Professor of Medicine Stony Brook University, United States
Introduction: After intubation, patients with hypoxic respiratory failure are often treated by continuous nebulization of vasodilators/bronchodilators. Nasal aerosol delivery during HFNC therapy may be an alternative therapeutic approach before intubation. Aerosol delivery using conventional nebulizers with fixed maximal output rates is limited and unpredictable under high flow conditions. This study measured regulated aerosol delivery to the lungs of normal volunteers using a nebulizer designed to overcome the limitations of HFNC therapy. The i-AIRE (InspiRx, Inc), a breath-enhanced jet nebulizer that, in series with the high flow catheter, utilizes the high flow through the nebulizer to increase aerosol output beyond that of conventional devices.
Methods: Nine normal subjects breathing tidally via the nose received HFNC humidified air at 60L/min. The breath enhanced nebulizer was connected to the HFNC system upstream to the humidifier and received radiolabeled saline as a marker for drug delivery (99mTc DTPA) infused by syringe pump (mCi/min). Dose to the subject was regulated at 12, 20, and 50mL/hr. Rates of aerosol deposition in the lungs (µCi/min) were measured via gamma camera for each infusion rate and converted to µgm NaCl/min.
Results: Subjects tolerated nebulization without complaint. Deposition rate, as expressed as µgm of NaCl/min, was closely related to infusion rate: 7.84±3.15 at 12ml/hr, 43.0±11.8 at 20ml/hr, and 136±45.3 at 50ml/hr. Deposition efficiency ranged from 0.44 to 1.82% of infused saline, with 6% deposited in the nose. Regional analysis indicated peripheral deposition of aerosol (central/peripheral ratio 1.04±0.31). Data were independent of breathing frequency.
Conclusions: Breath-enhanced nebulization via HFNC reliably and predictably delivered a wide range of aerosolized surrogate medication to the lungs by simply regulating the infusion rate. Clinical trials can be designed to provide lung dosing in the sickest patients requiring maximal high flow oxygen therapy by titrating the dose to the response at the bedside.
