Why have so few HFV studies on adult patients been conducted? ...

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Why have so few HFV studies on adult patients been conducted?
 
  A. because high-frequency ventilators lack adequate ventilation capabilities for adult subjects
  B. because adult subjects cannot tolerate receiving a Vt smaller than the Vd
  C. because the high mean airway pressures produced by high-frequency ventilators are likely to induce barotrauma in adults
  D. because adult subjects are incapable of enduring such high ventilation frequencies

Question 2

Which of the following factors appears to be responsible for the development of necrotizing tracheobronchitis that is observed in some neonates receiving HFJV? I. high mean airway pressures II. high gas velocity III. inadequate airway humidification IV. auto-PEEP
 
  A. I, II only
  B. II, III only
  C. I, III, IV only
  D. I, II, III, IV

[nhea]

Answer to Question 1

ANS: A
A. Correct response: Adult experience with HFV has been limited because devices with adequate ventilation capabilities for adults are few. Early jet devices have shown to provide reasonable gas transport with lower peak airway pressures in adult respiratory failure. Oscillators with the capabilities to support gas exchange in the adult have been more recently introduced and have shown the capability to support gas exchange safely.
B. Incorrect response: See explanation A.
C. Incorrect response: See explanation A.
D. Incorrect response: See explanation A.

Answer to Question 2

ANS: B
A. Incorrect response: See explanation B.
B. Correct response: Adequate humidification can be difficult to achieve when high gas flows and a large minute ventilation are used. The high gas velocity of HFV (especially HFJV) also may cause direct physical airway damage. These two factors (inadequate airway humidification and high gas velocities) are thought to be responsible for the development of necrotizing tracheobronchitis observed in some neonates receiving HFJV.
C. Incorrect response: See explanation B.
D. Incorrect response: See explanation B.

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