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VET 408: Cardio/Respiratory > Pulmonary Mechanics > Flashcards

Pulmonary Mechanics Flashcards

(70 cards)

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1
Q

total lung capacity (TLC)

A

sum of all lung volumes

MAXIMUM volume - after forced inspiration

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2
Q

tidal volume

A

volume moved in a normal breathing cycle

resting breath - NOT forced

small amount of TLC

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3
Q

residual volume (RV)

A

smallest volume possible in the lung inside of an intact chest

MINIMUM volume - after forced expiration

maintained by coupling of lung to chest wall

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4
Q

minimum volume (MV)

A

smallest volume possible in the lung of an open chest

absolute minimum value - requires uncoupling of lung to chest wall

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5
Q

inspiratory reserve volume (IRV)

A

the volume that can be moved during a forced inspiration up to total capacity

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6
Q

expiratory reserve volume (ERV)

A

volume that can be moved during a forced expiration down to residual volume

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7
Q

functional residual capacity (FRC)

A

volume left in the lungs at the end of a passive respiration

normal resting lung volume

maintained by equilibrium between inward lung recoil and outward chest wall recoil pressures (creates negative pressure)

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8
Q

what is the purpose of functional residual capacity

A

acts as a buffer of oxygen for gas exchange - prevents immediate hypoxia if you stop breathing

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9
Q

TLC equation

A

TLC = RV + ERV + VT + IRV

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9
Q

vital capacity (VC)

A

sum of all volumes in the lung that can be moved

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10
Q

IRV equation

A

IRV = TLC - VT

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11
Q

ERV equation

A

ERV = VT - RV

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12
Q

FRC equation

A

FRC = RV + ERV

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13
Q

VC equation

A

VC = VT + ERV + IRV

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14
Q

what drives air movement

A

pressure gradients (moves from high to low)

generated by the contraction/relaxation of inspiratory muscles

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15
Q

what are the inspiratory muscles

A

diaphragm and external intercostal muscles

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16
Q

inspiration

A

active process initiated by. the contraction of inspiratory muscles

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17
Q

steps of inspiration

A
  1. diaphragm and intercostal muscles contract, which increases the volume in the thoracic cavity
  2. increasing volume causes pressure inside thoracic cavity to drop, which decreases pressure in the pleural space and alveoli
  3. air moves from outside (high PB) to inside alveoli (low PA)
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18
Q

expiration

A

passive process initiated by the relaxation of inspiratory muscles

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19
Q

steps of expiration

A
  1. diaphragm and intercostal muscles relax, causing volume to decrease in thoracic cavity
  2. decreasing volume causes pressure to increase inside pleural space and alveoli
  3. air moves from inside (high PA) to outside (low PB)
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20
Q

how does expiration differ in horses

A

horses have ACTIVE end-expiration (contraction of expiratory muscles) during normal breaths

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21
Q

artificial ventilation

A

use of an external ventilator to generate positive pressure to force air into the lungs, causing an increase in pleural/alveolar pressure during inspiration

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22
Q

how does artificial ventilation differ from normal ventilation

A

pressure gradient is generated by an outside machine NOT by contraction of inspiratory muscles

causes pressure to increase in pleural space/alveoli during inspiration

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23
Q

what are the two mechanical properties of the airways and lungs

A
  1. elastic (compliance)
  2. resistance
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24
compliance
the ease by which the elastic structures of the respiratory system stretch
25
what two components of the respiratory system determine compliance
chest wall lungs
26
compliance equation
C = deltaV / deltaP delta P: the pressure difference from beginning to end of breath if C is high --> low pressure required to expand lungs if C is low --> high pressure required to expand lungs
27
resistance
obstructions to air movement USUALLY related to airway diameter high resistance = more pressure required to inflate lungs
28
what two components of the respiratory system determine resistance
airways tissues
29
elastic properties of the lungs
strong inward recoil caused by: 1. elastic composition (elastin + collagen) 2. alveolar surface tension
30
elastic properties of the chest wall
outward recoil due to relaxation at rest
31
why do the lungs and chest wall have opposing elastic properties
coupling of the chest wall and the lungs generates a positive pressure gradient across the alveoli, which keeps the alveoli open
32
what happens if the lung and chest wall become uncoupled
lung retracts/collapses, chest wall expands causes a loss of the pressure gradient leading to inability to breath
33
atelectasis
collapse of alveoli that causes a decrease in the amount of tissue available for gas exchange
34
LaPlace's law
P = 2T / r (T = tension; constant r = alveoli radius) THEORY that low radius (small) alveoli should be higher pressure than high radius (large) alveoli, causing air to flow from small to large alveoli, which collapses the small and overinflation of the large alveoli does NOT happen in normal lungs due to coupling of lungs to chest wall and production of surfactant
35
surface tension
the tendency of fluid-lined surfaces to "contract" due to the greater attraction of liquid molecules to each other than to air molecules present at all fluid-gas interfaces THEORY - should cause alveoli to collapse, but does not happen due to surfactant production
36
surfactant
phospholipid-protein-CHO complex that covers alveolar walls to reduce surface tension acts as a detergent that lowers surface tension and minimizes the effects of La Place's law by creating equal pressures in large and small alveoli
37
is surfactant more effective at high or low lung volumes
lower lung volumes
38
what would happen without surfactant
- alveolar collapse - decreased compliance - pulmonary edema requires external ventilation
39
pressure-volume (PV) curves
graphs the pressure required to generate a certain amount of volume into the lung
40
what is slope on a PV curve
compliance (C = deltaV / deltaP) steep slope = higher compliance shallow slope = lower compliance
41
hysteresis
the difference between the inspiratory and expiratory path on the PV curve caused by greater surfactant efficacy at lower lung volumes
42
function of PV curves
asses changes in compliance if slope is low: low compliance; more pressure needed to achieve normal lung volumes if slope is high: high compliance; less pressure needed to achieve normal lung volumes
43
what is total airway resistance determined by
1. airway resistance 2. tissue resistance
44
where does the majority of airway resistance come from
upper airways; especially medium sized bronchi small bronchioles have smaller radius BUT larger total cross sectional area, so less resistance
45
in what scenario does tissue resistance affect the lungs
lung disease - makes the lungs heavier and more resistant to air flow
46
what are the three airflow patterns
1. laminar 2. turbulent 3. transitional
47
laminar flow
- normal, straight flow - LOW resistance - inner air is faster than outer air
48
turbulent flow
- disorganized flow - present in LARGE, HIGH VELOCITY airways and bifurcations/bends - HIGH resistance
49
transitional flow
combination of laminar and turbulent flow common in airways due to bifurcations
50
ohm's law
R = deltaP / Q calculates resistance as a function of pressure gradient and volume
51
poiseuille's law
Q = (deltaP x pi x r^4) / 8nL calculates flow as a function of pressure gradient, radius, viscosity, and airway length
52
what is the main determinant of air flow
RADIUS (airway diameter)
53
Reynold's number
Re = 2rvd / n determines when flow changes from laminar to transitional to turbulent
54
what causes an increase in reynolds number
increases in radius, velocity and density more likely to become TURBULENT
55
what causes a decrease in reynolds number
increases in viscosity less likely to become turbulent
56
how does the ANS affect airflow
controls airway radius by innervating bronchial smooth muscle SNS: B2 receptors --> bronchodilation (dec. resistance) PNS: muscarinic receptors --> bronchoconstriction (inc. resistance)
57
how does lung volume affect airflow
increases in lung volume = expands lungs = opens/dilates airways = decreases resistance = increases flow
58
what are the 5 factors affecting resistive properties
1. radius of airways and gas viscosity 2. artificial airway radius (ET tube size) 3. flow pattern - turbulent vs laminar (reynolds number) 4. lung volume 5. ANS innervation
59
dynamic airway obstruction
obstructions to airflow that change based on inspiration or expiration ex. collapsing trachea
60
what part of respiration is affected by an extra thoracic collapsed trachea
inspiration
61
what part of respiration is affected by an intra thoracic collapsed trachea
expiration
62
pressure gradients throughout respiratory cycle
1. pre-inspiration (FRC): negative pressure in pleural space, 0 pressure in airways - POSITIVE PRESSURE GRADIENT 2. inspiration: air flow follows positive pressure gradient from airways --> alveoli 3. forced expiration: contraction of expiratory muscles increases pleural pressure (positive pleural pressure > airway pressure), leads to a normal decrease in airway diameter
63
total work of breathing
elastic work + resistive work increased WOB = high elastic work (low compliance) + high resistance
64
what is elastic work
compliance influenced by LUNG VOLUME (high vol = high elastic work = dec. compliance)
65
examples of states with decreased compliance (increased elastic work)
obestiy pneumonia
66
what is restrictive work
airway resistance influenced by RESPIRATORY RATE - tries to decrease total WOB (high RR = high RW = high resistance)
67
breathing at resting state
animal breathes at the rate and volume that results in the lowest WOB
68
breathing in states of increased elastic work (decreased compliance)
animal will increase RR and decrease lung volume to achieve the lowest total WOB
69
breathing in states of increased resistive work (increased resistance)
animal will decrease RR and increase lung volume to achieve the lowest total WOB (ex. lower airway disease)

VET 408: Cardio/Respiratory (38 decks)

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