What is the alleged benefit of using heliox mixtures to ventilate ...

[melina_rosy]

What is the alleged benefit of using heliox mixtures to ventilate patients who have severe airway obstruction?
 
  A. A lower tidal volume is generally needed.
  B. The adverse effects of applied PEEP tend to be less.
  C. Lung emptying is sometimes facilitated.
  D. Ventilators often operate better when heliox mixtures are used as the source gas.

Question 2

Which of the following statements apply to the use of extrinsic PEEP for the purpose of minimizing auto-PEEP? I. Adding extrinsic PEEP requires less effort on behalf of the patient to trigger a breath. II. The addition of extrinsic PEEP only affects breathing circuit pressure and pressure in the airways. III. The use of extrinsic PEEP increases pulmonary compliance throughout the lungs.
 
  A. I, II only
  B. I, IV only
  C. I, II, III only
  D. I, II, IV only

[milbourne11]

Answer to Question 1

ANS: C
A. Incorrect response: See explanation C.
B. Incorrect response: See explanation C.
C. Correct response: In severe airway obstruction, uses of heliox, which is a low density gas mixture, usually in the helium:oxygen proportions of 80:20, 70:30, and 60:40. Heliox purportedly helps reduce patient inspiratory work and facilitates lung emptying. If a helium-gas mixture is used, recall that many flow sensors must be recalibrated to account for the change in gas density. Some ventilators actually cannot function in the presence of heliox.
D. Incorrect response: See explanation C

Answer to Question 2

ANS: A
A. Correct response: Judicious amounts of extrinsic PEEP in the airway help equilibrate trapped pressure (auto-PEEP) with pressure throughout the ventilatory circuitry. The application of extrinsic PEEP requires less pressure by the patient to trigger inspiration. Extrinsic PEEP only compensates for 70 to 80 of the auto-PEEP. Up to this level, the extrinsic PEEP only affects the breathing circuit and the pressure in the patient's airways. Auto-PEEP in the alveoli is not balanced by the application of extrinsic PEEP. Instead, the use of extrinsic PEEP greater than that in the circuit and the patient's airways appears to begin elevating alveolar pressures and thus becomes counterproductive because regional overdistention develops in less obstructed regions.
B. Incorrect response: See explanation A.
C. Incorrect response: See explanation A.
D. Incorrect response: See explanation A.