Breath-Enhanced Jet Nebulizer for Continuous Infusion Aerosol Delivery During Mechanical Ventilation: In Vitro Comparison to Vibrating Mesh

Abstract

Background: Inhaled albuterol and prostacyclin continuous infusion aerosol delivery during mechanical ventilation (MV) evolved as a popular off-label treatment for refractory asthma and severe respiratory failure with pulmonary arterial hypertension and arterial hypoxemia. Initial protocols used a sidestream jet nebulizer (JN) and, more recently, a vibrating mesh nebulizer (VMN). Breath-enhanced (BE) JN has potential advantages. This study compared aerosol delivery of BEJN to VMN during continuous infusion. Methods: 4 samples of BEJN i-VENT (InspiRx, Somerset NJ) and VMN Solo (Aerogen, Galway Ireland) were used in rotation during testing. Using infusion pump flows between 1.5 - 12 mL/h, radiolabeled saline was infused into nebulizers during MV of a test lung. Four breathing patterns with 2 L/min bias flow, 5 cm H₂O PEEP and duty cycles (DC, % inspiratory time) ranging from 0.12 - 0.33 were tested. The VMN was placed on the dry (inlet) side of an F&P MR850 heated humidifier (run at 37°C to achieve temperature prior to all tests). The BEJN, placed on the wet (outlet) side, was operated by an air flow meter at 3.5 L/min. Test runs for each DC and humidifier placement were conducted for 1 h, after which radioactivity collected on a filter (Inhaled Mass, IM) at the test lung’s airway opening was measured by gamma scintigraphy and expressed as a percentage delivery rate of the radioactivity initially placed in the infusion syringe per hour (IM%/h). Humidifier retention of aerosol was also measured. Results: IM%/h vs infusion pump flow regression for VMN (y = 0.45x, R2 = 0.29) and BEJN (y = 0.61x, R2 = 0.93) showed greater scatter for VMN due to failures (Figure). At 10-12 mL/h, some VMNs did not keep pace with infusion rate, accumulated excess solution and failed to nebulize. Otherwise, IM%/h for both BEJN and VMN tended to plateau between 10-12 mL/h. The VMN dry side placement deposited 14.7%/h in the humidifier versus 0.2%/h for BEJN wet side placement. Conclusions: Our data demonstrate that continuous infusion aerosol delivery rate, IM%/h of the i-VENT breath-enhanced JN, which can be utilized for continuous albuterol and prostacyclin aerosol delivery during MV, is more consistent than VMN, suggesting that: (1) predictable dose delivery can be achieved with a breath-enhanced JN, (2) BEJN is more reliable than VMN, (3) 10 mL/h infusion flow is a practical maximum for both devices, and (4) BEJN avoids humidifier contamination.

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