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Respiratory Exam 1 > Statics: Lung Ventilation and Compliance > Flashcards

Statics: Lung Ventilation and Compliance Flashcards

1
Q

role of pulmonary surfactant

A
  • lower surface tension in the lung
  • imparts mechanical stability to alveoli
  • prevents collapse at low lung volumes
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2
Q

definition of minute ventilation

A
  • volume of gas moving in and out of the lungs per minute
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3
Q

minute ventilation calculation

A

inspired volume = expired volume = (tidal volume x respiratory frequency)

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4
Q

typical tidal volume of a person

A
  • 500 mL
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5
Q

anatomic dead space

A
  • conducting airways that do not participate in gas exchange
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6
Q

how much anatomic dead space exists in 500 mL tidal volume

A
  • 150 mL
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7
Q

alveolar ventilation

A
  • the total volume of inspired air that enters the alveoli per minute as is available for gas exchange
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8
Q

another source of dead space

A
  • alveoli who ventilation exceeds capacity of the blood flowing to those alveoli to exchange gases
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9
Q

what is physiologic dead space

A
  • combination of anatomic and alveolar dead space
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10
Q

physiologic dead space in normal healthy individuals

A
  • close to the anatomic dead space

- 25-30% of ventilation

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11
Q

elastance

A
  • property to resist being stretched

- and return to original state when released

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12
Q

elastic recoil of the lung opposes

A
  • inflation
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13
Q

elastic recoil of the lung assists

A
  • deflation
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14
Q

why is the slope of inspiration lower than that of expiration on the pressure-volume loop?

A
  • higher distending pressures are needed during inspiration to achieve a given lung volume
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15
Q

what is the name for the process in which the inflation and deflation limbs follow different paths

A
  • hysteresis
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16
Q

forces due to surface tension exist at

A
  • alveolar air-liquid interface
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17
Q

compliance of air filled lung determined by

A
  • tissue forces

- surface forces

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18
Q

what occurs due to the imbalance of cohesive interactions

A
  • force
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19
Q

what happens in a liquid filled lung in regard to compliance

A
  • air-liquid interface and surface tension forces eliminated

- compliance determined by tissue forces only

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20
Q

why is the surface tension of water high

A
  • polar water molecule interacts poorly with hydrophobic gas phase
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21
Q

pressure of small bubble radius

A
  • higher pressure needed to support surface tension
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22
Q

what happens to the radius of alveolar walls at end expiration

A
  • radius shortens
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23
Q

result of high surface tension on thin alveoli at low lung volumes

A
  • cause them to collapse
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24
Q

result of higher pressures within smaller alveoli

A
  • force them to empty into larger alveoli
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25
Q

pulmonary surfactant secreted by type II alveolar cells from

A
  • lamellar bodies
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26
Q

composition of lung lining

A
  • 90% lipid

- 10% protein

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27
Q

lipid fraction of lung lining composed of

A
  • DPPC
28
Q

which surfactant proteins are critical for formation of the surface layer

A
  • SP-B and SP-C
29
Q

which surfactant proteins participate in lung defense

A
  • SP-A and SP-D
30
Q

surfactant surface tension properties

A
  • dynamic

- vary as a result of compression or expansion of alveolar surface area

31
Q

density of surfactant as alveolar surface area decreases during expiration

A
  • density increases
32
Q

density of surfactant as alveolar surface area increases during inspiration

A
  • density decreases
33
Q

surface tension at high lung volumes

A
  • dynamically increases
34
Q

surfactant maximally reduces alveolar surface tension at ________ when tendency for alveolar collapse is greatest

A
  • end expiration
35
Q

best explanation for hysteresis in air-filled lung pressure volume curve

A
  • surfactant layer breaks up during lung expansion and increases surface tension
  • during deflation surfactant layer becomes more compressed and decreases surface tension
36
Q

premature infants have a great difficulty doing what

and are susceptible to

A
  • initiated and maintaining lung inflation

- susceptible to neonatal respiratory distress syndrome

37
Q

low compliance and the need to develop higher pressures to repeatedly expand collapsed lungs

A
  • increases work of breathing

- can lead to respiratory failure

38
Q

result of alveolar interdependence

A
  • interconnecting walls of neighboring alveoli support one another
39
Q

what happens when alveolar pressure falls to zero relative to atmosphere during each pause in spirometer testing

A
  • transmural pressure gradient is equal to the pleural pressure as measured by the esophageal balloon
40
Q

what is used to construct static lung compliance curves

A
  • volume of air exhaled

- intrapleural pressure

41
Q

elastic recoil and compliance in emphysema

A
  • elastic recoil decreased

- compliance increased

42
Q

lungs with emphysema in terms of inflating and deflating

A
  • inflate easily

- no elastance to deflate properly

43
Q

elastic recoil and compliance in pulmonary fibrosis

A
  • elastic recoil increased

- compliance decreased

44
Q

lungs with fibrosis in terms of inflating and deflating

A
  • difficult to inflate

- deflate more forcefully

45
Q

system compliance

A
  • algebraic sum of lung and chest wall acting together

- coupled by negative pressure in pleural space

46
Q

residual volume mainly set by

A
  • force of contracting expiratory muscles being opposed by the chest wall and ribs that resist further compression
47
Q

what sets the functional residual capacity

A
  • tendency of chest to spring outwards balanced by tendency of lungs to collapse
48
Q

at approximately 60% of vital capacity

A
  • chest wall at natural resting point

- recoil pressure mainly due to lung itself

49
Q

at lung volumes greater than 60% of vital capacity

A
  • both lung and chest wall must be distended by positive pressure
  • both actively contribute recoil
50
Q

at positive pressures greater than 30 cm H2O

A
  • lung reaches tensile limit

- further increases may rupture visceral pleura

51
Q

what is a pneumothorax

A
  • air entering the intrapleural space
52
Q

what happens if pleural pressure becomes equal to atmospheric pressure

A
  • lung may collapse
53
Q

what is a simple pneumothorax

A
  • one time leak

- air enters and leaves pleural space equally with each breath

54
Q

what is a tension pneumothorax

A
  • air that enters the pleural space, can’t leave, and builds up positive pressure
55
Q

how do we treat pneumothorax

A
  • relieve positive pressure with chest tube
  • apply suction to intrapleural space
  • re-expands lung and re-compresses rib cage to re-establish normal mechanical coupling
56
Q

the cycle of energy gain and loss for the lung is opposite that of

A
  • the chest wall
57
Q

the work of breathing is proportional to

A
  • product of changes in volume and pressure
58
Q

cost of tidal breathing

A
  • 5% of total body O2 consumption
59
Q

cost during exercise

A
  • about 30% during exercise
60
Q

work of breathing elevated in

A
  • obesity
  • pulmonary fibrosis
  • respiratory distress syndrome
  • pulmonary interstitial edema
  • obstructive lung disease
61
Q

why is work of breathing increased in obesity

A
  • chest wall load is increased

- chest wall compliance is reduced

62
Q

why is work of breathing increased in pulmonary fibrosis

A
  • compliance of the lung is reduced
63
Q

why is work of breathing increased in respiratory distress syndrome

A
  • lack of pulmonary surfactant decreases lung compliance and causes recurrent collapse
64
Q

why is work of breathing increased in pulmonary interstitial edema

A
  • stiff lung
65
Q

why is work of breathing increased in obstructive lung diseases

A
  • airway resistance increased

- elastic recoil reduced

66
Q

FRC in emphysema

why?

A
  • FRC increases

- harder to get air out of lungs so more would stay in there after expiration

Respiratory Exam 1 (27 decks)

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