Does Rate of Nebulization From a Vibrating Mesh Nebulizer During Continuous Nebulization Impact Driving Pressure During Mechanical Ventilation With Heliox?

Abstract

Background:

Continuous nebulization (CN) of the bronchodilator albuterol is often administered to ameliorate R_aw associated with status asthmaticus (SA) during mechanical ventilation (MV). The morphology effect of SA is bronchoconstriction which may increase driving pressures (DP) and cause suboptimal inhaled drug delivery. In vitro investigation with the vibrating mesh nebulization (VMN) Aerogen demonstrated that CN during MV is feasible. Helium/oxygen (heliox) in conjunction with MV has been used to treat respiratory acidosis and persistent hypercapnia associated with SA.¹ Previous study demonstrated that MV with heliox and CN had a positive impact on alveolar-arterial (A-a) gradient during treatment for SA.² Bias flow needed to power jet nebulizers may be problematic during MV. The aim of this study was to determine whether rate of nebulization during CN with a VMN would negatively impact DP during MV with heliox.

Methods:

A Servo-i ventilator equipped with heliox gas module was used for the study via lung model, high pressure gas lines were connected to a heliox G cylinder (80:20) and oxygen (1.0) source. Ventilator settings were: V_T 0.40 mL, VC-CMV 12 breaths/min, PEEP +8 cm H₂O, FIO₂ 0.40 oxygen equal heliox 60:40 ratio. Albuterol (0.5%) 20 mL was drawn up into a syringe that was attached to a syringe pump. Dose delivery on the syringe pump was programmed to administer 20 mg/h. The VMN was inserted on the dry side of the humidifier chamber and the control timer was set to continuous. The ventilator microprocessor monitored respiratory parameters; a 10% increase of measured values was considered undesirable.

Results:

Set delivery dose of 20 mg/h, was converted into a delivery volume of 4 mL/h, total rate of nebulization was 16 mL/h over 4h. Heliox+VMN+MV; expired V_T 0.40 mL ± 0.08, P_aw 22 cm H₂O ± 6, no auto-PEEP, breath stacking, or auto-cycling detected.

Conclusions:

Rate of nebulization output from the VMN and heliox did not grossly affect MV functionality. Therefore, did not subversively impact DP. Clinical investigation is needed to determine whether MV+heliox+CN via VMN can enhance inhaled drug delivery and impact clinical outcomes associated with SA. This study has several limitations, as other CN agents (eg, epoprostenol) have an alkaline (sticky) base that over time could inadvertently impact DP. Close monitoring of MV mechanics is prudent during any CN procedure. </br>References: 1. Gluck EH, et al. Chest 1990. 2. Schaeffer EM, et al. Crit Care Med 1999;27.