PT  - JOURNAL ARTICLE
AU  - Janice A Lee
AU  - Michael McPeck
AU  - Ann D Cuccia
AU  - Gerald C Smaldone
TI  - Aerosol Delivery via Nebulization From the Dry Side of a Heated Humidifier During Mechanical Ventilation
DP  - 2021 Oct 01
TA  - Respiratory Care
PG  - 3606676
VI  - 66
IP  - Suppl 10
4099  - http://rc.rcjournal.com/content/66/Suppl_10/3606676.short
4100  - http://rc.rcjournal.com/content/66/Suppl_10/3606676.full
AB  - Background: Previous work measured aerosol delivery for i-AIRE, a prototype inline breath-enhanced jet nebulizer (BEJN) located on the wet/outlet of the humidifier. Recent observations reported that placement of single-patient-use nebulizers in this location results in excess condensation in the inspiratory limb and nebulizer flooding. The present study tested i-AIRE in vitro compared to Solo, a vibrating mesh nebulizer (VMN) on the humidifier dry/inlet side of the ventilator circuit during continuous and bolus treatment nebulization. Methods: Two adult duty cycle (DC) breathing patterns were tested during continuous infusion (5 or 10 mL/h) with and without dynamic changes in infusion rate and DC, or bolus delivery (3 or 6 mL) of radiolabeled saline. Inhaled mass (IM) reported as a function of time was measured in real-time using a gamma ratemeter (µCi/min) and analyzed by multiple linear regression. Expiratory losses (EXP) were measured and reported as the IM:EXP ratio. Results: During simple continuous infusion, IM increased linearly for both nebulizer types. IM variability was attributable to DC (P < 0.001, 34%) and infusion flow (P < 0.001, 32%), but independent of nebulizer technology (P = 0.381, 7%). Dynamic continuous infusion studies mimicking clinical scenarios with ventilator and pump flow changes demonstrated a linear increase in the rate of aerosol that was dependent on pump flow (P < 0.01, 63%) and was minimally dependent on duty cycle (P = 0.03, 8%). During bolus treatments, IM increased linearly to plateau. IM variability was attributable to DC (P < 0.001, 40%) and residual nebulizer volume (P < 0.001, 20%). Separate analysis revealed VMN residual volume contributing 16% of the variability and BEJN 5%. IM variability was independent of bolus volume (P = 0.82, 1%). System losses were similar (BEJN: 32% residual in nebulizer; VMN: 34% in circuitry). IM:EXP ratio was approximately 10 times greater than predicted by the ventilator DC for both nebulizer types during bolus and continuous infusion. Conclusions: Aerosol delivery during continuous infusion and bolus delivery is comparable between the BEJN and VMN and determined by pump flow and initial ventilator settings. Once treatment is initiated, further adjustments in ventilator settings did not significantly affect drug delivery. Furthermore, placement of the nebulizer on the humidifier dry-side allows for a greater inhaled mass-to-expiratory loss ratio than predicted by ventilator DC.