respiratory and hemoglobin cards Flashcards
What factors decrease the affinity of hemoglobin for oxygen?
High Cl, H+, CO2, 2,3-BPG, and temperature. this leads to O2 unloading. (BAT ACE: BPG, altitude, temperature, acid, CO2, exercise)
What is methemoglobin?
oxidized form of Hb (ferric, Fe3+) that does not bind O2 as readily, but has an increased affinity for cyanide. threat it with methylene blue
How does methemnoglobinemia present?
cyanosis and chocolate colored blood
How can you treat cyanide poisoning?
use nitrites to oxidize Hb to methemoglobin, which binds cyanide. then, use thiosulfate to bind the cyanide, which forms thiocyanate, which is renally excreted.
What is carboxyhemoglobin?
form of Hb bound to CO in place of O2. this had decreased oxygen binding capacity with a left shift in the oxygen hemoglobin dissociation curve. there is less O2 unloading in tissues.
How is the myoglobin binding curve different from the hemoglobin binding curve?
myoglobin is monomeric and does not show positive cooperativity. the curve lacks the sigmoidal appearance of the hemoglobin curve.
What is the difference between perfusion-limited and diffusion-limited exchange?
perfusion limited means that the gases have fully equilibtated along the length of the capillary. by the time the blood reaches the end of the capillary, all of the exchange that can happen has happened; to increase exchange, you must increase blood flow. this is what is normally seen with O2, CO2, N2O.
In contrast, diffusion-limited exchange means that the gas does not equilibrate by the time blood reaches the end of the capillary. this is seen in O2 exchange for emphysema or fibrosis, and in CO.
Diffusion equation
Vgas= A/T X Dk(P1-P2).
A is area, T is thickness and Dk(P1-P2) is the difference in partial presures. A is decreased in emhysema; T is increased in fibrosis
Equation for pulmonary vascular resistance
(pressure in the pulmonary artery - pressure in the left atrium)/ cardiac output = pulm vascular resistance
R = change in pressure/ flow
R = 8 X viscosity of blood X vessel length / (piX radius ^4)
What is the alveolar gas equation?
PAO2 = PIO2 - (PaCO2/R)
alveolar O2 pressure equals pressure of inspired O2 - arterial PO2/ resp quotient. resp quotient is the CO2 produced/ O2 consumed.
usually PAO2 = 150- PaCO2/0.8
What the the lung zones in terms of V/Q matching? Where is the area with the greatest ventilation? With the greatest perfusion?
the apex of the lungs have a V/Q around 3- they have wasted ventilation
conversely, the base of the lungs have a V/Q around 0.6- wasted perfusion.
note that both ventilation and perfusion are greater at the base than at the apex.
How does ventilation and perfusion of the lungs change with exercise?
as cardiac output increases, the apical capillaries vasodilate. this allows the V/Q ratio to approach 1.
Why is it clinically relevant to understand the various zones of the lung?
organisms that thrive in an oxygenated environment will prefer the apex of the lung (TB).
How is carbon dioxide transported from the tissues to the lungs?
3 forms:
- HCO3- (90%)
- bound to hemoglobin (carbaminohemoglobin). Note that CO2 binds at the globin N-terminus, NOT the heme portion. CO2 binding favors O2 unloading. in contrast, oxygenation of Hb in the lungs promotes dissociation of H+ from hemoglobin, the equilibrium toward the formation of CO2.
- dissolved CO2
What are renal changes seen in high altitude? What about cardiac changes?
decr. PaO2 –> increase in ventilation and decrease in PaCO2. this could cause a respiratory alkalosis. to compensate, the kidney increases its excretion of HCO2.
Cardiac: decreased oxygen in the lungs causes vasoconstriction. In the long term, this can cause right ventricular hypertrophy.
