Author Question: The ventilator mode that allows the patient to breathe spontaneously between operator-selected ... (Read 64 times)

Mollykgkg · **on:** Jul 16, 2018

The ventilator mode that allows the patient to breathe spontaneously between operator-selected time-triggered volume and pressure-targeted breaths is which of the following?

a. Pressure support ventilation (PSV)
b. Continuous mandatory ventilation (CMV)
c. Intermittent mandatory ventilation (IMV)
d. Airway pressure release ventilation (APRV)

Question 2

A hemodynamically unstable patient being ventilated in the volume-controlled continuous man-datory ventilation (VC-CMV) mode is triggering inspiration at a rate of 25 breaths/min and has the following arterial blood gas results:

pH 7.50, partial pressure of carbon dioxide (PaCO2) 30 mm Hg, partial pressure of oxygen (PaO2) 98 mm Hg, arterial oxygen saturation (SaO2) 100, bicarbonate (HCO3) 24 mEq/L. The respira-tory therapist should perform which of the following?
a. Extubate and administer noninvasive posi-tive pressure ventilation (NIV).
b. Change the mode to pressure-controlled continuous mandatory ventilation (PC-CMV).
c. Change the mode to volume-controlled intermittent mandatory ventilation (VC-IMV).
d. Sedate and paralyze the patient.

cat123 · **Reply #1 on:** Jul 16, 2018

Answer to Question 1

ANS: C
The intermittent mandatory ventilation (IMV) mode allows the patient to breathe spontaneously between operator mandatory ventilator breaths. During these spontaneous breaths the baseline pressure may be set at ambient pressure or above ambient pressure. In addition, pressure support may be used during the spontaneous breathing period. Pressure support ventilation (PSV) has no time-triggered breaths, nor does it have volume-targeted breaths. Continuous mandatory ventila-tion (CMV) does not allow for spontaneous breathing; it only allows the patient to trigger the mandatory ventilator breath. Airway pressure release ventilation (APRV) does not have vol-ume-targeted breaths. It is designed to be two levels of continuous positive airway pressure (CPAP) where the patients breathe spontaneously at both levels.

Answer to Question 2

ANS: C
This patient has ventilator-induced hyperventilation as evidenced by the partial pressure of car-bon dioxide (PaCO2) of 30 mm Hg with a trigger rate of 25 breaths/min. Switching to the vol-ume-controlled intermittent mandatory ventilation (VC-IMV) mode will decrease the number of ventilator breaths the patient triggers by allowing the patient to breathe spontaneously between the mandatory ventilator breaths. This will reduce the patient's minute ventilation and normalize the PaCO2 and pH. Another potential advantage is to put less of a strain on an already hemody-namically unstable patient. There is nothing in this patient's scenario that suggests extubation and use of noninvasive positive pressure ventilation (NIV). Switching to the pressure-controlled con-tinuous mandatory ventilation (PC-CMV) mode will most likely not correct the patient's problem because the patient will still be able to trigger ventilator set breaths and could continue to hyper-ventilate. Although sedating and medically paralyzing the patient could normalize the patient's acid-base balance, it is not the treatment of choice because of the hemodynamic instability of the patient.