Resp Lecture 12

Front 1

How does O2 transport occur?

Back 1

98.5% O2 in blood is bound to Hb (capable of binding 4 molecules), the remainder is dissolved.

Front 2

The oxygen-haemoglobin saturation curve.

Back 2

Percentage of Hb that's saturated with O2 (all 4= 100% saturation).
Non-linear relationship to PO2 of blood because affinity of Hb for O2 changes with the number of O2 molecules bound; once one O2 molecule binds, increases affinity.
Hb loads with O2 where PO2 is high, and unloads where O2 is low.

Front 3

Why won't increasing the alveolar PO2 not result in a large increase binding to Hb?

Back 3

Bc Hb is almost 100% saturated.

Front 4

What causes unloading of O2?

Back 4

With increasing O2 requirements for tissues (exercise), tissue PO2 may drop to 25mmHg, which results in readily unloading.

Front 5

What is the PO2 at the level of the alveolus?

Back 5

The O2 pressure in the atmosphere is 150mmHg. Gradually decreases as it makes its way into the alveoli and then the blood stream as it is mixing with other gasses. Approx 100mmHg once reaches bloodstream.

Front 6

What will cause a curve shift to the right?

Back 6

1.Increase in PCO2 or acidity (known as the bhor effect), caused by an increase in exercise
2.Binding of CO2 to Hb (carbaminoharmoglobin) or H+ to Hb alters the conformation of the Hb reducing its affinity for O2.
3. Increasing the H+ of the blood during exercise results from both increased PCO2 and increased lactic acid as the metabolism changes to anaerobic metabolism.
4. Increase in body temperature (cooler in lungs, warmer in the tissues during exercise)
5. 2,3-diphosphoglycerate (DPG) present at varying levels, depending on physiological need (high in those that live at higher altitudes)

Front 7

What is the bohr effect?

Back 7

Results in readier dissociation of O2 from Hb at mid-range PO2 levels, but at PO2 of 100mmHg (as in the lung), saturation remains almost complete (it's a shift to the R, NOT a drop)

Front 8

CO2 transport

Back 8

CO2 is much more soluble in blood than O2. Majority is transported as HCO3- (60%), 30% is bound, and 10% is dissolved

Front 9

What is the haldane effect?

Back 9

Free Hb has greater affinity for both CO2 and H+ than it does O2

Front 10

How do the Haldane and Bohr effect work together?

Back 10

1. A decrease in O2 occurs in the tissues causing the RBC to readily unload the O2. (Bohr effect)
2. According to the haldane effect, this will increase the affinity of uptake for CO2 and H+
3. This, according to the Bohr affect, will amplify the unloading of the O2 from the RBC.
4. Once the blood reaches the lungs, there's an increased level of O2, which will increase the loading of O2 onto the RBC (Bohr effect).
5. This according to the haldane effect will decrease the affinity for CO2 and H+.
6. This according to the Bohr effect will further increase the affinity for O2.

Front 11

Respiratory acidosis

Back 11

Normal blood pH ~7.4.
Characterized by increased HCO3- and a low pH
Can result from increased PCO2 in blood due to inadequate ventilation

Front 12

Metabolic acidosis

Back 12

Characterized by low pH and low to normal HCO3-.
Occurs due to heavy exercise (lactic acid build up)
As a result of ketoacidosis (occurs in diabetes or any major physiological stress involving failure to meet energy needs)
When HCO3- is lost from the body (normally recycled in duodenum) due to severe diarrhea

Front 13

Respiratory alkalosis

Back 13

Characterized by high pH and low HCO3-.
Results from decreased PCO2 in blood due to hyperventilation (breathing more deeply or rapidly or both)

Front 14

Metabolic alkalosis

Back 14

Characterized by high pH with a normal or high HCO3- due to repeated vomiting.

Front 15

How can we distinguish between metabolic and respiratory acidosis/alkalosis?

Back 15

Measurement of pH and partial pressure of gasses in blood (done with arterial blood, venous blood wont tell us what's occurring at the level of the lungs). Based on these values, you can measure the HCO3- levels, carried out by blood gas analysis machines. If the change is metabolic, both the pH and the HCO3- will move in the same direction, if it's respiratory they move in opposite directions.

Front 16

How can we determine if there's a problem with ventilation or perfusion?

Back 16

if PaO2 is low in the presence of normal PaCO2 indicates diffusion defect (take arterial blood to determine levels)

Front 17

Respiratory alkalosis in birds

Back 17

When flying at high altitudes, birds overventilate=> decrease PaCO2 => severe alkalosis. They tolerate it much better. NOT hyperventilation they need the requirements to get enough O2 to assist with flying