Biomechanics of Breathing

Question 1

Obstructive lung disease have what kind of compliance?

Answer 1

Increased

increased lung volume
easy to inflate
Less elastic recoil

Question 2

Restrictive lung disease have what kind of compliance

Answer 2

Decreased
Decreased lung volume
hard to inflate
more elastic recoil

Question 3

equation for compliance?

Answer 3

compliance = change in volume / change in pressure

Question 4

Alveoli expand during blank and recoil during blank

Answer 4

inhalation and exhalation

Question 5

Sequence of breathing (alveolar pressure)

Answer 5

1- Inspiratory muscles contract
2- thoracic cavity expands
3- pleural pressure becomes more negative
4- trans-pulmonary pressure increases
5- lungs inflate
6- alveolar pressure becomes sub-atmospheric
7- air flows into the lungs until alveolar pressure equals atmospheric pressure

Question 6

Transpulmonary pressure at rest

Answer 6

5cm H2O

Question 7

Boyle’s Law

Answer 7

P1V1 = P2V2

Question 8

Inspiration

Answer 8

Pressure of alveoli < pressure atmosphere

Question 9

Expiration

Answer 9

Pressure of alveoli > Pressure atmosphere

Question 10

Muscles involved with forced expiration

Answer 10

abdominal muscles : rectus abdominus, external and internal obliques, transverse abdominus
Internal intercostals
Innermost intercostals
Transversus thoracis

Question 11

Mechanisms of quiet expiration

Answer 11

mostly due to recoil of the lungs
relaxation of inspiratory muscles, reduces the volume of thoracic cavity
Diaphragm relaxes

Question 12

Primary muscles during quiet & forceful inspiration

Answer 12

diaphragm

External intercostals

Question 13

Secondary muscles during forceful inspiration

Answer 13

scalene muscles
sternocleidomastoid
Internal intercostals

Question 14

Innervation of visceral pleura and parietal pleura

Answer 14

Visceral pleura has viscerosensory innervation (insensitive to painful stimuli)
(innervated by autonomic n)
Parietal pleura innervated by somatosensory nerves and is very sensitive to pain. And it is well localized
(innervated by phrenic and intercostal n.)

Question 15

Joints of the thorax

Answer 15

1. Costovertebral
2. Costotransverse
3. Sternocostal
4. Costochondral
5. Sternoclavicular
6. Manubriosternal
7. Xiphisternal

Question 16

Where is ventilation greatest during inspiration

and expiration

Answer 16

1. Base of the lung
   Has higher compliance
2. Apex of lung (low lung volume so pleural pressure at base becomes positive and air moves up)

Question 17

Law of Laplace

Answer 17

P=2T/r

Has radius decreases pressure increases
T is surface tension

Question 18

Surfactant

Answer 18

Produced by type II epithelium cells

Disrupts and lowers surface tension and increases compliance

Promotes alveolar stability at low lung volumes, lowers the surface tension and then smaller and larger alveoli have equal pressure

Question 19

Chest compliance is controlled by 2 factors

Answer 19

1. elastic tissue (collagen & elastin)

2. Surface tension

Question 20

Collagen high or low in obstructive disease

Answer 20

high

Collagen resists stretch and limits lung expansion at high lung volumes

Question 21

Are elastin levels high or low in restrictive diseases

Answer 21

high

Elastin is more distensible and can be stretched to almost double the resting length

Question 22

Infant respiratory distress syndrome (IRDS)

Answer 22

premature babies whose type II cells are not mature and cannot produce surfactant

Treat by put on a ventilator or giving artificial surfactant