Secondhand aerosol exposure during mechanical ventilation with and without expiratory filters: An in-vitro study

Abstract

Background: Concerns have been expressed about risk of exposure to exhaled aerosols to ICU personnel. AIM: To quantify amount of aerosol collected at the exhaust outlet of mechanical ventilators operated with and without filters in the expiratory limb. Methods: Two categories of ventilators were tested: (1) Ventilators without Proprietary Filters: Servo-i (Maquet) and Galileo (Hamilton) and (2) Ventilator with proprietary filters: PB 840 (Covidien). Each ventilator was attached to a simple test lung and operated with VT 500 ml, RR 20 bpm, PIF 50 L/min, PEEP 5 cmH2O. Four separate doses of albuterol (2.5 mg/3mL) were administered via jet nebuliser (eValueMed, Tri-anim) placed at the “Y”. In Experiment A, a filter (Respirgard 303) was placed at the exhaust port. In Experiment B, two filters were attached to the ventilators without proprietary filters: (1) at the end of expiratory limb and (2) at the exhaust outlet. Drug was eluted from filters and measured using spectrophotometry. Results: Drug deposited at the exhaust port without expiratory filtering was >160 fold higher than with expiratory filtering. The collecting filter used in this study was less efficient than the proprietary filter designed for use with the ventilator. Regardless of type of filter used, placement of filter in the expiratory limb reduced secondhand aerosol exposure significantly. Conclusion: Risk of secondhand exposure to exhaled aerosol can account for >45% of nominal dose as well as droplet nuclei produced by patients. Using expiratory filters decreases risk of exposure to aerosol released to the atmosphere during mechanical ventilation.