Lungs at extreme conditions Flashcards
what happens to FiO2 at altitude
constant
- same amount of oxygen at high altitudes, just different pressures
what is the alveolar gas equaiton
PAO2 = PiO2 - PaCO2/ R
what is PiO2 at sea level
21kPa
what is an equation for PiGas
PiGas = Patm x FiGas
what happens to lungs as you ascend
CO2 drops because hypoventilation occurs
- become alkalotic initially so pH rises
- pressure of inspired air falls
what is the adaptive change to hypoxia
alkalosis compensated by renal bicarbonate secretion
what is the effect of hyperventilation due to hypoxia
increased ,minute ventilation
PaCO2 de creases
alkalosis initially
tachycardia
what are risk factors for acute mountain sickness
recent travel ove r2500m
younger people
altitude/ rate of ascent/ previous AMS history
what are the criteria for AMS
headache and 1 other symptom, ascend over 2500m
lake louis scare > 3
can you continue ascent with AMS
NO!! never go higher
what does HAPE stand for
high altitude pulmonary oedema
what are criteria for HAPE
unacclimated individual, AMS, cough and shortness of breath, rapid ascent above 8000ft
what reduces risk of HAPE
Sleeping below 6000ft
what is the incidence of HAPE at 4000m
2%
what is the treatment for HAPE
oxygen, decsent, Gamow bag, steroids, calcium blockers
what does HACE stand for
high altitude cerebral oedema
what are the signs and symptoms of HACE
AMS is prerequisite
confusion
behaviour change
treatment for HACE
immediate descent and symptoms may resolve quickly
Gamov bag can be used to restore pressure
what happens to pressure as you descend
increases with depth
- every 10m sea water descended, add 1 addition atm (i.e. 20m below = 3atm)
what is Henry’s law
amount of gas dissolved in a liquid at given temperature is directly proportional to partial pressure
what is the relevance of Henry’s law on diving
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
what is Boyle’s law
at constant temperature, the absolute pressure of fixed mass of gas is inversely proportional to its volume
P1V1 = P2V2
what are the applications of Boyle’s law
barotrauma, arterial gas embolism, gas supplies
what are the physiological change of the dive reflex
apnoea, bradycardia, peripheral vasoconstriction
what is Dalton’s law
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
what is the presentation of CNS toxicity
conVENTID; vision (tunnel) ears (tinnitus) nausea twitching (extremities, facial muscles) irritability dizziness convulsion (often 1st sign)
what is pulmonary oxygen toxicity
Lorrain-Smith effect; PiO2 > 0.5 ata
- problem in itu patients
what is inert gas narcosis
most common is nitrogen
worsens with increasing pressure
narcotic potential related to lipid solubility
what is decompression ilness
N2 poorly soluble, ascent leads to fall in pressure leads to fall in solubility so gas bubbles form
what is type I decompression illness
cutaneous only
what is type II decompression illness
neurological
what is treatment for decompression illness
oxygen, supportive treatment, urgent recompression
what is an arterial gas embolism
gas enters circulation via torn pulmonary vein
small transpulmonary pressure can lead to AGE
normally occurs within 15 mins of resurfacing
what is the treatment of AGE
urgent recompression
what happens in pulmonary barotrauma
air leaks from burst alveoli
what are the causes of pulmonary barotrauma
pneumothorax
pneumomediastinum
subcutaneous emphysema
