Walsh: Perinatal and Pediatric Respiratory Care, 3rd Edition

Chapter 17: Mechanical Ventilators

Answers to Assessment Questions and Clinical Scenarios

1.	E
Rationale: Input power refers to the power source (or sources) required by the ventilator to perform the work of ventilation. Input power can be pneumatic or electric. Pneumatic power is usually provided by compressed gas pressurized to about 50 pounds per square inch gauge (psig). Electric power can be either alternating current (AC) or the direct current (DC) of a battery.(page 3)
2.	A
Rationale: Because only one variable can serve as the independent variable at a given time, consequently, only one variable can be controlled by a ventilator at any one time. The variable that a ventilator controls to effect inspiration is the control variable (page 5)
3.	D
Rational: Examples of dual control inspiration are volume-assured pressure-support ventilation, volume guarantee (VG), pressure-regulated volume control (PRVC), volume control plus (VC+), adaptive pressure control (APV), and volume support (page 7).
4.	C
Rationale: Pressure support breaths are typically cycled when inspiratory flow falls to a predetermined flow or percentage of the peak flow needed to reach the set pressure limit. A ventilator may also have a backup or safety cycle variable. Another example of a backup safety cycle variable is time; if inspiration does not meet preset pressure or flow criteria, the ventilator will cycle into exhalation on the basis of a predetermined time interval.
5.	D
Rationale: The AVEA ventilator (Cardinal Health) (Figure 17-6) is a pneumatically and electrically powered, electronically (microprocessor) and pneumatically controlled ventilator approved for use in neonatal, pediatric, and adult patients (page 21).
6.	C
Rationale: The Evita 4 can be operated in the following ventilation modes: CMV, SIMV, mandatory minute ventilation (MMV), pressure-controlled ventilation (PCV), airway pressure release ventilation (APRV), and CPAP. The machine volume mode is found on the AVEA ventilator (page 25).
7.	D
Rationale: The patient trigger variable can be set as either pressure or flow. Pressure triggering requires spontaneous patient effort to drop the circuit pressure below baseline by an amount equal to the set trigger sensitivity (0.1 to 20 cm H2O below PEEP). To accomplish flow triggering the ventilator delivers a base gas flow through the patient circuit during the expiratory phase of all breaths. This base flow is equal to the flow set as the trigger sensitivity plus 1.5 L/minute. As the patient breathes from the base flow, the ventilator detects a difference in the inspiratory and expiratory flow measurements. Flow triggering occurs when this flow differential equals the value set as the trigger sensitivity (0.1 to 20 L/min) 
8.	A
Rationale: NAVA is a new mode of mechanical ventilation that applies pressure in proportion to the electrical activation of the diaphragm (Edi). This electrical activity is obtained with a multiple-array esophageal electrode that doubles as a feeding tube. This new and novel mode of ventilation may offer true synchronization.