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Y1 - Respiratory > Physiology 2: Gas Exchange (L-3) > Flashcards

Physiology 2: Gas Exchange (L-3) Flashcards

1
Q

Define anatomical dead space

A
  • The volume of the airways in the lungs (Non-alveolar space)
  • Gas exchange doesn’t occur
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2
Q

Define pulmonary ventilation

A

The volume ventilated per minute

breath volume x Resp rate

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3
Q

Define alveolar ventilation

A
  • Volume of air exchanged between the atmosphere and alveoli per minute
  • Represents the new air available for alveolar/blood gas exchange
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4
Q

Why is the alveolar ventilation less than the pulmonary ventilation?

A

Due to the presence of anatomical dead space

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5
Q

Is it more beneficial to increase resp rate or breathing depth to increase oxygen uptake?

Why?

A

It is more beneficial to increase breathing depth

Because as you increase resp rate the alveolar ventilation decreases, as air in the anatomical dead space is ventilated first

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6
Q

Ventilation is best at which area in the lung?

A

The apex of the lungs

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7
Q

Is blood perfusion better at the top or bottom of the lungs?

A

Better in the inferior part of the lungs

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8
Q

What is meant by the V/Q ratio?

A

The ratio between lung ventilation and perfusion

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9
Q

Why does the V/Q ratio vary in different parts of the lungs?

A

Due to their differing perfusion and ventilation

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10
Q

Define alveolar dead space

A
  • Ventilated alveoli that are not adequately perfused

- Gas exchange is not effective

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11
Q

Define physiological dead space

A

Anatomical dead space
+
Alveolar dead space

(Total volume not actively exchanging gases)

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12
Q

Which local controls act to match ventilation and perfusion?

A

Smooth muscles in the airways and arterioles

vasodilation/constriction
bronchodilation/constriction

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13
Q

Describe what happens if the perfusion is greater than the ventilation

A
  • Alveolar carbon dioxide increased
  • So airway dilation, increased airflow
  • Alveolar oxygen decreased
  • So pulmonary vasoconstriction, blood flow decreases
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14
Q

Describe the response to high alveolar carbon dioxide

A
  • airway smooth muscle relaxes
  • Increases airway size, decreased airway resistance
  • Increased airflow
  • Reduced carbon dioxide
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15
Q

Describe the response to high alveolar oxygen

A
  • Pulmonary vasodilation
  • Increased blood flow to alveoli
  • The increase in oxygen can now be transferred to the blood
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16
Q

Describe what happens if the ventilation is greater than the perfusion

A
  • Alveolar carbon dioxide decreased
  • So airway constriction, decreased airflow
  • Alveolar oxygen increased
  • Pulmonary vasodilation, increased blood flow
17
Q

Describe the effects on pulmonary and systemic arterioles of decreased alveolar oxygen

A

Pulmonary arterioles:

  • Vasoconstriction
  • To get a better V/Q ratio

Systemic arterioles:

  • Vasodilation
  • Increase oxygen supply to tissues
18
Q

Describe the effects on pulmonary and systemic arterioles of increased alveolar oxygen

A

Pulmonary arterioles:

  • Vasodilation
  • To get a better V/Q ratio

Systemic arterioles:
- Vasoconstriction

19
Q

Describe the 4 factors that affect the rate of alveolar gas exchange

A
  • Partial pressure gradient of oxygen and carbon dioxide
  • Diffusion coefficient for oxygen and carbon dioxide
  • Alveolar surface area
  • Alveolar membrane thickness
20
Q

Define the partial pressure of a gas

A

The pressure that one gas in a gas mixture would exert if it were the only gas present in the volume occupied by the gas mixture

(at a constant temp.)

21
Q

Describe how gases move with regards to partial pressures

A

Gases move down partial pressure gradients

High partial pressure –> Low partial pressure

22
Q

Give the alveolar gas equation

A

PAO2 = PiO2 - [PaCO2 / 0.8]

0.8 = The resp exchange ratio

23
Q

Which has a greater partial pressure gradient CO2 or oxygen?

Why?

A

Carbon dioxide has a much smaller partial pressure gradient

Due to CO2 being more soluble in membranes than oxygen (has a greater diffusion coefficient)

24
Q

Which has a greater diffusion coefficient CO2 or oxygen?

Means what?

A
  • CO2 has a greater diffusion coefficient
  • 20 times greater
  • So CO2 more membrane soluble
25
Q

Describe the normal gradient between alveolar and arterial PO2

A
  • Usually a small gradient

- Gradient exists as V/Q ratio isn’t perfect

26
Q

Define:

  • PAO2

- PaO2

A

PAO2 - Alveolar PO2

PaO2 - Arterial PO2

27
Q

What percentage of the cardiac output is received by the pulmonary circulation

A

100%

28
Q

Describe the effect of surface area and membrane thickness on gas diffusion (Fick’s Law)

A

Gas movement is:

  • Proportional to surface area
  • Inversely proportional to thickness
29
Q

List non-respiratory functions of the respiratory system

A
  • Heat elimination
  • Water loss
  • Maintaining acid-base balance
  • Phonation
  • Olfaction

Y1 - Respiratory (7 decks)

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