Effective aerosol delivery during high-frequency ventilation in neonatal pigs
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BACKGROUND AND OBJECTIVE: Pulmonary delivery of aerosols during high-frequency oscillatory ventilation (HFOV) has not been studied in vivo. This study investigated the pulmonary delivery of aerosolized gadopentetate dimeglumine (Gd-DTPA) in a HFOV circuit in piglets using MRI to visualize contrast excretion in the kidneys. METHODS: Four ventilated piglets (3-7 days old, 1.7-2.4 kg at birth) received aerosolized Gd-DTPA in a HFOV circuit for different durations of time (60, 30, 20 and 10 min). Aerosols were generated using the MiniHeart jet nebulizer. As MR-compatible HFOV was not available, aerosolized Gd-DTPA was administered in the HFOV circuit outside the MR suite followed by MRI 10-20 min later. T1-weighted spin echo sequences were obtained using the Bruker/Siemens 4T MR scanner. RESULTS: Enhancement of the kidneys was observed 10 min after aerosol initiation in piglets who received Gd-DTPA aerosol for 60, 30 and 20 min in the HFOV circuit but not in the piglet who received aerosol for 10 min. Renal concentration of Gd-DTPA, determined from the signal intensity, increased linearly with time until 40 min post Gd-DTPA delivery. CONCLUSIONS: Effective pulmonary aerosol delivery during HFOV was confirmed by contrast visualization in the kidneys within 30 min of aerosol initiation reflecting, alveolar absorption, glomerular filtration and renal concentration.
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