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SGUL - Physiology 1 > Pulmonary Ventilation * > Flashcards

Pulmonary Ventilation * Flashcards

1
Q

What does tachypnoeic mean?

A

Elevated breathing rate

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2
Q

What does tachycardic mean?

A

Elevated heart rate

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3
Q

What does hypoxaemic mean?

A

Lower than normal levels of oxygen

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4
Q

What is Total Lung Capacity (TLC)?

A

The total amount of air the lungs can accommodate

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5
Q

What is tidal volume?

A

The volume of air being breathed in and out

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6
Q

What is Inspiratory Reserve Volume (IRV)?

A

Volume of air a person can forcefully inhale

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7
Q

What is Expiratory Reserve Volume?

A

Volume of air a person can forcefully exhale

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8
Q

What is the Residual Volume (RV)?

A

Volume of air remaining in a person’s lungs after fully exhaling

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9
Q

What is Functional Residual Capacity (FRC)?

A

Volume of air remaining in the lungs after passive exhalation

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10
Q

What is Vital Capacity (VC)?

A

Maximum volume of air a person can inhale after maximum exhalation

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11
Q

What can lung volume and capacity depend on?

A
  • Age
  • Sex
  • Lung properties (e.g. obstruction/damage due to disease)
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12
Q

Do we use our total lung capacity all the time when breathing?

A

No. At rest our tidal volume is much smaller than our total lung capacity

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13
Q

What is pulmonary ventilation?

A

Movement of air from the atmosphere to gas exchange surfaces within the lungs

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14
Q

Why is pulmonary ventilation important?

A
  • Maintains the O2 and CO2 gradients between air in the alveoli and the arterial blood
  • Allows a sufficient level of gas exchange to ensure adequate O2 supply and CO2 removal from respiring tissues
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15
Q

Describe the movement of oxygen from the atmosphere to respiring tissues. PART 1

A
  • Oxygen is taken in from the atmosphere into the alveoli in our lungs in the airways through pulmonary ventilation
    Through blood flow it travels to the heart, then enters systemic circulation and finally reaches respiring tissues
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16
Q

Describe the movement of oxygen from the atmosphere to respiring tissues. PART 2

A
  • In the alveoli gas exchange occurs and oxygen diffuses into the blood and enters pulmonary circulation.
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17
Q

Describe the movement of oxygen from the atmosphere to respiring tissues. PART 3

A
  • Through blood flow oxygen travels to heart, then enters systemic circulation and reaches respiring tissues
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18
Q

Describe the concentrations of oxygen and carbon dioxide in the atmosphere.

A

Very high conc. of oxygen and a very low conc. of CO2

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19
Q

Describe the concentrations of oxygen and carbon dioxide in the alveoli.

A

High levels of O2 and low levels of CO2

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20
Q

Describe the concentrations of oxygen and carbon dioxide in the capillaries.

A

Low levels of O2 and high levels of CO2

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21
Q

Describe the pressure gradient across the alveoli.

A
  • At the venous end, lower partial pressures of O2 and higher partial pressures of CO2 in the blood than in the alveoli
  • At arterial end the partial pressures level off and are equal in the blood and in the alveoli
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22
Q

How does the level of ventilation affect levels of gas exchange?

A
  • Higher levels of ventilation means steeper partial pressure gradient between the alveoli and blood
  • Steeper gradient means there is more gas exchange that occurs
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23
Q

How does the level of ventilation affect partial pressure of O2 in the alveoli?

A
  • As ventilation increases the level of oxygen in the alveoli increases
  • As we decrease ventilation the level of oxygen in the alveoli decreases as the oxygen is being pulled out of the alveoli at a faster rate than it is being replenished
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24
Q

Over time, as ventilation increases why do the partial pressures of oxygen plateau?

A

Partial pressure of oxygen in the atmosphere is the same as the partial pressure of oxygen in the alveoli

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25
Q

How does the level of ventilation affect partial pressures of CO2?

A
  • As ventilation increases partial pressure of CO2 decreases as more gas exchange occurs so more CO2 is being exhaled
  • However as ventilation decreases partial pressure of CO2 increases - builds up in alveoli
26
Q

What is the formula for total ventilation?

A

V = TV x f
V: minute volume (the total volume of air inhaled in all breaths over one minute)
TV: tidal volume (volume of air inhaled in each breathe)
f: frequency (number of breaths per minute)

27
Q

What does air within the lungs consist of ?

A
  • Consist of “stale” air and “fresh air”
  • Stale air is air that has remained from the last breathe
  • Fresh air is air that has just been inhaled
  • Therefore the alveolar air is not the same as the inspired air
28
Q

Why do we have stale air?

A
  • At end of each expiration there is a residual volume of air which remains in the airways and never takes part in gas exchange
  • When inhale again, the fresh air then mixes with this stale air
29
Q

What is the formula of alveolar ventilation?

A

Va= (TV - DV) * f
Va: Alveolar minute volume (the total volume of fresh air entering the alveoli across all breathes in a minute)
(TV-DV): volume of fresh air entering the alveoli in each breathe
TV: Tidal volume (volume of air being inhaled/exhaled)
DV: Dead space volume (volume of air remaining in the respiratory system at the end of expiration)
f: Frequency

30
Q

How does gas naturally move?

A

Down pressure gradients until equal areas of pressure re-established

31
Q

What is Boyle’s law?

A

P ∝ n/v
P: Pressure (the number of gas molecules in a given volume)
n: No. moles
V: Volume
If n is constant then as volume increases pressure decreases

32
Q

Where is Boyle’s Law derived from?

A

It is derived from the ideal gas equation: PV=nRT

33
Q

What are pleura?

A

Serous membranes that surround each lung which line the chest wall

34
Q

What is the pleural cavity?

A
  • Fluid filled space between the pleura (membranes which line the chest wall and the lungs)
35
Q

What is the purpose of the pleural cavity?

A
  • Reduces friction between lungs and chest
36
Q

What is the effect of the pleural cavity on volume?

A
  • The properties of the pleural cavity (i.e. sealed, fluid-filled) means they resist changes in volume
  • Hence changes in lung volume directly result from changes in the volume of the thoracic cavity
37
Q

How is the pleural cavity put under “negative pressure”?

A

Opposing elastic recoil of the chest wall (outward) and lungs (inward) results in the pressure within the pleural cavity being sub-atmospheric (or under negative pressure)

38
Q

What happens with negative pressure?

A

Lower number of molecules per volume (compared to surroundings) and so generates a collapsing force which pulls surfaces together

39
Q

What happens with positive pressure?

A

Increased number of molecules per volume (compared to surroundings) and so generates an expanding force which pushes the surfaces apart.

40
Q

How is an equilibrium in pressure established?

A

Either through the movement of liquid/gases or the collapse/expansion of a volume.

41
Q

How is air flow in the lungs generated during inspiration? PART 1

A
  • External intercostal muscles contract
  • Diaphragm contracts
  • Thoracic cavity expands.
  • Increase in thoracic cavity volume.
42
Q

How is air flow in the lungs generated during inspiration? PART 2

A
  • Intrapleural pressure becomes more negative so the lungs expand and increase lung volume
  • Alveolar pressure decreases below atmospheric pressure
  • This sets up a pressure gradient between the alveoli and the atmosphere and the air flows from the atmosphere (high pressure) into the alveoli (low pressure)
43
Q

How is air flow out of the lungs generated during expiration? PART 1

A
  • Diaphragm relaxes and respiratory muscles also relax
  • Lung recoils due to elastic fibres.
  • Thoracic volume decreases (so compresses the air) and intrapleural pressure increases
  • Lungs become compressed (only during forced expiration) and the volume decreases
44
Q

How is air flow out of the lungs generated during expiration? PART 2

A
  • Increase in alveolar pressure above the atmospheric pressure
  • This sets up a pressure gradient between the alveoli and the atmosphere and so the air flows from the alveoli (high pressure) to the atmosphere (low pressure)
  • The lungs deflate
45
Q

What is pneumothorax?

A

Occurs when air enters into the pleural cavity

46
Q

What happens if either of the pleura is ruptured? PART 1

A
  • Pleura cavity is no longer sealed and provides a passage for the air to move from one compartment to another
  • Due to the pressure gradient between the pleural cavity and the surrounding, air will enter (pneumothorax) until the intrapleural pressure is the same as atmospheric pressure.
47
Q

What happens if either of the pleura is ruptured? PART 2

A
  • Air will enter causing pleural cavity volume to increase. Lung volume decreases.
  • The lung tissue then recoils and expansion of chest (during inspiration) can draw more air into the pleural space
  • This reduces intrapleural pressure changes during inspiration, preventing the lungs from expanding properly as the chest wall moves outwards.
48
Q

What is open pneumothorax?

A

Occurs when the outer pleural membrane is ruptured

49
Q

What is closed pneumothorax?

A

If the inner pleural membrane or the lungs are ruptured

50
Q

What is the primary function of the respiratory system?

A
  • Supply respiring tissues with oxygen and remove excess carbon dioxide
  • Does this by ensuring adequate amount of gas exchange occurs
51
Q

What are hypoventilation and hyperventilation?

A
  • Insufficient levels of breathing relative to those required to meet the metabolic demands of the body
52
Q

What are the effects of hypoventilation?

A
  • Excessive levels of CO2 within arterial blood
  • Reduced alveolar oxygen pressure
  • Increased C02 pressure
53
Q

What are the effects of hyperventilation?

A
  • Reduced levels of CO2 within arterial blood
  • Increased alveolar oxygen pressure
  • Reduced carbon dioxide pressure.
54
Q

What does increasing and decreasing the rate of ventilation do?

A
  • Increasing the rate of ventilation increases alveolar oxygen partial pressure and decreases alveolar carbon dioxide partial pressure .
  • Decreasing the rate of ventilation has the opposite effects.
55
Q

What is the purpose of residual air?

A

Ensure the lungs do not collapse

56
Q

How are changes in pressure achieved?

A
  • Contraction/relaxation of respiratory muscles. This alters the volume of the thoracic cavity (with the opposite effect on alveolar pressure).
57
Q

With regards to the pleural cavity, how does pleural pressure allow inspiration to occur? PART 1

A
  • Contraction of respiratory muscles (eg. the diaphragm) generates sufficient force to pull the parietal pleura outwards.
  • This stretches the pleural cavity, decreasing the intrapleural pressure.
58
Q

With regards to the pleural cavity, how does pleural pressure allow inspiration to occur? PART 2

A
  • As the intrapleural pressure becomes more negative, the force pulling the two pleurae together increases.
  • When this force becomes greater than the force generated by the elastic recoil of the lung, the visceral pleura will be pulled outward, expanding the lung.
59
Q

With regards to the pleural cavity, how does pleural pressure allow expiration to occur? PART 1

A
  • Relaxation of respiratory muscles during inspiration occurs, reducing the outward force acting on the parietal pleura.
  • This reduces the degree to which the cavity is stretched, increasing intrapleural pressure.
60
Q

With regards to the pleural cavity, how does pleural pressure allow expiration to occur? PART 2

A
  • When the less negative intrapleural pressure no longer generates sufficient force to overcome the elastic recoil of the lung, the visceral pleura will be pulled inwards (along with the pleural cavity and parietal pleura)
  • Lung volume decreases
61
Q

With regards to the pleural cavity, how does pleural pressure allow forced expiration to occur?

A
  • Contraction of other respiratory muscles acts to provide further inward force on the parietal pleura
  • This compresses the pleural cavity (further increasing the intrapleural pressure)
  • Greater decline in lung volume

SGUL - Physiology 1 (68 decks)

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