Partial Pressure

Question 1

What is partial pressure and how do you calculate it?

Answer 1

Partial pressure is a portion of the total pressure exerted by a gas. It is the same value in liquid as in gas.

Partial pressure = Pressure of Atmosphere x the fraction that has the interested gas

EX: 02 makes up 21% of atm
P02 = Patm x F02
P02 = 760mmHg x 0.21 = 160mmHg

Question 2

what is atmospheric pressure value used in partial pressure calculations

Answer 2

760 mmHg

Question 3

What happens with partial pressure of a gas when it comes across a gas-liquid interface?

Answer 3

gas in a gaseous state adjacent to liquid come into equilibrium

so Partial pressure tells us whats happening in the gaseous state AND in water
• PO2 of the oxygen dissolved in the water is equal to the PO2 in the air above the water

Question 4

gas in a gaseous state adjacent to liquid come into ..

Answer 4

equilibrium

Question 5

Explain why you hear a champagne bottle POP

Answer 5

the pressure inside> pressure outside of bottle due to fermentation (CO2 made inside the bottle) compared to nearly 0 in the atmosphere

CO2 is at equilibrium with gas above liquid and gas in liquid

The POP happens because now we have equalization of the pressure of whats in the bottle to the Atm
equalization of pressure = POPing sound

• atm pressure inside bottle > outside atm – POP

Question 6

Explain why we get bubbles when we pop champagne

Answer 6

when we POP the bottle the CO2 that was accumulating above the liquid escapes into air

very little Co2 in atm and PCo2 in liquid dissolved that is very high– disequilibrium now for Co2
• this means that the dissolved gas will come out of the solution and form bubbles that rise to surface
• gas is released from surface and then leaves bottle then equilibrates with air

Question 7

It is the total pressure difference of atm that determines whether gas rushes in or out of the bottle. If total pressure of the gas inside the bottle is the same as the atmospheric pressure when the cork is pulled, what happens?

Answer 7

it is an anti-climatic soundelss event

• atm pressure inside bottle = outside atm – soundless event (regardless of PCO2)

Question 8

what is the alveolar-capillary interface? and what happens here?

Answer 8

this is between the lung alveolis and blood vessel capillaries
this is where oxygen enters and diffuses into blood vessels
oxygen is then picked up by hemoglobin

Question 9

describe the partial pressure of oxygen at the alveolar-capillary interface

Answer 9

PO2 blood = PO2 alveolus
* comes into equilibrium

total amount of oxygen in blood = dissolved + bound
• the two ways that oxygen exists in blood either bound to hemoglobin or dissolved in the blood
P02 in the blood helps us determine what the content of oxygen is in the blood

• partial pressure of oxygen ONLY includes the oxygen that is dissolved in the blood
• partial pressure of oxygen in blood in independent of hemoglobin

Question 10

twins with different hemoglobin levels 14g/100ml and 10g/100ml. what is partial pressure of oxygen in twins blood?

Answer 10

• partial pressure of oxygen ONLY includes the oxygen that is dissolved in the blood
• partial pressure of oxygen in blood in independent of hemoglobin
• so it is the same

Question 11

State Boyles law

Answer 11

P x V = k
there’s an inverse relationship of pressure and volume for fixed amount of gas

ex: scuba diver water pressure increases making it difficult to breathe bc lung volume decreases

Question 12

why would a scuba diver need to use a hyperbaric chamber (high pressure)?

Answer 12

decompression sickness - from nitrogen buildup in tissue (not as easily metabolized as oxygen)

chamber allows nitrogen to stay in solution (no bubbles will form) then they can gradually reduce pressure in chamber allowing the nitrogen to leave blood & tissue slowly (mimicking slow ascent to surface)

hyperbaric oxygen therapy - pressure is higher than normal atm, allows oxygen to travel quickly to tissues increasing oxygen supply

Question 13

is a hole in between R & L atria of heart (upper chambers)
everyone has it at birth but it closes after being born
PFO is what it is called when it fails to close after birth, an abnormality (1 in 4 ppl have)

Answer 13

patent foramen ovale

Question 14

oxygen moves from alveoli into the blood and then to hemoglobin sites
a reading of say 98% of this means the amount of oxygen that is bound to hemoglobin in the blood on hemoglobin sites
(correlate- a good measure of partial pressure)

Answer 14

Oxygen saturation