Respiratory strand: Lecture 4 - Principles of Gas Exchange Flashcards

1
Q

How is rate of diffusion, surface area (A) and pressure gradient related?

A

Rate of diffusion is directly proportional to A x ΔP

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2
Q

What is diffusion dependent on?

A

the physicochemical properties of the gas and nature of the membrane e.g thickness

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3
Q

What is the pressure gradient?

A

the difference in partial pressures of the respective gases in the alveolus and the blood

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4
Q

What is the partial pressure of a gas in a mixture of gases?

A

the pressure that it would exert if it was the only gas in the container

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5
Q

How do you calculate the partial pressure of a gas in a gas mixture?

A

the partial pressure of a gas in a gas mixture = total pressure x fractional concentration of the gas

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6
Q

Explain the partial pressures of gas in the atmosphere at sea level and at 5000m altitude

A
  1. Fractional concentration (%) 2. Partial pressure at sea level (kPa)
  2. Partial pressure at 5,000 m altitude (kPa)
    Oxygen 1 - 21 2- 21.3 3 - 11.8
    Carbon dioxide 1- 0 2- 0 3- 0
    Nitrogen 1- 79 2- 80 3- 44.2
    Total 1- 100 2- 101.3 3- 56
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7
Q

Why is partial pressure of oxygen in the alveoli lower than in room air?

A

-inspired air is humidified in the upper airway
-in the alveoli, oxygen is taken up while carbon dioxide is added
-the body consumes more 02 molecules than it produces CO2 molecules (typically 1.25x)
(our gases as we breath in mix wth our gases that we breath out)

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8
Q

at 37 degrees, what s the partial pressure of water vapour?

A

6.3 kPa

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9
Q

What is a typical value of alveolar pp of CO2?

A

5 kPa

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10
Q

How many O2 molecules are consumed as CO2 molecules produced?

A

1.25x

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11
Q

What is henry’s law?

A

The partial pressure of gas in solution is equal to the partial pressure of gas above it

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12
Q

How is partial pressure of a gas in solution linked to its solubility?

A

partial pressure of a gas in solution is inversely proportional to its solution

so the greater the solubility, the more molecules can be accommodated for a given partial pressure

high solubility = low partial pressure

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13
Q

How many times more soluble Is CO2 in water than oxygen is?

A

24 times
so for every molecule of oxygen, we can dissolve 24 molecules of CO2
but as CO2 is more soluble, you need more of it to create the same concentration of solution than oxygen

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14
Q

What is pulmonary fibrosis?

A

A restrictive lung condition where fibrous tissue builds up

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15
Q

How do we calculate oxygen diffusing capacity?

A

Oxygen uptake / (alveolar PO2 - mean pulmonary capillary PO2)

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16
Q

How do we calculate carbon monoxide diffusing capacity?

A

carbon monoxide uptake /

alveolar PCO

17
Q

Explain the diffusion pathway from the red blood cell and the capillary membrane?

A

slide 23 image

18
Q

Give 6 conditions where the alveolar capillary membrane is abnormal

A

slide 24

19
Q

What is adult respiratory distress syndrome?

A

White cells in alveoli
Thickened membrane
Opening of pores in capillaries so fluid and macrophages can come and attack

20
Q

What is atelectasis?

A

lung collapse

21
Q

What is compliance?

A

the ability of us to expand our lungs