Pulmonary Gas Exchange and the Diffusing Capacity for Oxygen and Carbon Dioxide

[@nidhs_gupta]

The physiology teacher i needed in first year of medschool. Thank you!

[@mutaharaameen]

Concept Best Explained, Thank you

[@ЕлизаветаСадовская-р8р]

Thank you so much!!!

[@razanaldajah1401]

Thank you so much for this explanation ❤❤

[@mishalshahab4913]

Best explanation

[@PeteMeighan]

Thank you!

[@amadeocelio1061]

That you for your awesome videos :) URGENT QUESTION : In your video, you mention that when taking into account both the diffusion capacity and partial pressure gradient of O2 and CO2, these gases diffuse the alveolar capillary membrane at the same rate. Nevertheless, a type 1 respiratory failure (e.g. pulmonary edema) is characterised by low pO2 levels and normale to low pCO2 levels. If both these statement are correct, how can a type 1 respiratory failure (e.g. pulmonary edema) only negatively affect pO2 levels if both O2 and CO2 diffuse the alveolar capillary membrane at the same rate?

[@PeteMeighan]

Thank you for the kind words. Excellent question, BTW. Under normal conditions, the rates of diffusion of O2 and CO2 are approximately equal. However, in a condition where the diffusion interface is impaired (i.e., Type 1 respiratory failure) the rate of diffusion can become imbalanced. For instance, fluid retention attendant to pulmonary edema effectively increases the thickness of the diffusion interface. Because of the poor water solubility of O2, this change will preferentially reduce O2 diffusion (with less effect on CO2 diffusion). The normal to reduced pCO2 levels are a consequence of compensatory tachypnea driven by the hypoxemia. Hope that helps!

[@amadeocelio1061]

@@PeteMeighan Thank you very much for your answer, it helps a lot. If I understand correctly, an increase in the thickness of the diffusion interface has a relatively low effect on the rate CO2 diffusion. If this is statement is correct, is the graph (at 9:40) still valid?

[@PeteMeighan]

@@amadeocelio1061 Good question. All things being equal, that relationship is still valid. A reduction in the diffusion capacity will still result in a decreased rate of CO2 diffusion (as that graph implies). However--depending on how DL is reduced--the reduction in the CO2 diffusion rate might not be as severe as the reduction in the O2 diffusion rate. Also--remember that during type1 respiratory failure there is the added complexity of the compensatory ventilatory response (i.e., increased alveolar ventilation). This masks the more subtle effect of reduced diffusion capacity on CO2 diffusion. Hope that helps!

[@zhwart.hassan2199]

thanx very helpful