UW Q-please explain - picu

[ArchivalUser]

84 year old brought to the ER due to fever, cough, and shortness of breath past 2 days. His cough is productive of small amounts of greenish sputum and he has mild left-sided chest pain with deep inspiration. Physical exam:decreased breath sounds, coarse rhonchi, increased fremitus over the left lower lung. SaO2= 94% when lying on his right side, drop 84% when lying on his left side. Which of the following mechanisms best explains the drop in SaO2 with position change?

Answer: increased physiologic shunting.

I understand consolidation causes shunting, but why drops on the left side? because consolidation should cause shunt on both sides. I am confused.

[ArchivalUser]

Any idea ??

[ArchivalUser]

When u r sleeping on ur left side means affected side due to gravitational force more blood flow will b there..so more shunting will occur as it is consolidated..but when u r on ur rt side means unaffected side blood will increase on rt side again due to gravity so less shunting will occur..consolidation is on lt side so shunting is happening in left side

[ArchivalUser]

Thank you so much asaha85. Now I got it.