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Pulm > Phys- Mechanics of Breathing > Flashcards

Phys- Mechanics of Breathing Flashcards

1
Q

Between breaths, ___ exactly opposes ___

A

Transmural pressure (-4) exactly opposes elastic recoil of the lung

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2
Q

Inspiratory muscles

A

Diaphragm

Accessory = external intercostals, scalenes, SCM

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3
Q

Expiratory muscles

A

Normally passive, but accessory = internal intercostals and abdominal muscles

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4
Q

How do the external intercostals assist in inspiration?

A

Move ribs up and out

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5
Q

How do the internal intercostals assist in inspiration?

A

Move ribs down and in

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6
Q

What occurs before transpulmonary pressure changes during breathing?

A

Chest wall expands/recoils, which causes the change in pressure (remember inverse relationship between volume and pressure)

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7
Q

What is the transpulmonary pressure mid-inhalation? Transrespiratory?

A

Both are negative, drawing air into lungs

more negative in case of Ptp

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8
Q

When is intrapleural pressure at its max?

A

End of inspiration = max lung capacity

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9
Q

What change occurs between mid-inhalation and mid-expiration?

A

Transpulmonary and transrespiratory pressures become less negative, drawing air out of the lungs

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10
Q

Describe the mechanism of pneumothorax.

A

Chest wall/pleura pierced
Pip becomes 0/equalizes with Patm
Chest wall then can spring out and lung can collapse

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11
Q

Slope of a pressure-volume curve

A

Compliance

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12
Q

Compliance =

A

V/P

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13
Q

Increased volume = ___ compliance

A

Increased

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14
Q

Decreased compliance = decreased __

A

Volume

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15
Q

Increased compliance = decreased ___

A

Pressure

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16
Q

What is hysteresis?

A

Difference in expiratory and inspiratory curves on pressure volume graph

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17
Q

What causes hysteresis?

A

Surfactant - When inspiration begins, alveoli must overcome surface tension to open (pressure builds but volume doesn’t increase); when expiration begins, there is no surface tension.

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18
Q

FRC =

A

ERV + RV

1.2 + 1.2 ~ 2.5L

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19
Q

The stiffer the lung, the (more/less) compliant

A

Less

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20
Q

The more elasticity a lung has, the (more/less) compliant

A

Less
(elasticity and compliance are inversely related: a thick rubber band with more elastic tissue has low compliance; a thin rubber band with less elastic tissue has high compliance)

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21
Q

A disease causing increased FEC1:FRC would cause (increased/decreased) compliance

A

Decreased
(Increased FEC1:FRC is a restrictive lung disease, meaning the lungs are stiffer = decreased compliance; fibrosis, pulm edema)

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22
Q

Obstructive lung diseases have (increased/decreased) FEC1:FRC and (increased/decreased) compliance

A

Decreased FEC1:FRC
Increased compliance
(decreased elasticity = increased compliance)

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23
Q

What is the consequence of increased elasticity in obstructive diseases?

A

Lungs are prone to collapse because pressure in the airways and alveoli is less so air can’t get out

24
Q

Why is the FEV1 decreased in obstructive diseases?

A

Takes longer to get air out

25
Q

Is lung compliance greater during inspiration or expiration?

A

Expiration

C=V/P, so when volume is greater at beginning of expiration, lungs are more compliant

26
Q

What is the obstructive ventilatory defect in emphysema?

A

Decreased pressure difference

(so decreased flow, F=P/R

27
Q

What is the obstructive ventilatory defect in asthma/bronchitis?

A 
Increased resistance
(so decreased flow, (F=P/R)
28
Q

Describe the flow volume loop for an obstructive disease.

A

Inspiratory phase is normal, but expiratory flow rate is reduced while expiratory volume is normal

29
Q

Describe the flow volume loop for a restrictive disease.

A

Volume of expiration and inhalation are reduced; inspiratory flow rate is reduced greatly; expiratory flow rate is also reduced

30
Q

Describe the volume flow loop in a healthy person.

A

Volume of inspiration and expiration are equal. Inspiratory flow rate makes a bell curve; expiratory flow rate peaks toward the end of expiration

31
Q

What two factors determine lung compliance?

A

Elastic forces of lung tissue

Surface forces

32
Q

Describe the support of alveoli structure

A

Interdependence - wall of one alveolus forms part of the wall of another; if one has tendency to collapse, it’s overcome by the expanding forces of surrounding alveoli

33
Q

What creates surface tension?

A

Nothing to counterbalance force on liquid molecules on top of solution so creates air-liquid interface

34
Q

Surfactant (increases/decreases) compliance

A

Increases

35
Q

What is the main component of surfactant?

A

PL (specifically DPPC)

36
Q

LaPlace’s Law

A

P=2T/r

37
Q

Small alveoli without surfactant have (increased/decreased) compliance. Why?

A

Decreased; C=V/P and P=2T/r; since r is decreased, P is increased and C is decreased; in other words, the strong intermolecular forces between water are strong in a small alveolus because they’re in closer contact.

38
Q

Where is surfactant made? Stored?

A

Type II pneumocytes; Lamellar bodies in those cells

39
Q

Why do we take a deep breath every few minutes?

A

Stretches type II pneumocytes, releasing surfactant

40
Q

What is respiratory distress syndrome of the newborn/hyaline membrane disease?

A

Preemies born before 24 weeks gestation can’t produce surfactant; this decreases compliance and prevents lungs from expanding so it’s a restrictive disease; small alveoli are unstable and pop upon expiration, releasing hyaline into the aveoli.

41
Q

Name for a collapsed airway

A

Atelectasis

42
Q

Why not have larger alveoli rather than surfactant?

A

Need small alveoli to increase surface area for gas exchange

43
Q

How does surfactant decrease surface tension?

A

Disrupts intermolecular forces between water lining alveoli via its amphipathic nature

44
Q

Flow =

A

P/R

45
Q

Resistance =

A

8nl/pi(r^4)

46
Q

If radius is halved, resistance (increases/decreases) by ___

A

Increased, 16

47
Q

4 factors determining airway resistance

A
  1. Anatomic factors
  2. Lung volume
  3. Bronchial smooth muscle contraction
  4. Density and viscosity of inhaled gas
48
Q

Which has more resistance: trachea or respiratory bronchiole?

A

Trachea

respiratory bronchioles have greater TOTAL surface area, so trachea has smaller radius = greater resistance

49
Q

What role do elastic fibers play in airway resistance?

A

They tend to attach to exterior of airway and pull out, thus opening the airway and increasing radius = decreasing resistance

50
Q

How does lung volume contribute to airway resistance?

A

Greater the volume, the more airway diameter increases; increased radius = decreased resistance

51
Q

How do asthmatic overcome increased resistance due to strong airway contraction?

A

They breathe at higher volumes = increased diameter = reduced resistance = increased flow
(Increased V also decreases P; R=FP, so R also decreases)

52
Q

3 diseases for which constriction of bronchial smooth muscle plays important role

A

Asthma, bronchitis, emphysema

53
Q

Neurotransmitter which causes dilation of BSM

A

Epi (via B2R)

54
Q

Mediators which cause constriction of BSM

A

ACh and leukotrienes

55
Q

How does asthma cause airway obstruction?

A

BSM contraction = decreased radius = increased resistance = decreased flow

Pulm (33 decks)

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