Quantifying Aerosol Delivery in Spontaneously Breathing Patients With Tracheostomy Using Different Humidification Systems With or Without Exhaled Humidity

Abstract

PURPOSE: Aerosol and humidification therapy are used in long-term airway management of critically ill patients with tracheostomy. The purpose of this study was to determine delivery efficiency of jet (JN) and mesh (MN) nebulizers combined with various humidification systems in a spontaneously breathing adult lung model with tracheostomy with or without exhaled humidity. METHODS: An in-vitro model was constructed to simulate spontaneously breathing adults (Vt: 400 mL, RR:20 bpm, and I:E ratio 1:2) with tracheostomy using a teaching manikin attached to a test lung through a collecting filter (Respirgard II, Vital Signs). Exhaled heat and humidity was simulated using a cascade humidifier set to deliver 37 °C and >95% relative humidity. Albuterol sulfate (2.5mg/3mL) was administered through JN (Misty Max, Airlife) and MN (Aeroneb Solo, Aerogen) using heated humidifier (HH), unheated large volume humidifier (LVH) at 40 lpm output and heat-moisture exchanger (HME). Inhaled drug was collected on a filter during each experiment and analyzed via spectrophotometry (276 nm). RESULTS: Percentage of dose (mean ± SD ) delivered distal to the trachea with JN (from 1.4 to 6.6%) and was less than MN ( 2.1 - 17.7%) under all conditions (p<0.05). Independent of nebulizer used, delivery was greatest in room air and lowest when HH with higher flows. Exhaled humidity decreased drug delivery up to 40%. CONCLUSIONS: Use of supplemental gas flow during aerosol can reduce inhaled dose with both JN and MN. This model simulating exhaled humidity demonstrated a reduction in drug delivery compared to models with nonheated/humidified exhalation.