Lecture 23: Blood Gas Transport Flashcards
Describe the pressure differences that cause oxygen to diffuse into the pulmonary capillary
PO2 in alveolus= 104
PCO2 in venous blood= 40
104-40= 64 mm Hg- initial pressure
1/3 distance through capillary PO@ rises mean: lungs are only working a 1/3 as hard as they could.
Fig 41-3 and 41-5
What factors allow the diffusion capacity of O2 to increase during exercise
There is increased SA of capillaries participating in diffusion. —increased # of capillaries being used.
There is a more nearly ideal V/Q ratio in the upper parts of the lungs.
Normal intracellular mean PO2=23mmHg
What factors determine tissue PO2?
Rate of oxygen transport to the tissues
Rate of oxygen consumption by the tissues.
Describe the effects of blood flow and metabolic rate on peripheral tissue PCO2?
Blood flow increases as metabolic rate increases. PCO2 is offloaded at higher rate when metabolic rate increases.
Blood flow rate decreases when metabolic rate decreases. PCO2 accumulates in interstitium at rest.
Compare O2 saturation in venous blood to that in arterial blood in r/t how much O2 is bound to heme groups.
Venous: ~75%-O2 bound to 3/4 of the heme groups.
Arterial: ~97%. Almost all heme groups bound to O2.
Be able to calc O2 utilization coefficient
1.34 x 15= 20.1 ml O2
% of blood that gives up its oxygen:
5 / 19.4= 25%
Strenuous exercise can be 75%-85%
Explain how hemoglobin can be viewed as a tissue oxygen buffer system
In order to release 5 ml of O2/dL of blood:
- PO2 must fall to about 40 mm Hg
- tissue PO2 cant rise above this level.
When PO2 is high(pulmonary capillaries), O2 binds to hemoglobin.
When PO2 is low (tissue capillaries) O2 is released from hemoglobin.
This is intuitive because we want these characteristics.
Relate PO2 an O2 saturation to the oxygen-hemoglobin dissociation curve
When PO2 is high(pulmonary capillaries), O2 binds to hemoglobin.
When PO2 is low (tissue capillaries) O2 is released from hemoglobin.
This is intuitive because we want these characteristics.
Relate PO2 to quantity of bound oxygen per unit of blood.
.never talked about…
Relate pH to oxygen-hemoglobin dissociation curve.
pH decreases w/ increase in PO2 and decreased hemoglobin saturation.
Increase PO2=decreases hemoglobin saturation= drop in pH
List and explain factors that shift the oxygen-hemoglobin dissociation curve to the right
Shift to the R:
- increased H+
- increased CO2
- increased temperature
- increased BPG
What is the bohr effect, and what effect does it have on the oxygen-dissociation curve?
Increase in blood [CO2] and H+ ions:
- shifts curve to R
- enhances release of O2 from the blood to the tissues
- enhances oxygenation of blood in lungs.
- helps to blow off CO2
Decrease in blood [CO2] and H+ ions:
- shifts curve to L
- occurs in lungs
List and describe the 3 ways CO2 is transported in the blood, and give approx. % of CO2 that is transported by each mechanism
3 ways CO2 transported in blood:
- Small amount dissolved in blood-7%
- transported as carbonic acid-70%
- as carbamino hemoglobin-23%
Define bohr effect and haldane effect and explain their effects on the oxygen-hemoglobin dissociation curve.
Bohr: increase in blood CO2 causes O2 to be displaced from hemoglobin. Shifts O2-hemoglobin curve to the R.
Haldane: binding of O2 w. Hemoglobin displaces CO2 from blood.
-binding O2 makes hemoglobin a stronger acid- which has less tendency to bind w/ CO2. Increased acidity causes it to release H+ ions. Shifts curve to R also.
Explain why blood may be bright red in carbon monoxide poisoning.
CO2 binds to hemoglobin 250x stronger than O2
Oxygen content of blood is greatly reduced but PO2 of the blood may be normal.
