent
  (decrease in barometric pressure)
• Symptoms result from gas expansion
• Above 25,000 feet distention could be large
  enough to produce severe pain
• May produce interference with breathing

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Gastrointestinal Tract

• Sources of Gas
• Swallowed air (including gum chewing)
• Food digestion
• Carbonated beverages

• Treatment
• Belching or passing flatus
• Expulsion aided by walking or moving about
• Massage the affected area
• Loosen restrictive clothing
• Use of a gas reducing agent (Pepto Bismol)
• Descent to a higher pressure

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The Middle Ear

• Ascent to altitude
• As barometric pressure decreases with ascent, gas
  expands within the middle ear
• Air escapes through the eustachian tubes to
  equalize pressure
• As pressure increases, the eardrum bulges outward
  until a differential pressure is achieved and a
  small amount of gas is forced out through
  eustachian tube and the eardrum relaxes

82
The Middle Ear

• Descent to altitude
• Equalization of pressure does not occur
  automatically
• Eustachian tube performs as a flutter valve and
  allows gas to pass outward easily, but resists
  the reverse
• During descent the ambient pressure rises above
  that inside and the eardrum is forced inward
• If pressure is not equalized
• Ear block may occur and it is extremely difficult
  to reopen the eustachian tube
• The eardrum may not vibrate normally and
  decreased hearing results

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Ear Block (Barotitis Media)

• Symptoms
• Ear congestion
• Inflammation
• Discomfort
• Pain
• Temporary impairment of hearing
• Bleeding (severe cases)
• Vertigo

• Contributing Factors
• Flying with head cold
• Flying with a sore throat
• Otitis media
• Sinusitis
• Tonsillitis

84
Ear Block (Barotitis Media)

• Treatment
• Yawning or swallowing
• Valsalva maneuver
• Nasal sprays best used prior to descent
• Pain medications
• For infants / children provide a bottle / straw
  to suck
• Politzer bag used to force air through the
  eustachian tube
• Ascend to safe altitude where symptoms subside
  and then slowly descend

85
Ear Block (Barotitis Media)

• Prevention
• DO NOT FLY WITH A HEAD COLD
• Stay ahead of your ears
• Valsalva during descent
• Use self-medications with vasoconstrictors with
  caution
• Rebound effects of nasal sprays may not allow
  swelling to subside

86
Delayed Ear Block

• Occurs in situations where crew members breath
  100 oxygen at altitude or in an altitude
  chamber, especially if oxygen was maintained
  during descent to ground level
• Symptoms occur 2 to 6 hours after descent
• Oxygen in the middle ear is absorbed and creates
  a decreased pressure
• Prevention valsalva numerous times after
  altitude exposure to prevent absorption

87
The Sinuses

• Most often involves frontal sinuses (above each
  eyebrow) and maxillary sinuses (both cheeks)
• Sinus ducts have openings into the nasal passage
• Gas vented with increases upon ascent most often
  without problems
• With descent, air moves back out through the
  ducts if they are open
• If the openings are swollen or are malformed, a
  blockage may occur

88
The Sinuses

• Symptoms
• Severe pain
• Possible epistaxis
• Possible referred pain to teeth

• Treatment
• Equalize pressure as quickly as possible
• Valsalva is sometimes effective
• Coughing against pressure is effective
• Ascent to safe altitude then slow descent
• Nasal sprays may help

89
The Sinuses

• Prevention
• DO NOT FLY WITH A COLD
• Try to maintain an equalized pressure
• Keep ahead of your ears

90
The Teeth (Barodontalgia)

• Incidence is low
• Pain is excruciating
• Altitude of occurrence varies greatly with
  individuals
• Air trapped within teeth expands with ascent
• Confirmed barodontalgia is experienced in
  previously restored defective teeth
• Untreated caries may cause pain at altitude
• Rarely caused by a root abscess with a small
  pocket of trapped gas

91
The Teeth (Barodontalgia)

• Treatment / Prevention
• Descent
• Pain medications
• Good dental hygiene

92
The Respiratory Tract

• Hypoxia
• Pneumothorax
• Diagnosis and treatment prior to flight
• Existing pneumothorax left untreated will expand
  with pressure decreases
• If the lung tissue continues to be compressed due
  to trapped gas expansion, intrathoracic pressure
  will increase
• Vascular structures within the chest may become
  compromised
• Potential tension pneumothorax

93
Effects Upon Mechanical Ventilators

• Pneumatic controlled and powered
• With decreased barometric pressure and increased
  altitude
• Increased inspiratory time
• Increased tidal volume
• Increased flow rate
• Increased expiratory time
• Decreased rate
• Opposite with descent

94
Effects Upon Mechanical Ventilators

• Electronic controlled and powered
• No effect on controls from altitude / pressure
  changes
• Flow rate of O2 may change
• Patient tidal volume may change

95
Thermal

• Air medical operations place crew members and
  patients in situations within a wide range of
  temperatures
• Ambient temperature decreases with increasing
  altitude
• Atmospheric temperature decreases 2 C for each
  1,000 ft increase in altitude
• Weather temperature variations can create air
  turbulence monitor for motion sickness and
  increased fatigue

96
Thermal

• Variations in Temperature Contribute to
• Stress
• Fatigue
• Motion sickness
• Dehydration
• Disorientation

• Contributing Factors
• Circulating air within cabin
• Amount of time exposed to thermal stress
• Type of clothing
• Personal physical conditioning

97
Heat Loss

• Minimizing Heat Loss Enroute
• Warm cabin environment
• Blankets and layering
• Avoid direct contact with cold surfaces
• Remove wet clothing
• Limit surface are of any wet dressings

• Preventive Measures
• Keep clothing dry
• Limit exposure to mechanisms of heat loss
• Radiation
• Conduction
• Evaporation
• Convection
• Avoid alcohol
• Monitor wind chill
• Wear layer of clothing

98
Gravitational Forces

• The force of gravity on a human body is referred
  to as G
• 1 G is the force exerted upon a body at rest
• During flight, an aircraft moves and maneuvers
  through the atmosphere with force (thrust) and
  centrifugal forces are applied along various axes
• These forces also apply to occupants

99
Gravitational Forces
100
Gravitational Forces

• Physiological Effects of G Forces
• G forces affect blood pooling
• Influenced by
• Weight and distribution
• Gravitational pull
• Centrifugal force

• Positive Gz
• Blood pooling in lower extremities
• Increased intravascular pressures
• Stagnant hypoxia
• Negative Gz
• Stagnant hypoxia
• Blood pooling in upper body
• Headache

101
Gravitational Forces

• Variations in G Force Application
• Motion sickness
• Vestibular apparatus within the middle ear
• Balance center is sensitive to changes is G force
• Excessive, abnormal or abrupt changes lead to
  motion sickness syndromes
• Spatial disorientation
• Inability to correctly orient oneself with
  respect to the horizon
• Body senses which assist in maintenance /
  equilibrium

102
Body Senses Which Assist in Maintenance of
Balance / Equilibrium

• Vision
• Most valid sense for maintaining orientation
• Vestibular Apparatus
• Otolith Organs
• Proprioception System

103
Vestibular Apparatus

• The structures for balance maintenance
• Located in the inner ear (semicircular canals)
• Monitors angular acceleration
• Three / ear on each axis yaw, pitch, roll
• Each canal is a bony, fluid-filled structure
• Enlarged area containing a sensory structure

104
Otolith Organs

• Monitor linear acceleration
• Located in same bony labyrinth as semicircular
  canals
• Composed of sensory hairs
• Hairs project into a membrane containing
  crystalline particles
• Gravity causes particles to bend hair cells

105
Proprioception System

• Often referred to by pilots as seat of the
  pants
• Acceleration causes a feeling of pressure in
  various parts of the body
• Least reliable of the balance systems

106
Types of Spatial Disorientation

• Leans
• A false sense of being moved in a nonlevel flight
  resulting in leaning to one side or the other
  (most common)
• Graveyard Spin / Spiral
• A false sense of spinning

107
Types of Spatial Disorientation

• Coriolis Illusion
• Most severe vestibular illusion occurs when the
  semicircular canal fluid flows in two planes of
  rotation simultaneously
• The aircraft must be turning
• Rapid head movement
• Occulogravic Illusion
• A false sensation of climbing

108
Spatial Disorientation

• Prevention
• Use visual clues from the horizon
• Minimize head movement
• Pilots
• Rely on instruments

• Treatment
• Relax
• Allow sensation to subside
• Do not panic
• Do not make rapid or sudden head movements
• Pilots
• Rely on instruments

109
Motion Sickness

• Treatment
• Oxygen
• Supine position
• Limit head movement
• Visual fixation on a point outside the aircraft
• Cool air blown to face
• Symptoms are subjective and so are the cures!

• Prevention
• Fear and anxiety contribute
• Motivation is a key factor in prevention
• Eating prior to flying may help

110
Clinical ApplicationsPatient Positioning

• To transverse the Gs if at all possible is
  optimum
• Counter the effects of the force by positioning
  opposite the direction of force
• Most EMS aircrafts do not have significant
  problems with G forces
• Ascent, descent, and banking are when effects are
  felt most often
• When encountered, most G forces in air medical
  transport are transient and limited in effect

111
Noise

• Transmitted through a medium such as air, solid,
  or liquids
• Hertz one oscillation per second
• Frequency number of times each second that
  these oscillations occur
• Audible range for the human ear
• 20 to 20,000 Hz

112
Noise

• Pitch description of frequency in terms of
  higher versus lower on a scale
• Intensity loudness, or a measure of sound waves
  in the ear canal measured in decibels
• Decibel measure of the pressure of noise /
  sound (dB)
• Human heart 10 dB
• Jet engine at full power 170 dB

113
Effects of Hazardous Noise

• Repetitive exposure can interfere with job
  performance and safety
• Temporary or permanent hearing loss may occur
• Interference with communications
• Produces side effects of fatigue and headache
• Hearing loss is insidious is nature by the time
  most crew members notice a change in hearing
  capabilities, permanent damage has occurred

114
Duration of Exposure to Noise

• A relatively non-hazardous noise can become
  hazardous with prolonged duration of exposure
• Hazardous exposure
• 80 dB for 16 hours is permissible unprotected
  exposure
• For each 4 dB increase above 80 dBA, the time
  limit is reduced by one half
• Unprotected exposure to levels above 114 dBA is
  not safe at any time level (hearing protection)

115
Duration of Exposure to Noise

• A good measure to remember is noise intensity
  that affects normal voice communication is the
  approximate level which begins the threat of
  hearing
• If after exposure to noise, you notice a fullness
  or ringing in your ears, assume you have been
  overexposed to noise

116
Daily Exposure Time Limits for Noise
117
Sources of Noise (Aircraft)

• Engines
• Blades
• APU
• Radio / Communications
• Wind
• It is common for the noise level inside the cabin
  of both fixed and rotor wing aircraft to remain
  100 to 125 dB

118
Modification of Noise Risk

• Distance from source
• Angle from source (varies with nature of sound
  waves)
• Location of source of noise
• Varies considerably at locations within aircraft
• Flight phase noise level varies with flight
  phases
• Acoustical insulation within aircraft bulkhead
• Monitor for flight line noise sources
• APU, air conditioner units

119
Reduce Time of Exposure

• A risk to hearing may exist even with noise
  reduction and use of personal protective gear
• Put noise attenuating devices on IMMEDIATELY when
  entering noise / aircraft area

120
Protection from Noise Exposure Hazards

• Earplugs
• Variation in size texture may alter
  effectiveness
• Best for reduction of low frequency noise
• Very effective to 115 dB

• Earmuffs
• More comfortable / convenient
• Easily donned / removed
• Interfere with headgear
• Better for higher frequency attenuation

121
Protection from Noise Exposure Hazards

• Headsets / Helmets
• Best for higher frequency attenuation
• Not very effective for low frequency noise
• Enable voice communication with mounted microphone

• Combination
• Best when exposed to combination of high and low
  frequency with high intensity noise
• Noise Reduction
• Eliminate the noise or reduce its level

122
Effects of Noise Exposure

• Air crew members must have audiometer
  examinations regularly
• Symptoms
• Distraction from task
• Fatigue
• Fullness / ringing in ears
• Nausea
• Headache
• Mild vertigo
• Temporary or permanent hearing loss

123
Operational Considerations

• All air crew members and patients on aircraft
  MUST wear hearing protection
• Noise interferes with certain patient care
  procedures
• Auscultation
• Percussion
• Alarm monitoring
• Communication / speech with patient
• Use of Doppler as alternative
• Development of astute palpation and observation
  skills a MUST

124
Vibration

• Defined as rapid up and down or back and forth
  rhythmic movement
• Described using the same parameters as sound
• Frequency
• Intensity
• Time
• Additional factors include
• Plane of vibration
• Direction of application

125
Vibration

• Vibrations of low frequency and high intensity
  are of most concern to human health
• Range of 1 to 100 Hz is most hazardous
• Human skull resonates at 20 to 30 Hz
• Human eye resonates at 60 to 90 Hz
• These vibrations may elicit a physiologic
  response which is distressing
• Vibration energy is passed through the body
  acoustically or directly mechanically

126
Sources of Vibration

• Aircraft power plant (engines)
• Rotors / Propellers

127
Effects of Exposure to Vibration

• Loss of appetite
• Loss of interest
• Perspiration
• Air sickness
• Nausea / emesis
• Increased heart rate
• Increased respiratory rate
• Increased metabolic rate

• Decreased motor function ability
• Decreased ability to concentrate on task
  performance
• Severe or prolonged exposure
• Fatigue
• Discomfort
• Pain

128
Protection from Vibration

• Limitation
• Isolation of vibration source
• Restraint of the body
• Limiting vibration to internal organs is critical
  to prevent impairment of normal physiologic
  function

• Protection
• Avoid direct contact with source of vibration
• Use of protective helmets / harnesses
• Good physical conditioning of crew members to
  increase tolerance

129
Third Spacing

• Decreasing barometric pressure (ambient) may
  cause leakage of intravascular space fluid into
  extravascular tissues
• Hypoxia-induced peripheral vasoconstriction may
  accentuate this
• Aggravated additionally by
• Temperature changes
• Vibration
• G-forces

130
Third Spacing

• Effects Physiologically of Third Spacing
• Seen on long distance transports
• Seen on high altitude flights

• Signs / Symptoms
• Edema
• Generalized
• Dependent
• Dehydration
• Increased heart rate
• Decreased blood pressure

131
Third Spacing

• Prevention / treatment of symptoms
• Encourage fluids
• Movement / ambulation when possible
• Avoid excessive vibration
• Monitor / protect against temperature extremes

132
Decreased Humidity

• Amount of water vapor in the air decreases as
  altitude increases
• 90 of the water vapor in the atmosphere is
  concentrated below 16,000 feet
• Pressurized aircraft cabins recirculate air
  approximately every 3 minutes without
  humidification
• Flight for extended periods at high altitudes
  exposes crew / patients for dehydration

133
Dehydration

• Physiology
• Decreased available moisture to respiratory
  membranes causes inflammation and decreased
  efficiency of gas exchange
• Respiratory secretions become thickened and
  further interfere with gas exchange
• Increases risk of hypoxia
• Stimulation of the hypothalamus to increase basal
  metabolic rate and oxygen demand

134
Dehydration

• Signs / Symptoms
• Thirst
• Heat cramps
• Headaches
• Diminished task performance
• Restlessness
• Fatigue

135
Sources of Dehydration

• Normal daily bodily losses approx 1 quart
• Urination
• Bowel
• Respiration
• Skin
• Sweating
• Profuse sweating can release 2 to 4 quarts an hour

• Pressurized aircraft cabins
• Not enough oral fluid intake
• Carbonated beverages further complicate and
  decrease water absorption in the GI tract
• Coffee / alcohol increase water loss

136
Dehydration

• Prevention / Treatment
• Drink more WATER
• Maintain hydration to prevent dehydration /
  fatigue
• Increase patients fluid intake (monitor closely
  high risk patients)
• Burn
• Pre-existing dehydration states

137
Fatigue

• A decrease in skill performance related to
  repetitive use and duration
• Also includes personal evaluation of a sense /
  feeling / perception of tiredness, discomfort or
  disorganization of muscular coordination
• Aggravated by physical, physiological, and
  psychological states

138
Fatigue

• INSIDIOUS in onset
• Noted by aviation community for many years as
  having a strong impact on flight safety and
  efficiency
• As length of fatigue increases, performance may
  become compromised and degraded, irritability
  increases, and random mistakes may occur
• Lowers thresholds for other stressors
• Fatigue factors are cumulative

139
Causes of Fatigue

• Extended flight times
• Insufficient rest
• High noise levels
• Long periods of inactivity / limited movement
• Pressurized / artificial cabins
• Vibration

• Barometric pressure changes
• Variations in temperature
• G-forces on takeoff / landing
• Poorly designed seats / restraints
• Circadian rhythm alteration

140
Circadian Rhythm Alteration

• Circadian (about a day)
• Time period approx 24 hours (variation between 20
  and 28)
• Referred to as the rhythmic biological clock to
  which functions are geared

• Intrinsic sleep / wake cycle or the external day
  / night cycle
• Diurnal variations in a persons
• Body temperature
• Heart rate
• Performance
• Hormone secretion

141
Time Zone Changes During Flight

• Jet Lag
• Studies have shown that complex bodily functions,
  such as those measurable by reaction time,
  performance and decision time are affected by
  rapid shifts through several time zones
• Without proper preparation and planning, it takes
  one 24-hour period per one hour shift in time
  zone to recover
• Crossing 4 time zones 4 x 24 hours to adjust
  bodily cycles

142
Types of Fatigue

• Acute single-mission skill fatigue
• Results from repeating tasks during long flights
  or from numerous repetitive short flights
• Very common
• Healthy persons recover with rest / sleep
• Symptoms
• Tiredness
• Lassitude
• Loss of coordination
• Inattention to details

143
Types of Fatigue

• Chronic skill fatigue
• Occurs when recuperative time is insufficient
• Overlapping with factors of acute fatigue
• Can occur with any repetitive maximum effort
  program / job

144
Increasing Personal Resistance to Fatigue

• Sleep
• Know personal requirements
• Physical conditioning
• Exercise recreation
• Proper diet
• Wear use personal protective gear
• Hearing protection
• Oxygen at altitude

• Vary the routine
• Range of motion if confined to seat
• Minor diversions to break monotony
• Avoid dehydration
• Water snacks
• Personal concerns
• Personal problems brought to work

145
Self Imposed Stressors/ Human Factors

• Stress can be ANYTHING that places a strain on an
  air crew members ability to perform at optimum
  level
• Certain stresses are inherent within the aviation
  environment
• Acceleration forces, hypoxia, barometric pressure
  changes
• Numerous others are a result of outside actions
  taken by the air crew member, which decrease
  tolerance to the routine stressors of flight

146
Self Imposed Stressors

• Alcohol
• Effects are magnified at attitude
• 1 drink at 10,000 feet equals 2 to 3 drinks at
  sea level
• Reduction of ability of the brain cells to
  utilize oxygen enhances hypoxia, which further
  impairs judgment and skill
• Additive effect of dehydration
• Chronic use effects as well as acute ingestion
  threaten safe flight

147
Self Imposed Stressors

• Drugs
• Self-medication has two potential dangers to safe
  flight
• Drugs mask unsafe conditions
• Drugs can make the crew member unsafe
• Treatment of illness requires a drug that treats
  the cause not just the symptom
• Air crew members who utilize over-the-counter
  (OTC) drugs must responsibly evaluate the impact
  of these drugs on their performance and the
  safety of the mission

148
OTC Prescription Drug Hazards

• Caffeine
• Nervousness
• Indigestion
• Insomnia
• Increased heart rate blood pressure
• Diuretic effect
• Antihistamines
• Depressant
• Drowsiness, dry mouth, impaired depth perception

• Amphetamines
• Force the body beyond normal capacities
• Recovery times enhanced
• Narcotics
• Drowsiness
• Respiratory depression
• Tranquilizers
• Cause stuffy nose, constipation, blurred vision,
  drowsiness
• Nasal decongestants
• Rebound congestion

149
OTC Prescription Drug Hazards

• Air medical crew members who self-medicate MUST
  be aware of
• Predictable side effects
• Overdose potentials
• Allergic reactions
• Synergistic effects

150
Diet

• Poor diet contributes to fatigue
• Often during long flights, reliance is placed
  upon glycogen stores rather than eating a meal at
  regular intervals
• Hypoglycemia is a SAFETY THREAT TO YOURSELF, YOUR
  CO-WORKERS, AND YOUR PATIENTS
• Crash or fad diets are a potential threat to
  safety
• Diet pills are amphetamines and are a hazard

151
Tobacco

• Tar
• Causes swelling and prevents natural cleansing of
  alveoli
• Nicotine
• Potent drug which affects nervous tissue and
  muscle
• May cause
• Skeletal muscle weakness and twitching
• Abdominal cramping, nausea, emesis
• Alters circulation of blood and nerve impulses
• Increases heart rate
• Decreases individual ability to adapt to other
  stress

152
Tobacco

• Carbon Monoxide (CO)
• Air medical crew members who smoke have 5 to 10
  total hemoglobin saturated with CO
• Will result in mild hypoxia at 8,000 feet
• Flying with a cabin altitude of 10,000 feet (very
  common in commercial fixed wing flights) will
  result in feeling physiologic effect of 15,000
  feet
• Decreased night vision accuracy related to hypoxia

153
Physical Fitness

• Physical fitness is more than muscle conditioning
• Regular aerobic / strenuous exercise increases
  the efficiency of supply and delivery of oxygen
  to the tissues, and reduced heart rate and blood
  pressure
• Air medical crew members who maintain good
  physical conditioning are better able to sustain
  prolonged exposure to stressors of flight

154
Personal Stress

• Flying is a stressful job by nature
• Patient care can be stressful
• Duties often require intense concentration
• Individuals who are experiencing outside personal
  stress cannot devote entirely to critical tasking
  at work
• Personal stress is not easy to leave away from
  work
• Constant effort must be maintained to avoid,
  reduce, or eliminate personal problems from
  interfering with work

155
Prevention

• Anticipate effects of the stresses of flight
  prior to transport
• Initiate interventions appropriately
• Monitor for hypoxia
• Avoid flying with a head cold
• Avoid gas producing foods
• Deep ahead of barometric pressure changes
• Develop effective stress management and time
  management techniques
• Minimize self-imposed stressors

156
Pressurized Cabin /Artificial Atmosphere

• Mechanical method to maintain a greater than
  outside ambient pressure within an aircraft cabin
• Protective environment against decreased
  temperature and pressure
• Each type and design of aircraft varies in
  capabilities and the air medical crew must be
  familiar with the aircraft they are working within

157
Advantages of a Pressurized Cabin

• Reduces possibility of hypoxia and evolved gas
  disorders
• Reduces gastrointestinal gas expansion
• Cabin temperature, humidity, and ventilation are
  controllable
• No use of encumbering life support equipment
  (suits)
• Minimizes fatigue and discomfort
• Able to easier protect from barotrauma by slow
  cabin descent

158
Disadvantages of a Pressurized Cabin

• Increase in aircraft weight and size
• Additional engineering, equipment, engine power
  and maintenance
• Decrease in maximum payload capabilities of
  aircraft
• Controls required to monitor for contamination by
  smoke, fumes, CO, CO2
• Decompression hazard

159
Slow Decompression

• Cabin pressure is depleted in greater than 3
  seconds
• May occur undetected
• Descent to 10,000 feet required if no
  supplemental O2 available
• Use of supplemental O2 until descent
• Evolved gas disorder and hypoxia possible

160
Rapid Decompression

• Occurs in under 3 seconds
• Lungs decompress faster than the cabin
• Hypoxia risk dependent upon altitude
• Emergency procedures
• Oxygen on yourself
• Oxygen on others
• Unclamp and clamped tubes
• Secure yourself / others
• Descend

161
Explosive Decompression

• Change in cabin pressure faster than the lungs
  can decompress
• Lung damage possible
• Decompression sickness probable

162
Factors AffectingSeverity of Decompression

• Volume of pressurized cabin
• Size of the opening (larger faster)
• Differential ration (greater faster)
• Flight altitude
• Higher altitudes create greater threats for
  physiological consequences
• Remember your Time of Useful Consciousness (TUC)

163
Physical Indicatorsof Decompression

• Flying debris
• Fogging (related to temperature drop)
• Temperature drop
• Pressure decrease symptoms
• Windblast

164
Decompression Sickness (Dysbarism) 2 Types

• Trapped Gas
• Gas within bodily cavities / organs
• Boyles Law
• Symptoms occur rapidly

• Evolved Gas
• Effects produced by evolution of gas from tissues
  and fluids of the body
• Henrys Law

165
Decompression Sickness

• When the atmospheric pressure is decreased
  rapidly to certain critical values, the nitrogen
  pressure gradient between the body and the
  outside air is such that nitrogen will come out
  of solution in the form of bubbles
• Can occur in the blood, other fluids, or in the
  tissues
• Symptoms do not appear rapidly

166
Severity and Rapidityof Onset Related to

• Rate of ascent
• More rapid sooner symptoms appear
• Altitude
• Below 25,000 feet is rare
• Above 25,000 feet may occur after leveling off
• Duration of exposure
• Physical activity
• Exercise lowers the threshold for manifestations,
  particularly the bends
• Individual susceptibility
• Unpredictable

167
SCUBA Diving

• Greatly lowers threshold altitude f