Flight Physiolgy Flashcards
Boyle’s Law
Algorithm
The pressure of a gas is inversely proportional to the volume of a gas at a constant temperature
P1 V1 = P2 V2
Affects ETT cups, Mast trousers, Air splints, IV drip rates (increases rates)
If the patient has a Pneumocephalus (air inside the cranial vault after trauma, usually from a direct blow, associated with depressed skull fractures) intracranial pressure will increase.
Dalton’s Law “Dalton’s Gang”
Algorithm
Law of partial pressures (this is an additive gas law)
The total pressure of a gas mixture is the sum of the partial pressures of all the gases in the mixture.
PT= P1 + P2 +P3+….
Responsible for soft tissue swelling at altitude (uptake of inert gasses into tissue)
Charles’s Law “Charlie is a cold Bitch”
Algorithim
At a constant pressure, the volume of gas is directly proportional to the absolute temperature of the gas
V1 / T1 = V2 / T2
When you charge an oxygen tank, the tank gets hot
This law has very little effect on the human body (we are at a relatively constant temperature)
Gay-Lussac’s Law
Algorithm
Directly proportional relationship between temperature and pressure
P1 / T1 = P2 / T2
Example - an oxygen cylinder left outside overnight will have a lower pressure reading in the morning due to temperature drop.
This is the gas law that explains the reason you need to add air to your tires in the winter (colder temps lower pressure)
Graham’s Law. “Grey Matter”
Law of Gaseous Diffusion
Gas exchange at the cellular level
The rate of diffusion of a gas through a liquid medium is directly related to the solubility of the gas and inversely proportional to the square root of its density
Limits gas ability to move though liquid
Example- gas bubbles coming out of exposed grey matter when at altitude
Henry’s Law. “Heineken”
Solubility of gas in liquid
The quantity of gas dissolved in 1cm cubed (1ml) of a liquid is proportional to the partial pressure of the gas in contact with the liquid
Affects divers, can lead to decompression sickness “the bends”
The bends are the most common form of decompression sickness
Decompression Sickness “The Bends”
Related to henry’s law
There are 6 different kinds of DCS
Type I - Nitrogen related, painful joints, mottled skin, pruritic (itching)
Patient may also feel like “ants are crawling on their skin”
Cutis marmorata-mottled skin, can often look like a sunburn
Type II - Neurological signs and symptoms, hypovolemic shock
Ground transport is preferred for all diving injuries/decompression sickness
Arterial Gas Embolism. (AGE)
Related to Boyle’s Law
Caused breath holding during ascent on a dive, air pushes through the alveoli and enters the skin in the neck/chest
*Causes a pneumothorax
Air is forced into the blood vessels
*The air bubble blocks blood vessels, causing ischemia
Patient presents with stroke-like symptoms (altered mental status, syncope, dizziness)
*May also have a cough and epistaxis (nosebleed)
AGE requires immediate hyperbaric treatment!
*Fly in a pressurized aircraft (fixed wing) or rotary wing <1000 MSL
Pulmonary Overpressurization
Related to Boyle’s Law
*A syndrome that occurs when “breath holding” compressed air during ascent. The greatest pressure differences are just below the surface of the water (
Atmosphere Calculations
Every 33 feet blow water 33=1 ATM (atmosphere)
Sea level=1 ATM
33 ft. Under water is 2 ATM
66ft. Under water is 3 ATM
Example: If you pick a patient that was diving at a depth of 33ft, they were exposed to 2 ATM of pressure. This may also be written as 2 atmospheres absolute (ATA)
Divers Alert Network
24 hour hotline for diving related injuries and questions
Www.diversalertnetwork.org (919-684-9111)
Physiologic Zone
Sea level to 10,000 feet (body can adapt to)
*Night vision is decreased beginning at 5,000feet
Physiologically deficient zone
10k - 50kft MSL
- Oxygen or pressurization required to survive at these altitudes
- In a pressurized cabin and a sudden decompression occurs Time of Useful Consciousness (TUC) is cut in half
- As a sign of compression loss is cooler temperatures in the cabin and window fogging
- Normally 90 seconds of useful consciousness at 30,000ft
- If a rapid decompression occurs, TUC is now around 45 sec
Example- If you were in an altitude chamber at 30K ft. And took your oxygen mask off, you would normally have around 90 seconds of consciousness. If you took your mask off and the chamber was rapidly decompressed, you would only have 45 seconds consciousness.
Space Equivalent Zone:
> 50Kft MSL
Oxygen Adjustment Calculation
(FiO2 x P1) / P2 = FiO2 required for ascent
FiO2 = Fraction of inspired oxygen P1= the pressure you are at (on the ground) P2= the pressure you are flying to (cruising altitude)
Pressure (P) Values.
Torr and mmHG are essentially the same thing
Sea Level 760 torr or mmHg. (1 ATM)
10k ft. MSL. 523 torr or mmHg
18k ft. MSL. 380 torr or mmHg. (1/2 ATM)
63 ft. MSL. 0 torr or mmHg. (O ATM)
Example- You have a patient on a Non-rebreather Mask at 0.5 FiO and you are at sea level. You will be flying to an altitude with a torr of 500. What will be the oxygen requirement at this pressure?
0.5 x 760
———- = 0.76 FiO2 required for ascent (%76 oxygen)
500
Hypemic Hypoxia
“Anemic”
- Reduction in the O2 carrying capacity of blood
- Anemia, hemorrhage
Histotoxic Hypoxia
Limits the use of available oxygen due to poisoning of the cytochrome oxidase system
Cynide, Alcohol, Carbon Monoxide (CO), Nitroglycerin, Sodium Nitroprusside (Nipride)
Hypoxic Hypoxia
“Not enough Oxygen in the air”
Low partial pressure of oxygen at altitude
Deficiency in alveolar O2 exchange
Cardiovascular/ Pneumothorax patients are more susceptible to this type of hypoxia
Stagnant Hypoxia
“Blood isn’t moving”
Reduced cardiac output or pooling of blood
High G forces, cadiogenic shock
Stages of Hypoxia “ICDC”
Stage of Hypoxia. Symptoms
Indifferent. Full reasoning abilities, some loss of night vision
Compensatory. Increased HR, ventilations, slowed judgement
Disturbance. Slurred speech, impaired judgment, “drunk”
Critical. No longer able to physiologically function, death
Imminent
The indifferent stage is important because you can still think.
Stressors of Flight
Self Imposed
Dehydration, Exhaustion, Alcohol, Tobacco, Hypoglycemia
Inherent
Thermal Changes, decrease in humidity, gravitational forces, fatigue, decreased partial pressure of oxygen, barometric pressure change, noise, vibration
Anterior / Posterior G forces
Best Tolerated
Example. Accelerating in your car
Vertical G Forces
Falling from a roof and landing on your feet
Lateral G Forces
Least tolerated
Being “T-Boned in a car wreck
G Forces
Cause blood pressure to drop
People are most affected by high G forces are those on B/P meds such as Beta Blockers
Those that are dehydrated
Altitude Effects
A cold, dry, high altitude environment has the greatest negative outcome to your patient
*Every 1,000 foot increase in elevation causes temperatures to drop 2 degrees celsius.
Temperature is inversely proportional to altitude
Barondontalgia
Occurs on Ascent
Air trapped in fillings expands due to Boyle’s law
Also referred to as Aerodontalgia
Barontitis
Occurs on Descent
Air trapped in the middle ear can’t vent through the blocked Eustachian Tube
(Eustachian Tube Dysfunction)
“Ear Block”
Barosinusitis
Can occur on Both Ascent and Descent
Can also cause pain in the maxillary teeth (but it is not the same as borodontalgia; that occurs only on ascent.
“Sinus Block”
