The scalars depicted here are flow, volume, airway pressure, and ...

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The scalars depicted here are flow, volume, airway pressure, and esophageal pressure. They were obtained from a patient receiving pressure-controlled ventilation. What problem is depicted by these ventilator graphics?
 
  A. inverse I:E ratio ventilation
  B. alveolar overdistention
  C. decreased lung compliance
  D. trigger dyssynchrony

Question 2

Interpret the significance of the arrow shown on breath C present on the pressure-time scalar.
 
  A. an inspiratory pause
  B. an expiratory pause
  C. alveolar overdistention
  D. flow-cycling criterion

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Answer to Question 1

ANS: D
A. Incorrect response: See explanation D.
B. Incorrect response: See explanation D.
C. Incorrect response: See explanation D.
D. Correct response: Focus primarily on the two pressure-time scalars.

Note that on the esophageal pressure-time (bottom-most) scalar, the arrows indicate an esophageal pressure change. The arrow on the left represents the beginning of patient inspiratory effort. Under normal circumstances, when no auto-PEEP is present, a drop in airway pressure would be taking place concurrently with the initial decrease in esophageal pressure, and an assisted breath would be triggered. However, the presence of auto-PEEP requires the patient to generate an inspiratory effort in excess of the auto-PEEP to trigger inspiration. In this situation, the esophageal pressure changed 25 cm H2O as 0.7 seconds elapsed before the airway pressure changed to trigger a breath. This level of pressure is a significant triggering workload on the patient.

Answer to Question 2

ANS: B
A. Incorrect response: See explanation B.
B. Correct response: The arrow on the pressure-time scalar under the breath labeled C, shown in rationale 13, indicates that an expiratory hold was applied at the time the third breath in the sequence of the three shown. Performing an expiratory hold at this point in the ventilatory cycle enables auto-Peep to equilibrate with the circuit pressure and be measured.
C. Incorrect response: See explanation B.
D. Incorrect response: See explanation B.

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Excellent

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