26. Mechanics of Ventilation 2

Question 1

How does the helium dilution technique work?

Answer 1

Helium/oxygen mix in spirometer
Amount of helium is same in spirometer and when patient inhales to FRC
Gives the equation: FRC=(C1xV1)/C2-V1

Question 2

What happens when a patient tries to breathe in in body plethysmography?

Answer 2

Chest and lungs expand
Pressure in lungs decreases
Expanding chest compresses the air inside the chamber
Air volume in the chamber decreases and pressure increases

Question 3

How is FRC calculated in body plethysmography?

Answer 3

Using Boyle’s law and measurements from pressure probes inside chamber

Question 4

What is dead space?

Answer 4

The volume occupied by gas in the lungs which does not participate in gas exchange

Question 5

What is anatomical dead space?

Answer 5

Air in respiratory tract that isn’t in the alveoli

Fowler’s method

Question 6

What is alveolar dead space?

Answer 6

Air in alveoli surrounded by pulmonary capillaries without blood flow

Question 7

What is physiological dead space?

Answer 7

Total dead space

Bohr’s method

Question 8

How does Fowler’s method work?

Answer 8

Pure oxygen is inhaled after FRC exhalation

Continuously exhaled nitrogen is measured

Question 9

How is physiological dead space calculated using Bohr’s method?

Answer 9

Measure partial pressures of carbon dioxide in alveoli and expired air