altitude physiology and the stresses of flight we will cover the following: the atmosphere...
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Altitude Altitude Physiology Physiology
and the and the Stresses of Stresses of
FlightFlight
We will cover the following:
The Atmosphere
• Composition
• Structure
• Physiologic Zones
GAS LAWSGAS LAWSUniversal Gas Law
Boyle’s Law
Charles’ Law
Henry’s Law
Dalton’s Law
Graham’s Law
Gay-Lussac’s Law
STRESSES OF FLIGHTSTRESSES OF FLIGHT
The Atmosphere
21%
OXYGEN
78% NITROGEN
1% O
ther
“Others” include: Argon, CO2, Neon, Helium, Krypton, Hydrogen
The AtmosphereAtmospheric composition percentages REMAIN THE SAME regardless of the
altitude.
O2 is 21%
N2 is 78%
Other is 1%
AT
Sea Level1,000 ft7,000 ft
14,000 ft30,000 ft
With an INCREASE in altitude, there is a DECREASE in pressure:
Alveolar 02 and Hgb Saturation Altitude Correction
ALTITUDE BAROMETRIC ALVEOLAR OXYGEN
(FEET) PRESSURE OXYGEN SATURATION
(mmHg) ( PAO2) % (SPO2)
Sea level 760 104 99
10,000 523 67 90
20,000 349 40 70
30,000 226 21 20
40,000 141 6 5
50,000 87 1 1
Oxygen transport in the blood:
Dependent on thepartial pressure of oxygen.
pOpO22
Universal Gas Law
GA
S LA
WS
Gas molecules of higher pressure move in the Gas molecules of higher pressure move in the direction of gas molecules of a lower pressuredirection of gas molecules of a lower pressure
PO2 = 100mmHg PO2 = 40mmHg
PO2 = 74mmHg PO2 = 66mmHg
Blood GaBlood Gass Exchange Exchange
PCO2 = 46 mm
PO2 = 100 mmPCO2 = 40 mm
PO2 = 40 mm
PO2 = 100 mm
PCO2 = 40 mmPCO2 = 46 mmPO2 = 1 - 60 mm
Arterial CapillaryArterial Capillary
Hemoglobin Saturation 98%Hemoglobin Saturation 98%
O2
O2
COCO22
O2
COCO22
O2
Venous CapillaryVenous Capillary
Hemoglobin Saturation 75%Hemoglobin Saturation 75%
Tissue Alveoli
TROPOSPHERE
Sea level to flight level 300 - 600 depending on temperature, latitude and season.
Physical Divisions of the Atmosphere
STRATOSPHERE
IONOSPHERE
EXOSPHERE
MOUNT EVEREST 29,028 FEET
1200 miles
600 miles
50 miles
Tropopause
Physiological Zones of the Atmosphere
EFFICIENT ZONE: Sea level to 10,000 feet
SPACE EQUIVALENT ZONE: 50,000 feet and above
DEFICIENT ZONE: 10,000 to 50,000 feet
10,000
50,000
18,000 ft
63,000 ft
The Principle of Atmospheric Pressure
• At sea level, the weight of a one square inch column of air extending to the edge of space is called “one atmosphere”. (ATM) 1 ATM weights 14.7 lbs (760 mmHg [torr]).
• As you ascend the pressure becomes less (0.5 ATM or 380 mm Hg at 18,000 ft)
• As you dive in water you increase the forces (or weight) on your body by 1 ATM for every 33 ft you are submerged. Hence the term diving “ 1atmosphere”.
GAS LAWS
Boyle’s Law
GA
S LA
WS
Robert Boyle
The volume of a gas is inversely proportional
to its pressure; temperature remaining
constant.
P1 x V1 = P2 x V2
DRY GAS EXPANSIONWET GAS EXPANSION1.8X 2.0X18,000
2.5X 25,000 3.0X
34,,000 5.0X
43,000
4.0X
9.5X6.0X
Gas Expansion
SEA LEVEL
Barotrauma and Boyle’s Law
• Free air in the Chest• Endotracheal Tubes• Gastrointestinal
Concerns– NG/OG tubes– Ostomies
• IV Fluids and Medications
• MAST
• Air Splints
• Dysbarisms– Barotitis Media– Barosinustitis– Barodontalgia
PN
EU
MO
MED
IASTIN
UM
PN
EU
MO
thora
x
PN
EU
MO
cep
halu
s
PN
EU
MO
perito
neum
-Ostomies and Gastic Tubes
• DO NOT allow air to become trapped in a closed –ostmy or NG/OG system. To include the space.
Endotracheal/ Trach. Tubes
• Air in the ET tube cuff should be replaced with sterile water/ NS prior to flight. Make sure to place in PCR and tell receiving hospital. Why?
• Some flight crews may elect to decrease and increase cuff pressure with ascent/decent.
• More prevalent in FW than RW (>1500 MSL)– Greater altitude span in FW– Longer exposure duration in FW
• Do not forget about Foley’s and NG Tubes
MAST/ Air Splints
• Document pulses prior to lift off.
• Monitor for decrease in circulation.
• Adjust pressure and document pulses at altitude as needed.
• Make sure to have pop-off values in place prior to take off.
DYSBARISMS
Barotitis Media
Barosinusitis
BarodontalgiaGastrointestinal
Changes
Barodontalgia
Tooth pain due to:
• Gum abscess: (dull pain on ascent)• Inflamed pulp: (sharp pain on ascent)• Inflamed maxillary sinus: (pain primarily on
descent)
Middle Ear Cavity
Eustachian Tube
Atmospheric Pressure
Tympanic Membrane
External Ear
Middle Ear Cavity
Eustachian TubeBlocked / Infected
Tympanic Membrane
External EarAtmospheric Pressure
Barotitis Media
Ear Block
Clear
Barosinusitis/ Sinus Blocks
Frontal
Ethmoid
MaxillarySphenoid
Treatment of Barosinusitis
• Stop the descent of the aircraft and attempt to clear by valsalva.
• If unable to clear, climb back to altitude until clear by pressure or valsalva.
• Descend slowly and clear ear frequently during descent.
• Use nasal spray (Afrin or Neosynephrine)
Charles’ LawAt a constant
pressure, the volume of a gas is directly proportional to the
absolute temperature of that gas.
V1/ T1 = V2/ T2
Charles’ Law in the Aero-Medical Environment
• For every 1° C temperature decreases gas volume will decrease by 1/273. Gas volume shrinks as temperature decreases.
• For every 1° C temperature increases gas volume will increase by 1/273. Gas volume increases as temperature increases.
1° C = V (-1/273)
1° C = V (+1/273)
Charles’ Law in the Aero-Medical Environment
1000’ Altitude
2 Degrees C
For every 1000 feet altitude increases,
Temperature decreases 2 degrees centigrade
Or
Climb 100m = 1°C drop
Charles’ Law in the Aero-Medical Environment
• Consider patients thermoregulatory status!– Warm blankets– Aircraft Heater– Warmed IV Fluids
• Consider effects on compress gases!– Oxygen/ medical air will compress/ expand
due to temperature changes.
Gay-Lussac’s LawDefines the relationship between pressure and temperature
At a constant volume, the pressure and absolute temperature of a gas are directly
proportional.
Example: O2/ SCBA bottles cool when opened & Heat when filling.
OR
That’s why if you check your bottle in the morning, you have less pressure then in the afternoon.
Gay-Lussac’s Law
Pressure
Pressure
Temperature
Temperature
Constant Volume
Henry’s Law• The amount of gas
dissolved in solution is directly proportional to the pressure of the gas over the solution.
Decompression Sickness
• Descend Immediately
• Compression greater than 1 atmosphere (ATM)
• 100% Oxygen
• Land at the nearest location where qualified medical assistance is available
Treatment
Evolved Gas Disorders
• Evolved gas disorders are considered serious medical emergencies and require emergent specialized care
WARNINGWARNING
Evolved Gas Disorders
The Bends (Limb Pain)
The Chokes (Respiratory Disturbances)
The Creeps (Skin Irritation)
The Staggers (CNS Effects)
Syncope (Cardiovascular Collapse)
Evolved Gas Disorders
• N2 bubbles become trapped in the joints. Onset is mild, but eventually painful !
The Bends
Evolved Gas Disorders
• N2 bubbles block smaller pulmonary vessels. Burning sensation in sternum. Uncontrollable desire to cough. Sense of suffocation ensures.
• N2 bubbles form along nerve tracts. Burning, tingling, itchy sensation and possibly a mottled red rash.
The Chokes The Creeps
Evolved Gas Disorders
• N2 bubbles affect spinal cord. Visual disturbances, paralysis, one sided tingling.
The Staggers
Dalton’s Law• The pressure exerted
by a mixture of gases is equal to the sum of the partial pressures of each gas in the mixture.
Pt = P1 + P2 +…+…
Dalton’s GangSimply stated, the sum of the partial
pressures is equal to the total pressure of a gaseous mixture.
P1 + P2 + P3 + P4 = P total
Oxygen Correction for Dalton’s Law
%FiO2 x P1 = %FiO2 needed at altitude
P2
P1= Beginning Barometric Pressure
P2 = Maximum Altitude Barometric Pressure
FiO2 35% x 760 (sea level) = FiO2% 51% needed
523 (10,000 ft )
Graham’s LawThe rate of diffusion of a gas through a liquid membrane is directly proportional to the solubility of the gas and is inversely proportional to the square root of its density or gram molecular weight.
How easily it moves across the membrane.
Graham’s Law and the Aero-Medical Environment
• CO2 has a solubility factor 20 times greater than O2 and will thereby, more readily diffuse across a liquid membrane.
Questions????1. The flight medic is more likely to feel the effects of altitude changes
when working in this environment?
1. Warm upper latitudes
2. Cold upper latitudes
3. Warm lower latitudes
4. Cold lower latitudes
2. When caring for the patient in the flight environment, the medic realizes that there are many flight stressors that affect the patient’s condition. Which of the following gas laws best describes the need to place supplemental oxygen on the patient during transport?
1. Boyle’s Law
2. Charles Law
3. Dalton’s Law
4. Gay-Lussac’s Law
Questions????
3. Medical equipment such as MAST/ air splints, IV drip rates, and endotracheal tube cuffs are more effected by which of the following?
1. Boyle’s Law2. Charles’ Law3. Dalton’s Law4. Henry’s Law
4. Which of the following gas laws is most responsible for soft tissue swelling during flight?
1. Boyle’s Law2. Charles’ Law3. Dalton’s Law4. Henry’s Law
Take a 5 minute Break!
The 8 Stressors of Flight• Hypoxia• Barometric Change• Thermal Change• G- Forces• Decrease Humidity• Noise• Vibration• Fatigue
Hypoxia
• Types of Hypoxia:– Hypoxic– Hypemic– Histotoxic– Stagnant
Hypoxia is a poor stimulus for respiration
Hypercarbia is much better
Hypoxic HypoxiaReduced
pO2 in the lungs
(high altitude)
Body tissueBody tissue
Red Red blood cellsblood cells
Inadequate Availability of Oxygen Molecules
Reduce pO2 in the lungs due to lower availability of oxygen molecules
Also Calle
d Altit
ude Hypoxia
Hypemic HypoxiaInability of the
blood to accept oxygen in
adequate amounts
++
++++
++
++++
++
++++
++
++
++
++ ++++
Medical Conditions
•COPD
•Pneumonia
•Pulmonary Edema
•Alcohol
•Pulmonary Embolism
Carbon m
onoxide
Histotoxic Hypoxia
Red blood cellsRed blood cells retain oxygenretain oxygen
Inability of the cell to accept or use oxygen
Poisoned tissuePoisoned tissue
AdequateAdequateoxygenoxygen
Medical Conditions
•Cyanide Toxicity
•CO Poisoning
•Anaphylaxis
•ETOH
•OD
Alcohol
Reduced bloodflow
Blood Blood movingmovingslowlyslowly
AdequateAdequateoxygenoxygen
Red blood cells Red blood cells not replenishing not replenishing
tissue needs tissue needs fast enoughfast enough
Stagnant HypoxiaMedical Conditions
• AMI
•Cadiomyopathy
•Cardiogenic Shock
•Crush Injuries
G-Forc
es
Hypoxia
Air HugerApprehension
FatigueNausea
HeadacheDizziness
Denial
Hot/ Cold FlashesEuphoria
BelligerenceBlurred Vision
NumbnessTingling
Symptoms
Subjective: Feel
HypoxiaSymptoms
Subjective: See
Hyperventilation
Mental Confusion
Cyanosis
Poor Judgment
WARNING !!!Failure to recognize the signs and symptoms of HYPOXIA in flight crew members may lead to a
Significant Emotional Event.
Stages of Hypoxia
Indifferent Stage
Compensatory Stage
Disturbance Stage
Critical Stage
Stages of Hypoxia
Indifferent Stage
Sea Level
10,000 ft.
Decrease in Night Vision at 4,000 ft.
MSL
Compensatory Stage
10,000 ft.
15,000 ft.
Impaired Efficiency Decreased Motor Skills Drowsiness Poor Judgment
Stages of Hypoxia
Stages of Hypoxia
Disturbance Stage
15,000 ft.
20,000 ft.
Marked loss in vision acuity. Marked loss of sensory function. Marked loss in audible acuity. Absence of memory. Loss of cognitive understanding. Complete loss of judgment
Disturbance Stage
Loss of Motor Coordination Speech Degradation Loss of Handwriting Skills
Performance Deficits
Time of Oxygen
1 Minute
2 Minutes
3 Minutes
4 Minutes
5 Minutes
6 Minutes
Put Back on Oxygen
Time of Useful Consciousness
• 5 minutes at 22,000 feet
• 18 seconds at 40,000 feet
• O2 required on all flights over 10’000 feet.
The elapsed time from exposure to oxygen deprived environment to the point where deliberate function is lost.
Protect yourself first !!!!!!!Protect yourself first !!!!!!!
Stages of Hypoxia
Critical Stage
20,000 ft.
ABOVE
Loss of Consciousness
Coma
Convulsion
Death
WWAARRNNIINNGG
WWAARRNNIINNGG
When Oxygen saturation falls to below 65%
serious cellular dysfunction occurs; and if
prolonged, will result in DEATH !!!!DEATH !!!!
Factors modifying hypoxia symptoms
• Pressure altitude• Rate of ascent
• Time at altitude
• Temperature
• Physical activity• Individual factors• Physical fitness• Self-imposed stresses
Self-Imposed Stresses
• Drugs
• Exhaustion
• Alcohol
• Tobacco
• Hypoglycemia
DDEEAATTHH
Be prepared to deal with these factors as seen
in your patients!!
Alcohol and Hypoxia
1 oz. of Alcohol is
physiologically equivalent to
2,000 ft.
1 oz.
2000 ft.
Tobacco and Hypoxia
3 Cigarettes smoked in rapid succession is equivalent to
5,000 ft.
3 chain smoked or ¼ pack in 4 hrs.
5,000 ft. MSL
Decreased Night Vision
Barometric Pressure Changes
Free Air in the Chest
ET Tubes
Pneumocephalis
GI/GU Concerns
NG/OG Tubes
Foley Catheters
Ostomies
Glass Bottles
PASG
Air Splints/ CAST
Dysbarism
Barotitis Media
Sinus Blocks
Barodontalgia
GAS LAWS
Thermal Stress
Increase in altitude produces a decrease in temperature.
Decrease in temperature produces an increase in metabolic demands.
What gas law covers this principle? CHARLES LAWCHARLES LAW
Gravitational Forces
Gravitational Forces
Col. John P. Stapp, USAF
632 mph acceleration in 5 sec. Decelerated to a complete stop in 1.4 seconds
Gravitational Forces
Gravitational Forces and the Medical Environment
• +G forces applied to Gz axis.
• Slow transition to horizontal flight.
• Little or no effect on hemodynamic status, perfusion or patient mental status
• Best of all options.Vertical Take Off
Gravitational Forces and the Medical Environment
• +G forces applied to Gx axis (seated) or –G axis (supine)
• Rapid transition to horizontal flight
• Significant effects on hemodynamic status, perfusion and mental status of the patient
• Take in consideration when deciding how to load the patient
Patient Positioning and Gravitational Forces
• Feet forward or head forward???
• Cardiac patient or Neurological patient?
• What about the high-risk OB patient?
Most patients are loaded along the long axis of the aircraft.
Decreased Humidity• An increase in altitude will produce a
decrease in humidity.
• Oxygen should be humidified for transports lasting longer than 1 hour.
• In general, most patients are dehydrated as a baseline.
• Consider fluid replacement early.
Noise Pollution
The Surgeon General has
established 85 decibels as the maximum level of continuous
unprotected exposure to steady-state noise for 8 hours
WWAARRNNIINNGG
WWAARRNNIINNGG
Noise Pollution Solution
Noise in the Aero-Medical Environment
Fixed Wing
• Most cabins are well insulated.
• Engines are placed away from patient and crew.
• Loudest during takeoff
• Does not require same protection
Rotor Wing
• Constant high noise environment.
• Engines directly over patient and crew.
•Greatly reduced communications.
• Requires soft plugs and headset/ helmet
Vibration
• Aircraft vibration can override the normal thermoregulatory mechanism, reducing
the body’s ability to generate or disperse heat.
Fatigue
Limit your self imposed stressors Drugs
Exhaustion
Alcohol
Tobacco
Hypoglycemia
Questions ????What is hypoxia?
The lack of oxygen to the tissues of the body
What are the four classifications of hypoxia?Hypoxic, hypemic, stagnant, and histotoxic
Give me an example of each classification of hypoxia:
Hypoxic – altitude; Hypemic – anemia, carbon mon-oxide poisoning; Stagnant – “G” forces, heart failure; Histotoxic – alcohol or drugs
What are the five signs (subjective) of hypoxia?
Hyperventilation, cyanosis, mental confusion, poor judgment, and muscle incoordinationWhat are the four stages of hypoxia with altitude?
Indifferent 0-10,000, compensatory 10,000-15,000, disturbance 15,000- 20,000 and critical stage 20,000- 25,000
Questions ????What are the SPO2 % with the four stages of hypoxia?
Indifferent 98%-90%, compensatory 89%-80%, disturbance 79%-70%, and critical stage 69%-60%
How can hypoxia be prevented?Use of oxygen, if available, or flights at lower altitudes
At what altitude will crew members start losing night vision?4,000 feet
How many times will carbon monoxide bind with hemoglobin molecules of red blood cells then to oxygen?
200 to 300 times
Smoking how many cigarettes in a rapid succession or how many in a 24 hour period will decrease your night vision by 20% and
give a physiological altitude of 5,000 feet?3/ 20
Lets play JeopardyLets play Jeopardy
This gas law states that gas expands as it rises What is Boyles Law
This gas law is responsible for decompression sickness What is Henry’s Law
This gas law states that as temperature increases so will volume
What is Charles’ Law
Alcohol and cigarettes decrease the ability for the hemoglobin to carry oxygen. Altitude has this same effect and is an example of this law What is Dalton’s Law
This law states that the rate of diffusion of gas is inversely proportional the square root of the density
What is Graham’s Law (Ex: C02 is more readily diffused across cell membranes)
SU
MM
AR
Y
Atmospheric Composition and Structure
Gas Laws in the Aero-
Medical World
Stresses Of Flight
Thank You for your
Attention!!!!