Mechanics of Breathing

Question 1

Differentiate between elastic and non-elastic resistance

Answer 1

Elastic resistance = recoil of chest wall and lungs.

Non-elastic resistance = airflow and viscous resistance

Question 2

What is compliance?

Answer 2

Disensitivility - ease at which lungs can expand.

Question 3

What is elastance?

Answer 3

Tendency to recoil after distension.

Question 4

What forces must be overcome for the lungs to expand?

Answer 4

Overcome elastic recoil of chest wall and lungs

Overcome surface tension of alveoli at low volumes

Question 5

What type of cells produce surfactant?

Answer 5

Alveolar type 2 cells

Question 6

What issues surround surfactant production and premature births?

Answer 6

Surfactant is only produced from 34 weeks, early birth can cause respiratory distress.

Question 7

Functional significance of low and high compliance in lungs?

Answer 7

Low compliance = stiff lung. More work required for normal inspiration. Occurs in fibrosis, TB

High compliance = floppy lung. Less elastic recoil, extra work required for expiration. COPD (emphysema, bronchitis)

Question 8

What are the two components to non-elastic resistance?

Answer 8

Airflow resistance (80%) and viscous resistanc (20%)

Question 9

How does the PNS change bronchoconstriction/dilation

Answer 9

Increase in PNS tone = bronchoconstriction (ACh acts on muscarinic receptors)
Decrease in PNS tone = bronchodilation

Question 10

What measure of lung function in spirometry is impacted by both resistance and compliance

Answer 10

FEV1

Question 11

Compare obstructive vs restrictive lung disease.

Answer 11

Restrictive = decrease in lung volume. MOre work is required to achieve same change in volume.

Obstructive = increase in airflow resistance. Change in flow rate is the problem. MOre work is required to overcome resistance to flow.
Decreased airflow = increased expiratory times = air trapped in lungs due to incomplete emptying = lungs expand.

Question 12

Give examples of restrictive and obstructive lung diseases.

Answer 12

Restrictive = fibrosis, TB

Obstructive = COPD, asthma

Question 13

How do obstructive and restrictive disorders affect FEV1, FVC, TLC and RV?

Answer 13

OBSTRUCTIVE:

• FEV1 is decreased
• FVC is decreased
• TLC Is normal/increased
• RV is normal/increased

RESTRICTIVE

• FEV1 is normal/increased
• FVC is decreased
• TLC is decreased
• RV is decreased