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Human Physiology and Pharmacology > Week 21: (B) Dynamic Mechanics of Breathing > Flashcards

Week 21: (B) Dynamic Mechanics of Breathing Flashcards

1
Q

What are the 3 factors of dynamic force?

A

Resistance
Flow
Turbulence

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2
Q

What is dynamic force?

A

How gas moves through the airways

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3
Q

What is Poiseuille’s Law? RESISTANCE

A

Suggests smallest tubes have greatest airway resistance…….but there are lots of them so the cumulative resistance is actually lower.

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4
Q

What part of the airways has the highest resistance?

A

Upper airways 90%

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5
Q

What are the factors that influence resistance?

A
  • Lung volume and branching
  • Bronchiolar smooth muscle tone
  • Density and viscosity of gases
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6
Q

What effects density and viscosity of gases?

A
  • Affected by altitude.
  • Important consideration in artificial environments (Space, deep sea).
  • Laminar flow is a function of gas viscosity but turbulent flow depends on gas density
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7
Q

What lines the upper airway?

A

smooth muscle

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8
Q

What causes a decrease in the radius of the ‘tube’ ?

A

muscular contraction

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9
Q

What induces the smooth muscle contraction in the airways?

A
  • Parasympathetic activity,
  • Ach neurotransmission
  • Irritants (smoke, allergens),
  • Decreased alveolar PCO2
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10
Q

What causes an increase in the radius of the ‘tube’?

A

muscular relaxation

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11
Q

What induces the smooth muscle relaxation in the smooth muscle?

A
  • Sympathetic activity
  • Pulmonary stretch (see last slide),
  • NAdr (neural – weak)
  • Adr (b2 – circulating, strong) [and Salbutamol].
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12
Q

What are the effects of beta blockers (propanol) for asthmatic people?

A

Muscle spasms that make it difficult to breathe.

Cause constriction of the airways

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13
Q

What is the effect of hyper reactivity of smooth muscle?

A

contracts more intensely with duration of exposure

HYPERTROPHY

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14
Q

What causes allergic inflammation of the airways? (2)

A

1) Dust mite fecal allergen
Der p 2, 5
2) Cat saliva allergen
Fel d 1

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15
Q

What are the consequences to an allergic inflammation of the airways?

A

Hyper-reactivity of airway smooth muscle contraction
Bronchial smooth muscle thickening
hypertrophy

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16
Q

What is the effect of contraction of parabronchial smooth muscle?

A

raises upper airway resistance

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17
Q

Where is the bulk of resistance?

A

trachea and branch generation 5

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18
Q

Gas moves into the lungs via convection until when?

A

low resistance zone when it moves via diffusion

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19
Q

What is the low resistance zone?

A

moves at crows oxygen permeation co-efficient
O2 moves forward at its own molecular rate of diffusion through bulk air.

Loses its convection effect, moves to respiratory acinus by diffusion as it moves into its own molecular velocity

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20
Q

In normal lungs where is the low resistance zone located ?

A

respiratory acinus

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21
Q

What is the effect of the upper airway resistance in the position of the low resistance zone? (asthma)

A

-Occurs at around branch 9 instead of ~19. meaning it has to diffuse at the slower rate for longer. need to difuse along branch 9-17 .

-Gas fails to penetrate to distal regions of respiratory
zone causing alveolar pCO2 to rise. decrease pH acidification

-Lung ceases to oxygenate Hb efficiently due to
Reversal of proper alveolar Bohr and Haldane
effects

22
Q

What is turbulence?

A

breath sounds

23
Q

What happens to convection, low resistance zone etc. when we exercise?

A

raise convection in the lung
molecular velocity occurs in the acinus zone
the O2 travels further into the acinus zone so gas exchange is quicker, less time in slow diffusion.
hence why we breathe heavier and quicker.

24
Q

What factors effect the flow resistance of the tubes in the airways?

A

Laminar flow
Transitional flow
Turbulent flow (lots of eddies)

25
Q

How do you measure airway resistance of whole body?

A

Whole Body Plethysmography

26
Q

How does the whole body plethysmography work?

A

enclosed space, breath in against a closed shutter. lung volume increases causing arterial pressure to decrease.
Due to no airflow, mouth pressure = arterial pressure.
The inspiration causes change in box pressure is proportional to the negative change in arterial pressure (decrease arterial pressure)
–> thus the change in box pressure provides a measure of arterial P

27
Q

What happens to resistance during inhalation?

A

Airway Resistance Falls as Gas Flow and Lung Volume Increase.

28
Q

What happens to the airway size during inhalation?

A

As lungs expand airways

are also physically widened.

29
Q

What happens to resistance as lung volume increases?

A

as lung vol increases, resistance decreases

30
Q

How does resistance of the upper airways help with exhalation?

A

helps to keep airway pressure high to maximise gas movement out of alveoli

31
Q

What is dynamic compression?

A 
Dynamic compression of the airways results when intrapleural pressure equals or exceeds alveolar pressure, which causes dynamic collapsing of the lung airways
Contraction of smooth muscle
The force (pressure) of the alveoli pushing air out must overcome the resistance of the upper airways.
32
Q

What is an Eddie in fluid dynamics?

A

The swirling of a gas and the reverse current created when the gas is in a turbulent flow regime.
Lots of eddies make up a turbulent flow

33
Q

What causes wheezing in the lungs?

A

Laminar flow is complicated by dichotomous branching and associated with Eddies and turbulence that can occur in the lung and are influenced by airway smooth muscle contraction.

34
Q

What is the driving pressure in the airways?

A

driving pressure of gas movement through the airways is going to be a product of laminar flow.

35
Q

What is Laminar flow?

A

Type of fluid (gas or liquid) flow in which the fluid travels smoothly or in regular paths, in contrast to turbulent flow, in which the fluid undergoes irregular fluctuations and mixing.

36
Q

What is transitional flow?

A

A mixture of turbulent flow and laminar, usually laminar at the edges and turbulent at the centre

37
Q

What is turbulent flow?

A

chaotic and rough movement of particles through a region.

38
Q

What are the steps in inspiration?

A

expanding chest cavity, reduce Pip significantly. pulls airway pressure down below atmospheric P, gas will enter airways (enter conducting zone)
alveolar pressure = -15

39
Q

What happens in early inhalation?

A

No gas movement, holding breath for a moment before exhale
interpleural pressure is negative due to tethering of lung to chest wall (expand and lower pressure)
airway pressure zero along mouth alveolus

40
Q

What are the steps in expiration?

A
  • Lungs collapse under elastic recoil (product of elastin fibre + surface tension)
  • Inward collapse produces dynamic compression of lung.

-Interpleural pressure increases (+10) in the alveolus. P in respiratory zone above atmospheric.
=DYNAMIC COMPRESSION

41
Q

What is gas movement completely dependent on? exhale

A

On dynamic compression in the alveoli to move across zones.

Where gas begins to meet the increasing resistance of the conducting zone, we need extra force (dynamic compression)

42
Q

What’s COPD characterised by?

A 
increased resistance to air flow
as they suffer from collapse of elastic structure in the airways and build up of mucous.
1. Alveoli destruction
2. Reduced surface area
3. Reduced elasticity
43
Q

What is airflow like in moderate COPD?

A

turbulent flow of gas, as it moves against the collapsed structures and increase mucous in the airways

44
Q

What is airflow like in severe COPD?

A

Inhalation phase not as turbulent as moderate
expiration- protracted, turbulent and a lot of resistance pressure
Can breathe in ok but gas that enters their airways becomes trapped there, unable to remove easily due to increased resistance = gas trapping

45
Q

Why do people with COPD purse their lips?

A
  • To main airway P high all the way through the conducting zone of the lungs.
  • Never actually get the fall-off that we see in the normal expiration.
  • maximum point of resistance up from airway to mouth
46
Q

Why do people with COPD hunch over?

A
  • Using dynamic compression by hunching over to raise airway P as above Pip all the way through the airways
  • Produce their own dynamic compression.
47
Q

What is a name for a person with COPD pursed lips and pinched over?

A

“blue puffer”

48
Q

What is an equation for work of the lung?

A

pressure* volume

pressures are always changing

49
Q

What is the work for breathing (inspiration)?

A

-Energy input required to overcome elastic component
ADD
- Energy input required to overcome surface tension

50
Q

What is the work for breathing (expiration)?

A

Energy input to overcome airway and tissue resistance

51
Q

What is the difference between panting and deep breathing?

A

panting: overcoming surface tension of the lung

Deep breathing: overcoming elastic fibre components

Human Physiology and Pharmacology (31 decks)

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