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Resp (SEM 2) > Pulmonary ventilation > Flashcards

Pulmonary ventilation Flashcards

1
Q

“State how inspiration leads to expansion of the lung through
intrapleural pressure?”

A

“1) Contraction of resp. muscles will pull the parietal pleura outwards

  • Stretches the cavity
  • Decreases intrapleural pressure (P ip)

2) As P (ip) becomes more -ve, the force pulling the pleura together increases.

3) Once force from P (ip) > Force from elastic recoil of lung,
- VIsceral pleura is pulled outwards
- Causing expansion of the lungs”

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2
Q

State the ideal gas law?

A

“Pv=nRT

P= pressure
v=volume
n=moles
R=Gas constant
T= tempeature”

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3
Q

What are differences in pressure between neighbouring spaces described as?

A

Unstable

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4
Q

Describe the passage of O2 from atmosphere to tissues

A
  1. Atmosphere (atmospheric air)
    - > Pulmonary ventilation (via airways). Inspiration
    - > Expiration occurs for CO2 in reverse of this step
  2. Lungs (alveoli- alveolar air)
    - > Gas exchange via diffusion
  3. Pulmonary circulation (capillary blood)
    - > Blood flow
  4. Heart
  5. Systemic circulation
  6. Tissues
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5
Q

What is positive pressure?

A

“increased number of molecules per volume (relative to surroundings)
→ generates expanding force (pushes surfaces of chest wall and lungs apart).
“

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6
Q

What is pneumothorax?

A

Abnormal collection of air in the pleural space between the lung and the chest wall.

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7
Q

Explain how the pleural cavity has -ve intrapleural pressure

A

“The opposing elastic recoil of the tissues of the chest wall (outward) and lungs (inward) attached to the pleura
It strecthes the sealed pleural cavity - decreasing its pressure due to greater volume but same molecules
It can resist changes in volume

Pressure within is sub-atmospheric (under negative pressure) known as -ve intrapleural pressure”

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8
Q

Describe what changes occur to the lung when inspiration occurs?

A

Diaphragm contracts
Thoracic cavity expands.
Alveolar pressure decreases

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9
Q

Describe how inspiration occurs?

A

“Respiratory muscles (e.g. diaphragm) contract
↓
Volume of thoracic cavity increases
↓
Intrapleural pressure becomes more negative
↓
Outward force exerted on visceral pleura becomes greater than inward recoil force
↓
Lungs expand, increasing volume
↓
PAlv (alveolar pressure) decreases below PAtm (atmospheric pressure)
↓
Air moves down pressure gradient, through airways into alveoli, expanding the lungs”

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10
Q

What is pulmonary ventilation required for?

A

Maintain O2 and CO2 gradients between alveolar air and arterial blood.

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11
Q

State the pressure gradients in the lungs during expiration

A

“Air within the lung is compressed.
↓volume = ↑alveolar pressure.
Palveoli > Patmosphere
Air flows from high (alveoli) to low (atmosphere) pressure.
“

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12
Q

What factors is the adequate transport of O2 from atmosphere to
respiring tissue dependent on?

A

Healthy levels of alveolar ventilation
Gas exchange
Cardiac output

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13
Q

Describe alveolar Pressure in terms of its effect during inspiration

A

“2) As the lungs expand, the increase in volume decreases PAlv.
As air enters the lungs, the pressure re-equilibrates once again
as the increased concentration of gas molecules compensates for the increased volume (P = n/V)”

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14
Q

How does the lung contain a mixture of fresh and stale air?

A

“Gas exchange only takes place in alveoli, but air must first pass through the airways (airways = “anatomic dead space”)

Also, a residual volume of air remains in the airway & lungs at the end of expiration (even maximal forced expiration)

This means that the final ≈150mL (dead space volume) of each inspiration never reaches the alveoli or takes place in gas exchange.
“

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15
Q

How can equilibrium be re-established

A

“In absence of sufficient opposing force,
Movement of liquid/gas
or
Collapse/expansion of volume (at the expense of surrounding structure)”

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16
Q

What factors are lung volume and capacitance dependent on?

A

Age
Sex
Height
Lung properties (compliance, obstruction/damage due to disease)

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17
Q

Describe Lung volume in terms of its effect during breathing

A

4) Entry of air into the lungs due to air flow leads to inflation and increased volume, which is reversed during expiration.

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18
Q

Describe the major consequences of a Pneumothorax?

A

”- Entry of air results in the loss of negative pressure.
(intrapleural pressure increases until it equals atmospheric pressure).
- This entry of air will lead to expansion of the pleural cavity volume (at the expense of lung volume, which decreases).
- Both of these factors then act to reduce intrapleural pressure changes during inspiration.
- Preventing the lungs from expanding properly as the chest wall moves outwards.
“

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19
Q

“Equation for alveolar minute volume
(the total volume of fresh air entering the alveoli across all breaths over one minute)”

A

“𝑉 ̇_𝐴=(𝑉_𝑇−𝑉_𝐷 ) ×𝑓

𝑉 ̇_𝐴= alveolar minute volume (alveolar venilation) (mL),
- the total volume of fresh air entering the alveoli across all breaths over one minute.

𝑉\_𝑇 = tidal volume (mL)
𝑉\_𝐷 = Dead space volume (mL), the volume of air
𝑓= frequency (min-1)

𝑉_𝑇−𝑉_𝐷 = the volume of fresh air entering the alveoli in each breath.
“

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20
Q

State how expiration leads to decreased lung volume through P (ip)

A

“1) Relaxation of resp. muscles will reduce the outward force on the parietal pleura

  • Reduces stretch of cavity
  • Increases p(ip)

2) Less -ve p(ip) doesn’t generate sufficient force to overcome the elastic recoil of the lung
- Visceral pleura is pulled inwards along with pariteal pleura

3) Decreases lung volume “

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21
Q

What is pulmonary ventilation?

A

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

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22
Q

State difference in effect between a normal expiration and a forced expiration?

A

“More pronounounced decline in lung volume
- In terms of both speed and magnitude

Forced expiratory volume ( FEV1) is the maximum amount of air you can forcefully exhale in one second”

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23
Q

State the pressure gradients in the lungs during inspiration

A

“The outer surfaces of the lung are pulled outwards (expansion).
↑volume = ↓alveolar pressure.
Palveoli < Patmosphere
Air flows from high (atmosphere) to low (alveoli) pressure”

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24
Q

State the 4 factors which relate to each other during breathing?

A

“Lung volume
Intrapleural pressure
Alveolar pressure
Airflow “

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25
Q

Explain what ‘fresh’ and ‘stale’ air mean in the context of the respiratory system

A 
Fresh= air that has just entered the respiratory system from the atmosphere
Stale= air that entered the lungs during a previous breath and which has already participated in gas exchange, respectively.
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26
Q

How do gases naturally move?

A

“From (connected) areas of higher to lower pressure
until an equilibrium is re-established”

27
Q

State Boyle’s law?

A

“P ∝ n/V as long as temperature is kept constant
P = pressure (Number of gas molecules within a given volume)
n= molar quanitiy (number of gas molecules present)
V= Volume
“

28
Q

What does a pneumothorax involve?

A

”- Entry of air into pleural cavity

  • Loss of negative intrapleural pressure
  • Collapse of lung tissue”
29
Q

What does alveolar ventilation correct?

A

Volume of inspired air which doesnt take part in gas exchange (due to dead space)

30
Q

Describe how changes in lung volume lead to air to flow?

A

Changes in lung volume via contraction/relaxation of resp. muscles -> changes in alveolar pressure -> generate pressure gradients between alveoli & atmosphere -> air to flow.

31
Q

Describe the relationship from boyle’s law?

A

As long as n is constant
Higher the volume= Lower the pressure

32
Q

Describe Air flow in terms of its effect during breathing

A

“3) When PAlv < PAtm the pressure gradient causes air to move into the lungs.
Where PAlv > PAtm air moves out.
The speed of airflow is dependent on the pressure gradient and level of airway resistance present.”

33
Q

Describe Intrapleural Pressure in terms of its effect during breathing

A

“1) As lung volume increases during inspiration
intrapleural pressure becomes more negative
due to the elastic properties of the lung generating increasing recoiling force.”

34
Q

State how the lung volume becomes constant at the end of expiration?

A

“System is at equilbirum:
Force pulling visceral pleura inwards (lung recoil) = Force pulling the visceral pleura outwards (-ve intrapleural pressure)

So lung volume will remain constant”

35
Q

What does the properties of the pleural cavity allow?

A

“It resists changes in volume.
Thus, changes in the volume of the thoracic cavity (due to resp. muscle activity) result in changes in lung volume. “

36
Q

State and describe the 3 forces which determine whether the lungs expand or
compress?

A

1) Elastic (outward) recoil of the chest wall and inspiratory respiratory muscle contraction (e.g. contraction of the diapraghm) acts to pull the chest wall outwards and expand the thoracic cavity.
2) Elastic recoil of the lungs acts to pull the visceral (inner) pleural inwards and compress the lung volume.
3) The degree of negative intrapleural pressure acts to pull the lungs and chest wall together.

37
Q

How can a Pneumothorax lead to lung collapse?

A

”- As the parietal and visceral pleurae are no longer being pulled together by negative intrapleural pressure.

  • They recoil in opposite directions. So elastic recoil of chest wall and lungs is no longer resisted
  • Causing particular regions of the lungs to collapse depending on the site and extent of the injury.

Collapsed lung= Smaller, compressed lung or regions of a lung”

38
Q

Describe how expiration occurs?

A

“Respiratory muscles (e.g. diaphragm) relax, lungs recoil due to elastic fibres
↓
Volume of thoracic cavity decreases
↓
Intrapleural pressure increases
↓
Lungs compressed*, volume decreases
↓
PAlv (alveolar pressure) increases above PAtm (atmospheric pressure)
↓
Air moves down pressure gradient, into atmosphere, deflating lungs.”

39
Q

What factors are ventilation dependent on?

A

Volume (depth) and rate of breathing

40
Q

Describe interpleural pressure and its importance in terms of inspiration

A

”- Intrapleural pressure is naturally sub-atmospheric.

  • Due to the opposing recoil of the chest wall and lungs.
  • Required to generate expansion of the lungs during inspiration.”
41
Q

What is the pleural cavity?

A

“fluid filled space between the membranes (pleura) that line the chest wall and each lung.
The membranes seperatae the chest wall and the lungs”

42
Q

Does alveolar air = inspired air?

A

No
alveolar air≠ Inspired air:
the lungs contain a mixture of ‘fresh’ & ‘stale’ air

43
Q

Function of pleural cavity?

A

helps to reduce friction between lungs and chest.

44
Q

Describe quantity of CO2 from cap. blood to initial alveolar air?

A

Cap. blood= High CO2
-> Diffusion
Alveolar air: Low Co2
-> Movement of gas via expiration
Iniital alveolar air: V.low CO2

45
Q

State the definition of ventilation?

A

Volume of fresh air that reaches respiratory surfaces over a given time

46
Q

How are pressure gradients maintained between alveoli and blood
and what is the advantage?

A

Mainted by Adequate (alveolar) ventilation= volume of fresh air reaching the alveoli per unit of time
↑ventilation = ↑partial pressure gradient (between alveoli and blood) = ↑gas exchange

So greater gas exhcange

47
Q

What is negative pressure?

A

“lower number of molecules per volume (relative to surroundings)
→ generates collapsing force (pulls surfaces of chest wall and lungs together).
“

48
Q

Describe the system for the respiratory system?

A

The respiratory system is two-way system;

  • > Air enters and leaves via the same path.
  • > Air must pass through airways (anatomic dead space) first during inspiration
49
Q

Describe what changes occur to the lung when expiration occurs?

A

“Diaphragm relaxes (and lung recoils).
Thoracic cavity volume decreases
alveolar pressure increases.”

50
Q

What is the importance of maintaining O2/CO2 gradients between
alveolar air and arterial blood?

A

Enables suffiicent level of gas exchange (partial pressure gradients) to take place
Therefore Ensure adequate O2 supply/CO2 removal to/from respiring tissues (via blood)

51
Q
A
52
Q

Describe quantity of O2 from initial alveolar air to cap. blood

A

Initial alveolar air: V.high O2
- Movement of gas via inspiration
Alveolar air: High O2
- Diffusion
Cap. blood: Low O2

53
Q

State the relationship between Partial pressure of CO2 within alveoli and
ventilation

A

PACO2 within alveoli decreases as ventilation increases

↓ventilation = ↑PACO2 = ↑PaCO2

54
Q

How does movement of air in/out of lungs occur

A

Via change in volume of throacic cavity

55
Q

State the pressure gradients in the lungs at rest

A

“At the end of expiration, Palveoli = Patmosphere,
there is no movement of air
“

56
Q

State the equation for ventilation and define?

A

𝑉 ̇=𝑉_𝑇×𝑓
𝑉 ̇ = minute volume (total ventilation) (mL)
- the total volume of air inhaled in all breaths over one minute.

𝑉_𝑇 = tidal volume (mL), the volume of air inhaled in each breath.
𝑓= frequency of breathing (min-1), the number of breaths per minute
- Also known as the respiratory rate

57
Q

State the two propeties of the pleural cavity?

A

“Sealed
Fluid-filled

  • Pressure within is sub-atmospheric (under negative pressure) known as intrapleural pressure”
58
Q

State the types of pleura and what they line?

A 
"Visceral = Line each lung
Parietal = Line throacic cavity (Chest, diaphragm and mediastinum)"
59
Q

State the relationship between Partial pressure of O2 within alveoli and
ventilation

A

PAO2 within alveoli increases as ventilation increases
-> Until it plataeus at hyperventilation rate (excessive breathing) due to can only being same level at max. atmosphere O2 level

↓ventilation = ↓PAO2 (alveoli) = ↓PaO2 =↓CaO2 (arterial O2 content)

60
Q

Why does compression of the lungs occur?

A

“Compression of the lungs due to increased intrapleural pressure only occurs during forced expiration.
In quiet breathing, elastic recoil is sufficient to decrease lung volume.
“

61
Q

What causes a Pneumothorax?

A

”- If either of the pleural membranes is ruptured.
- For example due to trauma, bleb formation or disease.
- The pressure gradient between the pleural cavity and the atmosphere/lungs will cause air to enter the pleural space.
until intrapleural pressure= atmospheric pressure “

62
Q

Compare effect of hyperventilation and hypoventilation on alveolar O2 pressure
and alveolar CO2 pressure

A

Hyperventilation/hypoventilation= Insufficient/excessive respectively levels of breathing relative to that
required to meet the metabolic demands of breathing

Hyper= ↑PAO2, ↓PACO2
Hypo= ↓PAO2, ↑PACO2
63
Q

What is inspiration/expiration?

A

Types of movement of gas via breathing

64
Q

What does expiration involve?

A

“Elastic recoil of lungs
Relaxation of respiratory muscles”

Resp (SEM 2) (3 decks)

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