Physiology--Diffusion

Question 1

What are the five causes of hypoxemia?

Answer 1

High altitude
Low alveolar ventilation
Diffusion defect (e.g., fibrosis)
Ventilation/perfusion mismatch
R to L shunt

Question 2

What is a useful formula/tool for determining the possible cause of someone’s hypoxemia?

Answer 2

A-a gradient PAO2 - PaO2

Question 3

What is hypercapnia?

Answer 3

Higher than normal arterial PCO2

Question 4

About how much oxygen in the blood is dissolved gas?

Answer 4

2%

Question 5

What is methemoglobin?

Answer 5

Hemoglobin with iron in the ferric state (Fe3+)

Question 6

What partial pressure of O2 is found in just-oxygenated blood, and also in systemic venous blood? How saturated is Hgb in veins?

Answer 6

100 mmHg, 40 mmHg

Still about 80% saturated

Question 7

Oxygen diffusion is governed only by what in the blood?

Answer 7

Dissolved portion of O2 (O2 from lungs must be dissolved as a gas before it can bind Hgb in the blood)

Question 8

Does Hgb-bound O2 contribute to blood PO2?

Answer 8

No!

Question 9

What is the Bohr effect?

Answer 9

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

Question 10

What factors shift the O2-saturation curve to the right?

Answer 10

DPG
High temp
Lower pH
Inc CO2

Question 11

What factors shift the O2-saturation curve to the left?

Answer 11

Decreased Co2
Inc pH
Dec temp
Dec DPG
HbF

Question 12

What are the 3 mechanisms of CO2 transport in the blood?

Answer 12

Dissolved
Protein carbamylation
Bicarbonate

Question 13

What is band three protein?

Answer 13

Anion exchange protein that move Cl- opposite of HCO3-

Question 14

What is Hamburger’s phenomenon?

Answer 14

As HCO3- leaves RBC, Cl- goes in and H20 follows it, causing swelling.

Question 15

What is the relative store of O2 compared to CO2?

Answer 15

Much less O2 than CO2

Question 16

What is the haldane effect?

Answer 16

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”)

Question 17

What are the two major determining compounds of blood pH?

Answer 17

HCO3- and CO2 (think H-H balance)

Question 18

What are some causes of respiratory acidosis?

Answer 18

Hypoventilation from -
Inhibition of medullary resp center
resp muscle paralysis
Airway obstruction
Poor gas exchange (ARDS, COPD, pneumo)

Question 19

Respiratory alkalosis causes?

Answer 19

Hyperventilation from -
Hypocapnia
Overstim of medullary resp center
Hypoxemia (five causes!)
Mechanical ventilation