Physiology--Diffusion Flashcards
What are the five causes of hypoxemia?
High altitude Low alveolar ventilation Diffusion defect (e.g., fibrosis) Ventilation/perfusion mismatch R to L shunt
What is a useful formula/tool for determining the possible cause of someone’s hypoxemia?
A-a gradient PAO2 - PaO2
What is hypercapnia?
Higher than normal arterial PCO2
About how much oxygen in the blood is dissolved gas?
2%
What is methemoglobin?
Hemoglobin with iron in the ferric state (Fe3+)
What partial pressure of O2 is found in just-oxygenated blood, and also in systemic venous blood? How saturated is Hgb in veins?
100 mmHg, 40 mmHg
Still about 80% saturated
Oxygen diffusion is governed only by what in the blood?
Dissolved portion of O2 (O2 from lungs must be dissolved as a gas before it can bind Hgb in the blood)
Does Hgb-bound O2 contribute to blood PO2?
No!
What is the Bohr effect?
As CO2 production increases, a decrease in blood pH is seen due to HCO3- and H+ increasing in concentration. The H+ causes decreased Hb affinity
What factors shift the O2-saturation curve to the right?
DPG
High temp
Lower pH
Inc CO2
What factors shift the O2-saturation curve to the left?
Decreased Co2 Inc pH Dec temp Dec DPG HbF
What are the 3 mechanisms of CO2 transport in the blood?
Dissolved
Protein carbamylation
Bicarbonate
What is band three protein?
Anion exchange protein that move Cl- opposite of HCO3-
What is Hamburger’s phenomenon?
As HCO3- leaves RBC, Cl- goes in and H20 follows it, causing swelling.
What is the relative store of O2 compared to CO2?
Much less O2 than CO2
What is the haldane effect?
Hb is the main acceptor of H+ in the blood. As it binds, it dec Hb O2 affinity (“we’re getting acidic in here and need more O2 because obviously the CO2 production has gone up so I’m guessing the tissues have ramped up metabolism”)
What are the two major determining compounds of blood pH?
HCO3- and CO2 (think H-H balance)
What are some causes of respiratory acidosis?
Hypoventilation from - Inhibition of medullary resp center resp muscle paralysis Airway obstruction Poor gas exchange (ARDS, COPD, pneumo)
Respiratory alkalosis causes?
Hyperventilation from - Hypocapnia Overstim of medullary resp center Hypoxemia (five causes!) Mechanical ventilation
