Mechanics of Breathing

Question 1

Main muscle for normal inspiration

Answer 1

Diaphragm

Question 2

Main muscle for normal expiration

Answer 2

NONE

Question 3

Muscles for forced inspiration

Answer 3

External Intercostals

Accessory muscles - SCM, anterior serrati, scalene, alae nasi, genioglossus, arytenoid

Question 4

Muscles for forced expiration

Answer 4

Internal Intercostals

Abdominal muscles - rectus abdominis, internal and external oblique, transversus abdominis

Question 5

Distensibility of the lungs and chest wall

Answer 5

Compliance

opposite to surface tension (collapse less)
opposite to elasticity (recoil)

Question 6

Has natural tendency to COLLAPSE

Answer 6

Lungs

Question 7

Has natural tendency to EXPAND

Answer 7

Chest wall

Question 8

Pneumothorax (presence of gas in pleural space)

Answer 8

Intrapleural pressure = atmospheric pressure

Lungs on the AFFECTED side collapse, chest wall EXPANDS

trachea shifts AWAY from the affected lungs

Question 9

Atelectasis (collapse of the lung parenchyma)

Answer 9

trachea shifts TOWARD the affected lungs

Question 10

Law of Laplace

Answer 10

collapsing pressure is directly proportional to surface tension and inversely proportional to radius of the alveoli

Question 11

In comparison to TERM infant, PRETERM infant has

Answer 11

INCREASED
pulmonary vascular resistance
pulmonary artery pressure (PAP)
pulmonary capillary hydrostatic pressure
pressure gradient from pulmonary artery to the aorta

DECREASED
pulmonary blood flow

Question 12

Major site of airway resistance

Answer 12

MEDIUM sized bronchi

Question 13

3 Factors Affecting Airway Resistance

Answer 13

Bronchial Smooth Muscle
Lung Volume
Viscosity/Density of Inspired Gas

Question 14

Causes Bronchodilation

Answer 14

Sympathetic (adrenergic)
Atropine
VIP

Question 15

Causes Bronchoconstriction

Answer 15

Parasympathetic (cholinergic)
Cool air, exercise
Irritants (sulfur dioxide)
Leukotrienes, histamine