2 - Mechanics of Breathing

Question 1

A smaller alveolus is [easier/harder] to keep open than a bigger alveolus.

Answer 1

Harder

Question 2

What is the purpose of surfactant?

Answer 2

It reduces and standardizes surface tension so alveoli of all sizes can be kept open using the same pressure

Question 3

What are the features of a lung compliance curve?

Answer 3

• initial increase in pressure results in minimal volume increase because of overcoming surface tension
• lung becomes more compliant as it inflates more
• lung deflates easily and proportionally to amount of pressure change

Question 4

Compliance is [increased/decreased] in emphysema.

Answer 4

increased (decreased elastic recoil)

Question 5

Compliance is [increased/decreased] in fibrosis.

Answer 5

decreased

Question 6

What mechanism is used to expand the lungs?

Answer 6

Create a negative pressure gradient in pleural space to suck lungs against inner chest wall; expand thorax = expand lungs

Question 7

In regards to Boyle’s Law (P1V1 = P2V2), how does pressure change in breathing affect airflow?

Answer 7

• lungs expand –> pressure drops –> pulls air in

- lungs contract –> pressure increases –> pushes air out

Question 8

What muscles are used during inspiration?

Answer 8

scalenes, external intercostals, pectoralis minor, diaphragm

Question 9

What muscles are used during expiration?

Answer 9

internal intercostals, abdominals

Question 10

How does minute ventilation change with exercise?

Answer 10

Increases by:

• increased RR
• increased TV by including inspiratory and expiratory reserve volumes in each breath

Question 11

What FEV1/FVC value indicates obstruction?

Answer 11

FEV1/FVC < 0.70

Question 12

What is the equal pressure point? What happens past this point?

Answer 12

The point where airway pressure and pleural pressure are equal; below EPP, smaller airways are compressed and flow limitation occurs

Question 13

What happens if someone forcefully expires starting at mid-lung volume?

Answer 13

The equal pressure point is reached too early in the airway system and the airway collapses; there is not enough pressure to fully expire

Question 14

What mechanism is used to expand the lungs?

Answer 14

Create a negative pressure gradient in pleural space to suck lungs against inner chest wall; expand thorax = expand lungs

Question 15

What are the two contributors to the elasticity of the lung?

Answer 15

1/3 elastic fibers, 2/3 surface tension

Question 16

The greater the lung elasticity, the [greater/lesser] the recoil

Answer 16

greater

Question 17

How do alveoli assist in decreasing resistance and maintaining airflow?

Answer 17

They are tethered to nearby bronchioles. In inspiration, they pull the airways open, decreasing resistance. In expiration, they tether the bronchioles to keep them from collapsing.

Question 18

What conditions lead to reduced compliance?

Answer 18

• restrictive diseases

- hyperinflation

Question 19

___ is the capacity at which the tendency for the lung to recoil inward and the chest wall to spring outward is balanced.

Answer 19

Functional residual capacity