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Module title = Tutorial: Congestive Heart Failure
Lesson title = Alveolar Edema
This is lesson 7 of 10 in this module
Following the path of the fluid, the pressure inside the left atrium increases leading to increased volume within pulmonary veins, leading to fluid leaking out in the interstitial spaces (walls of airways and septal spaces), ultimately leading to fluid leaking into alveolar spaces.
Fluid in the alveoli
sounds like crackles
when you listen with a stethescope.
Fluid in the alveoli looks like fluffy cotton balls in the lungs. However, the
distribution
of this fluffy white appearance is very important. You will
not see discrete cotton balls
at random locations. The pattern of pulmonary congestion caused by hydrostatic pressure overload is:
symmetrical
(equally in both lungs)
central
(near the hilar regions) more than peripheral (out near the edges of the heart)
follows gravity
(usually more prominent in bottom half of lungs than in top half)
Why does alveolar edema follow these patterns? Well, the fluid pressure will affect both lungs, so that is why it is
symmetrical
. The highest pressure starts in the heart and will be transmitted peripherally; that is why it is more
centrally located
. Finally, blood obeys the laws of gravity, so the highest blood volume and pressure will be in the dependent (lowest) parts of the lungs and when the patient is in the upright position (sitting or standing), the lower half of the lung will be dependent. Obviously, if they are lying on their back, then the posterior aspects of the lung will be dependent.
The expression "bat wing appearance" has been used many times to describe pulmonary edema caused by fluid overload in the lungs. Personally, I might be a bit dumber than most, but when I look at a photo of a bat, I am just
not able to see the resemblance
:
So I won't use this term to describe pulmonary edema. I hope that does not offend you too much and if you have chiroptophobia, I apologize for the photo.
Here are some examples of alveolar edema caused by increased hydrostatic pressure:
Lesson 7 of 10
That was the last lesson!
