Challenges to normal respiration

Question 1

How much oxygen is needed per minute at rest?

Answer 1

200ml/min aka 1 MET

Question 2

What is VO2 max?

Answer 2

The level work at which oxygen consumption no longer increases (anaerobic respiration.)
Plateau on graph. Measure of how fit an individual is.

Question 3

Is VO2 max improvable?

Answer 3

Yes

Question 4

What can VO2 max be used for in a medical setting?

Answer 4

Assesing whether a patient will survive surgery

Question 5

What 6 factors control change in oxygen consumption (VO2)?

Answer 5

Psychological factors
Neural input to the respiratory centre
Proprioceptors
ABG changes
Cardiovascular changes
Temperature regulation

Question 6

What is the most potent driver of respiration- lack of O2 or build up of CO2?

Answer 6

Build up of CO2

Question 7

What is atmospheric pressure at sea level?

Answer 7

101.3 kPa

Question 8

What is alveolar pressure of O2 at sea level?

Answer 8

13.3 kPa

Question 9

To work out alveolar pressure of oxygen you multiply partial pressure of O2 by (_____ minus _______)

Answer 9

Atmospheric pressure by partial pressure of water (6.3kPa)

Question 10

What happens to alveolar pressure of oxygen at altitude?

Answer 10

It decreases

Question 11

What is the body’s response to altitude? (5 things)

Answer 11

1. Hyperventilation and so compensatory respiratory alkalosis
2. Increased 2,3-DPG so more O2 released by Hb
3. Polycythaemia (higher blood count)
4. Bicarbonate excretion from CSF and kidneys
5. Diuresis and hyponatraemia

Question 12

What happens to the acid/base balance of the body at altitude?

Answer 12

Respiratory acidosis due to build up of CO2

Question 13

What are 5 symptoms of altitude sickness?

Answer 13

1. Headache
2. Nausea
3. Loss of apetite
4. Difficulty sleeping/exercising
5. Amnesia/dizziness

Question 14

How do you treat altitude sickness?

Answer 14

Acetazolamide

Rapid descent

Question 15

What are 2 severe complications of mountain sickness?

Answer 15

1. Cheyne Stokes respiration

2. Cerebral/pulmonary oedema

Question 16

How much does a 10m descent underwater increase atmospheric pressure?

Answer 16

1 atm

Question 17

What is the affect of descent underwater on partial pressure of oxygen?

Answer 17

It increases the ppO2

Question 18

What is the affect of increaed pressure on the chest and abdomen?

Answer 18

They are compressed

Question 19

Is it the descent or ascent that is a problem when diving?

Answer 19

Ascent due to reduction in ppO2 so hypoxia.

Question 20

What sort of oxygen is used at great depth when diving?

Answer 20

helium-oxygen. May be 2% O2 but at that pressure this still represents 20kPa

Question 21

At what depth does ‘the bends’ become a risk? What is necessary to prevent it?

Answer 21

> 40m, slow ascent with compression chamber

Question 22

What is the dive reflex?

Answer 22

Innate in many mammals- underwater they spontaneously hold their breath, slow HR and peripheral vasoconstriction.

Question 23

What causes decompression sickness?

Answer 23

Nitrogen dissolved in tissues which forms bubbles upon ascent.

Question 24

What is the scientific name for the bends?

Answer 24

Decompression sickness

Question 25

What condition can occur by breathing oxygen at a high partial pressure?

Answer 25

Cellular oxygen toxicity/ hyperoxia

Question 26

Why is hyperoxia dangerous?

Answer 26

Excess oxygen can form an oxygen free radical. This is extremely reactive and could form e.g. peroxide if reacted with a lipid or it could damage DNA.