Respiratory dynamics

Question 1

Airway resistance from mouth to alveolus is 2 cm H₂O-sec/liter. [These units are pressure/flow as in cm H₂O/(L/s)]. If alveolar pressure is + 10 cm H₂O, what is the magnitude and direction of the airflow?

Answer 1

5 L/s expiratory flow, (ref pg. 28 in iBook)

Question 2

At FRC with relaxed muscles, pleural pressure is -6 cm H₂O. If an inspiratory muscle force of 4 cm H₂O is suddenly applied and the airway resistance is 2 cm H₂O-s/L, what is the immediate airflow?

Answer 2

2 L/s (ref pgs. 23 and 28 in iBook).

Question 3

In normal, resting conditions, expiration requires the activation of expiratory muscles. (T/F)

Answer 3

False. (ref pg. 24 in iBook)

Question 4

In the P-V plot shown, the red-shaded area is:

1. energy required to overcome the airway resistance.
2. energy of inspiration turned in to heat or otherwise lost.
3. energy stored in the gas that has been inspired,
4. energy that has been stored in the elastic structures of the chestwall.
5. energy that has been stored in the elastic structures of the lung and chestwall.

Answer 4

Option 5 is correct. (ref pg. 27 in iBook)

Question 5

The larynx is a site of high resistance to airflow in the conducting airway path (T/F).

Answer 5

True. (ref pg. 28 in iBook)

Question 6

In normal subjects, peak inspiratory airflow in wakefulness is limited only by the peak inspiratory effort (T/F).

Answer 6

True. (airway resistance is not increased by a maximal effort: ref pgs. 31 in iBook)

Question 7

In normal subjects, peak expiratory airflow is limited only by the peak expiratory effort (T/F).

Answer 7

False. (ref pg. 32 in iBook)

Question 8

Expiratory flow limitation increases as lung volume _______________.

Answer 8

decreases. (ref pgs. 33 in iBook)

Question 9

The maximum volume contained in the lung is the _______________.

Answer 9

Total lung capacity (TLC). (ref pg. 33-4 in iBook)

Question 10

The largest tidal volume that can be inspired is called the ________________.

Answer 10

Vital capacity (VC). (ref pg. 33-4 in iBook)

Question 11

The residual volume (RV) is the __________________.

Answer 11

Smallest lung volume that can be achieved with maximal expiratory effort. (ref pg. 33-4 in iBook).

Question 12

Typically, FRC is about 2 liters and the residual volume is only a few hundred ml (T/F).

Answer 12

False- the FRC is about 2 liters, but the RV is only about 0.5-1 liter less (ref pg. 33 in iBook).

Question 13

Expiratory airflow limitation per se is a marker for airway disease. (T/F)

Answer 13

False. (iBook pg. 32.)