Mechanics of Ventilation

Question 1

Quiet inspiratory muscles

Answer 1

Diaphragm

Extenal intercostals

Question 2

Forced inspiratory muscles

Answer 2

Diaphragm
external intercostals
accessory muscles (scalenes, sternocleidomastoids)

Question 3

Quiet expiratory muscles

Answer 3

largely passive (relaxation of muscles, then inward recoil of elastic tissue)

Question 4

Forced expiratory muscles

Answer 4

Abdominal muscles
internal intercostals
neck & back muscles

Question 5

Conducting airways

Answer 5

Trachea to terminal bronchioles
No alveoli
Anatomical dead space

Question 6

Anatomical dead space volume

Answer 6

~150 mL (1 ml x lb bodyweight)

Question 7

Tidal volume

Answer 7

vol. of air inspired or expired during a respiratory cycle

resting Vt = ~500 mL

Question 8

Inspiratory reserve volume

Answer 8

IRV = max vol. that can be inspired from normal end inspiratory position (~3100 mL)

Question 9

Expiratory reserve vol

Answer 9

ERV = max vol. that can be exhaled from normal end expiratory position (~1200 mL)

Question 10

Residual volume

Answer 10

RV = vol. of air remaining at the end of max. expiration (~1200 mL)
cannot be measured by spirometry

Question 11

Functional residual capacity

Answer 11

FRC = ERV + RV = vol. gas at end of normal expiration

cannot be measured by spirometry

Question 12

Intrapleural pressure (Ppl) at FRC

Answer 12

-5 cm H2O

Question 13

Transpulmonary pressure (Ptp, PL)

Answer 13

Ptp = PA - Ppl

Question 14

Laplace’s equation

Answer 14

P = 2T/r
P = pressure inside alveolus
T = surface tension