Flight Physiology Flashcards
Boyles Law
•As altitude increases, atmospheric pressure decreases, and gas in an enclosed container expands(Boyles Balloon)
P1 V1=P2 V2
Charles Law
•Atmospheric pressure is constant
•Proportional relationship w/ Temp & Vol.
•q 1000’ elevation Temp decreases 2C
•q 150m elevation Temp decreases 1C
Daltons Law
•Total pressure of gas mixture is the sum of partial pressure of all gases.
Also describes how pressure affects partial pressures of a gases at certain altitudes.
How to apply
Increase FIO2(concentration of O2)
Henrys Law (Soda can)
•The amount of gas dissolved in a solution is directly proportional to the pressure exerted by gas over the solution.
How to apply
Place gas under pressure(BVM or Vent)
Ficks Law
•Rate of diffusion of a gas across a membrane is determined by: chemical nature of membrane, surface area, partial pressure gradient, and thickness of membrane.
How to apply
Change surface area(add peep)
Grahams Law (Equality)
•Rate of diffusion is proportional to the square root of its molecular weight.
*Lighter gas diffuses faster than heavier gas
*Gases move from higher to lower concentration until equality is achieved.
Atmospheric pressure at sea level
760mmHg or 760 torr
*equal to 1 atmosphere(ATM)
*Barometric pressure is the same thing but in a different unit of measurement(inHg).
Ex: Barometric pressure at sea level is 29.92inHg
of feet below sea level to gain 1 atmosphere?
For q 33’ below sea level you gain 1 atmosphere
P1V1=P2V2(solving for V2)
P1V1/P2=V2
P1- starting ATM @ lowest altitude
V1- starting volume of container
P2- highest ATM based on highest altitude
V2- Ending volume as impacted by the highest altitude
Barotitis Media
Ear pain
Test question
During descent!
Barosinusitis
Pain in sinuses
*Ascension problem
Barobariatrauma (the Bends)
•Acts like decompression sickness
•Seen in obese patients(fat holds onto Nitrogen)
•Nitrogen Narcosis during ascension
•Ascension problem
•Tx is high flow O2
Barodentalgia
Tooth pain(ascent problem)
Stop the flight and go to the dentist ASAP
Gay-Lusaacs Law
*Charles brother
•Temp and volume affect the pressure exerted on the sides of a container.
Difference between PaO2 & PAO2
•PAO2= partial pressure of O2 in Alveoli
•PaO2= partial pressure of O2 in arterial blood
D.E.A.T.H.
Drugs
Exhaustion
Alcohol
Tobacco
Hypoglycemia
Stressors of Flight
•Hypoxia*
•Barometric pressure
•Thermal changes
•Decreased humidity
•Noise
•Vibration
•Fatigue
•Gravitational forces
•Flicker vertigo(dizziness)—5-20Hz
•Spatial disorientation
Effects & symptoms of Hypoxia
(Subjective)
•Fatigue
•Anxiety
•Nausea
•HA
•Dizziness
•Denial
•Numbness/Tingling
•Hot & cold flashes
• Agitation
•Blurred vision
•Euphoria
Effects & Symptoms of Hypoxia
(Objective)
•Hyperventilation
•Confusion
•Poor decision making
•Cyanosis
•Lack of coordination
•Unconsciousness
Indifferent stage of Hypoxia(1)
•0-10k’
•SPO2 90-98%
•Decrease in night vision @ 4k’
• increase in HR & RR
•Unaware of symptoms
smokers lose 20% of night vision @ sea level(physiological altitude of 5k’
Compensatory Stage of Hypoxia(2)
•10-15k’
•SPO2 80-90%
•Advanced stage 1 symptoms
•Night vision < 50%
•CNS symptoms:
-poor judgement
-Irritable
-Drowsy
-Decrease coordination
Disturbance stage of Hypoxia(3)
•15-20k’
•SPO2 70-80%
•Senses:Vision, Touch, Pain, Hearing
•CNS: Memory, judgement, reliability, understanding.
•Personality: Happy drunk vs mean drunk
•Psychomotor function: coordination, flight control, speech, handwriting.
•Signs: hyperventilation and cyanosis
Critical stage of Hypoxia(4)
•20-25k’
•SPO2 60–70%
•Inability to remain upright
•Jerking upper limbs
•Seizures
•Rapid unconsciousness
•Coma & death
Time if useful consciousness(explosive decompression)
> 40k’ —Single digit seconds. The shortest time interval answer possible
Calculate desired O2 per altitude
*PaO2 decreases by 5mmHg for q 1k’ increase in altitude.
Calculation: (%FIO2xP1)/P2=FIO2 at new altitude.
P1- current barometric pressure
P2- new barometric pressure at altitude
(Altimeter and Barometric pressure are the same)
Quiz question:
an ARDS patient with the current SPO2 of 85% is being transferred. The current FiO2 via the mechanical ventilator is set at 50%. The current referring hospitals elevation is approximately sea level. The pilot advises the highest altitude you will be flying at will be 5000 feet. Using the following information calculate the required FiO2 change needed based on the desired FiO2 by altitude formula.
Answer:
FI02 @new altitude=(%FiO2xP1)/P2
P1=current barometric pressure
P2= new barometric pressure at altitude
Quiz question:
If the atmospheric pressure at 18,000 feet MSL is 380 torr, what is the partial pressure of oxygen at that altitude?
As we ascend an altitude, the concentration of O2 remains the same however, the decrease in atmospheric pressure also decreases the partial pressure of oxygen.
380 TORR x 0.21 = 79 PaO2
Quiz question:
When administering high concentrations of oxygen to alleviate hypoxic hypoxia, you are altering, which component of which gas law?
Answer:
Giving high concentrations of O2 is affecting Henry’s law and the solubility of oxygen diffusion. Henry’s law affects the concentration, solubility, and pressure that oxygen molecules need to be placed under to diffuse more rapidly into the solution.
Quiz question:
A patient suffering from decompression sickness is an example of which gas law?
Answer: Henry’s law
