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HUBS192 Respiratory System > respiratory physiology > Flashcards

respiratory physiology Flashcards

1
Q

total mouth ventilation

A

frequency (breaths/min) x tidal volume (ml/breath)

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2
Q

dead space

A

space where air that never reaches alveoli hangs out. Around 150mL

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3
Q

respiration

A

exchange of O2 and CO2 between the tissues and the environment.

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4
Q

5 steps involved in respiration

A

ventilation, gas exchange between alveoli and capillary, gas transport, gas exchange between capillary and cell, cellular respiration

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5
Q

VO2max

A

maximum volume of oxygen we can deliver to tissues in our blood

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6
Q

functions of respiratory system

A
  1. provide oxygen
  2. eliminate CO2
  3. filter, warm and humidify air we breathe
  4. communication
  5. regulate pH of blood
  6. sense of smell
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7
Q

abbreviations F, f, I, E, V, A, a, c, v, B, D, P, PX, T

A

Fraction of gas in a mixture; Respiratory frequency; inhaled; exhaled; volume; alveolar; arterial; capillary; venous; barometric; dead space; pressure; pressure exerted by gas X; tidal volume

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8
Q

dot over quantity

A

Amount occurring in one minute

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9
Q
A
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10
Q

dalton’s law

A

partial pressure = fraction of individual gas x total gas pressure

Pgas = Fgas x Ptotal

  • where Ptotal = Pbarometric = 760mmHg at sea level
  • FO2 = 0.2093
  • FCO2 = 0.0003
  • FN2 = 0.7904
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11
Q

Boyle’s law and consequences

A

P1V1 = P2V2. In order to get air into lungs we need to generate a pressure gradient by changing lung volume

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12
Q

mechanism of inspiration

A
  1. Diaphragm and external intercostal muscles contract
  2. Increase in thoracic volume (increases vertical length and diameter of thoracic cavity)
  3. Lungs expand, increase volume
  4. decrease pressure (relative to atmosphere)
  5. Air moves into lungs
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13
Q

mechanism of expiration

A
  1. Inspiratory muscles relax
  2. Diaphragm moves upwards
  3. Decrease in thoracic volume and hence lung volume
  4. Increase alveolar pressure (relative to atmosphere)
  5. Air moves out of lungs. Usually passive, driven by elastic recoil of respiratory system back to resting volume. However can use accessory muscles to assist expiration
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14
Q

intrapleural space

A
  • space between outside of lungs and inside of chest wall
  • Lung tends to recoil inwards and chest wall tends to expand outwards so they pull away from each other
  • Hence intrapleural pressure is sub-atmospheric
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15
Q

transpulmonary pressure

A

pressure difference between inside lungs and atmosphere. When you change this you change lung volume

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16
Q

lung compliance and effect of lung diseases on this

A
  • measure of how easy it is to change lung volume (lung stiffness)
  • With emphysema, less work is needed to change volume by the same amount (lungs are not very stiff)
  • With fibrosis, more work is needed to change volume by same amount (lungs are v stiff) - low compliance
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17
Q

fibrosis

A
  • Fluid lining alveoli exerts surface tension which causes them to contract / resist expansion - need to overcome this force to expand
  • Surface tension reduced by surfactant
18
Q

surfactant

A
  • Reduces surface tension in alveoli i.e. makes them easier to expand
  • Reduces attractive forces between fluid molecules lining alveoli
  • Produced by alveolar type II cells
  • mostly consists of phospholipids
  • absent in premature infants, resulting in respiratory distress syndrome
19
Q

factors affecting airway resistance

A

Resistance to flow determined by Poiseuille’s Law

  • R = 8nl/πr4
  • Where n = viscosity, l = length, r = radius
  • R inversely proportional to r4
20
Q

structures in airway affecting resistance

A
  • Bronchoconstriction/dilation are important elements in airway resistance e.g. asthma
  • Main area of resistance is in bronchi
  • Most of the resistance to airflow arises in the upper airway and the first 6 generations of the lower airway
  • Small airways contribute very little to airway resistance as they have very high total CSA
21
Q

measuring lung volume

A

Spirometer

  • breathe into and out of hollow bell inverted over water which measures volume exhaled/inspired
  • Can measure how much or how fast
  • Test response/effectiveness of therapy
22
Q

tidal volume

A
  • VT or TV
  • About 500ml
  • Volume of air moved in and out during normal quiet breathing
23
Q

Inspiratory reserve volume (IRV)

A
  • About 3L
  • Extra volume that can be inspired with maximal inhalation - external intercostal muscles
24
Q

expiratory reserve volume (ERV)

A
  • About 1.5L
  • Extra volume that can be exhaled with maximal effort - internal intercostal and abdominal muscles
25
Q

residual volume (RV)

A
  • About 1.2L
  • Volume remaining in lungs after maximal exhalation
26
Q

4 lung volumes

A
  1. tidal volume
  2. Inspiratory reserve volume (IRV)
  3. Expiratory reserve volume (ERV)
  4. Residual volume (RV)
27
Q

4 lung capacities

A
  1. vital capacity
  2. total lung capacity
  3. inspiratory capacity
  4. functional residue capacity
28
Q

vital capacity (VC)

A
  • About 5L
  • maximal breath in to maximal out – volume of air you can shift in/out of lungs
29
Q

total lung capacity (TLC)

A
  • About 6L
  • Total volume in lungs when maximally full = VC + RV
30
Q

Inspiratory capacity (IC)

A

tidal volume + IRV

31
Q

functional reserve capacity (FRC)

A
  • About 2.5L
  • Volume at end of normal breath out
32
Q

forced vital capacity

A

maximum breath in to maximum breath out (VC) - forced out as hard as possible

33
Q

FEV1

A

Forced expiratory volume in one second

  • Ratio of FEV1/FVC is normally around 0.80.
  • < 0.70 indicates airways obstructed
34
Q

alveolar ventilation VA

A
  • Measures the flow of fresh gases into and out of the alveoli
  • VA = frequency x (VT – VD)
35
Q

factors affecting gas exchange (fick’s law)

A
36
Q

how does diffusion constant affect gas exchange

A
  • Diffusion constant depends on gas solubility and its molecular weight
  • Per molecule, CO2 diffuses about 20x faster than O2 due to CO2 higher solubility
37
Q

effect of emphysema on gas exchange

A
  • Emphysema is a disease characterized by dilation of the alveolar spaces and - destruction of the alveolar walls.
  • Since there is a decrease in the surface area of the lung (A) in emphysema, Fick’s law helps understand why patients with emphysema have decreased PO2 in blood
38
Q

effect of fibrosis on gas exchange

A
  • Pulmonary fibrosis involves thickening and scarring of the alveolar membranes – can arise from chronic inflammation, drugs, industrial chemicals
  • Since there is an increase in the thickness of the alveoli (T) in pulmonary fibrosis, Fick’s law helps understand why such patients a decreased PO2 in blood
39
Q

upper and lower case in lung abbreviations

A
  • upper = gas phase
  • lower = blood phase
40
Q

Alveolar partial pressure of O2 (PAO2)

A
  • about 100mmHg
  • PAO2 depends on:
    1. PIO2 of inspired air
    2. Alveolar ventilation VA
    3. Oxygen consumption VO2
  • atmospheric PO2 is usually constant so it 2) and 3) that are most important
41
Q

Alveolar partial pressure of CO2 (PACO2)

A
  • Kept constant at 40mmHg
  • PACO2 depends on:
    1. PICO of inspired air
    2. Alveolar ventilation VA
    3. Carbon dioxide production VCO2
  • Alveolar PCO2 is usually determined only by the balance between carbon dioxide production and alveolar ventilation, because atmospheric PICO2 is negligible
42
Q
A

HUBS192 Respiratory System (1 decks)

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