Which of the following statements are true about ...

[EAugust]

Which of the following statements are true about negative-pressure ventilation (NPV)?
 
  1. NPV is similar to spontaneous breathing.
  2. Airway (mouth) pressure during NPV is zero.
  3. Expiration during NPV is by passive recoil.
  4. NPV decreases pressure at the body surface.
  a. 2 and 4 only
  b. 1, 2, 3, and 4
  c. 3 and 4 only
  d. 1, 3, and 4 only

Question 2

In which of the following types of ventilation is alveolar expansion during inspiration due to a decrease in pleural pressure? 1. Positive-pressure ventilation (PPV) 2. Negative-pressure ventilation (NPV) 3. Spontaneous ventilation
 
  a. 1 and 2 only
  b. 1 and 3 only
  c. 2 and 3 only
  d. 1, 2, and 3

[l.stuut]

Answer to Question 1

ANS: B
Mechanical NPV is similar to spontaneous breathing. NPV decreases pleural pressure (Ppl) during inspiration by exposing the chest to sub-atmospheric pressure. Negative pressure at the body sur-face (Pbs) is transmitted first to the pleural space and then to the alveoli (Palv). Because the airway opening remains exposed to atmospheric pressure during NPV, a transairway pressure gradient is created. Thus, gas flows from the relatively high pressure at the airway opening (zero) to the rela-tively low pressure in the alveoli (negative).

Answer to Question 2

ANS: C
NPV decreases pleural pressure (Pp1) during inspiration by exposing the chest to sub-atmospheric pressure.