The Science Journal of the American Association for Respiratory Care

2011 OPEN FORUM Abstracts

FEASIBILITY OF THE USE OF A MICROPUMP DURING THE BIVENT/APRV MODE OF VENTILATION

Enrique Ortega2, Bob Demers1, Manny Banderas1; 1Resp Care Services, Methodist Hospital of Southern California, Arcadia, CA; 2School of Respiratory Therapy, Platt College, Ontario, CA

We are about to deploy the Solo® micropump nebulizer (Aerogen Ltd., Galway, Ireland) for ventilator patients at our hospital. On occasion, a patient whose ventilator circuit already incorporates the micropump will be placed on the BiVent (also called “Airway Pressure Release Ventilation” or “APRV”) mode. We wondered to what extent high BiVent pressures might adversely affect our ability to deliver medicated aerosol with the micropump. In fact, we thought it distinctly possible that gas might migrate retrograde across the micropump’s mesh transducer, rendering the delivery of an aerosolized drug impossible. To ascertain the effects of BiVent on our ability to administer aerosols, we employed a lung model which has been described elsewhere (http://web.me.com/bobdemers/DCS_Website/BiVent_APRV.html) to simulate BiVent at the following settings: PHIGH = 30 cm H2O; PLOW = 0 cm H2O; tHIGH = 4.0 sec; and tLOW = 0.3 sec, resulting in a mean pressure of 28 cm H2O. 3.0 mLs of water was instilled into the micropump, and the elapsed time required for the elaboration of this entire aliquot was observed to be 332 seconds. Next, we verified the elapsed time necessary to deliver a three-milliliter aliquot during ventilation of the lung model by means of Pressure-Regulated Volume-Controlled (PRVC) ventilation at a tidal volume of 500 mLs, a respiratory rate of 15/min, and a positive end-expiratory pressure (“PEEP”) setting of 5 cm H2O, resulting in a mean pressure of 12 cm H2O. The time required to generate the entire aliquot as an aerosol under these conditions was observed to be 321 seconds, a time duration which was merely 3% shorter than that seen with BiVent. Our bench tests indicate that the employment of the Aerogen Solo micropump to administer aerosolized agents to patients during BiVent can proceed in precisely the same fashion as applies to more conventional modes. Although these agents could presumably be delivered during BiVent by means of a metered-dose inhaler (MDI), the performance of the micropump during conventional ventilation has been reported to be vastly superior to that of the MDI (Am J Respir Crit Care Med 1999; 159: 63-68). Specifically, the dose of albuterol delivered to a lung model by means of the micropump in that study was shown to be more than six times the dose generated by means of an MDI coupled to a spacer. Consequently, we would prefer to use the micropump in lieu of an MDI for aerosol dosing during BiVent.
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