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

Background:

Aerosol delivery may be improved during noninvasive ventilation (NIV) with an inspiration-synchronized nebulizer by reducing the medication lost during exhalation. This study aimed to compare aerosol delivery via a prototype of an inspiration-synchronized vibrating mesh nebulizer (VMN) with continuous VMN during NIV with a single limb circuit.

Methods:

An adult manikin was connected to a dual-chamber model lung that was driven by a critical care ventilator to simulate spontaneous breathing (Figure 1). An NIV ventilator (V60, Respironics) was connected to the manikin with a single limb circuit and with settings of 12/5 cm H₂O. The nebulizer was compared at two positions in the circuit (inlet of humidifier vs between mask and exhalation valve) with mask leak of 35 – 40 L/min and without mask leak. Two aerosol generation modes (inspiration-synchronized vs continuous) of VMN were compared, and a prototype VMN that generated aerosol particles < 3 µm was compared to a > 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. The drug was eluted from the filter and assayed with UV spectrophotometry (276 nm).

Results:

The inhaled dose was greater with inspiration-synchronized than continuous aerosol generation, regardless of the nebulizer type, placement, and leak conditions (Table 1). When the nebulizer was placed between the mask and the exhalation valve, the inhaled dose was higher than that with the nebulizer placed at the inlet of the humidifier, regardless of the nebulizer type, aerosol generation modes, and leak conditions. The prototype VMN (small particle) had a greater inhaled dose than VMN (Solo) only when inspiration-synchronized nebulizer was placed between the mask and exhalation valve with a leak (18.05 ± 0 .75 vs 13.63 ± 0.45%, P = .008) and when continuous VMN was placed at the inlet of the humidifier with no leak (7.28 ± 0.29 vs 5.43 ± 1.04%, P = .009).

Conclusions:

During aerosol delivery via NIV with a single limb circuit using a VMN, the inhaled dose was greater with inspiration-synchronized VMN than continuous VMN with nebulizer placed between the mask and exhalation valve, regardless of nebulizer types and leak conditions. At that position, smaller particles improved inhaled dose during leak.

Comparison of aerosol delivery via inspiration-synchronized vs continuous vibrating mesh nebulizers at different nebulizer positions

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Figure 1. Experiment Set-Up. An NIV ventilator was connected to the manikin with a single limb circuit and parameters were set to deliver 12/5 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 two positions in the circuit (inlet of humidifier vs between mask and exhalation valve) with mask leak of 35 – 40 L/min and without mask leak.