L11 Gaseous Transport and Exchange Flashcards Preview

Respiratory System Module > L11 Gaseous Transport and Exchange > Flashcards

Flashcards in L11 Gaseous Transport and Exchange Deck (23):
1

PaO2

0.21 x 760mmHg
=160mmHg
=21kPa

2

PmitoO2

~1mmHg
=0.1kPa

3

Humidification of air in the Upper Airway

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

4

Decline of PO2 within the alveoli

Not yet O2 in blood
But partial pressure of O2 has dropped from 160mmHg in atmosphere ---> 104mmHg in alveoli

5

PAO2

Partial pressure of O2 in the alveoli
104mmHg

6

Decline of PO2 across the alveolar capillary membrane

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

7

Arterio-venous shunts

blood that circulates but doesnt pass through the lungs
1. Anatomical shunts
2. Physiological shunts

8

Anatomical shunts

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

9

Patent (open) ductus arteriosis

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

10

Patent (open) Foreamen ovale

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

11

Physiological shunts

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

12

Decline of PO2 due to shunts

normally small, but can become large with illness

13

Decline of PO2 due to shunts Quantitative

Qs/Qt = (Cc'O2 -CaO2) / (Cc'O2-C_VO2)
=effectively dead space(blood not air)

14

Quantifying the decline of PO2 due to shunts in healthy individuals

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

15

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

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

16

Ventilation at rest

6L of air per min

17

Circulation at rest

5L of blood per min

18

Capillary and alveoli relationship

A single capillary serves only a single alveoli

19

Mixed venous blood oxygen content from periphery

146mL/L
-->200mL/L

20

PaO2

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

21

Decline of PO2 within the Systemic Capilaries

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

22

Final PO2 decline before mitochondria

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

23

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

1.5 / 1000 x 4,000,000 = 6000