Interpret the significance of the arrow shown on breath C present on the pressure-time scalar.

(Answer to Q. 1)  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.

(Answer to Q. 2)  ANS: C
A. Incorrect response: See explanation C.
B Incorrect response: See explanation C.
C. Correct response: A specific cycling problem can occur with PSV in patients with airway obstruction. The peak flow of the pressure-controlled breath may be diminished, and the decelerating flow profile may be slow. This situation may cause prolongation of the pressure support breath because the cycling flow value (often 25 to 35 of the peak flow) may take substantial time to reach. Consequently, shortened expiratory times may cause auto-PEEP. Methods of addressing this issue involve increasing the pressure support flow cycling criterion, for example, from 25 to 50 of the peak flow.
D. Incorrect response: See explanation C

(Answer to Q. 3)  ANS: C
A. Incorrect response: See explanation C.
B. Incorrect response: See explanation C.
C. Correct response: The three scalars presented here depict volume controlled mechanical ventilation.


No patient triggering is occurring. During the breaths labeled A and B, the expiratory flow does not return to the baseline before the ensuing inspiration begins. Inspiratory flow is delivered to the patient while expiratory flow from the patient takes place. This situation produces dynamic hyperinflation or auto-PEEP. The Pplateau is 30 cm H2O, which an acceptable pressure level. Keep in mind that in obstructive airway disease, overdistention of healthy lung regions may still occur despite a Pplateau of 30 cm H2O or less.
D. Incorrect response: See explanation C

(Answer to Q. 4)  ANS: A
A. Correct response: Pressure-regulated volume control (PRVC) is a pressure-control mode with a volume target. It is also classified as a dual control mode. The therapist selects a tidal volume, and the ventilator delivers a test breath. During the test breath, the ventilator calculates the system compliance and airway resistance to determine the pressure needed to deliver the set tidal volume. The ventilator may adjust the pressure delivery every breath in increments of 1 to 3 cm H2O up to the maximum pressure that equals the upper pressure limit minus 5 cm H2O. Therefore the delivered tidal volume will remain relatively constant as either or both lung compliance and airway resistance change.
B. Incorrect response: See explanation A.
C. Incorrect response: See explanation A.
D. Incorrect response: See explanation A.

(Answer to Q. 5)  ANS: B
A. Incorrect response: See explanation B.
B. Correct response: The presence of auto-PEEP can be evaluated via the following methods: (1) observing the persistence of expiratory flow at the end of the allotted expiratory time, which suggests incomplete lung emptying, and the presence of auto-PEEP, (2) observing from a flow-time scalar the failure of the expiratory flow to return to baseline and the initiation of an inspiration before expiratory flow ceases, (3) performing an end-expiratory hold following a mandatory breath devoid of any patient effort, and (4) using an esophageal balloon to detect the inspiratory triggering load imposed by any auto-PEEP. Esophageal pressure will be higher in the presence of auto-PEEP than in the absence of auto-PEEP.
C. Incorrect response: See explanation B.
D. Incorrect response: See explanation B.

(Answer to Q. 6)  ANS: C
A. Incorrect response: See explanation C.
B. Incorrect response: See explanation C.
C. Correct response: Pressure-controlled ventilation (PCV) does not guarantee a volume, rather it controls inspiratory airway pressure. Volume is the dependent variable, and will change as lung mechanics or patient effort change. Sudden worsening of airway resistance with pressure targeted ventilation results in a loss of volume, but maximal airway pressures will not rise.
D. Incorrect response: See explanation C

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