Lungs at Height and Depth

Question 1

What does FiO2 stand for and what is its usual value?

Answer 1

1) Fraction of Inspired oxygen

2) 0.21

Question 2

Over what height is the ‘death zone’

Answer 2

Over 8000m

Question 3

What is the alveolar gas equation?

Answer 3

PAO2 = PiO2 - PaCO2/R

Question 4

How do FiO2 and PiO2 change with altitude?

Answer 4

1) FiO2 stays constant at 0.21

2) PiO2 falls with altitude

Question 5

What is the usual high altitude response?

Answer 5

1) Hypoxia
2) Hyperventilation (^MV, V PaCO2, tachy)
3) Renal bicarbonate excretion to compensate for alkalosis

Question 6

Best way to treat Acute Mountain Sickness?

Answer 6

By descent

Question 7

Define Boyle’s Law

Answer 7

At a constant T, absolute Pa of fixed mass of gas = inversely proportional to its volume
(More pressure gas, smaller volume)
[P1V1=P2V2]

Question 8

Define Dalton’s Law

Answer 8

In a mixture of non reacting gases Ptotal = Pa + Pb. (P total is the sum of the pressures of individual gases).

Question 9

Define Henry’s Law

Answer 9

Solubility of gas proportional to PP of gas

[S1P1=S2P2]