The Science Journal of the American Association for Respiratory Care

2010 OPEN FORUM Abstracts


Hsin-Chun Liu1, Lan-Ti Chou1, Hsiu-Feng Hsiao1, Kuo-Chin Kao1,2, Gwo-Hwa Wan3, Chung-Chi Huang2,3; 1Department of Respiratory Therapy, Chang Gung Memorial Hospital, Taipei, Taiwan; 2Department of Thoracic Medicine, Chang Gung Memorial Hospital, Taipei, Taiwan; 3Department of Respiratory Care, Chang Gung University, Taipei, Taiwan

Background: Constant output nebulizer wastes aerosols during expiration phase. Furthermore, with it placed in the mechanical ventilator circuit, the waste aerosolized particles maybe capture by the bacterial filter on the expiratory limb end of the ventilator. The captured particles may increase the resistance of the filter, which may restrict patient’s breathing pattern. The purpose of this study was to determine the bacterial filter resistance change through time when mucolytic agents are administered via constant output nebulizer. Methods: 7 pleated hydrophobic filters were tested, 5 of them for collecting waste aerosol particles from a mucolytic agent, 10% Acetylcysteine, and 2 of them form 2% hypertonic saline. A ventilator (Galileo; Hamilton Medical, Switzerland) with a lung model was used within the followings: VT of 0.6L, frequency of 12 b/min, inspiratory times of 1 second, PEEP of 5 cmH2O, and inspiratory flow rate of 54 L/min with descending ramp pattern. The inhaled agents with constant output nebulizer were administered every 45 minutes. Each pressure drop was measured at 5, 15 and 30 minute after 15 minutes of nebulization. Pressure drop was measured against an air flow at 100 L/min by a flow analyzer (PF 300, imtmedical, Europe, Switzerland) before and after each test. The end point was 45 doses through nebulizer or when the filter was obstructed measured by the ventilator. The pressure drop after steam autoclaving was also measured. Median values were compared with Kruskal-Wallis, Mann-Whitney U, and Wilcoxon Signed Rank test; p < 0.05 considered significant. Results: The pressure drop of all 7 of the filters were increased after inhalation (9.95 ± 12.67 and 2.7 ± 0.58 cmH2O, respectively; p < 0.001). However, only 10% Acetylcysteine yielded a significant difference in the pressure drop before and after test (p < 0.05). It was also observed that after steam autoclaving, the pressure drop of all 7 of the filters were decreased, but could not return to the recommended safe value (< 4 cmH2O at 100L/min), as the filter was already been obstructed by the particles (p < 0.05). Conclusion: 10% Acetylcysteine aerosol particles increase the resistance of the bacterial filter during mechanical ventilation. The bacterial filter on exhaled limb should be replaced periodically, when 10% Acetylcysteine is regularly prescribed to prevent secondary effects that would harm the patients. Sponsored Research - None