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

Abstract

BACKGROUND: Aerosol and humidification therapy are used in long-term airway management of critically ill patients with a tracheostomy. The purpose of this study was to determine delivery efficiency of jet and mesh nebulizers combined with different humidification systems in a model of a spontaneously breathing tracheotomized adult with or without exhaled heated humidity. METHODS: An in vitro model was constructed to simulate a spontaneously breathing adult (tidal volume, 400 mL; breathing frequency, 20 breaths/min; inspiratory-expiratory ratio, 1:2) with a tracheostomy using a teaching manikin attached to a test lung through a collecting filter (Vital Signs Respirgard II). Exhaled heat and humidity were simulated using a cascade humidifier set to deliver 37°C and >95% relative humidity. Albuterol sulfate (2.5 mg/3 mL) was administered with a jet nebulizer (AirLife Misty Max) operated at 10 L/min and a mesh nebulizer (Aeroneb Solo) using a heated pass-over humidifier, unheated large volume humidifier both at 40 L/min output and heatand-moisture exchanger. Inhaled drug eluted from the filter was analyzed via spectrophotometry (276 nm). RESULTS: Delivery efficiency of the jet nebulizer was less than that of the mesh nebulizer under all conditions (P < .05). Aerosol delivery with each nebulizer was greatest on room air and lowest when heated humidifiers with higher flows were used. Exhaled humidity decreased drug delivery up to 44%. CONCLUSIONS: The jet nebulizer was less efficient than the mesh nebulizer in all conditions tested in this study. Aerosol deposition with each nebulizer was lowest with the heated humidifier with high flow. Exhaled humidity reduced inhaled dose of drug compared with a standard model with nonheated/nonhumidified exhalation. Further clinical research is warranted to understand the impact of exhaled humidity on aerosol drug delivery in spontaneously breathing patients with tracheostomy using different types of humidifiers.

Effects of Fill Volume and Humidification on Aerosol Delivery During Single-Limb Noninvasive Ventilation

“…Although the humidity change results were far different from most of the previously published in vitro studies, which recommend switching off the humidifier when delivering aerosol to ventilated patients, 9,19,20,[42][43][44][45] the results were very close to our previous findings of the effects of humidity change on aerosol delivery in auto-CPAP ventilated subjects 16 and invasively ventilated subjects. 21,22 This finding shows that there is no need to discomfort the patient by switching off the humidifier for aerosol delivery because the dry gas could potentially be harmful to the lung and the increase in delivered aerosol was insignificant.…”

Effects of Heat and Humidification on Aerosol Delivery during Auto-CPAP noninvasive Ventilation

“…Previous in-vitro studies recommended switching off the humidifi er for better delivery [8][9][10][11]. However, our results showed that the humidity had much less effect on aerosol delivery during Auto-CPAP NIV and those in-vitro studies over estimate the effect of humidity on aerosol delivery.…”

“…Most studies of humidifi cation effects on aerosol delivery were in-vitro and all of them recommend switching off the humidifi er while delivering aerosol to NIV patients for better delivery [5][6][7][8][9][10][11]. However, the undesirable effect of inhaled dry gas, e.g.…”

“…Humidifi cation of the ventilator circuit is one of the factors that were well studied for optimization of aerosol delivery in NIV patients [5][6][7][8][9][10][11]. Optimal humidifi cation of the inhaled gas could improve patient comfort, facilitate use of the mask, and improve bronchodilator effects in those requiring NIV [2].…”

Effect of Nebulizer Designs on Aerosol Delivery During Non-Invasive Mechanical Ventilation: A Modeling Study of In Vitro Data

“…Aerosol delivery in non-invasive ventilation (NIV) was proven to be of benefit and has been well studied [5,[7][8][9][10][11]. However, the effect of the change of design of nebulizers with the same mechanism on delivery has not been studied much.…”