I decided to give the ACE questions a try and am a bit confused because the explanations for some of their answers directly conflict with those in truelearn. For example, in regards to drowning truelearn states there is no difference between freshwater and seawater drowning and that hypoxia is due to washout of pulmonary surfactant. ACE says there is a difference between salt/fresh water drowning and that the cause of hypoxemia is pulmonary shunting. What do I trust for my ITE exam?
ACE question explanations conflict with truelearn explanations? Which do I trust for ITE?
- Thread starter Pablo94
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If you've eliminated the surfactant your alveoli collapse (or rather the larger alveoli tend to get larger while the smaller alveoli collapse as per law of laplace) and once collapsed are difficult to reinflate because of changes in surface tension. That leads to areas of the lung that are perfused but does not participate in gas exchange = the definition of shunting.
Ok thank you, ACE said that freshwater reduces sodium conc of surfactant causing what you just illustrated and that saltwater causes movement of water into alveoli also causing shunt. Which are different mechanisms for causing shunt. The issue is that truelearn said there is no difference in mechanism between fresh and saltwater, hence my confusion.
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I dont really care about the mechanism. I care about the consequence. V=0. Shunt. You will never be tested on the explanation for why salt water is different than fresh water drowning. I haven't specifically seen any studies that prove the mechanism described in your ACE question although physiologically I guess it makes sense.
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