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RESP > mechanisms of ventilation > Flashcards

mechanisms of ventilation Flashcards

1
Q

What is external respiration?

A
  • exchange of oxygen and carbon dioxide between the body and external environment
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2
Q

What is internal respiration?

A
  • Uptake and utilisation of oxygen by cells and release of carbon dioxide
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3
Q

What are pneumocytes?

A
  • surface epithelial cells of alveoli
  • type I: part of barrier, for gas exchange, flat and thin
  • type II: secrete surfactant to reduce surface tension + prevent alveolar collapse, large and cuboidal
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4
Q

How is ventilation driven?

A
  • by mechanical forces
  • air is moved into and out of lungs by pressure gradients
  • gas pressure is the force that gas exerts on the wall of its container
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5
Q

What is Boyle’s Law?

A
  • For a fixed mass of enclosed gas at constant temperature, PV remains constant
  • P1V1 = P2V2

PV = k, decreasing volume increases pressure (more collisions)

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6
Q

What is the relationship between pulmonary and pleural pressure? and why?

A
  • pleural pressure < pulmonary pressure
  • lungs are pulling inwards
  • thoracic wall pulls outwards

756<760, pleural sac seperates lung from thoracic wall

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7
Q

What changes the pressure equilibrium in the lungs?

A
  • Inspiration and Expiration
  • Air is drawn into or pushed out of lungs passively
  • pressure in lungs decreases during inspiration and increases during expiration
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8
Q

What are the 8 events of inspiration?

A
  • Inspiratory muscles contract
  • Thoracic cage diameters increase
  • Intrapleural pressure (PPL) becomes more negative
  • Transmural pressure (PTM) increases and further distends alveoli
  • Intra-alveolar pressure falls < atmospheric pressure
  • Air flows down pressure gradient from atmosphere to alveoli
  • Tidal volume (VT) of about 500 mls is added to resting volume or FRC
  • At end of inspiration – no airflow and intra-alveolar pressure = atmospheric pressure.
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9
Q

What is transmural pressure?

A

Intra-alveolar pressure - Intrapleural pressure

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10
Q

What are the primary inspiratory muscles?

A
  1. Diaphragm: moves down during inspiration, causes 75% of it
  2. External intercostals: lifts ribs upwards and outwards
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11
Q

What are the accessory inspiratory muscles?

A
  • Scalenes: raise first 2 ribs
  • Sternomastoid: raise the sternum

used during exercise and respiratory disease

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12
Q

What diseases require the use of accessory muscles?

A
  • Chronic bronchitis
  • Asthma
  • Emphysema
  • COPD
  • Bronchiolitis (RSV in kids)
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13
Q

What are the airway inspiratory muscles?

A
  • Laryngeal
  • Pharyngeal
  • Genioglossus
  • dilation of airway → reduced flow resistance → stabilisation of airway (pharynx) → preventing collapse
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14
Q

What is obstructive sleep apnea?

A
  • decreased upper airway muscle activity during sleep
  • pharynx can collapse due to negative pressure during inspiration

person has to wake up to open airways so muscles can activate

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15
Q

What are the 2 types of expiration?

A

Passive
- occurs at rest
- inspiratory muscles relax

Active
- contraction of abdominal muscles and internal intercostals

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16
Q

When is active expiration required?

A
  • coughing, sneezing, exercise, resp. diseases, screaming, singing, vomiting
17
Q

How do the expiratory muscles work?

A
  • Diaphgram and external intercostals relax
  • Abdominal muscles contract (pushes diaphragm up)
  • Internal intercostals contract (flattens ribs and sternum)
18
Q

What is Tidal volume (TV)?

seen on spirogram

A
  • Air taken in during a breath normally
  • 500ml
19
Q

What is IRV and ERV?

A
  • Inspiratory and expiratory reserve volume
  • breathing in and out as much as possible
  • IRV: 3000ml
  • ERV: 1000ml

both are additional air that you can breath in and out from normal

20
Q

What is VC?

A
  • Vital capacity: total volume of air expelled after a full inhalation

important as it is used to check a persons lung capacity

21
Q

What is RV and FRC?*

A
  • Residual volume: air left in lungs after breathing out to max
  • Functional residual capacity: volume of air left in lungs after normal breath (RV +ERV)
22
Q

Why can a spirometer not measure RV, FRC and TLC?*

A
  • All these values contain the RV, the air that cannot be expelled from the lungs during spirometry
23
Q

What is FEV1 and FVC?*

A
  • FEV1: Forced expiratory volume in one second
  • FVC: Forced vital capacity; max inhalation followed by max exhalation
  • FEV1/FVC ratio, 80% for healthy people

FEV1 determined in pulmonary function test

24
Q

What is PEFR?*

A
  • Peak expiratory flow meter
  • used to measure airway resitance
  • useful in asthma

max speed of expiration

25
Q

What are obstructive lung diseases?

A
  • reduction in air flow, difficulty exhaling
  • Asthma, COPD
  • FEV1 + FEV1/FVC reduced
  • RV higher

FEV1 can be normal or slightly decreased

26
Q

What are restrictive lung diseases?

A
  • reduction in lung volume, difficulty inhaling
  • lung fibrosis, scoliosis
  • reduced FEV1, but normal or increased FEV1/FVC
  • RV normal
27
Q

What is the function of a spirometer?

A
  • measures volume of air individual inhales or exhales as a function of time

can be set up with PC too

28
Q

What is the helium dilution technique?

A
  • used to measure RV, FRC, TLC
  • helium/oxygen mixture in spirometer
  • FRC = (C1 x V1)/C2 - V1

doesnt work with obstructive pulmonary disease

29
Q

What is body plethymosgraphy?

A
  • measures change in volume of an organ
  • FRC can be calculated using Boyle’s Law
  • patient sits in body box and breathes through mouthpiece (closed at FRC)

used for RV, FRC, TLC

30
Q

How does lung volume vary?

A
  • body size
  • age
  • sex
  • muscular training
  • posture
  • race
  • respiratory diseases
31
Q

What is dead space? and what are the 3 types?

A
  • Volume occupied by gas in the lungs which does not participate in gas exchange
  • Anatomical
  • Physiological
  • Alveolar
32
Q

What is anatomical dead space and how is it measured?

A
  • dead space in mouth, nose pharynx, trachea etc.
  • TV is 500ml, so 150ml occupied in dead space
  • Fowler’s method

350ml goes to alveoli. Tidal Vol = alveolar vol + dead space vol

33
Q

What is alveolar dead space?

A
  • Air in alveoli that are surrounded by pulmonary capillaries without blood flow
34
Q

What is physiological dead space and how is it measured?

A
  • TOTAL DEAD SPACE
  • Physiological dead space = anatomical dead space + alveolar dead space
  • Bohr’s method
35
Q

How is Fowler’s method done?

A
  • Nitrogen washout
  • exhaled N2 is measured
    3 phases:
    1. no N2 (DEAD SPACE vol)
    2. rapid rise in N2 - mixture of dead space and alveolar gas
    3. plateau of N2
36
Q

How is Bohr’s method done?

A
  • calculated by measuring partial pressures of CO2 in alveoli and expired air
37
Q

What is pulmonary/minute ventilation?

A
  • Total volume of air breathed per minute
  • VT x f = VT x RR
  • VT = tidal volume (L)
  • f = RR, respiratory rate (breaths/min)

tidal volume x resp rate, to find alveolar, just do VT - VD = VA

RESP (20 decks)

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