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Applied physiology > Respiration > Flashcards

Respiration Flashcards

1
Q

Purpose of respiratory system

A

maintain arterial blood-gas homeostasis

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2
Q

Respiratory system 4-step process

A

systemic gas exchange - CO2 into blood
gas transport
alveolar gas exchange - CO2 into alveoli
pulmonary ventilation - into atmosphere

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3
Q

Epiglottis

A

separate upper/lower respiratory tracts

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4
Q

Airways

A

trachea
bronchi
bronchioles
terminal bronchioles
respiratory bronchioles
alveolar ducts
alveolar sacs

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5
Q

Pulmonary gas exchange

A

across pulmonary capillary
diffusion high to low partial pressure

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6
Q

Type I alveolar cell

A

~95% of internal surface of alveolus
critical for gas exchange

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7
Q

Type II alevolar cells

A

release surfactant - a molecule that lowers surface tension
without = collapse

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8
Q

Fick’s law of diffusion

A

volume of gas proportional to surface area/thickness x diffusion coefficient x pressure gradient

proportional

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9
Q

Volume of gas dependent on

A

surface area
thickness
diffusion coefficient
pressure gradient (alveolar to arterial)

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10
Q

Why is the blood-gas barrier ideal for gas exchange?

A

very thin
vast surface

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11
Q

Mechanics of breathing

A

inspiration = volume thoracic activity increases as respiratory muscles contract
bucket hadle motion of ribs = increase lateral diameter of thorax
pump handle motion of ribs = increase anteroposterior diameter of thorax

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12
Q

Muscles of inspiration

A

diaphragm
external intercoastal muscles
scalenes
sternocleidomastoid
= increase pulmonary ventilation

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13
Q

Muscles of expiration

A

rectus abdominis
internal intercostal muscles
external oblique

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14
Q

Measure of diaphragmatic fatigue

A

bilateral phrenic nerve stimulation

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15
Q

Ohm’s law

A

current = voltage/resistance

flow directly proportional to pressure difference
inversely proportional to resistance

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16
Q

Poiseuille’s law

A

resistance dependent upon length and radius of tube

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17
Q

Exercise-induced asthma

A

flow limited during exercise
breath at high lung volume
end expiratory volume = higher at rest
resistance to flow becomes higer

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18
Q

Pulmonary ventilation equation

A

.v = vt x fb

v = volume
.v = volume per unit of time
t = tidal
fb = breathing frequency

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19
Q

Dead space

A

volume of air not particpiating in gas exchange (vd)
150mL in healthy individuals

Va = (vt - vd) x fb

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20
Q

Forced vital capacity

A

max volume air that can be forcefully expired after max inspiration

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21
Q

COPD

A

increased airway resistance
reduced forced vital capacity

sig reduced forced expiratory volume in one sec

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22
Q

Dynamic hyperinflation in COPD

A

increased end-expiratory lung volume
increased work of breathing
increased breathing discomfort

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23
Q

Respiratory muscle fatigue

A

not occur during prolonged heavy exercise

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24
Q

Ventilatory response to constant load steady-state exercise phases:

A

phase 1 - immediate increase in Ve
phase 2 - exponential increase in Ve
phase 3 - plateau - steady state

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25
Q

Hyperpnoea

A

PaCO2 regulation due to proprtional changes in alveolar ventilation and metabolic rate

insert equation

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26
Q

Ventilatory threshold

A

ventilation increases lineraly with exercise intensity until a point (Tvent)
~50-75% VO2 peak

after Tvent - ve increase exponentially resting in hyperventilation (decrease PaCO2)

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27
Q

Exercise-induced arterial hypoxaemia

A

50% highly-trained males duirng heavy exercise
majority females

reduction in PaO2 of >/10 mmHg from rest
occur because ventilatory demand exceeds capacity

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28
Q

EIAH caused due to:

A

diffusion limitation
V/Q mismatch
relative hypoventilation

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29
Q

Changes in breathing patterns during exercise

A

onset exercise - changes Ve achieved by increasing Vt
heavy exercise - Vt plateaus and further increase in Ve achieved by fb

insert diagram

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30
Q

Work equation

A

work = force x volume

total work = sum of elastic, flow-resistive and inertial forces

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31
Q

Oesophageal pressure

A

estimate of pleural pressure
used to calculate mechanical work of breathing during exercise

32
Q

Respiratory central pattern generators loacted

A

within brainstem
pons
medulla

33
Q

3 main groups of neurons

A

ventral respiratory group (inspiratory/expiratory)
dorsal respiratory group (inspiratory)
pontine respiratory group (modulatory)

34
Q

Motor outputs

A

effectors

resistance muscles
pump muscles (diaphragm)

35
Q

Feedback inputs

A

sensors

peripheral chemoreceptors
central chemorecptors

36
Q

Feedforwards inputs

A

muscle afferents
CO2 flow

37
Q

Peripheral chemoreceptors

A

detects changes in PO2 of blood perfusing systemic and cerebral circulation
located at aortic arch and cartoid body

relays sensory info to medulla via vagus nerves
decrease PaCO2 = increase Ve

temp, adrenaline and CO2 stimulate peripheral chemoreceptors

38
Q

Central chemoreceptors

A

loacted in ventral surface of medulla (RTN)

sensitive to change in PaCO2/H+ of cerebral spinal fluid
other areas sensitive - cerebellum

39
Q

Chemoreceptor feedback

A

Chemoreceptors detect error signals (disturbances to blood-gas homeostasis)

Central and peripheral chemoreceptors respond to increasing PaCO2ordecreasing PaO2or pH

Premotor neurons in the dorsal respiratory group areactivated

Inspiratory muscle contract, increasingሶVE

Changes inሶVEelicit changes in PaO2, PaCO2and pH, thusrestoring blood-gas balance

40
Q

Ventilatory response to O2

A

curvilinear
below ~65 mmHg

41
Q

Ventilatory responses to CO2

A

linear
changes in paCO2 elict much greater changes in Ve

42
Q

Ventilatory control during moderate exercise

A

no change in mean paCO2 = primary stimulus is feedforward in origin
central neurogenic
peripheral neurogenic
peripheral chemoreceptors - fine tune breathing

43
Q

Ventilatory control during heavy exercise

A

PaCO2 falls = inhibit breathing
Tvent metabolites accumulate = stimulate breathing
feedforward - central neurogenic, peripheral neurogenic
feedback - central chemorecptors, peripheral chemoreceptors

increased body temp
augmented muscle afferent input

44
Q

Effects of endurance training on respiration

A

Ve 20-30% lower vs untrained
decrease metabolite accumulation
decrease afferent feedback
decrease ventilatory drive

45
Q

How do lungs adapt to training?

A

lungs/airways not adapt

respiratory muscles stronger/more fatigue resistant
maladaptive adaptations = airways hyperresponsivensss in skiers/swimmers

46
Q

Pulmonary system limit max exercise performance?

A

Exercise-induced arterialhypoxaemia(EIAH)

Exercise-induced laryngeal obstruction (EILO)

Expiratory flow limitation

Respiratory muscle fatigue

Intrathoracic pressure effects on cardiac output

47
Q

Dalton law

A

total pressure of gas mixture is equal to some of pressure that each gas would exert independently

Pair = Pn2 + Po2 + PCo2

48
Q

Partial pressure of gas

A

Pgas = Fgas x Pbar

760mmHg sea level

49
Q

Partial pressure of inspired O2 and CO2

A

159
0.3 mmHg

50
Q

Gas exchange impairment

A

arterial PO2 (~100mmHg) slighlty less than alveolar PO2 (~105 mmHg)

51
Q

Cellular respiration

A

O2 consumed and CO2 produced

venous PO2 decreased to 40 mmHg
venous PCO2 increased to 46 mmHg

52
Q

Pulmonary circulation process

A

Pulmonary artery carries deoxygenated blood from the right ventricle to the lungs

Gas exchange between the alveoli and pulmonary capillaries occurs

Oxygenated blood is returned to the left atrium via the pulmonary vein

Oxygenated blood is pumped around the systemic circulation to systemic cells

53
Q

Pulmonary circulation

A

low pressure
low resistance
thin walled, little smooth muscle
accepts entire cardiac output
not redistribute blood flow

54
Q

Pulmonary vascular resistance

A

decreases during exercise
due to recruitment of pulmonary capillaries

55
Q

What does gas exchange require?

A

matching of ventilation to blood flow
ideal V/Q is 1

56
Q

Upright lung

A

blood flow increases disproportionatly more than ventilation from the top to bottom of lung
due to effects of gravity

57
Q

Upon exercise V/Q improves due to

A

increased tidal volume
increased pulmonary artery pressure
worsens during heavy exercise

58
Q

How is oxygen carried in the blood?

A

dissolved (2%)
combined with haemoglobin (98%)

59
Q

Henry’s law

A

amount dissolved O2 proportional to partial pressure

60
Q

Haemoglobin

A

blood chemically bound to haemoglobin
transport 4 molecules of O2

amount O2 transported as oxyhaemoglobin dependent upon Hb mass

61
Q

Bohr shift

A

oxygen dissociation curve
right shift
due to rise in H+ ions, CO2 and body temp from exercise
facilitates unloading of O2 in active tissue

62
Q

Myoglobin

A

O2 binding protein in muscles

high affinity O2 = unloads at very low PO2
shuttles O2 from muscle cell membrane to mitochondria for aeroic respiration
provides intramuscular O2 storage

63
Q

How is CO2 carried in the blood?

A

dissolved (10%)
bound to haemoglobin (20%)
bicarbonate (70%)

20x more soluble than O2

64
Q

Carbon dioxide transport

A

HCO3- leaves cell and Cl- moves into cell to maintain neutrality (chloride shift)
H+ binds to Hb to form HHb which binds to CO2 to create carboamino Hb

most CO2 forms reversable reaction when bound with water

CO2 + H2O <-> H2CO3 <-> H+ + HCO3-

65
Q

Ventilation and acid base balance

A

CO2 + H2O <-> H2CO3 <-> H+ + HCO3-

increase in CO2 during exercise = increase in H+ = decrease arterial pH = stimulate breathing via feedback loop

66
Q

How is CO2 transported in arterial blood?

A

bicarbonate

67
Q

Cartoid bodies

A

chemoreceptors sensitive to changes in arterial ph, PCO2 and PO2

68
Q

Tidal volume

A

amount of gas moved per breath

69
Q

FEV1/FVC pulmonary function test

A

ratio of forced expiratory volume in first second to forced vital capacity of lungs

0.60 = suggestive of airway obstruction
normal = 0.75-85

70
Q

Changes in ventilatory patterns during exercise

A

important to ensure optimal mechanics of breathing are realised
to reduced risk of respiratory fatigue
increased tidal volume = dead space ventilation remains small

71
Q

Graded exercise test

A

ventilation during transition from rest to moderate exercise achieved by:
increase breathing frequency
increase tidal volume

72
Q

Effect on ventilation

A

small increase arterial PCO2 = greater effect
compared to small decrease in PO2

73
Q

Ventilation-perfusion relationship

A

gas exchange requires a matching of ventilation to blood flow

ideal = 1
above 1 = more air than blood
below 1 = less air than blood

74
Q

Upright lung

A

blood flow increases disproportionately more than ventilation from top to bottom of the lungs
due to effects of gravity

75
Q

Lungs

A

enclosed within membranes (pleura)

intrapleural pressure < atmospheric pressure = prevent alveoli collapse

Applied physiology (24 decks)

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