Alveolar Ventilation

Question 1

What is alveolar ventilation?

Answer 1

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

Question 2

What is the tidal volume?

Answer 2

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

Question 3

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

Answer 3

Tidal volume

Question 4

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

Answer 4

Functional residual capacity

Question 5

What determines the functional residual capacity?

Answer 5

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

Question 6

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

Answer 6

~3L

Question 7

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

Answer 7

Residual volume

Question 8

What determines the residual volume?

Answer 8

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

Question 9

What volumes are included in the functional residual capacity?

Answer 9

The expiratory reserve volume and the residual volume

Question 10

What is the expiratory reserve volume?

Answer 10

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

Question 11

What is the inspiratory capacity? The inspiratory reserve volume?

Answer 11

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

Question 12

What is the vital capacity?

Answer 12

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

Question 13

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

Answer 13

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

Question 14

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

Answer 14

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

Question 15

What lung volumes/capacities are decreased in restrictive disease?

Answer 15

All values are compressed in restrictive lung disease

Question 16

What values can be determined by spirometry?

Answer 16

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

Question 17

What percent of the air is nitrogen?

Answer 17

80%

Question 18

What is the basic process of nitrogen washout?

Answer 18

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

Question 19

What are the drawbacks of the nitrogen washout method?

Answer 19

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

Question 20

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

Answer 20

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

Question 21

What is the gold standard for measuring functional residual capacity?

Answer 21

Body plethysmograph

Question 22

What concept is the body plethysmograph based on?

Answer 22

Boyle’s Law

Question 23

How is trapped gas measured using the body plethysmograph?

Answer 23

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

Question 24

What is anatomic dead space?

Answer 24

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

Question 25

What is the formula for calculating alveolar volume?

Answer 25

Alveolar volume= tidal volume - anatomic dead space

Question 26

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

Answer 26

1 : 0.8

Question 27

What technique can be used to measure anatomic dead space?

Answer 27

Fowler's technique

Question 28

What is physiologic dead space?

Answer 28

Anatomic dead space plus alveolar dead space

Question 29

What is alveolar dead space?

Answer 29

Alveoli that are ventulated but are not receiving blood supply

Question 30

What could cause alveolar dead space?

Answer 30

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

Question 31

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

Answer 31

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

Question 32

What is the guesstimated value for anatomic deadspace?

Answer 32

1 mL/ lb

Question 33

What percent of the air is carbon dioxide?

Answer 33

~0.04%

Question 34

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

Answer 34

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

Question 35

How can hyperventilation caue fainting?

Answer 35

Hyperventiltion lowers PCO2, and lowering PCO2 causes cerebral vasocontriction

Question 36

Increasing ventilation has what effect on alveolar PCO2?

Answer 36

Alveolar PCO2 goes down

Question 37

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

Answer 37

False

Question 38

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

Answer 38

47 mmHg

Question 39

What is the alveolar air equation?

Answer 39

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

Question 40

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

Answer 40

Lower parts

Question 41

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

Answer 41

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

Question 42

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

Answer 42

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

Question 43

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

Answer 43

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

Question 44

What is the closing volume?

Answer 44

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

Question 45

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

Answer 45

Emphysema patients

Question 46

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

Answer 46

They increase because of decreased elasticity