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NBME 23 Answers

nbme23/Block 2/Question#40

A 22-year-old man is brought to the emergency ...

Peak inspiratory pressure (alveolar): positive;
End-tidal pressure (alveolar): positive;
Peak inspiratory pressure (intrapleural): positive;
End-tidal pressure (intrapleural): positive


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submitted by soph(16),

you need to know diff bt negative pressure ventilation (which is normal ventilation) and positive presssure ventilation (which is mechanical ventilation). In negative pressrue ventilation the diaphragm contracts making a - intrapleural pressure which allows alveoli to expand. in positive ventilation (the pt diaphragm is not contracting thus not expanding chest cavitiy and not creating the - pressure) the machine is creating positive pressure inside alveoli so so alveoli expands. :)





Can anyone explain how 10cm H20 positive PEEP leads to Peak Inspiratory PA, End Tidal PA, Peak Inspiratory Pip and End Tidal Pip all being positive?

tea-cats-biscuits  In PEEP, bc of how mechanical ventilation works, all the inspiration part of breathing is done by the machine actively pushing air into the lungs. As a result, there is no negative pressures in the system compared to the normal lung which needs the negative inter-pleural pressure to draw air in. +10  
yotsubato  " As a result, there is no negative pressures in the system compared to the normal lung which needs the negative inter-pleural pressure to draw air in. " Thats totally what threw me off. TIL +