O2 and CO2 Transport and Acid-Base Balance

Question 1

Fick’s Law of Diffusion

Answer 1

Vgas (rate of gas movement) = (A/T)Dgas(pA-pB)

Question 2

Diffusion Equilibrium

Answer 2

When pA = pB

Question 3

2 Reasons why O2/CO2 diffusion rate similar despite much larger O2 p gradient

Answer 3

CO2 more soluble in blood and has higher diffusion coefficient

Question 4

Diffusion Limiting Gas Exchange (description and 3 scenarios)

Answer 4

Diffusion eq reached in about 0.25s and blood is in capillaries for about 0.75s so diffusion is almost never limiting
Normal: never
Diseased: possibly on exercise
High altitude: possibly on rest

Question 5

How to Measure Diffusion Capacity

Answer 5

Use CO because partial pressure doesn’t change along length of capillary. Short inhalation. Measure rate of uptake of CO (Vco) and partial pressure of CO in alveolar/expired air (pA) and then can calculate DLco = (Vco)/pAco. This measures A/T x Dco, but Dco is similar to Do2

Question 6

Dissolved O2

Answer 6

Very small normall, but gives Hb the push so amount on Hb depends on its presence. At 100% O2 ventilation it can be substantial

Question 7

3 Reason to Keep Venous Hb at 75% Saturatio of O2

Answer 7

Keep Hb affinity for O2 high enough (cooperative binding)
Safety factor
Some organs need more and from venous blood, like liver

Question 8

4 Things that Shift O2/Hb Saturation curve to Right (facilitate offloading of O2)

Answer 8

Increased temperature, 2,3-DPG, CO2, and decreased pH

Question 9

Acidic pH Use

Answer 9

Offloading O2 in tissues more than lungs

Question 10

2 Reasons why CO Dangerous

Answer 10

Binds to O2 sites of Hb w/ higher affinity (shifts curve to L)
Makes it harder to release O2 into tissues

Question 11

CO2 transport (2 mechs, and another point about Hb involved)

Answer 11

Main: combine w/ water to form bicarbonate + H+
Other: Binds Hb to be carbaminoHb
Other H+ binds to Hb to buffer acidity from HCO3- rxn

Question 12

Alveolar Ventilation Equation (2)

Answer 12

VA = (K x VCO2)/pACO2
Or a proportionality thing:
VA(1) x pACO2(1) = VA(2) x PACO2(2)

Question 13

Henderson-Hasselbalch Equation (and what takes care of each term)

Answer 13

pH = 6.1 + log(HCO3-)/0.03pCO2 - trying to keep that last relationship, kidneys do numerator and lungs do denominator