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+ CAPS 301: Respiratory, Renal, GI, Endocrinology, Reproduction > Mechanics of Breathing > Flashcards

Mechanics of Breathing Flashcards

1
Q

What are the two compartments of the mechanical respiratory system? What is a common property that they share?

A
  • lungs
  • chest wall – pump that moves lung

both have elastic properties

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2
Q

Describe the state of the respiratory system, chest wall, and lungs at functional residual capacity (FRC).

A
  • respiratory system is at rest
  • outward recoil of chest wall
  • inward recoil of lungs

these two opposing elastic properties are equal in magnitude, but opposite in direction

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3
Q

What is a pleural sac?

A

sac filled with ~!0 mL of fluid that lies between lungs and chest wall, one surrounding each lung

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4
Q

What do the cohesive forces of pleural fluid do? (2)

A

attach chest wall and lungs together

  • allows lungs to inflate and deflate with chest wall movement
  • movement of chest wall is followed by movement of lungs

reduce friction as lung tissue glides past chest wall during breathing

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5
Q

What are the units for pressure in respiratory mechanics? Why?

A

centimetres of water (cm H2O)

  • mmHg is much larger relative to cm H2O
  • cm H2O allows easier visual detection of pressure change
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6
Q

Where is atmospheric/barometric pressure?

A

surrounds chest wall and opening of airways

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7
Q

Why do we set PB = 0?

A

atmospheric pressure can change

when observing pressures, we observe them relative to atmosphere

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8
Q

What are the pressures (PA and Ppl) at FRC if the glottis is open (open airway to alveoli)?

A

PA = PB = 0, as long as you are at the end of a normal breath

Ppl = -5

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9
Q

What is transmural pressure?

A

pressure across wall (inside - outside)

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10
Q

What are the two types of transmural pressures?

A
  • transpulmonary pressure (Ptp)

- chest wall transmural pressure (Ptw)

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11
Q

What is transpulmonary pressure (Ptp)?

A

pressure gradient across lung

Ptp = PA - Ppl = 0 - (-5) = 5 cm H2O

keeps lungs open at FRC, against their inward elastic recoil tendency

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12
Q

What is chest wall transmural pressure (Ptw)?

A

pressure gradient across chest wall

Ptw = Ppl - PB = -5 - 0 = -5 cm H2O

keeps chest wall from recoiling outward

(same as Ptp in magnitude, but opposite in direction)

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13
Q

Describe the state of chest wall and lung at FRC.

A

chest wall is squishing lung

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14
Q

What is the pressure of the respiratory system with 0 transmural pressure?

A

respiratory system is at rest with 0 transmural pressure

Prs = PA – PB = 0 - 0 = 0

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15
Q

What is a pneumothorax?

A

air entering pleural cavity, causing collapsed lung

  • can be large/small which results in complete/partial collapse of lungs
  • can be life threatening/fatal (ie. tension pneumothorax
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16
Q

Pneumothorax

What pressure has consequences?

A

-5 average Ppl

17
Q

What is a traumatic pneumothorax?

A

puncture wound in chest wall that results in opening to pleural space

  • opens chest wall
  • allows air to enter (from higher to lower pressure)
  • can also result in hemothorax (blood entering pleural cavity)
18
Q

What is a spontaneous pneumothorax?

A

spontaneous rupture/hole in lung that results in opening to pleura from inside of airway

  • allow air from lung to enter pleura
  • air enters until the two pressures in pleura, and outside become the same
  • results in air-filled pleura and collapsed lung
19
Q

What is Boyle’s law?

A

relationship between pressure and volume

  • pressure is related inversely to volume at constant temperature
  • closed system
20
Q

What is pressure?

A

force per unit area caused by gas molecules striking walls of container

21
Q

Respiratory Pressures During Quiet Breath – Inspiration

A

see notes

22
Q

Respiratory Pressures During Quiet Breath – Expiration

A

see notes

23
Q

What are the muscles of active expiration? (2)

A

internal intercostal muscles
abdominal muscles

recall: normal quiet breathing is passive – these muscles have to do with active breathing, such as taking deeper breaths, or forcing breath out (blowing)

24
Q

What are the accessory muscles of inspiration? (2)

A

muscles in neck used for very large/deep breaths, in patients who have problems breathing

  • sternocleidomastoid
  • scalenus
25
Q

What are the major muscles of inspiration? (2)

A

diaphragm

external intercostal muscles – between ribs, closest to skin

26
Q

Muscles of Inspiration

What does the diaphragm do? Describe the movement.

A
  • 75% of air that moves into lung is due to diaphragm

- moves downward, increases vertical dimension of chest wall

27
Q

Muscles of Inspiration

What do external intercostal muscles do? Describe the movement.

A

brings lower rib up to rib above it

up-down bucket handle motion

  • elevates rib upward and outward
  • increases horizontal dimension of chest wall
28
Q

Muscles of Inspiration

What do accessory muscles do? Describe the movement.

A

attached to sternum and upper ribs – lifts them upward and outward

  • sternocleidomastoid: lift sternum
  • scalene muscle: lift first 2 ribs

up-down pump handle motion

  • sternum moves upward and outward
  • increases front-back dimension of chest wall for air to move into lungs
29
Q

Muscles of Expiration

What are internal intercostal muscles? What do they do? Describe the movement.

A

layer below external intercostals, run 90º to them

contraction bring ribs down
- further reduces horizontal and front-back dimensions of chest wall

30
Q

Muscles of Expiration

What are abdominal muscles? What do they do? Describe the movement.

A

3 layers

contraction pushes abdominal cavity towards diaphragm
- further reduces vertical dimension of chest wall

31
Q

What happens when inspiratory muscles relax?

A

diaphragm, ribs, and sternum return to resting position, which restores thoracic cavity to pre-inspiratory size

32
Q

What innervates muscles of quiet inspiration?

A

C3-C5 (cervical spinal roots), which give rise to phrenic nerves that supply hemi diaphragms

  • two phrenic nerves – one left, one right
  • if one gets hurt, the other is still functional on their side of the diaphragm
33
Q

What innervates muscles of quiet expiration?

A

passive expiration: none – due to inward recoil of lung

active expiration: T7-L1 – abdominal muscles active, especially transversus abdominus

34
Q

What innervates external or internal intercostal muscles?

A

T1 - T11

35
Q

What innervates sternomastoid muscle?

A
  • accessory nerve

- C2-C3

+ CAPS 301: Respiratory, Renal, GI, Endocrinology, Reproduction (32 decks)

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