Exhaled air leakage during manual ventilation by healthcare workers with different levels of experience

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Background: Intubation & manual ventilation (MV) before intubation were aerosol-generating procedures that increased the risk of nosocomial transmission of SARS in 2003. Aims: We examined the exhaled air dispersion during MV of a human patient simulator(HPS) by different groups of healthcare workers in a negative pressure isolation room with 12 air changes/hr. Methods: 5 of each group of intensivists/anaesthetists, medical officers, nurses & medical students performed MV with common resuscitator bags.The HPS was programmed to mimic different severity of lung injury. Airflow was marked with intrapulmonary smoke for visualization. A leakage jet plume was revealed by a laser light-sheet and images captured by video. Normalized exhaled air concentration in the plume was estimated from the light scattered by the smoke particles. Results: Intensivists/anaesthetists demonstrated the best performance in preventing excessive exhaled air leakage through the mask interface during MV. When using the Laerdal resuscitator, the intensivists /anaesthetists demonstrated exhaled air dispersion distance of 161mm, which was 43% less than that performed by the nurses. Leakage of exhaled air was observed at the interface between the face mask and face in all cases ranging from 128 to 267mm in the transverse plane. Addition of a viral-bacterial filter was effective in reducing the spread of expired smoke from the Ambu resuscitator. Conclusion: Experience and skills in ensuring good mask fit are important in preventing excessive exhaled air leakage through the mask interface during manual ventilation apart from adding a viral-bacterial filter. Funded by the HMRF (#12110392), Food & Health Bureau, HK.

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