Aerosol delivery during high frequency jet ventilation: an MRI evaluation.

Background: We have previously demonstrated aerosol delivery during conventional and high frequency oscillatory (HFOV) ventilation using magnetic resonance imaging (MRI) in piglets. There are no reports on aerosol delivery during high frequency jet ventilation (HFJV).

Objective: To compare delivery of aerosolized gadopentetate dimeglumine (Gd-DTPA) in 3 neonatal ventilator circuits: conventional mechanical ventilation, HFOV, and HFJV.

Methods: Aerosols of Gd-DTPA (0.025 mol/L) generated using a jet nebulizer placed in the inspiratory limb of each ventilator were delivered into an in vitro lung model simultaneously. Multi-slice T1-weighted spin-echo sequence scans were obtained prior to and after 10 and 20 min of cumulative aerosol delivery. Gd-DTPA concentration was calculated from signal intensity changes, and the total amount of Gd-DTPA was estimated.

Results: Gd-DTPA was visualized in the lung model at 10 and 20 min for all 3 ventilators. Gd-DTPA delivery was highest with conventional mechanical ventilation (1.92 μmol at 10 min, 2.89 μmol at 20 min), followed by HFJV (1.59 μmol at 10 min, 1.98 μmol at 20 min) and HFOV (0.79 μmol at 10 min, 1.00 μmol at 20 min).

Conclusions: This is the first report of effective aerosol delivery in a neonatal HFJV circuit. Future studies are needed for more accurate quantification of aerosol deposition.