Lungs at extremes Flashcards
What is PiO2 at sea level?
Pi02 = 101kPa x 0.21 = 21kPa
What are normal blood gases?
PaO2
PaCO2
pH
PaO2 = 10.5 - 13.5KPa
PaCO2 = 4.5 - 6KPa
pH = 7.36 - 7.44
What is equation for pressure of inspired gas?
Pressure of inspired gas = Atmospheric Pressure x Fraction of gas
inspired
PAO2 = PiO2 – PaCO2/R
R= resp. quotient (CO2 produced / O2 consumed =0.8)
What occurs when gain in altitude?
Decrease in pressure
When does hypoxia occur?
What are symptoms?
Comp?
Hypoxia occurs at 10,000ft
Hyperventilation, tachycardia, resp. alkalosis
Peripheral chemoreceptors respond to low PaO2, causing increased vent.
Compensation by kidney increasing excretion of bicarb.
How is acute mountain sickness diagnosed?
Lake Louise score
1. Ascent over 2500m within the last 4 days
2. Presence of a headache
PLUS
3. Presence of at least one other symptom
4. A total score of 3 or more from: headache
GI issues
fatigue
dizziness
sleep disturbance
(each on a scale of 0-3)
Name 3 diseases caused by altitude?
1) Acute mountain sickness
2) High altitude pulmonary oedema- ascend too quick for
acclimatisation
- decreased bicarb
3) High altitude cerebral oedema- confusion, ataxia
Aircraft cabin pressurised to equivalent of 8000ft
O2 is 15.1% of air at sea level
What ppl would need supp O2?
kPA= 15
Pts. with O2 sats <92% require O2 supp. to fly
What happens to pressure every 10m descended?
Pressure increase 1 atm/ 10m
How does increasing pressure effect lung volume?
Reduce lung volume
Boyle’s law
Does more or less gas dissolve into tissues at depth?
More
Henry’s law
What are issues caused by being at depth?
Causes
1) Pulmonary O2 toxicity- Lorrain Smith effect–PiO2 > 0.5 ATA
- cause: tunnel vision, tinnitus, convulsions
2) Inert gas narcosis- normally N2
- high pressure cause increase gas lipid
solubility (collects in cells of brain)
- increased confidence to death
3) Decompression sickness- N2 relatively insoluble
quick ascent
form bubbles in circulation due to
drop in pressure
bends
4) Arterial gas embolism- overexpansion of pulmonary veins on
resurfacing
- cause vessel walls tear and gas entry
(pulmonary barotrauma)
- gas bubbles collect in arteries- embolism
- also caused decompression sickness-
reduced solubility of gases cause bubbles
to rise
What causes the bends?
Decompression sickness- N2 relatively insoluble, quick ascent, form bubbles in circulation due to drop in pressure- bends
What causes shift left of O2 dissociation curve?
Decreased temperature
Decreased H+
What causes shift right of O2 dissociation curve?
Increased temperature
Increased H+
Draw O2 dissociation graph
Draw O2 dissociation graph
