Respiratory System Under Stress

Question 1

What happens fo O2 consumption in exercise?

Answer 1

it increases drastically - can reach 3-6 L/min from a baseline of 250 ml/min

Question 2

What happens to CO2 production during exercise?

Answer 2

increases drastically - up to 3 L/min from 200 ml/min baseline

Question 3

During exercise the respiratory quotient can increase to 1 or higher. How can it go over 1?

Answer 3

During exercise you have the production of lactic acid in the skeletal muscles, leading to a metabolic acidosis

this means you’re using the bicarb buffer to deal with the increased H+, leading to more CO2 production than you get from just burning glucose alone

Question 4

What is VO2 max?

Answer 4

when there is no greater rise in O2 consumption even with increased exercise load

Question 5

What happens to diffusion capacity during exercise? Measured how?

Answer 5

increases 3-fold

measured as CO uptake per partial pressure gradient

Question 6

What happens to cardiac output during exercise? Why?

Answer 6

increases 3-4 fold

because both heart rate and stroke volume increase from sympathetic stimulation

Question 7

What happens to blood pressure during exercise?

Answer 7

systolic increases, but diastolic remains the same, so pulse pressure increases and MAP increases

Question 8

Why does diastolic decrease or stay the same?

Answer 8

because of sympathetic vasodilation of activated muscles leads to decreased TPR and thus decreased diastolic pressure

Question 9

What happens to pO2 and pCO2 during exercise?

Answer 9

not much actually - pO2 might rise slightly and pCO2 might decrease slightly

Question 10

What happens to pH during exercise and why?

Answer 10

usually decreased - lactic acid buildup

Question 11

What equation can we use to determine the amount of inspired pO2 given an atmospheric pressure?

Answer 11

(atmophseric pressure - 47) x .2093

the 47 is the vapor pressure of water

Question 12

What is the most critical adaptation for high altitudes?

Answer 12

hyperventilation

Question 13

What is the hyperventilation driven by at high altitude? Why is this different from usual?

Answer 13

hypoxia! unusual because pCO2 is the usual respiratory drive, but not in this instance

Question 14

How low can pCO2 be reduced due to the hyperventilation at high altitudes?

Answer 14

8 mmHg

Question 15

What is the blood’s adaptation for high altitude?

Answer 15

polycythemia - increased RBC numbers in response to hypoxia, increasing the O2 carrying capacity of the blood

Question 16

How does hypoxia cause polycythemia?

Answer 16

triggers erythopoietin production in the kidneys

Question 17

What effects does breathing 100% oxygen have?

Answer 17

it’s damaging - breathing it chronically will decrease vital capacity and cause pulmonary edema
also atelectasis

Question 18

Why does breathing 100% O2 for too long cause atelectasis?

Answer 18

I changes the gas pressure int he alveoli to pO2 of 668, pCO2 45 and pH20 47

comaring this to the venous blood with a pO2 of 55, there is such an enormous diffusional gradient that air will move into the blood so quickly that the alveoli can’t be reventilated in time and they collapse

Question 19

What are three physiological effects of space flight?

Answer 19

Reduced perfusion inequality of the lung since there’s no gravity

calcium loss from bone bc there’s no weight bearing

postural hypotension on return to earth bc not used to gravity and they’re usually volume depleted

Question 20

What happens to gas-containing structures like the inner ear and lungs during diving?

Answer 20

they will compress on descent with the increased pressure and expand on ascent with the decreased pressure

Question 21

What happens in “the bends”?

Answer 21

Nitrogen is poorly soluble in blood but high pressures can force it into solution
the N2 will equilibrate with tissues at high pressure but it will return to the blood at low pressures
So if decompression is too quick, nitrogen will escape from the blood as bubbles causing pain and neurological damage if the bubbles form in the cranial circulation

Question 22

How can you avoid the bends?

Answer 22

replace the nitrogen with helium (?)

Question 23

When do we use hyperbaric oxygen as a treatment?

Answer 23

carbon monoxide poisoning

gas gangrene