Ventilation - Trachte Flashcards

1
Q

What does ventilation refer to?

A

The amount of air entering and leaving the lungs per minute.

Describes how gas (oxygen) gets to the alveoli.

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2
Q

What is alveolar ventilation?

A

The amount of air exchanging with blood.

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3
Q

What are the different lung volumes?

A
  • Total lung capacity
  • Vital capacity
  • Tidal volume
  • Residual volume
  • Functional residual capacity
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4
Q

What is the total lung capacity?

A
  • Vital capacity + residual volume
    • usually about 6,000 mL depending on size of person & altitude
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5
Q

Can the total lung capacity be measured directly?

A

NO

Measured indirectly by dilution of a nonexchangeable gas (He) or with a body plethysmograph.

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6
Q

What is the Vital Capacity?

A
  • The maximum volume of air that can be exhaled after a maximum inspiration
    • usually about 6,000 mL
      • depends on size & altitude
      • decreases with age
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7
Q

Can the Vital Capacity be measured directly?

A

Yes

(measured with spirometer)

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8
Q

What is the Residual Volume?

A
  • The amount of air remaining in the lungs after a maximal expiration.
    • usually about 1,500 mL
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9
Q

Can the Residual Volume be measured directly?

A

NO

Measured indirectly by dilution of a nonexchangeable gas (He) or with a body plethysmograph.

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10
Q

What is the Functional Residual Capacity?

A
  • The amount of air remaining after a typical exhalation
    • the natural resting state when the lungs and chest wall are not expanded (at rest)
      • usually about 2,500 mL
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11
Q

Can the functional residual capacity be measured directly?

A

NO

Measured indirectly with a gas dilution technique using a nonexchangeable gas (He) or with a body plethysmograph.

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12
Q

What is the Tidal Volume?

A
  • The amount of air normally inhaled & exhaled per breath
    • usually 500 mL per breath
      • 500 mL x 15 breaths/min = 7,500mL/min
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13
Q

Can the Tidal Volume be measured directly?

A

Yes

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14
Q

What is the relationship between CO2 concentration in alveolar gas and ventilation?

A
  • [CO2] in alveolar gas is INVERSELY related to ventilation
    • Alveolar ventilation = VCO2/PCO2 x K
      • amount of CO2 in the exhaled air divided by the fractional concentration of CO2 in the expired air
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15
Q

What is anatomic dead space?

A
  • Conducting airways
    • The amount of a breath not reaching alveoli.
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16
Q

How do you measure the dead space volume?

A
  • Measured by breathing in pure O2
    • expired gas is plotted vs. N2 in expired gas
    • the [N2] increases with expiration until it reaches a constant level = pure alveolar gas
    • Dead Space = the volume that corresponds with the midpoint [N2] or half-maximal [N2]​
      • it measures the midpoint in the transition from dead space to alveolar ventilation
17
Q

What is physiologic dead space?

A

The amount of a breath not exchanging with blood.

18
Q

How can physiologic dead space be measured?

A
  • Measured by ration of CO2 in expired air vs. arteries
  • taking the fraction of CO2 in expired gas and comparing it to alveolar gas
    • Vd/VT = (PACO2 – PECO2)/PACO2
      • ​Called the Bohr equation
19
Q

Are the lower or upper regions of the lungs more/better ventilated? Why?

A

LOWER

Lower regions of the lung are perfused better (more blood goes to lower region due to gravity)