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Kaplan Qbank USMLE



Author2 Posts
  #1

1. Could someone explain why an increase in the pulmonary venous pressure produces a decrease in the lung compliance ?

2. Could someone explain why a more negative intrapleural pressure increases capillary filtration ?

3. In restrictive lung diseases, the lung recoil increases … therefore there should be an increased force of expiration .. which means more FEV1 and FVC. But these two components are decreased. Is the reduction in the TLC in restrictive lung diseases the reason for the decrease in FEV1 and FVC ?

4. Like how lung recoil influences changes in the lung compliance, what influences the changes in the compliance of the chest wall alone ? Please explain the increases and decreases of the chest wall compliance curve with the factors influencing the changes.

Any input is appreciated

Renin.

  #2

1. believe the fluid backing up into the lungs makes it stiffer.
2. more fluid being drawn into the RV on inspiration means more fluid being pushed into the lungs (higher EDV) increasing pressure. know the pulmonary vessels expand too, which should offset some by decreasing resistance, but think the overall effect is increased pressure and filtration.
3. force is different from volumes. think of a stiffer, smaller balloon. air gets pushed out faster, but you're still at smaller volumes overall, right?
4. the only factor i can think of offhand is breakage of ribs (flail chest) which increases compliance.







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