Hypoxemia without hypercapnia problem

[pezzang]

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In patients with emphysema and pneumonia, hypoxemia occurs without hypercapnia. I realize that Pco2 is directly related to ventilation rate so these patients hyperventilating lowers arterial Pco2 (hypocapnia). So why does it reduce arterial Pco2 but not Po2? Is it because the diffusion rate of CO2 is much higher because of its higher solubility?

It seems from my understanding low V/Q should make the patient hypoxemic and hypercapnic because gas exchange is impaired from the loss of surface area (emphysema) and blocking exudates in alveoli (pneumonia) but somehow CO2 exchange is spared whlie O2 exchange is impaired.

Could anyone help me understand this, please?

 

[USMLE01]

In patients with emphysema and pneumonia, hypoxemia occurs without hypercapnia. I realize that Pco2 is directly related to ventilation rate so these patients hyperventilating lowers arterial Pco2 (hypocapnia). So why does it reduce arterial Pco2 but not Po2? Is it because the diffusion rate of CO2 is much higher because of its higher solubility?

It seems from my understanding low V/Q should make the patient hypoxemic and hypercapnic because gas exchange is impaired from the loss of surface area (emphysema) and blocking exudates in alveoli (pneumonia) but somehow CO2 exchange is spared whlie O2 exchange is impaired.

Could anyone help me understand this, please?

interesting question. hope someone can chime in with an explanation. i only googled it for a few seconds and did not find anything.

technically if O2 goes DOWN, it has to be that CO2 goes up. there was an article in french but i dont speak enough of it to understand....