Author Question: A patient is being mechanically ventilated via the pressure-controlled CMV ventilation (PC-CMV) ... (Read 89 times)

craiczarry · **on:** Jul 16, 2018

A patient is being mechanically ventilated via the pressure-controlled CMV ventilation (PC-CMV) mode, and abruptly experiences an increase in airway resistance. How will the delivered tidal volume be affected by this development?

A. The patient's tidal volume will be virtually unaffected.
B. The delivered tidal volume will be increased.
C. The patient's tidal volume will decrease.
D. The delivered tidal volume will fluctuate.

Question 2

While mechanically ventilating a patient for respiratory failure from airflow obstruction, when is increasing the delivered tidal volume up to 8 ml/kg appropriate?

A. when the patient has difficulty triggering a breath
B. when the patient demonstrates a severe respiratory acidosis
C. when the Pao2 falls below 70 mm Hg
D. when the inspiratory flow is inadequate

makaylafy · **Reply #1 on:** Jul 16, 2018

Answer to Question 1

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

Answer to Question 2

ANS: B
A. Incorrect response: Increasing the tidal volume when a patient is experiencing difficulty triggering a breath is inappropriate. The sensitivity setting may need to be adjusted, or the presence of auto-PEEP needs to be determined. If auto-PEEP is present, the following methods can be employed to reduce it: (1) increasing the inspiratory flow, (2) lengthening Te, (3) reducing the Vt, (4) reducing the respiratory rate, (5) using low resistance exhalation valves, (6) using a larger ETT, and (7) instituting applied PEEP.
B. Correct response: Increasing the Vt to 8 ml/kg may be appropriate when mechanically ventilating a patient for respiratory failure from airflow obstruction when the patient experiences severe patient-ventilator dyssynchrony or severe respiratory acidosis.
C. Incorrect response: Generally, the Fio2 is increased, or PEEP is added to elevate a patient's Pao2.
D. Incorrect response: Increasing the tidal volume when the inspiratory flow is inadequate is counterproductive. If the inspiratory flow is determined to be too low, the therapist should then increase that setting.