Pulmonary Physiology: Breathing Mechanics

Question 1

How does alveolar surface tension change with inspiration and expiration, respectively?

Answer 1

With inspiration the alveolar surface tension decreases and with expiration it increases.

Question 2

Due to the forces of surface tension within a sphere, it is harder to expand a _____ (big or small) sphere than it is a _____ (big or small) sphere. Which equation explains this?

Answer 2

Harder to expand a small sphere than a big sphere. LaPlace explains this: P (pressure) = 2 x T (tension) x r (radius)
P=2Tr

Question 3

What molecule gives surfactant its amphiphatic property and its ability to interfere with H-bonding?

Answer 3

phospholipids

Question 4

Explain the stabilizing effect that surfactant has on alveoli.

Answer 4

With surface tension, more pressure is required to expand a smaller alveoli than a larger one. Surfactant lowers the surface tension such that different alveoli in the lung are able to inflate at equal pressures no matter their size.

Question 5

Alveoli are “interdependent.” What does that mean?

Answer 5

They are connected to each other by CT, which helps keep them open.

Question 6

What are the two ways to inflate the lung?

Answer 6

1. Positive pressure from inside the lungs

2. Negative pressure surrounding the lungs

Question 7

Why can’t the two lung pleura be pulled apart? What can they do instead?

Answer 7

Surface tension is too high. They can slide against each other instead.

Question 8

The thoracic pressure is ___ mmHg lower than the atmospheric pressure due to the recoil of the thoracic cavity and the surface tension of the intrapleural space.

Answer 8

5 mmHg

Question 9

When the diaphragm __________ it flattens, pushing the abdominal contents down, expanding the rib cage, and drawing air into the lungs.

Answer 9

contracts

Question 10

What are the external intercostal muscles’ role in breathing?

Answer 10

Their contraction expands the ribs upward and outward during inspiration, increasing the anterior-to-posterior diameter of the thoracic cavity.

Question 11

What are the scalenes and sternocleidomastoids’ role in breathing?

Answer 11

These are accessory muscles that activate during heavy breathing. Scalenes lift the first two ribs and sternocleidomastoids lift the sternum.

Question 12

What are the internal intercostal muscles’ role in breathing?

Answer 12

Their contraction helps decrease anterior-posterior diameter of the thoracic cavity when actively exhaling.

Question 13

By which two mechanisms do minute ventilation increase during heavy breathing?

Answer 13

1. Increased frequency

2. Increased tidal volume through increased expiration AND inspiration

Question 14

With increasing frequency of breathing, the time available for filling the lungs _________ (increases or decreases) and the tidal volume _________ (increases or decreases).

Answer 14

time available for filling decreases and so does tidal volume

Question 15

FEV1/FVC is an assessment of airway ________.

Answer 15

resistance

Question 16

What is a normal FEV1/FVC?

Answer 16

around 80%

Question 17

What does a FEV1/FVC of 50% indicate?

Answer 17

Obstructive pulmonary disease

Question 18

What is the relationship between expiratory flow and lung volume?

Answer 18

As lung volume decreases, so does flow. In other words, you can exhale faster at first, but as your lungs empty, your exhale gets weaker.

Question 19

What three things affect the elastic recoil of the lungs?

Answer 19

1. Lung tissue stretch. Increased stretch = increased recoil force.
2. Alveolar surface tension forces.
3. Stiffness of the chest wall and expiratory muscle forces.

Question 20

Name two ways by which emphysema decreases exhalation ability.

Answer 20

1. Airway narrowing

2. Loss of elastic recoil

Question 21

Can total lung capacity and residual volume both increase in the setting of emphysema?

Answer 21

Yeah