25 breathing in unusual environments

Question 1

what are the 3 phases to the respiratory response to exercise?

Answer 1

1 - immediate neural phase (anticipation)
2 - humoral phase, response to changes in O2, CO2, K+ etc
3 - steady phase, proportional to metabolic rate required

Question 2

What is the relationship between oxygen consumption and ventilation?

What does this suggest about the way our ventilation is controlled?

Answer 2

linear positive correlation

how is this so well matched?
It doesn’t oscillate, so it can’t just be down to our carotid bodies

Question 3

When does acidosis occur relative to ventilation?

Answer 3

the increase in metabolism is too much fr ventilation to cope

this forms the anaerobic threshold, seeing the accumulation of lactic acid

Question 4

At what point is V(a) not proportional to V(CO2)

Answer 4

when metabolism is about 5x the basal rate, after this V(A) increases disproportionately (hyperventilation

Question 5

What is the metabolic hyperbola and how would exercise effect this?

Answer 5

As we increase ventilation, PaCO2 decreases
(therefore the level CO2 drives ventilation)

exercise will shift thisup and right

Question 6

What 2 lines need to be considered when determining the ventilation at any given metabolic rate?

Answer 6

controller equation (shows that a rise in PaCO2 increases ventilation to remove it)
metabolic hyperbola (demonstrates the decrease in PaCO2 acieved by increased ventilation

Question 7

What is our PaCo2 and V(A) set by?

Answer 7

the intersection of the metabolic hyperbola and the controller equation

(ie the effect of CO2 on ventilation and ventilation on CO2)

Question 8

Why must the metabolic hyperbola be shifted up in exercise?

Answer 8

to prevent hypercapnia with increased metabolism

Question 9

What causes the sharpening of CO2 sensitivity seen inexercise (as their PaCO2 are the same as or even lower than resting individuals)?

Answer 9

this could be adrenaline, as we lose this effect when we use propranolol (a beta blocker)

Question 10

What happens to oxygen partial pressure with altitude increase?
What effect does this have?

Answer 10

fall in oxygen partial pressure
we begin to hyperventilate to rid ourselves of CO2, giving us respiratory alkalosis, inhibiting ventilation

as you go higher, hypoxia wins, so you get more alkalosis!
your kidney has to acclimatise to this, and we need more RBC’s

Question 11

How might you reach the top of Everest without supplemental oxygen?

Answer 11

let your kidneys adjust to the level of alkalosis, acclimatising

your Bohr shift will ultimately shift to the right

Question 12

How might we replicate negative gravity?

Answer 12

drop a plane lmao

Question 13

How much of V/Q distribution does gravity account for?

Answer 13

15%

the rest is down to the fractal nature of our lungs

Question 14

How does a decrease in altitude change when we dive?

Answer 14

outside of water, an increase in altitude will see gases decompress exponentially

water is incompressable, so when we dive, pressure increases linearly, no exponentially

Question 15

Why is the snorkel length limited to 40cm?

Answer 15

there is pressure on your thorax and you are breathing in atmospheric air

a longer tube also means there is a lot more dead space, which

this would be fixed by a narrow tube, but the resistance would also be increased so

Question 16

how long could a snorkel realistically be?

Answer 16

1.3m maximum

Question 17

What happpens if you go deeper than 50m?

Answer 17

gas gets very dense, so people use heliox

Question 18

What happens when you go up from deep waters?

Answer 18

the gases already in your body decompress quickly (faster than the water as water is incompressable!
it will escape from your lungs, middle ear, intracranial sinuses, joints, etc

Question 19

What happens in nitrogen narcosis?

Answer 19

as nirogen dissolves into brain tissue you get a general anaesthetic effect, making things confusing

Question 20

What 3 things limit the length of a snorkel?

Answer 20

dead space
resistance
maximum inspiratory pressure

Question 21

What is maximum inspiratory pressure?

Answer 21

intrapulmonary pressure = ambient pressure at surface
pressure on chestwall = pressure exerted by water at depth

maximum pressure generated by chestwall = 13kPa (130cm*2 water)

Question 22

What is decompression sickness?

Answer 22

nitrogen has quite a rubbish solubility, but at high pressure in the deep, more is forced into solution

during acent this comes out, and the time taken for this to be exhaled out is long

it can hence form bubbles inhibiting circulation

Question 23

What can nitrogen sickness cause?

Answer 23

pain (joints)
deafness
imparied vision
convulsion
dyspnoea

Question 24

How can nitrogen sickness be prevented?

Answer 24

regulated ascent
limit dive to 40m
use inert carrier (He), which is less soluble than N2 and is more diffusable

Question 25

How can nitrogen sickness be treated?

Answer 25

high pressure (decompression chamber)
recompress bubbles into solution and allow slow equilibration

Question 26

How do saturation divers operate?

Answer 26

they allow their tissues to become saturated with nitrogen

work in 28 shifts, 14 days at pressure, 14 days to decompress

Question 27

How do free divers go so deep?

Answer 27

they halt all unecessary means of metabolism, and enter a coma-like state, before they wake themselves up and go back

Question 28

What solution is there using liquid in our lungs?

When are hey used?

Answer 28

flouro-carbons have high oxygen solubility

used with premature newborns, so you don’t damage their lungs with high gas pressures

they also have anti-inflammatory effect, limiting coughing

Question 29

What are the avantages to liquid repiration?

Answer 29

lungs are filled with incompressable liquid, with no external pressure
no need to breathe high pressure gas
just ‘dial in’ mix of oxygen and nitrogen mix to be equal to that of atmospheric air

Question 30

What are the problems with liquid ventilation?

Answer 30

how is it circulated?
how do you replace lost oxygen and scrub XS CO2
how to ecacuate lungs afterwards
pneumothorax???