Pressure control ventilation: Three anesthesia ventilators compared using an infant lung model

We compared three ventilators - Servo 900C (Siemens Medical Systems, Danvers, MA), Aestiva 3000 (Datex-Ohmeda, Madison, WI), and NAD 6000 (North American Drager, Telford, PA) - set to deliver pressure control ventilation using an infant test lung model. Ventilator settings were selected to test 'near-maximum' settings that would be used for a neonatal patient (peak inspiratory pressure [PIP] 30 cm H₂O) or older child (PIP 60 cm H₂O). When adjusted for set inspiratory pressure and compliance, the average tidal volume (V(t)) produced by the NAD 6000 was 5.8 mL less than the Servo 900C (P = 0.103), and the average V(t) produced by the Aestiva 3000 was 18.9 mL less than the Servo 900C (P < 0.001). The Servo 900C generated increased peak pressures, tending to overshoot the set maximum inflating pressures, especially during rapid respiratory rates with decreased inspiratory times. The Aestiva 3000 did not achieve the set PIP during testing conditions of decreased inspiratory times, and the NAD 6000 was not greatly affected by changes in inspiratory time. All three ventilators measured expiratory V(t) to be larger than the actual V(t) delivered to the lung; however, the NAD 6000 was more accurate.