Altitude
Physiology
and the
Stresses of
Flight
We will cover the following:
The Atmosphere
• Composition
• Structure
• Physiologic
Zones
GAS LAWS
Universal Gas Law
Boyle’s Law
Charles’ Law
Henry’s Law
Dalton’s Law
Graham’s Law
Gay-Lussac’s Law
STRESSES OF FLIGHT
The Atmosphere
OXYGEN
21%
78%
NITROGEN
“Others” include: Argon, CO2, Neon, Helium, Krypton, Hydrogen
The Atmosphere
Atmospheric composition percentages
REMAIN THE SAME regardless of the
altitude.
O2 is 21%
N2 is 78%
Other is 1%
AT
Sea Level
1,000 ft
7,000 ft
14,000 ft
30,000 ft
With an INCREASE in altitude, there is a
DECREASE in pressure:
Alveolar 02 and Hgb Saturation
Altitude Correction
ALTITUDE
(FEET)
BAROMETRIC
PRESSURE
(mmHg)
ALVEOLAR
OXYGEN
( PAO2)
OXYGEN
SATURATION
% (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 the
partial pressure of oxygen.
pO2
GAS LAWS
Universal Gas Law
Gas molecules of higher pressure move in the
direction of gas molecules of a lower pressure
PO2 = 100mmHg
PO2 = 40mmHg
PO2 = 74mmHg
PO2 = 66mmHg
Blood Gas Exchange
Venous Capillary
Hemoglobin Saturation 75%
PCO2 = 46 mm
CO2
Tissue
PO2 = 1 - 60 mm
PCO2 = 46 mm
PO2 = 40
mm
Alveoli
PO2 = 100 mm
O2
PCO2 = 40 mm
O2
O2
PCO2 = 40
mm
PO2 = 100 mm
Arterial Capillary
Hemoglobin Saturation 98%
CO2
O2
Physical Divisions of the Atmosphere
1200 miles
EXOSPHERE
600 miles
IONOSPHERE
50 miles
STRATOSPHERE
Tropopause
MOUNT EVEREST
29,028 FEET
TROPOSPHERE
Sea level to flight level 300 600 depending on temperature,
latitude and season.
Physiological Zones of the Atmosphere
63,000 ft
SPACE EQUIVALENT ZONE: 50,000 feet and above
DEFICIENT ZONE: 10,000 to 50,000 feet
18,000 ft
EFFICIENT ZONE: Sea level to 10,000 feet
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
GAS LAWS
Boyle’s Law
The volume of a gas is
inversely proportional
to its pressure;
temperature remaining
constant.
Robert Boyle
P1 x V1 = P2 x V2
Gas Expansion
9.5X
43,000
6.0X
4.0X
2.5X
34,000
5.0X
3.0X
25,000
1.8X
18,000
SEA LEVEL
2.0X
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
MEDIASTINUM
PNEUMO
thorax
PNEUMO
cephalus
PNEUMO
peritoneum
PNEUMO
-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
Barodontalgia
Gastrointestinal
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)
Barotitis Media
Tympanic
Membrane
Middle Ear Cavity
External Ear
Atmospheric
Pressure
Clear
Eustachian Tube
Middle Ear Cavity
Tympanic
Membrane
External Ear
Eustachian Tube
Blocked / Infected
Atmospheric
Pressure
Ear Block
Barosinusitis/ Sinus Blocks
Frontal
Ethmoid
Maxillary
Sphenoid
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’ Law
At 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
For every 1000 feet
altitude increases,
Temperature decreases
2 degrees centigrade
1000’
Altitude
Or
Climb 100m = 1°C
drop
2 Degrees C
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 Law
Defines 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
Temperature
Constant Volume
Pressure
Temperature
Henry’s Law
• The amount of gas
dissolved in
solution is directly
proportional to the
pressure of the
gas over the
solution.
Decompression Sickness
Treatment
• Descend
Immediately
• 100% Oxygen
• Compression
greater than 1
atmosphere (ATM)
• Land at the nearest
location where
qualified medical
assistance is
available
Evolved Gas Disorders
WARNING
• Evolved gas disorders
are considered
serious medical
emergencies and
require emergent
specialized care
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
The Bends
• N2 bubbles become
trapped in the joints.
Onset is mild, but
eventually painful !
Evolved Gas Disorders
The Chokes
The Creeps
• 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.
Evolved Gas Disorders
The Staggers
• N2 bubbles affect
spinal cord. Visual
disturbances,
paralysis, one sided
tingling.
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 Gang
Simply 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)
523 (10,000 ft )
= FiO2% 51% needed
Graham’s Law
The 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 AeroMedical Environment
• CO2 has a solubility factor 20 times
greater than O2 and will thereby, more
readily diffuse across a liquid membrane.
Questions????
1.
2.
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
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.
4.
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 Law
2. Charles’ Law
3. Dalton’s Law
4. Henry’s Law
Which of the following gas laws is most responsible for soft tissue
swelling during flight?
1. Boyle’s Law
2. Charles’ Law
3. Dalton’s Law
4. 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
Hypoxia is a poor stimulus for respiration
Hypercarbia is much better
• Types of Hypoxia:
– Hypoxic
– Hypemic
– Histotoxic
– Stagnant
Hypoxic Hypoxia
Inadequate
Availability
of Oxygen
Molecules
Reduce
pO2 in the
lungs due
to lower
availability
of oxygen
molecules
Body tissue
Reduced
pO2
in the lungs
(high
altitude)
Red
blood cells
Hypemic Hypoxia
Inability of the
blood to accept
oxygen in
adequate amounts
+
+
+
+
+
+
+
+
•COPD
+
+
+
Medical Conditions
•Pneumonia
+
+
•Pulmonary Edema
•Alcohol
+
+
•Pulmonary Embolism
Histotoxic Hypoxia
Adequate
oxygen
Medical Conditions
•Cyanide Toxicity
Inability of the
cell to accept
or use oxygen
•CO Poisoning
•Anaphylaxis
•ETOH
•OD
Poisoned tissue
Red blood cells
retain oxygen
Stagnant Hypoxia
Adequate
oxygen
Reduced
blood
flow
Blood
moving
slowly
Medical Conditions
• AMI
•Cadiomyopathy
•Cardiogenic Shock
•Crush Injuries
Red blood cells
not replenishing
tissue needs
fast enough
Hypoxia
Symptoms
Subjective: Feel
Air Huger
Apprehension
Fatigue
Nausea
Headache
Dizziness
Denial
Hot/ Cold Flashes
Euphoria
Belligerence
Blurred Vision
Numbness
Tingling
Hypoxia
Symptoms
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
10,000 ft.
Sea Level
Decrease
in Night
Vision at
4,000 ft.
MSL
Stages of Hypoxia
Compensatory Stage
15,000 ft.
Impaired Efficiency
Decreased Motor
Skills Drowsiness
Poor Judgment
10,000 ft.
Stages of Hypoxia
Disturbance Stage
20,000 ft.
15,000 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
Performance Deficits
Loss of Motor Coordination
Speech Degradation
Loss of Handwriting Skills
Time of Oxygen
1 Minute
2 Minutes
3 Minutes
4 Minutes
5 Minutes
6 Minutes
Put Back on Oxygen
Time of Useful Consciousness
The elapsed time from exposure to oxygen
deprived environment to the point where
deliberate function is lost.
Protect yourself first !!!!!!!
• 5 minutes at 22,000 feet
• 18 seconds at 40,000 feet
• O2 required on all flights over 10’000 feet.
Stages of Hypoxia
Critical Stage
ABOVE
Loss of Consciousness
Coma
Convulsion
Death
20,000 ft.
W
A
R
N
I
N
G
When Oxygen saturation
falls to below 65%
serious cellular
dysfunction occurs; and if
prolonged, will result in
DEATH !!!!
W
A
R
N
I
N
G
Factors modifying hypoxia
symptoms
• Pressure altitude
• Physical activity
• Rate of ascent
• Individual factors
• Time at altitude
• Physical fitness
• Temperature
• Self-imposed stresses
Self-Imposed Stresses
D
E
A
T
H
• Drugs
Be prepared to
• Exhaustion deal
with these
factors as seen
• Alcohol
in your
patients!!
• Tobacco
• Hypoglycemia
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
GAS LAWS
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
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 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???
Most patients are loaded along the
long axis of the aircraft.
• Cardiac patient or
Neurological
patient?
• What about the
high-risk OB
patient?
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.
W
A
R
N
I
N
G
Noise Pollution
The Surgeon General has
established 85 decibels as the
maximum level of continuous
unprotected exposure to steadystate noise for 8 hours
W
A
R
N
I
N
G
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 incoordination
What 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 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)
SUMMARY
Atmospheric
Composition
and Structure
Gas Laws in
the AeroMedical World
Stresses Of
Flight
Thank You for
your Attention!!!!