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Respiratory Sytem > Ventilation And Lung Mechanics > Flashcards

Ventilation And Lung Mechanics Flashcards

1
Q

What is Venilation?

A

The process of inspiration and expiration

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2
Q

What neurons are responsible for normal involuntary breathing? How?

A

Neurons in respiratory centres of brain generate automatic rhythmic impulses, which travel via spinal cord and peripheral nerves to the inspiratory muscles

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3
Q

What is the Tidal Volume?

How much in most people?

A

Volume of air which enters and leaves lungs with each breath

400-500ml

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4
Q

What is the IRV? (Inspiratory Reserve Volume)

A

Additional amount of air that can be inhaled after a normal inhalation

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5
Q

What is the ERV? (Expiratory Reserve Volume)

A

Additional amount of air that can be exhaled after a normal exhalation

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6
Q

What is the Residual Volume?

A

The amount of air left in lungs, even after a forced expiration (cannot be breathed out)

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7
Q

Lung capacities are defined relative to 3 points in the breathing cycle;

  • Maximum inspiration
  • Maximum expiration
  • End of quiet expiration

What is the Inspiratory Capacity?

A
  • From end of quiet expiration to maximum volume

IRV + Tidal Volume

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8
Q

Lung capacities are defined relative to 3 points in the breathing cycle;

  • Maximum inspiration
  • Maximum expiration
  • End of quiet expiration

What is the Functional Residual Capacity?

A
  • Volume of air in lungs at end of quiet expiration

ERV + RV

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9
Q

Lung capacities are defined relative to 3 points in the breathing cycle;

  • Maximum inspiration
  • Maximum expiration
  • End of quiet expiration

What is the Vital Capacity?

A
  • Inspiratory capacity (TV + IRV) + ERV

Amount of air you can forcefully breath in and expire
(Returns you to Residual Volume)

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10
Q

What is the total lung capacity?

A

Vital capacity + Residual Volume

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11
Q

Only part of the Tidal Volume is available for gas exchange, the rest fills the anatomical dead space

What is the Anatomical Dead Space?

A

The volume of the conducting airways that does not take part in gas exchange

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12
Q

What is the Alveolar Dead Space?

A

The alveoli that do not take part in gas exchange (may be due to damage/ lack of perfusion)

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13
Q

What is Physiological Dead Space?

A

Anatomical Dead Space + Alveolar Dead Space

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14
Q

How do you calculate Tidal Volume using anatomical dead space and air in alveoli?

A

Air in alveoli + air in anatomical dead space

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15
Q

How do you calculate total pulmonary ventilation/ minute volume?

A

Tidal Volume * Respiratory rate

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16
Q

How do you calculate alveolar ventilation?

A

(TV- Dead Space)* respiratory rate

17
Q

Of Inspiration and Expiration, which is passive and active?

A

Inspiration- Active (Muscles contact)

Expiration- Passive (Muscles relax, lung’s elastic recoil returns thoracic cavity to original position)

18
Q

At rest, at the end of quiet expiration describe the 2 forces acting on the lungs

What is the net effect?

A
  • Inward: Lung’s elasticity and surface tension generate an inwardly directed force
  • Outward: Elasticity of rib cage’s muscles and connective tissues generate in outwardly directed force
  • Balance each other out, creating a negative pressure within Intrapleural space (visceral pleura pulled inwards and parietal pulled outwards)
19
Q

How much pleural fluid is there normally?

A

10ml

20
Q

Briefly describe the intrapleural pressure changes During the breathing cycle

A
  • Negative pressure at rest
  • Becomes more negative during inspiration
  • Returns to resting negative pressure at end of quiet expiration
21
Q

What are 2 sources of the Elastic Recoil of the lungs?

A
  • Elastic tissue in lungs

- Surface tension forces of fluid lining alveoli?

22
Q

What if the pleural seal was broken?

A

During expansion of rib cage, lungs would not expand but would collapse inwards on themselves

23
Q

In forced inspiration (exercise/ disease affecting lungs), accessory muscles are used

Name the 4 of them

A
  • SCM
  • Scalene muscles
  • Serratus Anterior
  • Pec Major
24
Q

Name 2 groups of Accessory muscles used in Forced Expiration

A
  • Internal Intercostal muscles

- Abdominal Wall Muscles (RA, EO and IO)

25
Q

What are 2 ways energy is expended during breathing

A
  • To stretch the lungs

- To overcome airway resistance

26
Q

What is the Compliance of the lungs?

How is it defined?

A
  • Distensibility (stretchiness) of the lungs

Volume change per pressure change

27
Q

Describe the effect of the film of fluid lining the alveoli

A
  • The fluid’s Surface Tension opposes any increases in alveolar surface area

(Decreased compliance makes it difficult for alveoli and therefore lungs to expand)

28
Q

Describe the substance we use to counter the Surface Tension of the fluid lining the alveoli?

Why do they float on the surface of the lining fluid?
(It has detergent properties)

A
  • Surfactant (mix of phospholipids and proteins) secreted by Type II Pneumocytes
  • Hydrophilic ends lie in alveolar fluid, Hydrophobic ends project into alveolar gas
29
Q

How does Surfactant act to reduce the effect of the fluid lining the alveoli?

A
  • Interspersed between fluid molecules
  • Distrupting interaction between them
  • Thus reducing surface tension
30
Q

Explain why less force is needed to expand smaller alveoli

A
  • In larger alveoli, surfactant molecules are further apart so are less efficient, so surface tension is greater
  • In smaller ones, surfactant molecules are closer so more efficient, so surface tension is weaker

(Also applies to when alveoli expand)

31
Q

Alveoli are basically a series of interconnected bubbles, the pressure of which is determined by the Law of Laplace.

LoL: Pressure =2T/r (T is Surface tension, r is radius)

What 3 things would happen if T was constant in all alveoli?

A
  • Smaller alveoli would have higher pressures so would empty into large alveoli with lower pressures
  • Thus, smaller alveoli would collapse into larger ones to form a few huge air filled spaces (Bullae)
  • This significantly reduces surface area for gas exchange
32
Q

How does Surfactant prevent Bullae forming and reducing SA for gas exchange?

A
  • As alveolus expands, surfactant is less effective, so Surface Tension increases, increasing pressure inside it
  • Therefore different sized alveoli can have same pressure preventing Bullae formation

(Pressure= 2T/r)

33
Q

Other than Increasing Lung compliance and Preventing small alveoli collapse into larger ones, what 3rd thing does surfactant do?

A

Prevents surface tension in alveoli creating a suction force which can cause transudation of fluid from pulmonary capillaries into alveoli

34
Q

Why is the resistance of the small airway tubes low?

Which part of the RT has the most resistance to breathing

(At rest work of breathing only consumes 0.1% of total O2 consumption)

A

Connected in parallel hence very large effective diameter

Therefore most of resistance to breathing is in Upper RT

35
Q

How are Elastance and Compliance related?

A

Inversely proportional

36
Q

Diameter is the main factor affecting airway resistance

What are 3 things that affect the diameter?

A
  • Mucus in airways
  • Pulmonary pressure gradients (High intrapulmonary pressures increase diameter)
  • Radial Traction
37
Q

What is Radial Traction?

How is it affected in expiration?

A

Outward pulling on bronchiole from Alveolar walls

(Prevents bronchiole collapse)

In expiration, alveolar walls are less effective (due to low alveolar pressure) at keeping bronchioles open so their diameter reduces to an extent

38
Q

Why is there increased airway resistance in expiration

A

Increased intrapulmonary pressure compresses airways, decreasing their diameter

Respiratory Sytem (21 decks)

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