Aviation Physiology Flashcards
Boyle’s Law
Boyle’s balloon; Volume
P1V1=P2V2
Wet gas expands>dry gas at given altitude
Dalton’s Law
P=P1+P2+P3+…
Percentages of gases is always the same w altitude though actual amount may decrease w altitude
Henry’s Law
Henry’s Heineken->think of beer/soda and gas coming out of solution. I.e. solubility
Quantity of gas dissolved in a given volume of liquid is proportional to the partial pressure of the gas in contact (above) the liquid.
Pulmonary capillary blood flow does what at altitude?
Globally decreases-> therefore
Water vapor pressure
Water vapor pressure=47mmHg
Therefore lungs can never provide less than 47mmHg water vapor
Oxyhemoglobin Dissociation Curve
L shift
R shift
L shift->O2 uptake->initial exposure to altitude, low temp, CO, methemoglobin
R shift->O2 offloading->elevated 2,3-DPG, increased temp (exercise), high pco2/acidosis
4 types of hypoxia
- Hypoxic: deficiency in alveolar exchange, decreased FiO2
- most common in aviation & non-pressurized aircraft - Hypemic:reduced O2 carrying capacity of bld. Eg Anemia, CO poisoning
- Stagnant: reduced CArdiac output. Eg sustained G forces, DCS bubbles
- Histotoxic: toxins at tissue level that cause inability to use O2. Eg cyanide; ethyl alcohol, hydrogen sulfide
Stages of hypoxia
- Indifferent-87-98%; no observable impairment
- Compensatory-80-87%; start to see increase in HR, fatigue, decreased judgment
- Disturbance-65-80%; 1st of the uncompensated stages; can’t compensate for decreased O2. Signs/symptoms of hypoxia are obvious (motor control, mental processing etc)
- Critical stage-60-65% SaO2; confusion, dizziness, LOC
Time of Useful Consciousness (TUC)
Time from loss of O2 supply/exposure to O2 poor env’t to time when deliberate function is lost.
Affected by: altitude, rate of ascent (or decompression), duration of hypoxia exposure, individual tolerance, environmental conditions, physical fitness, physical activity
TUC at various altitudes 45,000 ft MSL 35,000 ft MSL 30,000 ft MSL 22,000 ft MSL 20,000 ft MSL
45,000 ft MSL–>9-15seconds
35,000 ft MSL–>30-60 secs
30,000 ft MSL–>1-2 minutes
22,000 ft MSL–>5-10 minutes
20,000 ft MSL–>30mins
Rapid descent–> halve TUC
PRICE Check
Pressure-O2 oressure Regulator-no cracks, grease Indicator-black/white, follow RR Connections-pos pressure Emergency signals
Tx of hypoxia
100% O2 Check O2 equipment Descend below 10,000 ft Check regulator, connections Control breathing Communicate w ATC
Decompression Sickness
-Nitrogen bubbles released with decreased pressure (Henry’s law); bubbles can cause stagnant hypoxia.
-usually occurs within 1hr; can occur up to 24hrs later
-rare at altitudes ground x 72hrs
Pain-only alt DCS-> tx w ground level O2 x 32hrs, 24hr obs, recompression if sxs recur
Type 2->ground x 1momth, DQ, typically get waiver; recurrent or type II-> Initial applicants denied
Motion sickness
Simulator sickness
Normal response to abnormal environment
“Motion maladaptive syndrome”
Simulator sickness: cognitive sxs are more severe, can last for hrs
Risk factors: Female 2x > Male Decreases w age after puberty Eating prior to motion High level aerobic conditioning Fear/anxiety Non-pilot crew
Types of vision
Photopic
Mesopic
Scotopic
