Gas exchange - L4

Question 1

What is total pressure the sum of?

Answer 1

Total pressure is the sum of all the indiviual gases the Partial Pressures
Ptotal = P1 + P2 + P3 + … Pn

Question 2

What does partial pressure of a gas depend on?

Answer 2

Fractional concentration of the gas - quantity of gas relative to total quantity of gas in mixture
Total pressure of gas mixture

Question 3

Formula for P gas?

Answer 3

Pgas = % gas x Ptotal

Question 4

Composition of air:

Answer 4

79% Nitrogen
21% Oxygen
Trace amounts: carbon dioxide, helium, argon, etc.
Water can be a factor - depending on humidity (i.e. at
100% humidity then water takes 6.2% of air)

Question 5

What is PN2 at sea level with 0% humidity?

Answer 5

At sea level our pressure is 760mmHg and assuming 0% humidity, the partial pressure of nitrogen is 600 mm Hg
PN2 = 0.79 x 760 = 600 mmHg

Question 6

What is PO2 at sea level with 0% humidity?

Answer 6

PO2 = 0.21 x 760 mm Hg = 160 mm Hg

Question 7

What is the pressure of air at sea level with 0% humidity

Answer 7

P air = 760 mm Hg = PN2+PO2

Question 8

PCO2? at sea level with

Answer 8

Air is only 0.03% CO2
PCO2 = 0.0003 x 760 mm Hg = 0.23mm Hg

Question 9

at 100% humidity P air?

Answer 9

P air = 760 mm Hg = PN2+PO2+PH20

Question 10

PN2 at 100% humidity?

Answer 10

PN2 = 0.741 x 760 mm Hg = 563 mm Hg

Question 11

PO2 at 100% humidity?

Answer 11

PO2 = 0.196 X 760 mm Hg = 149 mm Hg

Question 12

PH20 at 1005 Humidity?

Answer 12

H20 = 0.062 x 760 = 47 mmHg

Question 13

PCO2 at 100% humidity?

Answer 13

PCO2 = 0.00027 x 760 = 0.21 mmHg

Question 14

Is alveoli pressure different to atmospheric?

Answer 14

Yes

Question 15

Is the partial pressure higher or lower in the interstitial fluid surrounding the capillaries?

Answer 15

The interstital fluid surrounding capillaries partial pressure is lower, because the respiratory tissue consume oxygen and PCO2 is higher around 46 and PO2 is around 40 or lower

Question 16

What happens when O2 and CO2 diffuses down pressure gradients?

Answer 16

when o2 and co2 diffuse down pressure gradients, o2 goes from blood to tissues and co2 moves from tissue to blood

Question 17

What m is considered moderate altitude

Answer 17

2,000m considered moderate altitude

Question 18

Fick’s law of diffusion

Answer 18

Diffusion rate V gas through a sheet of tissue depends on partial pressure gradient of gas, the surface rate of respirtaoyr membrane, thckness of emmbrane through which gas is diffused and diffsuion constant

Question 19

exercise - fick’s law?

Answer 19

surface area increased as pulmonary blood pressure is raised by increased cardiac output - previous closed pulmonary capillaries are forced open
alveoli membrants are stretched further due to larger and deeper breaths
can increase with pathologies

Question 20

what is the diffusion constant related to? which is higher CO2/O2?

Answer 20

solubility to the gas and to its molecular weight - inversely

CO2 is higher than that of O2
approx 20 times of O2

Question 21

What is the diffusion process affected by?

Answer 21

Exercise and the thickening of the blood-gas barrier

Question 22

Due to the diffusion process it is affected by exercise what do highly trained athletes face a risk of?

Answer 22

Risk of exercised induce arterial hypoxemia (EAIH)

Question 23

PULMONARY OEDEMA - what is it characterised by?

Answer 23

Fluid accumulation in alveoli and/or interstitial space

Question 24

treatment for pulmonary oedema

Answer 24

administering oxygen and diuretics

Question 25

emergency case of treatment for pulmonary oedema

Answer 25

reduce altitude as fast as possible

Question 26

What 4 things does this fluid accumulation that characterises pulmonary oedema do?

Answer 26

1. Impairs diffusion (higher distance from alveoli to blood) 2. Leakage in unprotected capillaries 3. Increases work of breathing (decreased lung compliance) 4. Arterial blood shows lower PO2 and higher PCO2

Question 27

What are the causes of pulmonary oedema? 2 reasons

Answer 27

Increased capillary pressure via left heart failure which has an inability to supply sufficient BF Reduced atmospheric pressure at high altitude

Question 28

What happens to the body at 3000m altitude?

Answer 28

3,000m altitude inspired oxygen already down to 95 and PO2 is approx 60% - dangerous zone in this altitude, Oxyhametoxylin goes very steep curve and with a small increase in altitude from then on you will lose quite a lot of o2 so very challenging if above this altitude.

Question 29

What is the highest m that humans live at and what happens to the body here?

Answer 29

5,000m altitude - highest that humans live at - arterial PO2 down to around 50 - body has adaptative responses such as making more RBCs so that we can eventually survive here

Question 30

What is located greater than 5000m? What happens to the body here?

Answer 30

Greater than this - Highest mountain summits: MT Everest: 8800m - recorded PO2 values is about 25 mm Hg - very low - must properly acclimitiase to get to this altitude - unliveable really

Question 31

What is the air in alveoli saturated with and does this take up more or less of the gas available?

Answer 31

air in alveoli is saturated with water vapour so air is going to take more of the concentration of available gas

Question 32

Changes of gases occurring continuously between alveoli air and capillary blood, what happens upon respiration and where?

Answer 32

Upon respiration, fresh atmospheric air mixes with air rich in CO2 and relatively poor in O2 in dead space of conducting zone