When a therapist progressively decreases the mandatory rate when ...

[Brittanyd9008]

When a therapist progressively decreases the mandatory rate when ventilating a patient with VC-SIMV, what can the therapist expect to observe as the spontaneous VT decreases and the VD/VT ratio increases?
 
  A. an increased spontaneous respiratory rate
  B. ventilationperfusio n mismatching
  C. an increased shunt fraction
  D. a decrease in the spontaneous ventilatory effort

Question 2

What problem is the therapist likely to observe when a mechanically ventilated COPD patient continues to receive inspiratory flow while the patient is actively exhaling?
 
  A. auto-triggering
  B. flow starvation during inspiration
  C. ineffective triggering
  D. respiratory muscle unloading

[macybarnes]

Answer to Question 1

ANS: A
A. Correct response: When SIMV is used alone (i.e., without pressure support ventilation),, a decrease in the number of ventilator breaths produces a decrease in the average VT of the spontaneous breaths. At the same time, the patient's VD/VT ratio increases. To compensate for the smaller spontaneous tidal volumes and the increased VD/VT ratio, the spontaneous respiratory rate often increases.
B. Incorrect response: See explanation A.
C. Incorrect response: See explanation A.
D. Incorrect response: See explanation A.

Answer to Question 2

ANS: C
A. Incorrect response: Auto-triggering results from an overly sensitive triggering system.
B. Incorrect response: An inspiratory flow that does not meet the patient's inspiratory demands tends to cause flow starvation during inspiration.
C. Correct response: Dynamic hyperinflation and auto-PEEP develop when the ventilator continues to provide inspiratory flow while the patient actively exhales. Subsequently, the patient will be required to breath through any applied PEEP and trapped air, thus, causing ineffective triggering and patient-ventilator dyssynchrony.
D. Incorrect response: The situation described here would tend to cause the muscles of respiration to work hard.