ALTITUDE
PHYSIOLOGY
OUTLINE
Classifications of Hypoxia
Signs and symptoms of Hypoxia
Stages of Hypoxia
Prevention of Hypoxia
Provisions of AR 95-1
Provisions of AR 40-8
REFERENCES
FM 1-301, Aeromedical Training for Flight
Personnel, May 1987
AR 95-1, Flight Regulations, september 1997
AR 40-8, Temporary Flying Restrictions Due to
Exogenous Factors
Hypoxia
State of oxygen [O2]
deficiency in the blood cells
and tissues sufficient to
cause impairment of
function.
Types of Hypoxia

Hypemic

Stagnant

Histotoxic

Hypoxic
Hypemic Hypoxia
+
+
+
+
+
+
+
+
+
+
Inability of the
blood to
accept oxygen
in
adequate
amounts
+
+
+
+
+
Stagnant Hypoxia
adequate
oxygen
Blood
moving
slowly
Reduced
blood
flow
Red blood cells
not replenishing
tissue needs
fast enough
Histotoxic Hypoxia
adequate
oxygen
Inability of
the
cell to accept
or use
oxygen
Red blood cells
retain oxygen
Poisoned tissue
Hypoxic Hypoxia
Reduced
pO2
in the
lungs
(high
altitude)
Red
blood cells
Body tissue
Hypoxia
Symptoms
Subjective: Feel
Air hunger
Apprehension
Fatigue
Nausea
Headache
Dizziness
Denial
Hot and Cold Flashes
Euphoria
Belligerence
Blurred vision
Numbness
Tingling
Hypoxia
Signs
Objective: See
Hyperventilation
Cyanosis
Mental confusion
Poor Judgment
Lack of muscle coordination
Stages of Hypoxia

Indifferent Stage

Compensatory Stage

Disturbance Stage

Critical Stage
Indifferent Stage

Altitudes
Air:

0
-
10,000 FEET
Symptoms:
decrease in
night vision
@ 4000 feet
Compensatory Stage

Altitudes
Air :

Symptoms:
10,000 -
15,000 FEET
impaired efficiency
drowsiness
poor judgment
decreased coordination
CAUTION!
Failure to recognize symptoms and
take corrective action may result in
an aircraft mishap
Disturbance Stage

Altitudes
Air:
15,000 -
20,000 FEET
Disturbance Stage
symptoms
 Sensory

Vision

Touch & pain

Hearing
Disturbance Stage
symptoms
 Mental




Memory
Judgment
Reliability
Understanding
Disturbance Stage
symptoms
 Personality

Happy Drunk
versus the

Mean Drunk
Disturbance Stage
symptoms
 Performance




Coordination
Flight Control
Speech
Handwriting
Time off Oxygen
1 minute
2 minutes
3 minutes
4 minutes
5 minutes
6 minutes
put back on oxygen
CAUTION!
Failure to recognize symptoms
and take corrective action may
result in an aircraft mishap
Disturbance Stage
 Signs

Hyperventilation

Cyanosis
Critical Stage

Altitudes
Air:

Symptoms:
20,000 FEET and above
loss of consciousness
convulsions
death
WARNING!
When hemoglobin saturation falls to
65%
serious cellular dysfunction occurs;
and if prolonged, can cause death
WARNING!
Factors modifying hypoxia
symptoms

Pressure altitude

Physical activity

Rate of ascent

Individual factors

Time at altitude

Physical fitness

Temperature

Self-imposed stresses
it’s a no brainer!
Drugs
Alcohol
Tobacco
Exhaustion
Hypoglycemia
keep self imposed stresses out of the aircraft
alcohol
B
U
Z
Z
Expected Performance Times
FL 430 & above
9-12
seconds
FL 400
15 - 20
seconds
FL 350
30 - 60
seconds
FL 300
1-2
minutes
FL 280
2 1/2 - 3
minutes
FL 250
3-5
minutes
FL 220
8 - 10
minutes
FL 180
20 - 30
minutes
Expected performance time for a crew member
flying in a pressurized cabin is reduced
approximately one-half following
loss of pressurization such
as in a:
RD
rapid decompression
Hypoxia

Prevention

limit time at altitude

breathing oxygen

pressurized cabin
Hypoxia

Treatment

oxygen

descend to a safe altitude
AR 95-1
Altitude Restrictions and Oxygen Requirements
Unpressurized
14,000
Supplemental Oxygen Required
30 Min Total
1 Hour Total
12,000
10,000
25,000
14,000
10,000
Crew O2 masks readily available
10 Min Supply of O2 for all occupants
Maintain Cabin PA at or below 10,000
Pressurized
AR 95-1
Altitude Restrictions and Oxygen Requirements
 If pressurization is lost above 14,000’, an immediate
descent will be made to a cabin pressure altitude of 10,000’
or below.
 Then unpressurized restrictions apply
AR 40-8
Flight Restrictions Due to Exogenous Factors
• Flying duty is prohibited for 24 hours after SCUBA diving
• Aircrew members will not be regular blood donors.
• After blood donation, aircrew members will be
restricted from flying for 72 hours
• Performance of flying duty is prohibited for 12 hours after any altitude chamber flight
Questions?