Abstract
Background:
Previous publications have identified the risk of ventilator malfunction when aerosolized medications are deposited upon exhalation filters or valve assemblies1. Our policy based on prior testing with the Hudson RCI Isogard HEPA Lite filter was to change the filters Q2 hours during epoprostenol delivery. To determine if the frequency of change for added expiratory filters could be reduced, we tested 4 commercially available filters with large surface areas during the delivery of inhaled epoprostenol to a test lung.
Methods:
The test consisted of monitoring each of the following HEPA filters for 24 h on 2 different days with a different minute ventilation and filter each day. (See table) The filters tested were the CareFusion Airlife, Hudson RCI 2605, DAR Sterivent, and PALL BB50. The same PB 980 ventilator was used for all testing with the circuit changed and ventilator processed between testing of each filter type. A Teleflex dual heated wire circuit and Hudson RCI Neptune heated humidifier set per departmental standard were used for each testing sequence. Epoprostenol (Flolan), at a concentration of 1.5 g/50 mL with original diluent producing a pH of 10.2 — 10.8, was continuously nebulized via an Aerogen Solo nebulizer at a rate of 10 mL/hour. The nebulizer was positioned on the proximal or dry side of the humidifier chamber. The epoprostenol syringe was replaced Q5 hours to ensure continuous delivery of medication.
Results:
No significant changes in exhaled tidal volume or minute ventilation were observed over the 24 h monitoring period. The CareFusion Airlife produced lower exhaled volumes on Day 1 as compared to the other models and the volumes remained consistently low throughout the day. In addition, no occlusion alarms occurred during testing of any filter.
Conclusions:
During testing of 4 different HEPA filters added to the expiratory circuit during continuous inhaled epoprostenol delivery, no significant change in exhaled volumes or occlusion alarms occurred within the 24 h monitoring period. A reduction in the HEPA filter change frequency to Q24 h will save approximately $6,500 annually. More importantly, the frequency at which the circuit must be disconnected causing a loss of circuit pressure can be significantly reduced thus lessening the risk of ventilator associated events (VAE) 2. In an abundance of caution, and until further testing can occur, we have elected to change the HEPA filters Q12 h.
Exhaled Tidal Volumes (mL) During Expiratory Filter Testing
PALL
DAR
RCI
Carefusion
Day 1: AC/PC, f 30, Pinsp 15, PEEP 5
422.7 +/- 9.5
412.9 +/- 4.6
416.1 +/- 34.1
240.6 +/- 5.9
Day 2: AC/PC, f 15, Pinsp 20, PEEP 5
548.5 +/- 4.7
541.9 +/- 5.1
550.3 +/- 4.2
580.3 +/- 10.5
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