2004 OPEN FORUM Abstracts
USE OF THE MONAGHAN 225 MRI COMPATIBLE VENTILATOR FOR INFANT AND PEDIATRIC VENTILATION
Siobal BS RRT, Roger Kraemer CRT, Respiratory Care Services, San
Francisco General Hospital, UCSF Department of Anesthesia.
Background: During MRI studies, ventilation of infant and pediatric patients requires low mechanical deadspace to minimize CO2 rebreathing. We developed a hybrid ventilator circuit to achieve this using components from infant and adult disposable circuits. The modified circuit uses a neonatal “Y” and adapters from an infant circuit, and an exhalation valve manifold from an adult circuit (see diagram). Performance of the ventilator and circuit was verified by lab bench testing.
Method: A Monaghan 225 MRI ventilator was operated in the pressure limit mode. Infant and pediatric test lungs (compliance 1.2 and 3.6 mL/cm H2O) were ventilated through 3.0 and 4.0 ETT at RR of 20 and 30 /min. Working pressure (WP) of 10, 15, 20, 25, and 30 cm H2O, flow rate (FR) settings of 1 to 5, and set volume (SV) of 100, 150, and 200 mL were tested. Delivered Vt, PIP, inspiratory time, and peak inspiratory flow were recorded with a Ventrak 1250 monitor at each setting. Results were used to established a range of settings for 3 to 6 kg and 6 to 12 kg patients.
Results: Setting ranges appropriate for 3 to 6 kg patients (WP 10 to 25 cm H2O, SV 100 to 150 mL, FR 2 to 3) delivered Vt of 18 to 50 mL at PIP of 20 to 40 cm H2O. Setting ranges appropriate for 6 to 12 kg patients (WP 10 to 25 cm H2O, SV 150 to 200 mL, at FR 2 to 3) delivered Vt of 40 to 100 mL at PIP of 15 to 35 cm H2O. The mean inspiratory time at these settings was 0.52 ± 0.04 seconds. The peak inspiratory flow varied between 5 and 16 L/min. Measure PIP was greater than the set WP by 5 to 15 cm H2O because of the resistance of the exhalation valve.
Conclusion: Ventilation parameters and tidal volume size of 6 to 8 mL/kg appropriate for 3 to 12 kg infant and pediatric patients can be delivered using this modified circuit during MRI studies.