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BMEG 350 > Respiratory System - Ventilation and Gas Exchange > Flashcards

Respiratory System - Ventilation and Gas Exchange Flashcards

1
Q

key processes in respiratory phys

A
  1. pulmonary ventilation: air is added or removed from airways
  2. gas exchange: O2 and Co2 are exchanged between airways/blood and blood/tissue
  3. blood gas transport: o2 and CO2 transported between tissues and lungs
  4. control of breathing: bodily needs are met by ventilation adjustments
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2
Q

trachea seperation

A

splits into three lobes on the right and two lobes on the left (left room cause the heart)
- right: upper lobe, middle lobe, and inferior lobe of right lung
- left: upper lobe and lower lobe of left lung

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3
Q

role of upper airway mucosal lining in conditioning of inhaled gas

A

inspiration: loss of heat and moisture from the airway lining to warm and humidify the air
expiration: partial recovery of heat and moisture from expired air, and remaining recovery from blood supplying upper airway
**look at diagram for photo

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4
Q

movement of air through tracheobronchial tree

A

conducting zone (bulk flow, requires energy to contract respiratory muscles to create a pressure difference between airway and atmosphere resulting in air flow)
- trachea
- main bronchus
- bronchus
- bronchiole
- terminal bronchiole

respiratory zone (by diffusion, no need for energy input, depends on pressure gradient of gases)
- respiratory bronchiole
- alveolar duct
- alveolar sac

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5
Q

of alveolar sacs

A

2^23!

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6
Q

structural changes in airway wall

A

trachea/bronchus –> bronchiolus –> alveolus
1. decrease in epithelial height
2. loss of cartilage, smooth muscle, mucous glands
3. capillaries remain

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7
Q

alveolar gas exchange

how many alveoli?

A

~ 500 million alveoli in your lungs
- each is in contact with hundreds of pulmonary capillaries

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8
Q

alveolar cell types

A

cell type I: type I pneumocyte
- flat (squamous epithelium) like a fried egg with nucleus in middle
- covers 95% of alveolar surface area
- very thin 0.1-0.3 microns in width
- total alveolar surface area = 80-200 m^2

cell type II: type II / granular pneumocyte
- cuboidal shape
- contain lamellar inclusion bodies that store pulmonary surfactant
- pulmonary surfactant is a mixture of lipids and proteins that reduces alveolar surface tension

alveolar macrophage: dust cell
- migratory and phagocytic defend against foreign invaders
- on stains, these cells look angry! black dot with lighter coloured brush around them

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9
Q

blood air barrier

thickness

A

very thin!

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10
Q

airway clearance

different molecule size

A

particles > 10 micrometers in diameter
- filtered and trapped by nasal hairs
- irritant receptors that line nasal passage initiate sneeze reflex

particles 2-10 micrometers
- mucociliary clearance (MCC) system lining the airways proximal to terminal bronchioles
- irritant receptors in airway lining initiate cough

particles < 2 micrometers
- reach alveoli
- migrating and phagocytic macrophages engulf and degrade foreign particles
- non degradable particles (silica dust and asbestos fibers) injure alveolar epithelium resulting in inflammation, deposition of collagen to scar, and pulmonary fibrosis –> can lead to lung cancer

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11
Q

MCC transport system

A

mucociliary clearance transport system
- two layered mucous blanket
1. viscous and sticky gel layer
2. aqueous periciliary layer that is low viscosity and facilitates cilia beating stroke
- human lung processes 10,000 L of air daily for gas exchange
- MCC 1 trillion motile cilia beating @ 12-15 Hz
- propels mucus through vocal chords and into pharynx
- 30 ml mucus expectorated daily

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12
Q

impairment of MCC

A
  1. cigarette smoking: ciliary length goes down, and increased mucus production
  2. pathogenic microbes: release substances that paralyze and slow ciliary motion
  3. primary ciliary dyskinesia: inherited genetic mutation that reduces ciliary motility - airway particle clearance takes 1 week in PCD vs 12 hours in healthy ppl
  4. cystic fibrosis: inherited genetic mutation of cystic fibrosis transmembrane conductance regulator (CFTR) that is involved in water and sodium transport to maintain mucus osmolarity –> increased mucus viscosity
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13
Q

pleural space and compartments

A

outer parietal pleura
inner visceral pleura
middle pleural sac

cohesive forces of the pleural fluid
1. attach chest wall and lungs allowing lungs to inflate/deflate with chest wall movement
2. reduce friction when lungs glide past chest wall

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14
Q

pressures of lung compartments

A

pressures described relative to atmosphere in cm H2O
- pressure inside lungs/airways - alveolar pressure Pa = 0 cmH2O
- pressure inside pleural cavity Ppl = -5 cmH2O

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15
Q

respiratory system as a mechanical structure

A
  • lungs want to collapse
  • chest wall wants to extend
  • outward recoil of chest is equal in magnitude to inward recoil of lungs –> opposite forces maintain lung shape
  • constant balance of pressures that change during expiration and inspiration
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16
Q

pneumothorax

traumatic vs spontaneous

A
  • collection of air outside lung but inside pleural cavity
    1. traumatic pneumothorax: hole in chest wall
    2. spontaneous pneumo: hole in lung
    both lead to –> collapsed lung with expanded chest wall
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17
Q

boyle’s law

A

at constant temperature, pressure and volume are inversely related:
p1v1 = p2v2

18
Q

inspiration

steps

A
  1. inspiratory muscles contract
  2. chest wall expands –> intra-thoracic pressures decrease (Ppl by 3 cm H2O and Pa by 1 cm H20)
  3. air flows into lungs
    –> volume change precedes pressure change
19
Q

expiration

A
  1. inspiratory muscles stop contracting
  2. lungs recoil inward (both Ppl and Pa increase)
  3. air flow out of lungs
    –> Pa goes above atmospheric pressure which drives air out of lungs, so expiration is passive
20
Q

lung compliance and elastance

A
  • how easily can lungs be stretched
  • elastance is the tendency of an object to oppose stretch, and is it able to return to its original form
  • compliance = 1/elastance
21
Q

static compliance of lungs (C sub L) and key factors that impact it

A

slope of the relaxation P-V curve during deflation
1. lung volume: smaller volume means smaller compliance
2. tissue elastic recoil:
- emphysema = disappearing lung disease (caused by cigarette smoke or genetically) destroys alveolar wall and increases compliance (floppy lungs) –> very vertical curve
- pulmonary fibrosis = collagen deposition in alveolar walls (in response to lung injury like asbestosis) and decreases compliance making stiff lungs –> very horizontal curve
3. alveolar surface tension: water molecules from humidified air cover alveolar surface and collapses the alveolus –> neonatal respiratory distress syndrome (NRDS) is stiff lungs that are hard to inflate because of inadequate production of pulmonary surfactant (which reduces surface tension)

22
Q

restrictive vs obstructive ventilatory defect

A

res: problem with airflow into airways, inability to expand lungs or chest wall –> reduced compliance/enhanced elastance
obstructive: problem with airflow out of airways due to narrowed airways –> increased resistance

23
Q

airway resistance

2 resistive forces

A

2 resistive forces
1. inertia of the respiratory system (negligible)
2. friction
- lung and chest wall surfaces gliding past each other (little)
- airways gliding past each other (little)
- air flowing through airways (80% of total airway resistance) –> 60% from upper airways and 40% from tracheobronchial tree

24
Q

what decreases frictional resistance to airflow?

A

increasing total cross sectional area

25
Q

airway branching in healthy vs smokers

A

healthy: major contributor to airway resistance are larger airways (upper airways)
smoker: smaller respiratory airways with reduced luminal size –> airflow is measured instead of resistance to quantify impact

26
Q

relationship of flow, pressure (delta P), and resistance (R)

A

flow = delta P / R
R is proportional to 1/ radius ^4

27
Q

if radius of airway is halved, how is flow changed?

A

factor of 1/16

28
Q

airway and autonomic nervous system + asthma

A

parasympathetic: contraction of smooth muscle via acetylcholine release from vagus nerve –> dominant at rest
sympathetic: relaxation of smooth muscle via adrenaline release from adrenal medulla

–> in asthma, both mechanisms are exploited with medication

29
Q

lung volumes and capacities

A

capacities:
- inspiratory capacity
- functional residual capacity
- vital capacity
- total lung capacity
volumes:
- inspiratory reserve volume
- resting tidal volume
- expiratory reserve volume
- residual volume

30
Q

factors influencing static lung volumes

A
  1. height - taller has more lung vol
  2. gender - males have larger lung
  3. age - 20-25 is max lung volume
31
Q

important volume ratio

A

FEV1 (forced expiratory volume in 1 second) / FVC (forced vital capacity) –> understand if there are problems

32
Q

diagnosing respiratory disease

A
  1. slow vital capacity maneuver –> static lung volumes and capacities are reduced in restrictive diseases and FEV1/FVC is increased
  2. forced vital capacity maneuver –> FEV1/FVC will be < 75% in obstructive diseases
33
Q

conditions that reduce chest wall compliance

A
  • scoliosis
  • obesity
  • neuromuscular disorders
34
Q

relaxation static pressure-volume curves

A

see slide (resp 1 page 74)

35
Q

surface area of adult human lung

A

80-200 m^2

36
Q

arterial blood –> partial pressure of alveolar gases

A

gas exchange = end capillary blood gases that are in equilibrium with the partial pressure of gases in the alveoli

37
Q

driving pressure for gas exchange

A

across pulmonary capillaries:
- PO2 gradient alveoli to blood is 60 mm Hg
- PCO2 gradient blood to alveoli is 6 mm Hg

across tissue capillaries:
- PO2 gradient blood to tissue is 60 mm Hg
- PCO2 gradient tissue to blood is 6 mm Hg

38
Q

ventilation and perfusion

A

high ventilation: air goes in
low perfusion: no blood to exchange with
–> dead space

the opposite system
–> “shunt like”

39
Q

surface area and thickness of alveoli + gas exchanges

A

emphysema: destruction of walls –> increased compliance and reduced area for gas exchange
pulmonary fibrosis: collagen deposition –> reduced compliance and increased thickness
pneumonia: fluid and puss accumulation in and around alveoli

40
Q

pulmonary transit time

A
  • gas exchange between alveoli and blood
  • at rest PTT is 3/4 sec

BMEG 350 (14 decks)

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