2004 OPEN FORUM Abstracts
USE OF THE MONAGHAN 225 MRI COMPATIBLE VENTILATOR FOR INFANT AND PEDIATRIC VENTILATION
Mark
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.
