Flight Physiology 101 Jeremy Maddux, NREMTP.

Flight Physiology 101 Jeremy Maddux, NREMTP

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

Components of the Atmosphere
Oxygen 21% Nitrogen 78% Others 1% 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

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)

Average Barometric Pressures
Altitude (1000 feet) Barometric Pressure mm Hg Psi Temperature Cº Temperature Fº 760 14.70 + 15.0 + 59.0 1 733 14.17 + 13.0 + 55.4 2 706 13.87 + 11.0 + 51.8 3 681 13.67 + 9.1 4 656 12.69 + 7.1 5 632 12.23 + 5.1 6 609 11.78 + 3.1 7 586 11.34 + 1.1 8 565 10.92 - 0.9 9 542 10.51 - 2.8 +26.96 10 523 10.11 - 4.8 12 483 9.35 - 8.8 + 16.6 14 447 8.63 - 12.7 +9.4 16 412 7.97 - 16.7 +1.94 18 380 7.34 - 20.7 - 5.26 20 349 6.75 - 24.6 24 295 5.70 - 32.6 28 247 4.78 - 40.5 - 40.9 30 228 4.36 - 44.4 32 206 3.98 - 48.4 36 171 3.30 - 55.0 67 42 128 2.47 48 96 1.86

Measures of Altitude True Altitude Absolute or Tapeline 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

Measures of Altitude An Altitude Reference – standard day conditions
When the pressure is 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

Physiologic Divisions of the Atmosphere
Physiologic Zone Physiologically Deficient Zone Partial Space Equivalent Zone Space Equivalent Zone

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

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

Physiologic Zone Symptoms of Prolonged Exposure Treatment
Shortness of breath Dizziness Headache Sleepiness Sinus and ear disturbances Treatment Supplemental oxygen Descent

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

Partial Space Equivalent Zone
50,000 feet to 120 miles Similar to space Pressurized suits required Changes in gravity affect the body

Space Equivalent Zone Above 120 miles
Artificial atmosphere/pressure suits mandatory for life Weightlessness effects “Outer space”

Gas Laws The body responds to barometric pressure changes in temperature, pressure, and volume. Boyle’s Law Henry’s Law Charles’ Law Dalton’s Law Graham’s Law

Boyle’s 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

Boyle’s Law Boyle’s 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)

Boyle’s 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

Boyle’s 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

Henry’s 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

Henry’s 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

Henry’s Law Henry’s 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

Henry’s 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

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

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

Dalton’s 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

Dalton’s 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 = mm Hg Oxygen at 8,000 feet O2 = 21% and PO2 = 21% x 565 mm Hg = mm Hg THE PECENTAGE OF OXYGEN REMAINS THE SAME with changes in altitude

Dalton’s Law Dalton’s Law Formula Where Pt = P1 + P2 + P3…Pn
Pt = total pressure P1…Pn = partial pressures of constituent gases of the mixture

Dalton’s Law Air sample at seal level: Air sample at 18,000 feet
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%

Graham’s 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

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

Types of Stresses Physical Physiological Psychological Psychosocial
Size Shape Build Physiological Sleep State Fatigue Alcohol Psychological Mental State Psychosocial Motivation Goal Direction Money Family Pathological Health / Wellness

The 9 Stresses of Flight Hypoxia Barometric Pressure Thermal
Gravitational Forces Noise Vibration Third-Spacing Decreased Humidity Fatigue

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

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

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

Hypoxic Hypoxia As altitude increases the partial pressure (PaO2) decreases (Dalton’s Law) As the PaO2 falls in the alveoli, the amount of O2 which diffuses into the blood decreases (Henry’s Law) Results in a decrease in oxygen available to the tissues

Changes in Oxygen Saturation in the Blood with Altitude Increases
Altitude (feet) Oxygen Saturation PaO2 10,000 87% 60 12,500 85% 50 18,000 48% 26 25,000 9% 7 35,000 0%

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

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

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

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

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

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

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

Signs / Symptoms of Hypoxia
Symptoms are the same regardless of the nature of the hypoxia Early symptoms mimic alcohol intoxication or extreme fatigue Each person’s 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

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

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

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

Symptomology & Altitude Frequency of Occurrence
5,000 ft 10,000 ft 15,000 ft 18,000 ft Blurred vision Hyperventilation Belligerence Cyanosis Tunnel vision Impaired task management Euphoria Confusion Decreased night vision Air hunger Sleepiness Poor judgment Apprehension Slow thinking Muscle coordination Fatigue Headache Dizziness Numbness / Tingling

Stages of Hypoxia There are 4 general stages Indifferent Stage
Compensatory Stage Disturbance Stage Critical Stage

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

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%

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

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

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

Disturbance Stage (Symptoms)
Personality Euphoria Aggressive or belligerent Depression Over confident Performance Decreased coordination Slowed speech Impaired handwriting Cyanosis

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

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)

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)

Explained by the gas laws Henry’s 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

Altitude in Feet / Flight Level TUC 12,000 to 20,000 feet (FL 200) 20 to 30 minutes 25,000 feet (FL 250) 3 to 5 minutes 30,000 feet (FL 300) 1 to 2 minutes 35,000 feet (FL 350) 30 to 60 seconds 40,000 feet (FL 400) 15 to 20 seconds 50,000 feet (FL 500) 9 to 12 seconds

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

Factors Involved in Hypoxia
Altitude Rate of ascent Duration of exposure Individual tolerance Physical fitness Physical activity Environmental temperatures Self-imposed stresses

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

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

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 A patient on .50 IO2 is flown from sea level (760 mm Hg) to 5,000 feet (632 mm Hg) 50% x 760 = .25 IO2 required = .60 IO2 required

Oxygen Delivery / Adjustment Altitude Chart
FIO2 SL 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 .21 159 153 148 143 138 132 128 123 118 113 109 .22 167 161 155 150 144 139 134 129 124 119 115 .24 182 176 170 163 157 152 146 141 135 130 126 .28 213 205 198 191 184 177 164 158 147 .30 228 220 212 204 197 190 183 169 .34 258 250 240 232 223 215 207 199 192 178 .36 274 264 254 245 236 219 211 203 195 188 .40 304 293 283 272 262 253 244 235 226 217 209 .44 334 322 311 300 289 278 268 248 238 230 .50 380 366 353 341 328 316 282 271 .55 418 403 389 375 361 348 335 310 298 288 .60 456 440 424 409 394 379 365 352 339 325 314 .65 494 476 459 443 427 411 396 381 367 340 .70 532 513 495 477 426 410 395 .75 570 550 530 511 492 474 457 423 406 393 .80 608 586 565 545 525 506 487 469 452 434 419 .85 646 623 601 579 558 537 518 498 480 461 445 .90 684 660 636 613 591 569 548 528 489 471 .95 722 696 671 647 557 536 515 1.00 760 733 707 681 656 609 542 524

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

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

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

Oxygen Concentration Available with Common Adjuncts at Sea Level
Device Liters / Minute % IO2 Nasal Cannula 1 24 2 28 3 32 4 36 6 44 Simple Mask 5-6 40 6-7 50 7-8 60 Partial Nonrebreather Mask 7 70 8 80 10 > 90

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

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

Calculation of Duration of Oxygen Availability
Example: D cylinder 12.7 cu.ft. x 28.3 x (1,500 ÷ 2,200) 10 liters per minute lpm = 24.5 minutes of available oxygen =

Liquid Oxygen (LOX) Each liquid liter = 860.3 gaseous liters
860.3 gaseous liters = 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 = cu.ft.

Barometric Pressure (Boyle’s 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

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

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

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

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

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

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

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

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

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

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

The Sinuses Symptoms Treatment 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

The Sinuses Prevention DO NOT FLY WITH A COLD
Try to maintain an equalized pressure “Keep ahead of your ears”

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

The Teeth (Barodontalgia)
Treatment / Prevention Descent Pain medications Good dental hygiene

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

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

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

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

Thermal Variations in Temperature Contribute to Contributing Factors
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

Heat Loss Minimizing Heat Loss Enroute Preventive Measures
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

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

Gravitational Forces Direction of Force Standard Terminology
Pull head toward feet +Gz Pull foot toward head -Gz Pull from chest to back Pull from back to chest Pull from right to left Pull from left to right

Gravitational Forces Physiological Effects of G Forces Positive Gz
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 Blood pooling in upper body Headache

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

Body Senses Which Assist in Maintenance of Balance / Equilibrium
Vision Most valid sense for maintaining orientation Vestibular Apparatus Otolith Organs Proprioception System

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

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

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

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

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

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

Motion Sickness Treatment Prevention 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

Clinical Applications Patient Positioning
To “transverse the G’s” 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

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

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

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

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)

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

Daily Exposure Time Limits for Noise
Decibels (dB) Exposed Permissible Unprotected Exposure Time Limit 80 16 hours 84 8 hours 88 4 hours 92 2 hours 96 1 hour 100 30 minutes

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

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

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

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

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

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

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

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

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

Sources of Vibration Aircraft power plant (engines)
Rotors / Propellers

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

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

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

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

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

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

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

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

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

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

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

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

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

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 person’s Body temperature Heart rate Performance Hormone secretion

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

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

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

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

Self Imposed Stressors / Human Factors
Stress can be ANYTHING that places a strain on an air crew member’s 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

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

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

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

OTC & Prescription Drug Hazards
Air medical crew members who self-medicate MUST be aware of Predictable side effects Overdose potentials Allergic reactions Synergistic effects

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

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

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

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

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

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

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

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

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

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

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

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

Factors Affecting Severity 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)

Physical Indicators of Decompression
Flying debris Fogging (related to temperature drop) Temperature drop Pressure decrease symptoms Windblast

Decompression Sickness (Dysbarism) 2 Types
Trapped Gas Gas within bodily cavities / organs Boyle’s Law Symptoms occur rapidly Evolved Gas Effects produced by evolution of gas from tissues and fluids of the body Henry’s Law

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

Severity and Rapidity of 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

SCUBA Diving Greatly lowers threshold altitude for the occurrence of decompression sickness when flying Cases of decompression sickness have occurred in individuals who fly in cabins as low at 5,000 feet If within 6 hours of diving Recommended at least 24-hour delay between diving with SCUBA and flying

Decompression Sickness (DCS)
Skin manifestations Mild Mottled and diffuse rash Tingling of the skin Believed to be caused by bubbles of gas evolving under the skin Symptoms themselves are not serious HOWEVER they are a WARNING that bubbles may form elsewhere Continued exposure may lead to more serious forms of decompression sickness

The Bends Generally located around / near articulating joints of the body Pain from mild to unbearable Factors of exercise, increased altitude, and increased time of exposure will increase severity of symptoms Descent to below altitude of onset

The Chokes Rare but potentially life-threatening Nitrogen bubbles in the blood vessels of the lungs Symptoms Deep and sharp pain or burning sensation under the sternum Shortness of breath Dry, progressive, nonproductive cough Feeling of suffocation with decreasing ability to take a breath Results in hypoxia

False Chokes (NOT DCS) Caused by mouth breathing and cool, dry aircraft air Throat irritation and discomfort Relieved with fluid intake

Neurologic Manifestations (CNS) Very rare Rarely may effect brain or spinal cord More common Visual disturbances (blind spots, flushing, or flickering vision – Scotoma) Persistent headache Partial paralysis Inability to speak or hear Loss of orientation

Emergency Treatment 100% oxygen for everyone onboard Declare an emergency Descent as rapidly as possible Immobilize affected areas Treat shock Land as soon as possible Medical evaluation by a QUALIFIED flight surgeon / hyperbaric physician ASAP Decompression chamber therapy if required

Unpressurized Aircraft
Altitude within the cabin equals aircraft altitude Little control is available over the effects of the gas laws Effects seen in human discomfort and equipment effectiveness Programs that operate at high altitudes (mountains or high plains) with unpressurized aircraft need be aware and alert for altitude symptomology

Unpressurized Aircraft
Air pressure changes in Body cavities / hollow organs Tube cuffs Enclosed equipment with fluid / air interference Respiratory variations FiO2 Tidal volume Respiratory rate

The End! Any Questions?

Flight Physiology 101 Jeremy Maddux, NREMTP.

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Flight Physiology 101 Jeremy Maddux, NREMTP.

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