In Vitro Comparison of Inspiration Synchronized and Continuous Vibrating Mesh Nebulizer During Noninvasive Ventilation With a Dual Limb Circuit

Background: Aerosol delivery may be improved during noninvasive ventilation (NIV) with an inspiration-synchronized nebulizer by reducing the amount of medication lost during exhalation. This study aimed to compare aerosol delivery via a prototype of an inspiration-synchronized vibrating mesh nebulizer (VMN) during NIV with a dual limb circuit. Methods: An adult manikin was connected to a dual-chamber model lung that was driven by a ventilator to simulate spontaneous breathing (Figure 1). A ventilator (PB980, Medtronic) with a dual limb circuit was connected to the manikin via a full face mask, and NIV mode was used with △ pressure of 7 cm H2O and PEEP of 5 cm H2O. The nebulizer was compared at two positions (inlet of humidifier vs between mask and y-piece) with and without mask leak of 35–40 L/min. Two aerosol generation modes (inspiration-synchronized vs continuous) were compared, and a prototype VMN that generated aerosol particles 4 µm commercially available VMN (Solo, Aerogen). 1 mL of albuterol (2.5mg/mL) was used in each run (n = 5). The collection filter was placed between the manikin and the model lung and removed after each run. The drug was eluted from the filter and assayed with UV spectrophotometry (276 nm). Results: When inspiration-synchronized VMN was used, inhaled dose was greater with the nebulizer placed between the mask and y-piece than placed at the inlet of humidifier, regardless of nebulizer types and leak conditions (Table 1). However, no significant differences were found between placements with continuous VMN. When the nebulizer was placed between the mask and y-piece, the inhaled dose was greater with inspiration-synchronized than continuous aerosol generation (all P < .05), regardless of nebulizer types and leak conditions. However, when the nebulizer was placed at the inlet of the humidifier, the inhaled dose was greater with continuous than inspiration-synchronized aerosol generation when a leak was present (all P < .05). Leak reduced the inhaled dose with inspiration-synchronized VMN, regardless of the nebulizer types or placements (all P < .05). However, leak improved the inhaled dose with continuous VMN, except when VMN Solo was placed at the inlet of the humidifier. Conclusions: During NIV with a dual limb circuit, the optimal inhaled dose can be achieved with an inspiration-synchronized VMN placed between the mask and y-piece without mask leak. A prototype VMN that generated smaller aerosol particles can improve inhaled dose by 1/4 - 1/3.Comparison of aerosol delivery via inspiration-synchronized vs continuous vibrating mesh nebulizers at different nebulizer positionsNebulizer TypePlacementMask LeakInhaled Dose of Different Aerosol Generation Modes (%)P-Value Inspiration-SychronizedContinuous Prototype VMN (Small Particle)Inlet of HumidifierNo Leak6.77 ± 2.68.26 ± 0.50.602Leak2.42 ± 1.0610.24 ± 0.680.009p-value0.0160.009 Between Mask and Y-PieceNo Leak26.69 ± 2.611.26 ± 1.120.009Leak21.57 ± 1.314.71 ± 1.60.009p-value0.0090.009 VMN SoloInlet of HumidifierNo Leak7.03 ± 1.147.83 ± 0.880.295Leak3.53 ± 0.578.54 ± 0.780.009p-value0.0090.117 Between Mask and Y-PieceNo Leak20.63 ± 1.458.13 ± 0.390.009Leak15.21 ± 1.029.93 ± 0.870.009p-value0.0090.009 Figure 1. Experiment Set-Up. A ventilator with a dual limb circuit was connected to the manikin via a full face mask. An NIV mode was used to deliver a delta pressure of 7 cm H2O and PEEP of 5 cm H2O. The manikin was connected to a dual-chamber lung model that was driven by a critical care ventilator to simulate spontaneous breathing. The vibrating mesh nebulizer (VMN) was compared at the inlet of humidifier vs between mask and exhalation valve with and without mask leak of 35 – 40 L/min.