Face Mask Leak Determines Aerosol Delivery in Noninvasive Ventilation

Abstract

Background: Aerosol transport during non-invasive positive pressure ventilation (NIV) follows the flow of pressurized gas through the NIV circuit, vented via leak port and face mask, and inhaled by the patient. Recommendations for nebulizer placement are based on in vitro models that have focused primarily on aerosol losses via the leak port; face mask leaks have been avoided. The present study tested aerosol delivery in the setting of controlled face mask leak.

Methods: Three nebulizer technologies (Aerogen Solo, Aerogen, Galway Ireland; i-AIRE, InspiRx, Somerset NJ; and Hudson MicroMist, Teleflex Medical, Morrisville NC) were studied on a bench model using a lung simulator with a face mask placed onto a manikin head. Radiolabeled aerosol delivery (Inhaled Mass, IM) was determined by mass balance using filters and a gamma camera; testing effects of nebulizer location and face mask leak. Low (15-20 L/min) and high (55-60 L/min) mask leaks were used to mimic realistic clinical conditions.

Results: IM (% nebulizer charge) was a function of nebulizer technology (with nebulizer at ventilator outlet position: Aerogen 22.8%, InspiRx 11.1%, and Hudson 8.1%, P = .001). Location of the nebulizer before or after the leak port was not important (P > .99). Aerosol delivery was minimal with high mask leak (IM 1.5-7.0%). Aerosol losses at the leak port at low mask leak were 28-36% vs 9-24% at high mask leak. Aerosol losses via the mask leak were16-20% at low mask leak vs 46-72% at high mask leak. Furthermore, high face mask leak led to significant deposition on the mask and face, up to 50% of nebulizer charge with Aerogen.

Conclusions: During NIV, nebulizer placement at the ventilator outlet, a more practical position, is effective and minimizes deposition on face and mask. Aerosol therapy during high face mask leak should be avoided.

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Experimental Set-up