25 breathing in unusual environments Flashcards
what are the 3 phases to the respiratory response to exercise?
1 - immediate neural phase (anticipation)
2 - humoral phase, response to changes in O2, CO2, K+ etc
3 - steady phase, proportional to metabolic rate required
What is the relationship between oxygen consumption and ventilation?
What does this suggest about the way our ventilation is controlled?
linear positive correlation
how is this so well matched?
It doesn’t oscillate, so it can’t just be down to our carotid bodies
When does acidosis occur relative to ventilation?
the increase in metabolism is too much fr ventilation to cope
this forms the anaerobic threshold, seeing the accumulation of lactic acid
At what point is V(a) not proportional to V(CO2)
when metabolism is about 5x the basal rate, after this V(A) increases disproportionately (hyperventilation
What is the metabolic hyperbola and how would exercise effect this?
As we increase ventilation, PaCO2 decreases
(therefore the level CO2 drives ventilation)
exercise will shift thisup and right
What 2 lines need to be considered when determining the ventilation at any given metabolic rate?
controller equation (shows that a rise in PaCO2 increases ventilation to remove it) metabolic hyperbola (demonstrates the decrease in PaCO2 acieved by increased ventilation
What is our PaCo2 and V(A) set by?
the intersection of the metabolic hyperbola and the controller equation
(ie the effect of CO2 on ventilation and ventilation on CO2)
Why must the metabolic hyperbola be shifted up in exercise?
to prevent hypercapnia with increased metabolism
What causes the sharpening of CO2 sensitivity seen inexercise (as their PaCO2 are the same as or even lower than resting individuals)?
this could be adrenaline, as we lose this effect when we use propranolol (a beta blocker)
What happens to oxygen partial pressure with altitude increase?
What effect does this have?
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
How might you reach the top of Everest without supplemental oxygen?
let your kidneys adjust to the level of alkalosis, acclimatising
your Bohr shift will ultimately shift to the right
How might we replicate negative gravity?
drop a plane lmao
How much of V/Q distribution does gravity account for?
15%
the rest is down to the fractal nature of our lungs
How does a decrease in altitude change when we dive?
outside of water, an increase in altitude will see gases decompress exponentially
water is incompressable, so when we dive, pressure increases linearly, no exponentially
Why is the snorkel length limited to 40cm?
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
how long could a snorkel realistically be?
1.3m maximum
What happpens if you go deeper than 50m?
gas gets very dense, so people use heliox
What happens when you go up from deep waters?
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
What happens in nitrogen narcosis?
as nirogen dissolves into brain tissue you get a general anaesthetic effect, making things confusing
What 3 things limit the length of a snorkel?
dead space
resistance
maximum inspiratory pressure
What is maximum inspiratory pressure?
intrapulmonary pressure = ambient pressure at surface
pressure on chestwall = pressure exerted by water at depth
maximum pressure generated by chestwall = 13kPa (130cm*2 water)
What is decompression sickness?
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
What can nitrogen sickness cause?
pain (joints) deafness imparied vision convulsion dyspnoea
How can nitrogen sickness be prevented?
regulated ascent
limit dive to 40m
use inert carrier (He), which is less soluble than N2 and is more diffusable
How can nitrogen sickness be treated?
high pressure (decompression chamber) recompress bubbles into solution and allow slow equilibration
How do saturation divers operate?
they allow their tissues to become saturated with nitrogen
work in 28 shifts, 14 days at pressure, 14 days to decompress
How do free divers go so deep?
they halt all unecessary means of metabolism, and enter a coma-like state, before they wake themselves up and go back
What solution is there using liquid in our lungs?
When are hey used?
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
What are the avantages to liquid repiration?
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
What are the problems with liquid ventilation?
how is it circulated?
how do you replace lost oxygen and scrub XS CO2
how to ecacuate lungs afterwards
pneumothorax???
