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Respiratory > Week 2 Mechanics Of Respiration > Flashcards

Week 2 Mechanics Of Respiration Flashcards

1
Q

What are the goals of respiration?

A
  • distribute air and blood flow for gas exchange
  • provide oxygen to cells in body tissues
  • remove CO2 from body
  • maintain constant homeostasis for metabolic needs
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2
Q

What are the functions of respiration?

A

Respiration is divided into four functional events:

  1. Mechanics of pulmonary ventilation
  2. Diffusion of O2 and COS2 between alveoli and blood
  3. Transport O2 and CO2 to and from tissues
  4. Regulation of ventilation and respiration
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3
Q

What is external respiration?

A
  • mechanics of breathing
  • the movement of gases into and out of body
  • gas transfer from lungs to tissues of body
  • maintain body and cellular homeostasis
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4
Q

What is internal respiration?

A
  • intracellular oxygen metabolism
  • cellular transformation
  • krebs cycle: aerobic ATP generation
  • mitochondria and O2 utilization
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5
Q

What is the main purpose of ventilation?

A

-to maintain an optimal composition of alveolar gas

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6
Q

The lungs make up what percentage of body weight?

A

1.5%

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7
Q

What is the alveolar surface area?

A
  • 40x the external body surface

- 70m2 internal surface area

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8
Q

What is the benefit of short diffusion pathways for gases?

A
  • Permits rapid and efficient gas exchange into blood
  • 1.5um between air and alveolar capillary into blood
  • blood volume in lung - 500mL (10% of total blood volume)
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9
Q

What are the factors required to alter lung volumes?

A
  • respiratory muscles generate force to inflate and deflate lungs
  • tissue elastance and resistance impedes ventilation
  • distribution of air movement within the lung, resistance within the airway
  • overcoming surface tension within alveoli
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10
Q

How does air flow during breathing cycle?

A

It moves from higher to lower pressure.

During inspiration, alveolar pressure is sub-atmospheric, allowing airflow into lungs

Higher pressure in alveoli during expiration than atmosphere allows airflow out of lung

Changes in alveolar pressure are generated by changes in pleural pressure

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11
Q

What is the active phase of breathing cycle?

A

Inspiration

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12
Q

what nerve transmits motor stimulation to diaphragm?

A

Phrenic nerve: Cervical segments 3, 4, 5

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13
Q

The diaphragm does what percentage of the work of breathing?

A

75%

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14
Q

The external intercostal muscles does what percentage of the work of breathing?

A

25%

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15
Q

The act of spontaneous inhalation is what type of ventilation?

A

Negative pressure ventilation

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16
Q

What happens during contraction of diaphragm?

A
  • abdominal contents forced downward and forward
  • rib margins are lifted and moved outward
  • diaphragm moves down 1cm during normal inspiration
    • during forced inspiration diaphragm can move down 10cm
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17
Q

What is transdiaphragmatic pressure?

A

Effect of abdominal pressure on chest wall mechanics is transmitted across the diaphragm

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18
Q

What happens when increasing abdominal pressure pushed diaphragm cephalad into thoracic cavity?

A

FRC decreases

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19
Q

What are examples of things that would increase intra-abdominal pressure and reduce FRC?

A 
Pregnancy
Obesity
Bowel obstruction
Laparoscopic surgery
Ascites
Abdominal mass
Hepatomegaly
Trendelenburg position
Valsalva maneuver
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20
Q

What positions decrease abdominal pressure and allow easier lung ventilation?

A

Upright
Reverse trendelenberg
Prone

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21
Q

What happens if there is paralysis of external intercostal muscles?

A

Does not seriously alter inspiration bc diaphragm is so effective

Sensation of inhalation is decreased

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22
Q

When are accessory muscles used during inspiration?

A

During periods of stress or exercise

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23
Q

What are accessory muscles for respiration?

A
  • scalene muscle
    • elevate the first 2 ribs during forced inspiration
  • sternocleidomastoid muscle
    • raise the sternum during forced inspiration
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24
Q

What is the passive phase of the breathing cycle

A

Exhalation/expiration

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25
Q

What are the muscles of active expiration?

A
  • reclusive abdominus/abdominal oblique muscles
    • contraction raises intra-abdominal pressure to move diaphragm upward. Intra thoracic pressure raises and forces air out from lung

Internal interconstals muscles

 - assist in expiration by pulling ribs downward and inward
 - decrease thoracic volume

*these muscles contract forcefully during coughing, vomiting and defecatioin

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26
Q

What is transpulmonary pressure?

A
  • the pressure difference between the alveolar pressure and pleural pressure on outside of lungs
  • the alveoli tend to collapse together while the pleural pressure attempts to pull outward
  • the elastic forces tend to collapse the lung during respiration is recoil pressure
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27
Q

What are the partsof the pleural membrane?

A
  • visceral pleura: this serosal membrane that envelope the lobes of the lung
  • parietal pleura: lines the inner surface of the chest wall, lateral mediastinum, and most of diaphragm
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28
Q

What separates the pleural membranes?

A

A thin layer of serous fluid

*a large amount would be a pleural effusion as seen in CHF, CA, infection

29
Q

What is the function of pleural fluid?

A
  • functions as a lubricant between the membranes
  • causes visceral and parietal pleura to adhere together, maintains surface tension
  • lymphatic drainage maintains constant suction on pleura (-5cmH2O)
30
Q

What is pleural pressure?

A
  • the pressure of the fluid in the space between the lung pleura and chest wall
  • always negative
  • holds the lungs open at rest
  • if becomes positive, the lung will collapse:pneumothorax, hemothorax, chylothorax (lymph)
31
Q

What is normal pleural pressure?

A
  • at rest: -5cmH2O

- during inspiration becomes more negative: -7.5cmH2O, allowing for negative pressure respiration

32
Q

What is vital capacity?

A

The greatest volume of breath that can be expelled from the lungs after taking the deepest possible breath

VC = IRV + TV + ERV

33
Q

What is inspiration capacity?

A

The total amount of air that can be drawn into the lungs after normal expiration

IC = TV + IRV

34
Q

What is inspiration reserve volume?

A

The maximal amount of additional air that can be drawn into lungs by determined effort after normal inspiration

35
Q

What is expiratory reserve volume?

A

The additional amount of air that can be expired from the lungs by determined effort after normal expiration

36
Q

What is tidal volume?

A

The lung volume representing normal volume of air displaced between normal inhalation and exhalation when extra effort is not applied

37
Q

What is total lung capacity?

A

The volume of air contained in the lungs at the end of maximal inspiration

TLC = IRV + TV + ERV + RV

38
Q

What is functional residual capacity?

A

The volume of air present in the lungs at the end of passive expiration

FRC = ERV + RV

39
Q

What spirometry values cannot be measured?

A

-residual volume

Thus functional residual capacity and total lung capacity cannot be determined using spirometer alone

40
Q

What is lung compliance?

A

It’s a measure of the distensiblity of the lungs

Compliance = change in lung/change in lung pressure

41
Q

How do lung volumes change related to transpulmonary pressure?

A

In the presence of increased airway resistance or decreased lung compliance, an increased transpulmonary pressure is required to produce a given tidal volume and thus the work of breathing is increased

42
Q

What creates the elastic forces of the lungs?

A
  • elastic lung tissue
    • elastin and collagen fibers of lung parenchyma
    • natural state of these fibers is contracted coils
    • recoil force assists to deflate lungs
  • surface air-fluid interface
    • 2/3 of total elastic force of lung
    • surfactant in the alveoli fluid reduces surface tension, keep alveoli from collapsing
43
Q

Does surfactant work better when molecules are closer together or farther apart?

A

Closer together

44
Q

What are the functions of surfactant?

A
  • lowers surface tension of alveoli and lung
    • reduces work of breathing
    • increases compliance of lung
  • promotes stability of alveoli
    • surfactant reduces forces causing atelectasis
  • prevents transduction of fluid into alveoli
    • decreases fluid from getting pulled in
45
Q

What is minute ventilation or total ventilation?

A

Minute ventilation = Vt x frequency

Total volume of air conducted into lungs per minute

46
Q

What is alveolar ventilation?

A
  • volume of fresh air entering alveoli each minute (70% of total ventilation or minute ventilation)
  • anatomical dead space and its portion of tidal volume (30%) affect amount of gas exchanged in alveoli
47
Q

What is wasted ventilation?

A

The concept of physiologic dead space (Vpd) describes a deviation from ideal ventilation relative to blood flow

-for example: PE, air emboli, fat emboli

48
Q

What is closing volume?

A

Volume of the lung at which small airways close. If CV > FRC then small airways collapse during normal TVs leading to atelectasis and hypoxemia

49
Q

What are features of laminar flow?

A
  • is parallel streams of flow

- velocity in center of airway is twice as fast than at edges of tube

50
Q

What is Poiseuille’ Law

A

Describes resistance to flow through a tube

 - pressure increases proportional to flow rate and gas viscosity
 - smaller airway radius and longer distances increase flow resistance

*huge increase in resistance by narrowing radius

51
Q

What is Ohm’s Law?

A

P = F x R

P: pressure
F: flow
R: resistance

52
Q

At what flow rate does turbulent flow occur?

A

Higher flow rates

53
Q

What increases turbulent flow?

A
  • density
  • velocity
  • airway resistance
54
Q

What is the chief site of airway resistance?

A

Major resistance is at the medium-sized bronchi

55
Q

What factors determine airway resistance?

A

Lung volume
-as lung volume is reduced - airway resistance increases

Bronchial smooth muscle
- contraction of airways increases resistance

Density and viscosity of inspired gas

 - increased resistance to flow the elevated gas density 
 - changes in density rather than viscosity have more influence on resistance
56
Q

What helps to provide a stable alveolar environment?

A

The 2 ventilation phases
-inhalation and exhalation

  • oxygen ins constantly removed from alveolar gas by blood
  • CO2 continuously added to alveoli from blood
57
Q

What nerve innervates the external intercostal muscles?

A

Intercostal nerves T 1-11

Originate from the ventral rami of T1-11

58
Q

What happens to movement of the diaphragm when paralyzed?

A

*paradoxical movement of diaphragm

  • upward movement with inspiratory drop of intrathoracic pressure
  • occurs when the diaphragm muscle is denervated
59
Q

What is abdominal pressure compared to atmospheric pressure in supine position when respiratory muscles are relaxed?

A

Abdominal pressure is equal to atmospheric pressure

60
Q

When is exhalation active?

A

During hyperventilation and exercise

61
Q

What is spirometry?

A

Measure the volumes of respriration

62
Q

What is a Flow-Volume Loop?

A

A graph of the rate of airflow as a function of lung volume during a complete respiratory cycle consisting of a forced inspiration followed by a forced exhalation.

  • used in assessing pulmonary function.
  • Inspiration on bottom, expiration on top, looks like an upside down ice cream cone
63
Q

What reduces lung compliance?

A
  • Higher or lower lung volumes
  • higher expansion pressures
  • venous congestion
  • alveolar edema
  • atelectasis and fibrosis
64
Q

What increases lung compliance?

A
  • age

- emphysema secondary to alterations of elastic fibers

65
Q

What is a compliance diagram?

A

Lung volume changes related to transpulmonary pressure

66
Q

What is hysteresis?

A

Different curve for inhalation and exhalation, different lung volumes for each

67
Q

What can be used to determine the work of breathing?

A

Oxygen conusumption

68
Q

What is the chemical name of surfactant?

A

DPPC-Dipalmitoyl phosphatidyl choline

69
Q

What is the Bernoulli effect?

A

When you breath through a pipe with various sizes, the flow is fastest through the narrowest portion. This can cause lower pressures at that point and airways to collapse

Respiratory (4 decks)

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