gas exchange

Question 1

what are the gas laws relating to gaseous exchange?

Answer 1

henry’s law-@ a constant temperature, the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas ; Dalton’s law- in a mixture of gasses each gas carries its own individual partial pressure as though it was acting on its own in the same volume.

Question 2

Define diffusion.

Answer 2

It is the exchange of gasses from a high to a low concentration across a semi-permeable membrane.

Question 3

What are the factors affecting diffusion?

Answer 3

solubility and pressure

Question 4

What are the medical conditions that decreases surface area for gaseous exchange?

Answer 4

emphysema, TB, pneumonia, pulmonary edema and atelectasis

Question 5

What are the normal values of PaO2 in the alveoli and tissues?

Answer 5

ALVEOLI- PaO2 104mmHg and TISSUE- < 40mmHg

Question 6

What anatomical factors permit normal diffusion?

Answer 6

functional alveoli,thin interstitial space, thin functional capillaries

Question 7

Give 3 factors that influences the movement of oxygen and carbon dioxide across the respiratory membrane.

Answer 7

Partial presssure gradients and gas solubility, atching of the alveolar-ventilation and pulmonary blood perfusion and structural characteristics of the respiratory membrane

Question 8

What is the total time needed for transit of blood through the respiratory membrane during exercise and at rest?

Answer 8

0.25 seconds -during exercise , 0.75 seconds -@ rest

Question 9

@ rest how long does it take for PaO2 and PaCO2 to reach equilibrium until it is perfuion-limited?

Answer 9

0.25 seconds

Question 10

When oxygen is released to the tissues, which direction does the Oxy-Hb dissociation curve shift?

Answer 10

To the right

Question 11

@ which PaO2 does the body recognise that it needs to hold on to oxygen?

Answer 11

PaO2 60mmHg

Question 12

How many heme groups are present in an adult?

Answer 12

2

Question 13

What are the normal values (%) of atmospheric gasses?

Answer 13

Nitrogen 78.6% , Oxygen 21% , Carbon Dioxide 0.04% , H2O 0.46%

Question 14

Why is the partial pressure of oxygen lower in the alveoli compared to the atmosphere?

Answer 14

movement of air down the airway passage , anatomical dead spcae must be taken into account ,mixing of alveolar gasses with each breath , CO2 diffusion into the alveoli to be blown off -due to the cascade effect (lower down into the airway, lower pressures)

Question 15

What are the factors affecting Oxy-Hb dissociation curve?

Answer 15

pH , temperature , 2.3 dpg ,PaCO2

Question 16

What does the sigmoid curve of the Oxy-Hb dissociation curve mean?

Answer 16

The curve has a steep slope-with decreasing pressures theres rapid fall in Hb saturation and a plateau slope-heme unable to saturate further (fully saturated)

Question 17

How many oxygen molecules can bind to a hemoglobin molecule?

Answer 17

4

Question 18

@ which partial pressure is the Oxy-Hb curve said to be fully saturated?

Answer 18

>PaO2 80-100mmHg

Question 19

What cells produce surfactant in the alveoli?

Answer 19

Type 2

Question 20

What happens when the respiratory membrane thickens?

Answer 20

decreases diffusion rate, causes anatomical shunt and pulmonary vasoconstriction

Question 21

Does diffusion defect lead to type 1 or type 2 respiratory failure?

Answer 21

Type 1