Arterial blood gases and acid-base disorders Flashcards
what is the role of dissolved oxygen?
diffuses from lungs into blood
enters RBCs
binds Hb
what are the features of the T form of Hb?
- oxygen binds to alpha subunit of Hb
- conformational change increases oxygen affinity of second alpha subunit
- rotation of two a/B dimers with respect to each other
T form to R form transition
- oxygen binding sites on beta subunits available
2. beta subunits rapidly bind oxygen
which Hb form has high affinity for oxygen?
R
what stabilizes the T form of Hb? what is the implication for oxygen affinity?
anything that increases or strengthens contact between subunits (salt bridges, eg)
reduced oxygen affinity
what do lower 2,3-BPG and high [CO2] do to Hb?
stabilize T form
reduced oxygen affinity - oxygen unloading in tissues
what stabilizes the R form of Hb? what is the implication for oxygen affinity?
anything that dminishes or weakens the contacts between subunits
increased oxygen affinity
what do higher 2,3-BPG and low [CO2] do to Hb?
increase oxygen affinity
CO2 attaches to Hb as what compound?
N terminal carbamates
CO2 is transported in the blood as what forms? what is the major form?
dissolved
N terminal carbamates (Hb)
bicarbonate ion (majority)
what is generated by the formation of carbamates and bicarbonate?
protons
what is the Haldane effect?
CO2 concentration of blood varies as a function of bloody oxygenation
less total CO2 in oxygenated blood
more total CO2 in deoxygenated blood
which is a stronger base - deoxyHb or oxygenated Hb?
deoxyHb
what does proton binding do to oxygen affinity of Hb? what does it facilitate?
decreases - facilitates oxygen unloading
what is the major buffering system in the blood?
bicarbonate buffer system
what is treated as the acid in the blood?
CO2
how are gases reported in the clinic?
partial pressures
blood pH equation
pH = 6.1 + log [HCO3-] / (0.03) x pCO2
what is the effect of hypoventilation on blood pH?
low pH (respiratory acidosis)
what is the effect of hyperventilation on blood pH?
high pH (respiratory alkalosis)
respiratory acid-base imbalances are a result of changes in the partial pressure of what compound?
pCO2
metabolic acid-base imbalances are a result of changes in the partial pressure of what compound?
[HCO3-]
blood pH is a function of the ratio of what factors?
pH = 6.1 + log [HCO3-] / [CO2dissolved]
6.1 is a constant
what is the theme for the body’s compensation to changes in acid-base chemistry?
maintaining the ratio of bicarb to pCO2
what organ regulates the excretion of protons and bicarb concentration?
kidney
