L11 Gaseous Transport and Exchange

Question 1

PaO2

Answer 1

0.21 x 760mmHg
=160mmHg
=21kPa

Question 2

PmitoO2

Answer 2

~1mmHg

=0.1kPa

Question 3

Humidification of air in the Upper Airway

Answer 3

P1O2= F1O2 (PB - PH2O)
(partial pressure/saturation of water at body temp)
=0.21 (760-47)
=0.21 x 713
=150mmHg = at bottom of dead space
=20kPa

Question 4

Decline of PO2 within the alveoli

Answer 4

Not yet O2 in blood

But partial pressure of O2 has dropped from 160mmHg in atmosphere —> 104mmHg in alveoli

Question 5

PAO2

Answer 5

Partial pressure of O2 in the alveoli

104mmHg

Question 6

Decline of PO2 across the alveolar capillary membrane

Answer 6

PaO2 = 104mmHg
PcO2= 100mmHg
partial pressure difference in order for diffusion to occur
a drop of about half kPA (~0.5kPa)
deltaPO2 = 4mmHg
despite 2=300nm (very small) , reflecting the low value of O2 solubility

Question 7

Arterio-venous shunts

Answer 7

blood that circulates but doesnt pass through the lungs

1. Anatomical shunts
2. Physiological shunts

Question 8

Anatomical shunts

Answer 8

1) most of the bronchial circulation
- tissues of the lungs have to be oxygenated
2) The Thebesian component of the coronary circulation
- drainage where some o2 blood leaks out and doesnt return to the coronary circulation
3. Any pulmonary arteriovenous fistula
- fistular=shortcircuit=shunt
- connect artery to vein, and can miss lungs
4. A patent ductus arteriosus
5. A patent foreamen ovale

Question 9

Patent (open) ductus arteriosis

Answer 9

Oxygenated blood coming out of left ventricle
some coming directly back into lung circulation
-therefore this blood nor its oxygen is going out to its perifephery

Question 10

Patent (open) Foreamen ovale

Answer 10

Blood flows directly from Left –> Right atrium
and vice versa
mixing blood together and diminishing the amount of O2 it is carrying

Question 11

Physiological shunts

Answer 11

ANY admixture of systemic mixed venous blood with that from the pulmonary capillaries

• blood that has returned to the lungs, but has gone directly to the arterial system without passing through oxygenation region
• wouldnt last long if all blood went through this path
• blue=venous red=arterial
• gets mixed downstream and sent out

Question 12

Decline of PO2 due to shunts

Answer 12

normally small, but can become large with illness

Question 13

Decline of PO2 due to shunts Quantitative

Answer 13

Qs/Qt = (Cc’O2 -CaO2) / (Cc’O2-C_VO2)

=effectively dead space(blood not air)

Question 14

Quantifying the decline of PO2 due to shunts in healthy individuals

Answer 14

In healthy individuals ~=
2-4mmHg (0.25-0.5kPa)
=only lose a very small amount

Question 15

Quantifying the decline of PO2 due to shunts in ill-health individuals

Answer 15

In ill health individuals, this can be MUCH larger…
due to the sigmoidal shape of the oxyhaemaeglobin equilibrium relation
-healthy shunt = 200mL/L-1 and 100mmHg
-moderate shunt = 200–190 =>small decrease in O2 carrying capacity due to shunt can have large effect on partial pressure
–want to keep partial pressure of O2 as high as possible as is driving force of O2 from circulation –> cells –> mitochondria

Question 16

Ventilation at rest

Answer 16

6L of air per min

Question 17

Circulation at rest

Answer 17

5L of blood per min

Question 18

Capillary and alveoli relationship

Answer 18

A single capillary serves only a single alveoli

Question 19

Mixed venous blood oxygen content from periphery

Answer 19

146mL/L

–>200mL/L

Question 20

PaO2

Answer 20

96mmHg
=13kPa
-lost partial pressure due to shunt and difference in ventilation between top and lower part of lung

Question 21

Decline of PO2 within the Systemic Capilaries

Answer 21

arterial supply + venous drainage
=link (capillaries) between them with cells consuming O2 (drop in partial pressure)
96mmHg –> 40mmHg
-cells closer to the arteries will have rich O2 partial pressure

Question 22

Final PO2 decline before mitochondria

Answer 22

Decline of PO2 accompanying the diffusive flux of O2 across the capillary membrane, interstitial space, cell membrane & cytoplasm to the mitochondria

• driving pressure will become very low during extreme rates of exercise
• cells will become anoxic

Question 23

The birth rate in NZ is approx 1.5 per 1000. Approx how many people died in NZ in 2015?

Answer 23

1.5 / 1000 x 4,000,000 = 6000