Ventilation Theory

Question 1

Define Tidal Volume

Answer 1

normal volume of air that moves in and out of the lungs with each respiratory cycle

7mL/kg IBW
Between 400 and 500 mL

Question 2

Define inspiratory reserve volume

Answer 2

Extra volume of air able to be inspired with maximal effort after normal inspiration

1900 to 3300mL

Question 3

Define expiratory reserve volume

Answer 3

Extra volume of air able to be expired with maximal effort after normal expiration

1100-800mL

Question 4

Define residual volume

Answer 4

The volume of air remaining in the lungs after maximal expiration.

1200mL

Question 5

Define functional residual volume

Answer 5

The volume of air remaining in the lungs after normal expiration.

FRV = RV + ERV
= 3000mL

Question 6

____ x ____ = minute ventilation?

Answer 6

Respiratory rate x tidal volume

Question 7

Alveolar ventilation = YY x ZZ (VV)?

Answer 7

Respiratory rate x tidal volume - dead space

Question 8

What is the difference between alveolar and anatomical dead space?

Answer 8

Anatomical dead space = conducting zone

Alveolar dead space = alveoli that are ventilated but not perfused

Question 9

What is the role of anatomical dead space?

Answer 9

Raises/lowers air temperature and humidifies to increase affinity of O2 to haemoglobin

Question 10

What percentage of Tidal Volume does anatomical dead space occupy in an adult?

Answer 10

1/3 - 150mL. More in small paediatrics, maximal in pre-term infants.

Question 11

What is alveolar pressure at rest?

Answer 11

0cm H2O, equivalent to atmospheric pressure (760mmHg).

Question 12

What is the intrapleural pressure at rest?

Answer 12

-4cm H2O - there must always be a slight negative pressure gradient in this space to keep the lungs inflated

Question 13

Which nerve innervates the diaphragm, and where does it arise?

Answer 13

Phrenic nerve - C3,4,5 keeps the diaphragm alive.