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Physiology Block 2- Pulmonary Physiology > Alveolar Ventilation > Flashcards

Alveolar Ventilation Flashcards

1
Q

What is alveolar ventilation?

A

The air that comes into and out of the alveoli per time

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2
Q

What is the tidal volume?

A

The volume of air coming into and out of the nose/mouth per time

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3
Q

Which lung volume is the hardest to measure in a conscious person?

A

Tidal volume

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4
Q

What is the volume of air in the lungs following a normal tidal expiration?

A

Functional residual capacity

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5
Q

What determines the functional residual capacity?

A

The balance point between inward alveolar recoil and outward chest wall recoil

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6
Q

What is the typical functional residual capacity of a 70 kg person?

A

~3L

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7
Q

What is the volume that remains in the lungs following a maximal expiratory effort?

A

Residual volume

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8
Q

What determines the residual volume?

A

The outward recoil of the chest wall and the compression of small airways leading to trapped gas

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9
Q

What volumes are included in the functional residual capacity?

A

The expiratory reserve volume and the residual volume

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10
Q

What is the expiratory reserve volume?

A

The air blow out starting at the FRC down to the residual capacity

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11
Q

What is the inspiratory capacity? The inspiratory reserve volume?

A

The inspiratory capcity is the maximal air taken in from the FRC up to the TLC; The inspiratory reverse volume is the volume of air between the top of a tidal breath to the TLC

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12
Q

What is the vital capacity?

A

The volume of air expired from the TLC down to the residual volume

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13
Q

What happens to the functional residual capacity moving from standing to laying down? Which volume(s) are changing? Why?

A

The FRC decreases by a third when laying down because the expiratory reserve volume is decreased and IC and IRV increase; When you are standing, gravity pulls the diaphragm down, which adds to the outward recoil of the chest wall

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14
Q

What lung volumes/capacities are increased in obstructive disease? Decreased?

A

RV, FRC, and TLC increase; ERV and Vital capacity decreases

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15
Q

What lung volumes/capacities are decreased in restrictive disease?

A

All values are compressed in restrictive lung disease

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16
Q

What values can be determined by spirometry?

A

Tidal volume, vital capacity, inspiratory capacity, inspiratory reserve volume and expiratory reserve volume

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17
Q

What percent of the air is nitrogen?

A

80%

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18
Q

What is the basic process of nitrogen washout?

A

Person breathes in pure oxygen and then exhales into a different bag. As the pure oxygen is breathed in the nitrogen is diluted and can be measured and multiplied by 1.25 to get TLC

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19
Q

What are the drawbacks of the nitrogen washout method?

A

If a person has many high resistance, small airways it will take very long to wash all the nitrogen out, and if airways collapse they will trap air which will cause a low measurement of TLC

20
Q

What is the equation used to calculate lung volume using helium dilution?

A

Initial helium concentration (FHEi) * initial spirometer volume (VSPi)= Final helium concentration(FHEf)* (final spirometer volume plus lung volume)

21
Q

What is the gold standard for measuring functional residual capacity?

A

Body plethysmograph

22
Q

What concept is the body plethysmograph based on?

A

Boyle’s Law

23
Q

How is trapped gas measured using the body plethysmograph?

A

Breathing in against the close airway will open up the collapsed airways

24
Q

What is anatomic dead space?

A

The part of the respiratory tract where gas exchange is not occuring because gas is not in contact with pulmonary capillaries

25
Q

What is the formula for calculating alveolar volume?

A

Alveolar volume= tidal volume - anatomic dead space

26
Q

What is the typical ration of O2:CO2 on a typical western diet?

A

1 : 0.8

27
Q

What technique can be used to measure anatomic dead space?

A

Fowler’s technique

28
Q

What is physiologic dead space?

A

Anatomic dead space plus alveolar dead space

29
Q

What is alveolar dead space?

A

Alveoli that are ventulated but are not receiving blood supply

30
Q

What could cause alveolar dead space?

A

Pulmonary emboli, low right ventricular output (blood loss), or very high alveolar pressure (mechanical ventilation)

31
Q

How can the Bohr equation be used to calculate alveolar dead space?

A

1- Calculate physiologic dead space, guesstimate anatomic dead space and subtract it from physiologic dead space

32
Q

What is the guesstimated value for anatomic deadspace?

A

1 mL/ lb

33
Q

What percent of the air is carbon dioxide?

A

~0.04%

34
Q

What is displayed on a capnograph? What can it be used for?

A

Partial pressure of carbon dioxide at the mouth per time; If end-tidal PCO2 is lower than arteriole PCO2 then that person has alveolar dead space

35
Q

How can hyperventilation caue fainting?

A

Hyperventiltion lowers PCO2, and lowering PCO2 causes cerebral vasocontriction

36
Q

Increasing ventilation has what effect on alveolar PCO2?

A

Alveolar PCO2 goes down

37
Q

True or False: There is a direct relationship between alveolar PO2 and ventilation

A

False

38
Q

What is the partial pressure of water vapor at body temperature?

A

47 mmHg

39
Q

What is the alveolar air equation?

A

Alveolar PO2= Fractional concentration of oxygen in inspired gas (about 0.21 in air) * (barometric pressure in mmHg- partial pressure of water vapor) – alveolar PCO2/ resp. exchange ratio

40
Q

When upright, where does the most ventilation occur in the lung?

A

Lower parts

41
Q

How does the intrapleural pressure at the FRC differ depending on the location within the pleural cavity?

A

The intrapleural pressure is more negative at upper portions of the lung

42
Q

How does increased intrapleural pressure at the top of the lung affect the upper alveoli?

A

They will experience greater transmural pressure, making them bigger and less compliant than bottom alveoli

43
Q

Where is most of the lungs’ FRC, RV, and IC volume?

A

RV, FRC is mostly at the top; inspiratory capcity is mostly at the bottom

44
Q

What is the closing volume?

A

The lung volume at whoch airway closure begins during a forced expiration

45
Q

Patients with what condition would liekly have the highest closure volumes?

A

Emphysema patients

46
Q

What happens to the FRC, RV, and closing capacity as you age? Why?

A

They increase because of decreased elasticity

Physiology Block 2- Pulmonary Physiology (8 decks)

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