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Respiratory Block > 1- gas exchange > Flashcards

1- gas exchange Flashcards

1
Q

what is anatomical dead space in airways?

A

where some inspired airways remain in airways and isn’t available for gas exchange

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2
Q

how do you calculate pulmonary ventilation?

A

tidal volume x respiratory rate

e.g. 0.5 L x 12 breaths/min = 6 L/min under resting conditions

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3
Q

is alveolar ventilation or pulmonary ventilation lower?

A

alveolar is less because of presence of anatomical dead space

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4
Q

how to calculate alveolar ventilation?

A

(tidal volume - dead space volume) x respiratory rate

e.g 0.5-0.15 x 12 = 4.2 L/min

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5
Q

what is the effect of dead space volume on exchange of tidal volume between atmosphere and alveoli?

A

dead space volume means that even though 500 ml of air moves in and out between atmosphere & respiratory system, only 350 ml is actually exchanged between atmosphere & alveoli

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6
Q

what is pulmonary ventilation?

A

volume of air breathed in and out per minute

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7
Q

what is alveolar ventilation?

A

volume of air exchanged between atmosphere & alveoli per minute

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8
Q

why is alveolar ventilation more important than pulmonary ventilation?

A

alveolar represents new air available for gas exchange with blood

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9
Q

what about your breathing should be increased to increase pulmonary ventilation for example during exercise?

A

pulmonary ventilation = volume of air breathed in and out per minute

  • to increase pulmonary ventilation increase both depth (tidal volume) and rate of breathing
    = because of dead space, it’s more advantageous to increase depth of breathing
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10
Q

what is normal tidal volume, respiratory rate, dead space volume? and how do they change in
a) deep slow breathing
b) shallow rapid breathing

A

tidal volume = 0.5 L
respiratory rate = 12 breath/min
dead space volume = 0.15 L

a) tidal volume increases to 1.2 L and rate decreases to 5 breaths/min
b) tidal volume decreases to 0.15 L and respiratory rate increases to 40 breaths/min

*dead space volume doesn’t changes

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11
Q

what is ventilation?

A

rate at which gas is passing through the lungs

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12
Q

what is perfusion?

A

rate at which blood is passing through the lungs

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13
Q

how does blood flow and ventilation vary from bottom to top of lungs?

A

higher in bottom of lungs than top with blood flow higher than ventilation at bottom and ventilation higher than blood flow at top

which means average arterial and alveolar partial pressures of O2 are not exactly the same

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14
Q

what is alveolar dead space?

A

Ventilated alveoli which are not adequately perfused with blood

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15
Q

when does alveolar dead space become significant?

A

in normal healthy people it’s small and not very important but it can increase significantly in disease

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16
Q

how does accumulation of carbon dioxide in alveoli impact and airflow?

A

accumulation of CO2 as a result of increased perfusion = decreased airway resistance = increased airflow

*since more perfusion is more blood flow which means enhanced lung compliance - expansion & contraction

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17
Q

how does increase in alveolar oxygen concentration affect airflow?

A

increased oxygen as a result of increased ventilation = pulmonary vasodilation = increases blood flow to match larger airflow

18
Q

what happens in area in which perfusion is greater than ventilation?

A

perfusion = blood flow, ventilation = airflow
perfusion greater means oxygen leaving more so decreased and CO2 arriving so increased

CO2 increased = dilation of local airways = airflow increased
O2 decreased = constriction of local blood vessels = blood flow decreases

19
Q

what happens in area in which ventilation greater than perfusion?

A

perfusion = blood flow, ventilation = airflow
increased ventilation means more oxygen breathed in and less CO2 arriving back from blood vessels

CO2 decrease = constriction of local airways = airflow decrease
O2 increase = dilation of local blood vessels = blood flow increases

20
Q

what is effect of decreased O2 and increased O2 on
a) pulmonary arterioles
b) systemic arterioles

A

a) decreased O2 = vasoconstriction, increased O2 = vasodilation
b) decreased O2 = vasodilation, increased O2 = vasoconstriction

21
Q

what are the 4 factors that influence rate of gas exchange across alveolar membrane?

A
  1. Partial Pressure Gradient of O2 and CO2
  2. Diffusion Coefficient for O2 and CO2
  3. Surface Area of Alveolar Membrane
  4. Thickness of Alveolar Membrane
22
Q

what is total pressure exerted by gaseous mixtures a sum of?

A

a sum of partial pressures of each individual component in gas mixture

23
Q

what determines the pressure gradient for each specific gas?

A

the partial pressure for that gas

24
Q

what is partial pressure?

A
  • pressure that gas 1 would exert if it alone occupied the entire volume of the gas mixture, in the absence of other gases.
  • Example: If we have a mixture of gases and the total pressure of the mixture is 100 kPa, and half of the mixture is made up of gas 1, then the partial pressure of gas 1 would be 50 kPa.
25
Q

how do you calculate the partial pressure of oxygen in alveolar air?

A

partial pressure of oxygen in inspired air - (partial pressure of CO2 in arterial blood/0.8)

*0.8 is respiratory exchange ratio

26
Q

what is partial pressure of oxygen in atmospheric air?

A

160 mmHg (21 kPa) (mmHg/7.5 = kPa)

total pressure = 760 mmHg (600 mmHg from N2)

27
Q

what is the pressure of inspired air?

A

total atmospheric pressure - water vapour pressure (as respiratory tract is saturated with air)

760 - 47 = 713 mmHg

28
Q

what is partial pressure of oxygen of inspired air?

A

713 (pressure of inspired air by total-water vapour) x 0.21 (oxygen is 21% of total atmospheric pressure)

29
Q

across pulmonary capillaries:
a) what is oxygen partial pressure gradient?
b) CO2 partial pressure gradient?

A

a) 60 mmHg (8 kP) = from alveoli to blood
b) 6 mm Hg (0.8 kP) = from blood to alveoli

*for systemic capillaries from blood to tissue and vice versa, both pressures are lower

30
Q

why is there a difference in partial pressure between CO2 and O2?

A

CO2 is more soluble in membranes than O2. The solubility of gas in membranes is known as the Diffusion Coefficient for the gas

31
Q

what does a big pressure gradient between alveolar oxygen partial pressure and arterial oxygen partial pressure suggest?

A

big gradient between the 2 indicates problems with gas exchange in the lungs or a right to left shunt in the heart

(small gradient is completely normal)

32
Q

what is ficks law of diffusion?

A

Theamountofgasthatmoves across a sheet of tissue in unit time isproportional to the area of the sheetbutinversely proportional to its thickness

(higher surface area = better diffusion. higher thickness = worse diffusion)

33
Q

what makes lungs have high surface area?

A
  • The airways divides repeatedly to increase the surface area for gas exchange
  • The small airways form outpockets (the alveoli). This help increase the surface area for gas exchange in the lungs
  • The lungs have a very extensive pulmonary capillary network
34
Q

is there a large thickness distance that needs to be crossed by alveoli?

A
  • alveoli are very thin walled = just consists of mainly of single layer of flattened type 1 alveoli (some type 2)
  • pulmonary capillaries encircle each alveolus but are also thin
  • there is also narrow interstitial space

so no - thin walls to diffuse across

35
Q

what has the biggest influence in rate of gas transfer?

A

partial pressure gradients of O2 and CO2

36
Q

what is relationship between diffusion coefficient and rate of gas transfer?

A

rate of transfer increases as diffusion coefficient decreases

37
Q

how does exercise impact surface area?

A

exercise increases surface area (deeper breathing expands alveoli & pulmonary capillaries open up when cardiac output increases)

38
Q

when does surface are decrease?

A

emphysema, lung collapse, pneumonectomy

39
Q

when does thickness of alveolar membrane increase?

A

pulmonary oedema, pulmonary fibrosis, pneumonia

40
Q

what are non-respiratory functions of respiratory system?

A
  • Route for water loss and heat elimination
  • Enhances venous return (Cardiovascular Physiology)
  • Helps maintain normal acid-base balance (Respiratory and Renal Physiology)
  • Enables speech, singing, and other vocalizations
  • Defends against inhaled foreign matter
  • Removes, modifies, activates, or inactivates various materials passing through the pulmonary circulation
  • Nose serves as the organ of smell

Respiratory Block (46 decks)

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