GAS TRANSPORT IN BLOOD

Question 1

henry’s law

Answer 1

effect of partial pressure on gas solubility

amount of O2 dissolved in blood is proportional to the partial pressure

Question 2

normal O2 concentration in arterial blood

Answer 2

200 ml/L at normal arterial PO2 (13.3 kPa) and normal Hb concentration (150 g/L)

Question 3

% O2 carried by Hb

Answer 3

98.5 %

Question 4

O2 present in the blood in 2 forms

Answer 4

1. carried by Hb (98.5 %)

2. physically dissolved O2 (1.5%)

Question 5

when is Hb considered fully saturated?

Answer 5

when all Hb present are carrying their maximal load of O2

Question 6

what is the primary factor that determines the % saturation of Hb with O2 ?

Answer 6

PO2

Question 7

O2 Hb dissociation curve shape

Answer 7

sigmoidal

due to cooperativity

Question 8

O2 delivery index

Answer 8

DO2L = CaO2 x CI
DO2L - oxygen delivery index (ml/min/m2)
CaO2 - oxygen content of arterial blood (ml/L)
CI - cardiac index (L/min/m2) - cardiac output to body SA

Question 9

CaO2

Answer 9

CaO2 = 1.38 x [Hb] x SaO2

[Hb] - g/L

Question 10

what can impair O2 delivery to tissues

Answer 10

resp disease
heart failure
anaemia

Question 11

what does the partial pressure of oxygen depend on?

Answer 11

Patm

proportion of O2 on gas mixture

Question 12

how much does the water vapor pressure contribute to the total lung pressure ?

Answer 12

47 mmHg

Question 13

p of inspired air = Patm - Pwv

Answer 13

760 - 47 = 713 mmHg

Question 14

resp disease

Answer 14

decrease arterial PO2
decrease Hb saturation with O2
decrease O2 content in the blood

Question 15

heart failure

Answer 15

decrease cardiac output

Question 16

anaemia

Answer 16

decrease [Hb]

decrease O2 content in the blood

Question 17

flat upper portions

Answer 17

moderate fall in alveolar PO2

doesn’t affect O2 loading much

Question 18

steep lower portion

Answer 18

peripheral tissues get more O2 from a small drop in capillary PO2