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pulmonary physiology Flashcards

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USMLE® Step 1 flashcards
1
Q

___ is the gold standard for gas exchange

A

ABG (O2 tension in blood)

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2
Q

Q is proportional to

A

P/R

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3
Q

R is proportional to

A

length x viscosity / radius ^4

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4
Q

Q =

A

VA (velocity x area)
so velocity is Q/A

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5
Q

mVe =

A

Vt x RR
minute ventilation = tidal volume x respiratory rate (depth x frequency)

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6
Q

VT=

A

VD + VA
dead space + alveoli

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7
Q

compliance =

A

volume/pressure

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8
Q

Fick’s law of diffusion is proportional to

A

diffusion constant x (A x P)/T

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9
Q

PaCO2 is proportional to

A

VCO2/VA

CO2 in blood is dependent on/proportional to CO2 produced/alveolar ventilation

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10
Q

Henderson-Hasselbach

A

pH = pK + log(HCO3-/C02)

simplified: pH ~ HCO3- (pH directly related to bicard - base)

pH ~ 1/PaCO2 (pH inversely related to CO2 in blood)

CO2 + H2O H2CO3 H+ + HCO3-

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11
Q

respiratory system can be divided

A
  • conduction portion
    • condition the inspired air: warm to body temp, filter (remove particles), saturate with H20 vapor
    • bulk transport of air
  • respiratory portions
    • gas exchange function (in alveolar sacs)
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12
Q

ventilation

A
  • process by which air moves into lungs (inspiration) and out of lungs (expiration)
    • how: muskulotskeletal pump
    • why: need tiniest pressure gradient for exchange
  • pressure fluctuations
  • accomplished by coordination of respiratory muscles, rib cage, and lungs
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13
Q

dead space and alveolar volume

A
  • efficacy of breath tells you nothing about depth of breath
  • VT = VD + VA (tidal volume = dead space volume + alveolar volume)
  • still some dead space in respiratory zone
    • respiratory bronchioles only have a few alveoli
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14
Q

hypoventilation

A

retaining CO2: if you only ventilate dead space and alveoli

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15
Q

hyperventilation

A

blowing off CO2: raises pH (alkaline)

why you use brain paper bag in panic attack

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16
Q

hypoxemia

A

low O2 in blopd

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17
Q

hypoxia

A

low O2 in tissues

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18
Q

ischemia

A

lack of blood flow

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19
Q

dead space and alveolar volume

A
  • VD - dead speace volume
    • physiologic: non-perfused alveolus, changeable
    • anatomic: areas without alveoli, not changeable
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20
Q

mVe =

A
  • mVe = VT x RR = (VD + VA) x RR
    • mVe is volume of air inhaled in one minute, and ventilation is dead space and alveolar ventilation
  • dead space increases in COPD
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21
Q

distribution of blood flow

A
  • majority of breath to the bottom of the lung
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22
Q

lung compliance

A
  • change in volume/change in pressue
  • 1/elasticity
  • ability of tissue to expand
  • decreased compliance = stiffer
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23
Q

surface tension and compliance

A
  • surface tension wants to collapse alveoli
  • surfactant lessens surface tension – produced by T2 pneumocytes
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24
Q

surfactant

A
  • breaks bonds on liquid molecules to lessen surface tension and increase compliance for easier breathing
    • reduces surface tension to decrease muscular effort to ventilate lungs
  • composed of lipids and proteins
    • lipoprotein: secreted by alveolar epithelium (T2 cells) into alveoli
  • both hydrophilic (on inside of air-liquid interface) and hydrophobic/lipophilic (outside)
    • break H+ bonds of interface to increase compliance
    • separate with breathing in – keep small alveoli from collapsing
  • anti-bacterial, prevents infection: immune effect to protect against invaders (proteins A and D)
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25
Q

alveoli

A
  • alveolar walls are T1 pneumocyte, surfactant is T2
  • alignment of surfactant molecules
  • resident macrophage
  • air:liquid surface
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26
Q

static pressure-volume (PV) curve

A
  • lungs get stiffer with greater volume
  • compliance = volume/pressure
    • higher change in volume for change in pressure is compliance
    • lower change in volume for change in pressure is stiff
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27
Q

the top of the lung has ____ compliance than the bottom of the lung

A

lower

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28
Q

with decreased compliance, patients breathe ____ to compensate

A

faster (increase RR)

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29
Q

factors that impact air flow and resistance

A
  • Q = P/R
    • laminar (easy to move)
    • turbulent: need greater pressure
  • resistance
    • radius, airway length, gas viscosity, lung volume
  • larger airways generally have higher velocity and thus more turbulent flow
    • Q = VA: as cross section area of branching airways increase -> slower velocity -> laminar flow (less resistance, so less pressure needed)
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30
Q

cross sectional area and bronchial tree

A
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31
Q

sympathetic stimulation stimulates ____ for ____, and parasympathetic stimulation stimulates ____ for ____

A
  • sympathetic stimulation (NE) stimulates beta2 receptors for bronchodilation
  • parasympathetic stimulation (ACh) stimulates muscarinic receptors for bronchodilation
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32
Q

non-uniform lung ventilation

A
  • regional obstruction
    • asthma, foreign body, mucus plug
  • regional changes in elasticity
    • pneumonia, pulmonary fibrosis, atelectasis
  • regional dynamic compression - hole/bullous in lung
    • COPD, pneumothorax
  • regional limitation to expansion
    • scoliosis, burn injury, rib fracture/muscle guarding
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33
Q

work of breathing

A
  • work of respiratory muscles to over come the elastic and resistance factors from airways, lungs, and chest wall to expand the chest and lungs
    • elastic factors: compliance (stiffness) of lungs, chest wall, and abdominal contents
    • airway resistance: bronchospasm, airway inflammation, and swelling and secretions
  • work to get air in
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34
Q

conducting zone

A

trachea to terminal bronchioles

35
Q

upper respiratory tract

A
  • nose, pharynx, and larynx
  • provides 1st line of defense against infection
    • filters, warms, humidifies air
36
Q

lower respiratory tract

A
  • trachea begins at C6
  • directly superior to beginning of trachea is larynx (vocal chords)
  • trachea bifurcates (carina) into 2 mainstem bronchi (right and left) at sternal angle (2nd rib space)
    • T4/T5 when supine, T7 when standing
  • trachea is 16-20 cartilaginous rings (hyaline cartilage)
    • flexible but rigid to keep trachea open
    • each ring is open posteriorly (for flexibility) covered by trachealis muscle
37
Q

tracheal/bronchial epithelium

A

psudostratified columnar epithelium

  • ciliated: into sol layer (more liquid), push gel layer up into airway to catch gunk - airway defense
    • spit out or to stomach
  • mucus secreting goblet cells and glands
  • lymphoid tissue
  • airway secretions (mucus) line RT and form 2 layers - sol and gel layers
  • bronchial wall epithelium lined by cilia in sol layer
    • sol layer is less viscous than gel layer, allowing cilia to beat freely
  • during forward stroke, cilia tips hit gel layer to propel it centrally to larger airways and mouth
38
Q

___ bronchioles have ____ and continue as ____ bronchioles, which then open into ____ and individual ___

A

terminal bronchoiles have no alveoli and continue as respiratory bronchioles (have alveoli), which then open into alveolar ducts and individual alveoli

39
Q

gas exchanging zone

A
  • acinus describes functional gas exchange unit, consiting of
    • respiratory bronchioles
    • alveolar ducts, alveolar sacs, alveoli
  • acinus is distal to terminal bronchiole
40
Q

alveoli

A
  • walls composed of squamous epithelium (T1 and T2)
  • T1 are very thin
    • 95% of alveolar surface area
    • function for gas exchange
  • T2 synthesize and secrete
    • reduce surface tension and allow alveoli to remain open
  • also may be resident alveolar macrophages (dust cells)
41
Q

respiratory cycle

A
  • inspiration
    • external pressure > intrathoracic pressure
  • expiration
42
Q

musculoskeletal pump

A
  • external intercostal muscles: aid in quiet and forced inhalation
    • elevation of ribs, expand thoracic cavity
  • internal intercostal muscles: aid in forced expiration (quiest is passive)
    • depress ribs, decrease dimensions
  • both external and internal innervated by intercostal nerves
43
Q

Boyle’s law

A

P related to 1/v

  • PV = k (pressure x volume = constant)
44
Q

zone of apposition

A

angle formed by rib cage and diaphragm

more acute is normal

45-90 is “flattened diaphragm”

45
Q

rib cage moves in ___ movement, and sternum moves in ___

A

bucket handle

pump handle

46
Q

abdominal paradox

A
  • sign of diaphragmatic dysfunction
  • paradoxical inward motion of abdomen as rib cage expands in inspiration
  • seen in high SCI (C5 or above)
47
Q

sniff test

A
  • assesses motion of diaphragm during a short, sharp inspiratory effort through nostils
    • descent of diagphragm will be seen in people without disorder
  • with unilateral/bilateral diaphragm paralysis, there is a paradoxical (cephalad) movement of paralyzed diaphragm
48
Q

flail chest

A
  • multiple fractures in a single rib – multiple floating segments
49
Q

pulmonary function testing (PFT

A
  • MIP, MEP, MVV
50
Q

maximal inspiratory pressure (MIP)

A
  • lowest pressure developed during a forceful inspiration against an occluded airway
    • primarily measures inspiratory muscle strength
  • recorded as negative number in cm H20 or mmHg
  • AKA negative inspiratory force (NIF)
51
Q

maximal expiratory pressure (MEP)

A
52
Q

maximal voluntary ventilation (MVV)

A
  • total volume of air exhaled during 12 seconds of rapid, deep breathing
    • primarily measures breathing reserve (respiratory muscle endurance)
  • liters/minute
  • rapid, deep breathing for 12-15 seconds: measured volume is indication of respiratory muscle endurance
53
Q

respiratory muscle fatigue

A
  • supply: energy availability
    • muscle blood flow, O2 content
  • demand: energy requirements
    • work of breathing, strength, mechanical efficiency
  • psychologic and neurologic factors
54
Q

factors that influence breathing

A
  • hypothalamus – emotions, pain
  • cortex – voluntary control
  • chemoreceptors
55
Q

chemoreceptors and breathing

A
  • central: in medulla oblongata
    • responds to increase CO2 that passed through BBB
    • H+ stimulates receptors for increased breathing depth and increased rate
  • peripheral: in aortic/carotid bodies
    • responds when PaO2 < 60 mmHg –> increase ventilation
      • synergistic with higher PaCO2
    • also responds to pH decreases –> increase ventilation
    • hypoxic drive
56
Q

changes in peripheral chemoreceptors

A

normal CO2 is 40

normal O2 is 90

57
Q

hypoxic drive with chronic elevated PCO2 levels

A

seen in emphysema

58
Q

FIO2

A
  • fraction inspired air O2
  • 0.21 = 21% (dry) room air
    • inhaled air: 0.21 x 760 mmHg = 160 mmHg of O2
  • PAO2 = alveolar O2
  • PaO2 = O2 dissolved in arteries
59
Q

henry’s law

A
  • explains how gases dissolve across alveoli-capillary membrane
  • amount of gas absorbed by a liquid is directly proportional to the partial pressure and solubility of the gas in the liquid
    • air-liquid interface = alveolar-capillary membrane
    • CO2 is 20xs more soluable than O2
      • CO2 diffuses across alveolar-capillary membrane faster than O2
60
Q

fick’s law of diffusion

A
  • passive exchange of gas between lung and blood/blood and tissues and organs is dependent on
    • concentration gradient (changes in partial pressures) of gases
      • supplemental O2 changes pressure gradient of alveolus and venous blood
    • solubility of the gases (CO2 > O2) - diffusion constant
    • surface area (A) available for diffusion
    • membrane thickness
61
Q

gas diffusion and lung

A
  • alveoli provide high SA for gas exchange with pulmonary blood
    • average 480 million
62
Q

at rest, there is ____ time for full equilibration of oxygen

A
  • sufficient
  • resting conditions: pulmonary capillary blood is in contact with alveolus for about 0.75 seconds total and fully equilibriuated with alveolar oxygen after about 0.25 seconds
63
Q

lung disease ____ diffusion

A
  • impairs
  • in exercise: pulmonary blood flow is quicker (less time for gas exchange)
    • those with lung disease are unable to oxygenate pulmonary blood fully and thuss have a limited ability to exchange gases
    • limits performance and ADLs
64
Q

CO2 diffuses across alveolar-capillary membrane ____ times fast than oxygen

A
  • 20
  • so factors are less likely to compromise CO2 transfer from blood to alveoli
65
Q

O2 content of blood (delivered to tissues) is dependent on

A
  • PaO2 (dissolved O2 in blood)
  • hemoglobin concentration (Hgb)

also blood flow (CV function)

66
Q

O2 transportation

A
  • 2 forms
    • dissolved in plasma (2%)
    • reversibly bound to hemoglobin (98%)
67
Q

Bohr effect

A
  • increased CO2 (decreased pH) –> decreased Hb affinity for O2
    • promotes “unloading” (think muscle)
68
Q

oxyhemoglobin dissociation curve

A
69
Q

CO2 transport (VCO2)

A
  • 3 ways CO2 is transported
    • bicarbonate (HCO3-) in RBC and plasma (60%)
    • carbaminohemoglobin (30%)
    • dissolved gas (10%)
70
Q

haldane effect

A
  • deoxyhemoglobin (after “unloading”) can carry more CO2
71
Q

pulmonary circulation pressures

A
  • P system artery > P pulmonary artery
72
Q

pulmonary circulation

A
  • Q = P/R
  • rate of blood flow through pulmonary circulation = flow rate through systemic
    • but RV driving pressure is very low (10-15 mmHg)
73
Q

pulmonary vascular resistance (afterload) is

A
  • low
  • low capillary hydrostatic pressures produce less net filtration than produced in system capillaries
    • lungs are “dry”
74
Q

pulmonary circulation autoregulation

A
  • hypoxic vasoconstriction – pulmonary arterioles constric when alveolar PO2 decreases (decrease PAO2)
  • matches ventilation/perfusion ratio
75
Q

recruitment and distention in responses to increased ____

A
  • cardiac output
  • PVR (afterload) remains low even with increase CO
76
Q

distribution of pulmonary blood flow and ventilation

A
  • blood flow and ventilation is greater at the base than at the apex
77
Q

are ventilation and perfusion evenly matched across the lung

A
  • no, under normal circumstances, they are not evenly matched
  • Ventilation = V
  • Perfusion = Q
78
Q

low V/Q

A

shunt

V < Q

79
Q

high V/Q

A

dead space

Q < V

80
Q

V = Q

A
81
Q

perfusion is ____

A
  • regional – heterogenous
    • gravity effect
    • cardiac output
    • pulmonary vascular resistance (PVR)
  • zone I: alveoli > arterial > venous
    • airflow > blood flow (dead space)
  • zone II: arterial <> alveoli > venous
    • airflow <> blood flow (mixed)
  • zone III: arterial > venous > alveoli
    • blood fow > airflow (shunt)
82
Q

ventilation and perfusion

A
83
Q

blood gas changes with exercise

A
  • SpO2 and PaO2 constant
  • pH and PaCO2 down
  • mVe = RR x Vt
84
Q

ventilation/perfusion relationships

A

medical conditions 1 (8 decks)

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