Lungs at extreme conditions

Question 1

what happens to FiO2 at altitude

Answer 1

constant

- same amount of oxygen at high altitudes, just different pressures

Question 2

what is the alveolar gas equaiton

Answer 2

PAO2 = PiO2 - PaCO2/ R

Question 3

what is PiO2 at sea level

Answer 3

21kPa

Question 4

what is an equation for PiGas

Answer 4

PiGas = Patm x FiGas

Question 5

what happens to lungs as you ascend

Answer 5

CO2 drops because hypoventilation occurs

• become alkalotic initially so pH rises
• pressure of inspired air falls

Question 6

what is the adaptive change to hypoxia

Answer 6

alkalosis compensated by renal bicarbonate secretion

Question 7

what is the effect of hyperventilation due to hypoxia

Answer 7

increased ,minute ventilation
PaCO2 de creases
alkalosis initially
tachycardia

Question 8

what are risk factors for acute mountain sickness

Answer 8

recent travel ove r2500m
younger people
altitude/ rate of ascent/ previous AMS history

Question 9

what are the criteria for AMS

Answer 9

headache and 1 other symptom, ascend over 2500m

lake louis scare > 3

Question 10

can you continue ascent with AMS

Answer 10

NO!! never go higher

Question 11

what does HAPE stand for

Answer 11

high altitude pulmonary oedema

Question 12

what are criteria for HAPE

Answer 12

unacclimated individual, AMS, cough and shortness of breath, rapid ascent above 8000ft

Question 13

what reduces risk of HAPE

Answer 13

Sleeping below 6000ft

Question 14

what is the incidence of HAPE at 4000m

Answer 14

2%

Question 15

what is the treatment for HAPE

Answer 15

oxygen, decsent, Gamow bag, steroids, calcium blockers

Question 16

what does HACE stand for

Answer 16

high altitude cerebral oedema

Question 17

what are the signs and symptoms of HACE

Answer 17

AMS is prerequisite
confusion
behaviour change

Question 18

treatment for HACE

Answer 18

immediate descent and symptoms may resolve quickly

Gamov bag can be used to restore pressure

Question 19

what happens to pressure as you descend

Answer 19

increases with depth

- every 10m sea water descended, add 1 addition atm (i.e. 20m below = 3atm)

Question 20

what is Henry’s law

Answer 20

amount of gas dissolved in a liquid at given temperature is directly proportional to partial pressure

Question 21

what is the relevance of Henry’s law on diving

Answer 21

proportionally more gas dissolved in tissue at depth; if ascent at rate that exceeds body’s capacity to clear this excess gas, inert bubbles may form in tissues leading to DCI

Question 22

what is Boyle’s law

Answer 22

at constant temperature, the absolute pressure of fixed mass of gas is inversely proportional to its volume
P1V1 = P2V2

Question 23

what are the applications of Boyle’s law

Answer 23

barotrauma, arterial gas embolism, gas supplies

Question 24

what are the physiological change of the dive reflex

Answer 24

apnoea, bradycardia, peripheral vasoconstriction

Question 25

what is Dalton's law

Answer 25

total pressure extered by mix of gases is equal to sum of pressures that would be exerted by each of the gases if it were alone and occupied the total volume

Question 26

what is the presentation of CNS toxicity

Answer 26

``` conVENTID; vision (tunnel) ears (tinnitus) nausea twitching (extremities, facial muscles) irritability dizziness convulsion (often 1st sign) ```

Question 27

what is pulmonary oxygen toxicity

Answer 27

Lorrain-Smith effect; PiO2 > 0.5 ata | - problem in itu patients

Question 28

what is inert gas narcosis

Answer 28

most common is nitrogen worsens with increasing pressure narcotic potential related to lipid solubility

Question 29

what is decompression ilness

Answer 29

N2 poorly soluble, ascent leads to fall in pressure leads to fall in solubility so gas bubbles form

Question 30

what is type I decompression illness

Answer 30

cutaneous only

Question 31

what is type II decompression illness

Answer 31

neurological

Question 32

what is treatment for decompression illness

Answer 32

oxygen, supportive treatment, urgent recompression

Question 33

what is an arterial gas embolism

Answer 33

gas enters circulation via torn pulmonary vein small transpulmonary pressure can lead to AGE normally occurs within 15 mins of resurfacing

Question 34

what is the treatment of AGE

Answer 34

urgent recompression

Question 35

what happens in pulmonary barotrauma

Answer 35

air leaks from burst alveoli

Question 36

what are the causes of pulmonary barotrauma

Answer 36

pneumothorax pneumomediastinum subcutaneous emphysema