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Respiratory Physiology > Airway Resistance > Flashcards

Airway Resistance Flashcards

1
Q

What is pressure gradient?

A

Difference between alveolar and atmospheric pressure
Pressure gradient = resistance X flow

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2
Q

What is airway resistance?

A

Pressure difference between atm and alv/flow rate
R = change in P/F

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3
Q

What are the 3 flow rates?

A

Laminar flow
Unsteady eddies
Turbulent

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4
Q

What does an increase in air viscosity cause?

A

increased airway resistance

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5
Q

What do longer airways mean for resistance?

A

Increased airway resistance

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6
Q

What flow is most common at resting flow rates?

A

laminar

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7
Q

Where is turbulent flow normally found?

A

Branch points and large airways

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8
Q

What does the probabilty of turbulence increase with?

A

Increasing radius and veolcity

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9
Q

What is Poiseuille’s law?

A

Flow = ∆Pπr4/8ηl
decreased radius = increased resistance

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10
Q

What is the resistance in smaller airways?

A

Overall cross sectional area is increased -> lower resistance

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11
Q

What are the major sites of resistance?

A

larger airways and medium sized bronchioles

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12
Q

How does lung volume affect resistance?

A

Total airway resistance declines with increasing lung volume
bronchiolar diameter increases with increasing lung volume

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13
Q

What happens at low lung volumes?

A

Airways close completely preventing complete deflation of isolated lungs

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14
Q

How does airway SM regulate resistance?

A

Regulates diameter by bronchoconstriction/dilation

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15
Q

What does cholinergic PNS stimulation cause?

A

Bronchoconstriction rvia M3 muscarinic cholinergic receptors
comes from vagus

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16
Q

What does beta adrenergic SNS stimulation cause?

A

Bronchodilation from circulating adrenaline

17
Q

What is ventolin?

A

beta adrenergic agonist

18
Q

What is limiting expiratory flow?

A

dynamic compression of airways

19
Q

What is transpulmonary pressure?

A

Pressure that holds lungs open at 4mmHg along End expiration airways
Ptp = Palv - Pip

20
Q

What is Palv, Patm and Pip?

A

Palv = 0mmHg
Patm = 0mmHg
Pip = -4mmHg

21
Q

What happens as pressure travels towards the mouth?

A

As airway pressure decreases towards atmospheric pressure at mouth, collapsing pressure increases

22
Q

What pressure is exerted on all airways/

A

Intrapleural pressure

23
Q

What happens when Palv drops below Pip?

A

Ptp becomes negative -> equal pressure point

24
Q

What is the equal pressure point?

A

Point at which pressure inside the airway equals pressure outside (intrapleural pressure)

25
Q

What happens when Palv is above the equal pressure point?

A

Tendency for collapse

26
Q

What prevents the tendency to collapse?

A
  • opposed by cartiliaginous support in larger airways and traction by alveolar elastic recoil in smaller airways
27
Q

What does emphysema cause?

A

Increased compliance
loss of elastic recoil

28
Q

What happens in emphysema during expiration?

A

Dynamic airway collapse - increase +ve pressure as more muscles recruited to expire
contributes to hyperventilation (increased FRC)
Increased airway resistance

29
Q

What happens in chronic bronchoitis?

A

Narrow lumen of airways from thickening of airway wall

30
Q

What does asthma cause?

A

Increased airway resistance
Excessive bronchial SM contraction
thickened airway wall
dynamic airway collapse
Hyperinflation

31
Q

How can we test for increased airway resistance?

A

Clincial pulmonary function testing

32
Q

What is FVC?

A

Amount of air breathed in and out at forced expiration

33
Q

What is the difference between obstructive and restrictive lung diseases?

A

O = airway narrowing eg asthma
R = reduced compliance eg pulmonary fibrosis

Respiratory Physiology (17 decks)

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