Which level of FiO2 and what time of exposure has been associated ...

[charchew]

Which level of FiO2 and what time of exposure has been associated with oxygen toxicity? 1. FiO2 of 0.5 2. FiO2 of 0.7 3. FiO2 of 0.6 4. 24 to 48 hr
 
  a. 1 and 2 only
  b. 3 and 4 only
  c. 2 and 3 only
  d. 1 and 4 only

Question 2

The increased work of breathing associated with auto-positive end expiratory pressure (PEEP) during mechanical ventilation is due to:
 
  1. Hyperinflation or impaired contractility of the diaphragm.
  2. Large alveolar pressure drops required to trigger breaths.
  3. Increased volume of the intrathoracic airways.
  a. 1 and 2 only
  b. 1 and 3 only
  c. 2 and 3 only
  d. 1, 2, and 3

[GCabra]

Answer to Question 1

ANS: B
An FiO2 of 0.5 or more for longer than 24 to 48 hr is associated with the development of oxygen toxicity.

Answer to Question 2

ANS: A
First, hyperinflation caused by auto-PEEP stretches the lung, and the stretching impairs the con-tractile action of the diaphragm. Second, in pressure- or flow-triggered breaths, the high alveolar pressure caused by auto-PEEP must be overcome before any airway pressure change can occur.