Flashcards in Flight Physiology Deck (31):
Boyles law, air in middle ear expands on ascent, escapes via Eustachian tube (dumps into nasopharynx).
-on descent, atmospheric pressure increases on ear drum, air is drawn back into ear. If tube is blocked, air cannot get back in,
Air trapped beneath dental work. (New or foreign)
-expanding air cannot escape. Pushed down on nerve.
-Slow ascent. Analgesics.
-air trapped in sinuses.
Ascent / Descent problem. Expanding air cannot escape.
Pressure in sinus tissues,
-slow climb out, nasal decongestions (neosynephrine), analgesics
-nitrogen absorbed in adipose tissue, expands on rapid ascent.
-attempts to release into plasma then to lungs.
-cannot blow off quickly enough = nitrogen toxicity, bends
-FiO2 to 100%
ETT considerations for Boyles law.
ETT cuff not typically an issue in RW
-30,000 ft plus requires replacement w/ water
-cabin decompression = cuff rupture.
Boyle law Cast considerations
Tissue under cast is rich with air, can expand.
-casts less than 7 days old require bi-valve
-cut on medial and radial aspect, wrap with ace bandage.
Chest tube considerations concerning Boyle's law
Has moving through tube into collection device.
-needs vented to atmospheric air so it can equalize.
-otherwise gas will expand on ascent - escapes into chest.
-pop hemilick valve in line with the atrium.
At constant pressure, volume of a gas is directly proportionate to the absolute temperature of the gas.
-heat a gas, volume expands,
-cool a gas, volume contracts
-V1/T1 = V2/T2
Celsius temp drops 1 degree for q meters climbed.
Volume of a gas is inversely proportionate to its pressure under constant temp.
Same as Charles law only vessel is fixed container
-directly proportional between temp and pressure.
Aeromedical application: O2 tank, cools on climb, O2 pressure drops
At constant temp: the amount of a given gas dissolved in a type and volume of liquid is directly proportional to the partial pressure if that gas in equilibrium with that liquid.
Henry's law aeromedical application, cabin decompression
Leer jet at 30k feet- explosive decompression
-partial pressure of plasma O2 is greater than that of lungs
-O2 will not dissolve for, lungs into plasma
-O2 will reverse from plasma into lungs
-Results in sudden LOC
(Another application is decompression sickness)
Law of gaseous diffusion.
-diffusion rate of a gas through a liquid medium is directly related to the solubility of the gas and inversely related to the square root of its density.
-at equal pressures/temps, gases with smaller mass diffuse faster,
O2 smaller than CO2, but CO2 more soluble.
-CO2 diffuses across fluid faster than O2
Factors that influence Graham's law
Surface area, diffusion gradient, diffusion distance, molecular size, solubility.
The total pressure of a gas mixture is the sum of the partial pressures of all gases in the mixture.
P1 = fractional [P1] x barometric pressure.
DEATH - factors effecting flight stressors
Exhaustion (predisposes spatial disorientation)
Night vision loss, smokers considerations
Loss of night vision: 5000 msl
Smokers loose 4000 ft of night vision capabilities
Rods vs cones
Rods: night vision, periphery of eye
Cones: day vision, center of eye.
What is most susceptible to hypoxia?
1 ATM weighs
14.7 pounds, or 760 Hg (torr)
-per square inch
-on perfect day: 59 degrees F
Greater atmospheric change noted as sea level with ascent than starting at higher elevation.
-ascent, pressure becomes less (0.5 ATM or 389 Hg at 18,000 ft)
-as you dive, 1 ATM = 33 feet under water..
Diver has dove 66 feet, how many atmospheres are in him?
-2 atmospheres of water
-1 atmosphere of air
Sea level to 10,000 ft.
Great compensation unless ailments exist
Physiological Deficient zone
10k to 50k ft
-healthy individuals notices compensatory attempts
- most would not experience significant symptoms
250k or higher
Deficiency in alveolar O2 exchange (aka altitude hypoxia)
-drop in available O2, apnea, altitude, venous mixing
Failure of the tissues ability to use presented O2
-commonly results of poisoning, or metabolic disorders
-cyanide (not only displaces O2 from Hgb, also interferes with mitochondrial ability to utilize O2) interferes wi electron transport chain in cellular respiration.
Reduced cardiac output, or pooling of blood
-heart failure, PE, Shock
-able to get O2 from lungs, blood is not going anywhere.
-localized stagnant hypoxia: compartment syndrome