Diffusion and Blood Gases

Question 1

Henry’s Law

Answer 1

(Amount of Dissolved Gas) = (Solubility) x (Partial Pressure)

Question 2

V(.)

Answer 2

V(.) = DL x (PA - Pc)
V(.) = rate of flow of gas (mL per min)
DL = diffusing capacity of the lung (mL per min per mm
Hg)
PA = Alveolar gas partial pressure (mm Hg)
Pc = Capillary gas partial pressure (mm Hg)

Question 3

steady state technique

Answer 3

uses CO to measure diffusing capacity (DL)
assumes PcCO is 0 because hemoglobin has high CO affinity

Therefore
V(.) = DL x (PA)
-> DL = V(.)(CO)/PA(CO)

Question 4

dilution of inert gases in lung

Answer 4

used to calculate VA using Boyle’s Law (P1V1=P2V2)

usually uses inert gas like Ne or He

PE(Ne)VI=PI(Ne)VA

Question 5

dissolved O2

Answer 5

.003 ml O2/100ml blood per mmHg

Question 6

hematocrit

Answer 6

volume of packed red cells per 100ml blood, (%)

normal ~ 45%

Question 7

hemoglobin

Answer 7

grams of hemoglobin per 100 ml of blood

~14g/100ml

Question 8

Pa(O2)

Answer 8

arterial oxygen partial pressure

~90-100mm Hg

Question 9

Pv(O2)

Answer 9

mixed venous oxygen partial pressure

~40mm Hg

Question 10

oxygen capacity

Answer 10

how much O2 per 100 ml of blood can be carried by hemoglobin
~1.39mlO2/1gm hemoglobin
-> 20ml O2/100ml blood

Question 11

saturation of hemoglobin

Answer 11

~97% in arterial blood

~75% in venous blood

Question 12

O2 content

Answer 12

the amount of O2 bound to the hemoglobin plus the amount of O2 dissolved in the blood

Question 13

oxyhemoglobin dissociation curve

Answer 13

convert between values of blood oxygen partial pressure and hemoglobin saturation

Question 14

shifts in dissociation curve

Answer 14

PCO2 shifts right (Bohr effect)
>37* shifts right
<37* shifts left
no 2,3-diphosphoglycerate (BPG) shifts left
added 2,3-BPG shifts right

Question 15

Bohr effect

Answer 15

increased CO2 -> increased carbonic acid -> H+ ions bind to hemoglobin and shifts dissociation curve right

Question 16

Carboxyhemoglobin

Answer 16

(COHb) 1% non smokers, 5% smokers

higher levels cause toxicity

Question 17

blood CO2 forms

Answer 17

1) dissolved
2) bicarbonate
3) carbamino compounds

Question 18

respiratory acidosis

Answer 18

Pa(CO2) > normal

Question 19

Haldane effect

Answer 19

converse of Bohr effect

Oxygen binding to hemoglobin will change blood CO2 content for a given CO2 partial pressure

for a given CO2 partial pressure, blood with a low oxygen partial pressure (such as mixed venous blood) holds more CO2 than blood with a high oxygen partial pressure (such as arterial blood).

Question 20

O2 - CO2 diagram

Answer 20

x-axis is oxygen partial pressure and the y-axis is CO2 partial pressure

illustrates Haldane effect by plotting blood carbon dioxide contents as a function of oxygen and carbon dioxide partial pressure