Ventilation and Compliance

Question 1

What is ANATOMICAL DEAD SPACE?

Answer 1

1) Volume of Gas in the Conducting Airways
2) This Gas is Not Available for Exchange
3) Volume = 150ml

Question 2

What is the MAXIMUM VOLUME of air that can be VOLUNTARILY EXHALED following a MAXIMUM INSPIRATION?

Answer 2

(Forced) Vital Capacity

Tidal Volume + Inspiratory Reserve Volume + Expiratory Reserve Volume

3-5 litres in Healthy Adults

*Varies with Age, Gender, Height, Mass and Ethnicity

Question 3

What is the VOLUME of air breathed IN or OUT of the lungs at EACH BREATH?

Answer 3

Tidal Volume

Question 4

What are the TWO TYPES of VENTILATION?

Answer 4

1) Pulmonary (Minute) Ventilation

2) Alveolar Ventilation

Question 5

What is PULMONARY (MINUTE) VENTILATION?

Answer 5

Total Air Movement Into and Out of the Lungs

*Little Functional Significance

Question 6

What is ALVEOLAR VENTILATION?

Answer 6

Volume of Fresh Air, per unit of time, Reaching the Alveoli; Available for Gas Exchange

(Tidal Volume - Anatomical Dead Space) x Respiratory Rate

Question 7

What are the TWO TYPES of CELL that make up the ALVEOLAR WALLS and what are their FUNCTIONS?

Answer 7

1) Type I Pneumocytes - Permit Gas Exchange

2) Type II Pneumocytes - Secrete Surfactant

Question 8

What is the PURPOSE of SURFACTANT FLUID?

Answer 8

1) < Surface Tension on Alveolar Surface Membranes

2) Prevents Alveoli from Collapsing

Question 9

How does SURFACTANT FLUID BENEFIT breathing?

Answer 9

1) > Lung Compliance
2) < Tendency for Recoil
3) > Ease of Breathing

Question 10

At HOW MANY WEEKS of GESTATION does surfactant production begin?

Answer 10

25 Weeks Gestation

Question 11

When is surfactant production COMPLETE and WHY is this IMPORTANT?

Answer 11

By 36 Weeks Gestation

Premature babies (i.e. born before 36 weeks) Have Not Yet Produced Sufficient Amounts of Surfactant to Keep their Alveoli Open

Suffer from Infant Respiratory Distress Syndrome (IRDS)

Question 12

What is COMPLIANCE?

Answer 12

Change in Volume Relative to Change in Pressure

Stretchability of the Lungs

Question 13

Is INSPIRATION an ACTIVE or a PASSIVE process?

Answer 13

Active

Question 14

Is EXPIRATION, normally, an ACTIVE or a PASSIVE process?

Answer 14

Passive

Question 15

How is the WORK of BREATHING RECOVERED during passive expiration?

Answer 15

Elastic Recoil of the Lungs

Question 16

In EMPHYSEMA, is the WORK of BREATHING increased or decreased?

Answer 16

Increased

• Due to Loss of Elastic Fibres Surrounding the Alveoli; Preventing Recoil and Prolonging Expiration
• Obstructive Disease

Question 17

In PULMONARY FIBROSIS, is the WORK of BREATHING increased or decreased?

Answer 17

Increased

• Due to Inert Fibrous Tissue Which > the Effort Required for Inspiration by < Lung Compliance
• Restrictive Disease

Question 18

Where are the ALVEOLI BEST VENTILATED?

Answer 18

Base of the Lung

*Alveolar Ventilation Declines with Height from the Base to the Apices

Question 19

Where is COMPLIANCE BEST in the LUNGS?

Answer 19

Base of the Lung

• Alveoli at the Apex are More Inflated due to Functional Residual Capacity
• Alveoli at the Base are Compressed Between the Weight of the Lung and Diaphragm; Hence More Compliant on Inspiration

Question 20

What is OBSTRUCTIVE LUNG DISEASE?

Answer 20

Obstruction of Air Flow, due to > Airway Resistance; Especially on Expiration

Exs) COPD; Asthma; Bronchiectasis; Lung Cancer

Question 21

What is RESTRICTIVE LUNG DISEASE?

Answer 21

1) Restriction of Lung Expansion
2) Loss of Lung Compliance

Exs) Pulmonary Fibrosis; Pulmonary Oedema; Pneumonia; Pneumothorax; Infant Respiratory Distress Syndrome (IRDS)

Question 22

What CANNOT be DIRECTLY MEASURED via SPIROMETRY?

Answer 22

1) Functional Residual Capacity (Expiratory Reserve + Residual Volume) 2) Residual Volume

Question 23

What would be the PREDICTED NORMAL FORCED EXPIRATORY VOLUME in 1 SECOND (FEV1) for healthy males?

Answer 23

4.0L

Question 24

What would be the PREDICTED NORMAL FORCED VITAL CAPACITY (FVC) for healthy males?

Answer 24

5.0L

Question 25

What would be the PREDICTED NORMAL FEV1:FVC for healthy males?

Answer 25

80%

Question 26

What would the EXPECTED FEV1, FVC and FEV1:FVC in OBSTRUCTIVE disease?

Answer 26

< FEV1, i.e. 1.3L
< FVC (but not as drastically as FEV1), i.e. 3.1L

< FEV1:FVC, i.e. 42%

Question 27

What would the EXPECTED FEV1, FVC and FEV1:FVC in RESTRICTIVE disease?

Answer 27

< FEV1, i.e. 2.8L
< FVC, i.e. 3.1L

Normal (or, in some cases, >) FEV1:FVC, i.e. 90%

*Absolute Rate of Airflow is

Question 28

What are the LIMITATIONS of SPIROMETRY in diagnosing disease?

Answer 28

Normal FEV1:FVC is Not Always Indicative of Health

*Can Occur in Restrictive Disease