Effectiveness of Negative Pressure Booths in Mitigating Airborne Infection Risk During Transesophageal Echocardiography

Transesophageal echocardiography (TEE) is essential for cardiovascular imaging. However, it is considered an aerosol-generating procedure, posing a potential risk for airborne infection to health care workers.1Nicoara A. Maldonado Y. Kort S. et al.Specific considerations for the protection of patients and echocardiography service providers when performing perioperative or periprocedural transesophageal echocardiography during the 2019 novel coronavirus outbreak: council on perioperative echocardiography supplement to the statement of the American Society of Echocardiography Endorsed by the Society of Cardiovascular Anesthesiologists.J Am Soc Echocardiogr. 2020; 33: 666-669Abstract Full Text Full Text PDF PubMed Scopus (29) Google Scholar,2Kirkpatrick J.N. Swaminathan M. Adedipe A. et al.American Society of Echocardiography COVID-19 statement update: lessons learned and preparation for future pandemics.J Am Soc Echocardiogr. 2023; 36: 1127-1139Abstract Full Text Full Text PDF PubMed Scopus (0) Google Scholar Despite the importance of preventing airborne infections during TEE in the echocardiography laboratory, a standardized method has not yet been established.1Nicoara A. Maldonado Y. Kort S. et al.Specific considerations for the protection of patients and echocardiography service providers when performing perioperative or periprocedural transesophageal echocardiography during the 2019 novel coronavirus outbreak: council on perioperative echocardiography supplement to the statement of the American Society of Echocardiography Endorsed by the Society of Cardiovascular Anesthesiologists.J Am Soc Echocardiogr. 2020; 33: 666-669Abstract Full Text Full Text PDF PubMed Scopus (29) Google Scholar,2Kirkpatrick J.N. Swaminathan M. Adedipe A. et al.American Society of Echocardiography COVID-19 statement update: lessons learned and preparation for future pandemics.J Am Soc Echocardiogr. 2023; 36: 1127-1139Abstract Full Text Full Text PDF PubMed Scopus (0) Google Scholar Negative pressure booths with high-efficiency particulate air (HEPA) filters were widely used in medical settings during the COVID-19 pandemic, but there are no reports of their application during TEE. We aimed to evaluate the effectiveness of a negative pressure booth in reducing aerosol counts and controlling the risk for airborne infection associated with TEE. This study was conducted with the approval of the Medical Ethics Review Committee of the University of Tsukuba Hospital. Informed consent was obtained from all patients using an opt-out method on a website (https://www.md.tsukuba.ac.jp/clinical-med/cardiology/images/research_group/07/clinical_research/kenkyuu156.pdf). We installed a negative pressure booth (Cambridge Filter Corporation) in an echocardiography laboratory, with HEPA filters installed in the ceiling supply air port and the side wall exhaust port near the head of the examination bed (Figure 1A ). The booth meets the ventilation conditions recommended by the Centers for Disease Control and Prevention,3Sehulster L Chinn RYW Guidelines for environmental infection control in health-care facilities. Recommendations of CDC and the Healthcare Infection Control Practices Advisory Committee (HICPAC).MMWR Recomm Rep. 2003; 52: 1-42PubMed Google Scholar including maintaining ≥ 50 ft3/min exhaust air volume, a minimum of 12 air changes per hour, a negative pressure difference of 2.5 Pa between supply and exhaust air, and the use of a HEPA filter for air recirculation. The proper direction of airflow was confirmed by visualizing vapor and simulated cough aerosols using a laser light (Supplemental Video). Next, we used particle counters (Handheld 3016 IAQ, Lighthouse Worldwide Solutions) to quantify reductions in the number of ≥0.3-, ≥0.5-, and ≥1.0-μm aerosols in the booth under personnel-free ventilation. When the booth ventilation system was activated, the aerosol count at the TEE examiner's position significantly dropped after 3 min compared with when no ventilation was applied (Supplemental Figure). After 8 min, it had decreased to about 30% of the baseline value. Regarding the ventilation of the entire booth, Figure 1B illustrates that aerosols decreased more quickly near the head of the examination bed, which was closer to the exhaust port, and the removal rate reached 70% after 9 min of ventilation. Aerosol counts gradually decreased even at positions distant from the exhaust port, with 50% to 60% removed after 9 min of ventilation. Thus, aerosols were effectively removed throughout the booth. Subsequently, we prospectively investigated changes in aerosol counts at the positions of the examiner and assistant during TEE among 180 patients who underwent TEE for clinical indications. The cohort had a mean age of 67 ± 17 years, with 118 men (65.6%). The mean duration of TEE was 8 ± 4 min. The frequency of discomfort reflexes (coughing, sneezing, and gagging) during TEE for each patient was recorded every minute throughout the examination and averaged. Discomfort levels during TEE were graded as follows: ≤4 times/min, mild; 5 to 10 times/min, moderate; and >10 times/min, severe. Forty patients (22%) experienced severe discomfort. In accordance with the guidelines, physicians with <150 transesophageal echocardiographic examinations were defined as inexperienced,4Hahn R.T. Abraham T. Adams M.S. et al.Guidelines for performing a comprehensive transesophageal echocardiographic examination: recommendations from the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists.J Am Soc Echocardiogr. 2013; 26: 921-964Abstract Full Text Full Text PDF PubMed Scopus (908) Google Scholar and 56 subjects (31%) were examined by these physicians. Figure 2 illustrates that aerosol count at the position where the examiner faced the patient's mouth showed a transient increase immediately after the start of TEE, a change that was significant in the mixed-model analysis. However, about 8 min after the start of TEE, corresponding to the average examination duration, aerosol count reverted to baseline levels. There was no significant change in the number of aerosols at the position of the assistant operating the console of the echocardiographic machine behind the patient. Multiple regression analysis showed that inexperienced TEE examiners and patients' discomfort level during TEE were independent risk factors (β = 0.376 [P = .003] and β = 0.355 [P = .005], respectively) for increased aerosol levels during TEE, despite effective ventilation.Figure 2Changes in aerosol counts during TEE. (A) Top view of the standing positions of the examiner and assistant during TEE. (B) The change in the number of ≥0.3-μm aerosols per minute from 5 min before to 20 min after the start of TEE is shown. Mean and SD values at the examiner (red line) and assistant (blue line) positions are indicated by markers and error bars. The yellow square indicates the range of mean duration of TEE. P values are from a mixed-model analysis conducted to evaluate the temporal trends of the data for each group.View Large Image Figure ViewerDownload Hi-res image Download (PPT) This study had several limitations. First, the particle counter measured all atmospheric particles, including unrelated dust, not just patient-generated aerosols. Second, the transesophageal echocardiographic protocol was brief (8 min) because more than half of the cases involved checks for intracardiac thrombus in patients with atrial fibrillation. The booth's efficacy for longer transesophageal echocardiographic procedures should be confirmed in future studies. Third, the location of echocardiographic machines and the assistant's standing position might vary by institution, potentially affecting results. Finally, ethical constraints limited participants to those without COVID-19, hindering direct virus measurement. Thus, the effectiveness of negative pressure booths in reducing airborne infection spread remains uncertain. In conclusion, negative pressure booths regulate airflow around patients and TEE examiners, effectively decreasing the aerosols associated with TEE. This demonstrates the potential utility of negative pressure booths in mitigating airborne infections during TEE in future pandemic scenarios. However, future work will be required to understand whether they reduce transmission rates in patients with active infections. This work was supported by Ibaraki CIC Laboratory Co., Ltd. The funders were not involved in the analysis and interpretation of the data, the writing of the manuscript, or the decision to submit the manuscript for publication. eyJraWQiOiI4ZjUxYWNhY2IzYjhiNjNlNzFlYmIzYWFmYTU5NmZmYyIsImFsZyI6IlJTMjU2In0.eyJzdWIiOiJiOTliNjlkNTQxODMwZjc3ZGVhNjU3MTkxMWE2NTAwZiIsImtpZCI6IjhmNTFhY2FjYjNiOGI2M2U3MWViYjNhYWZhNTk2ZmZjIiwiZXhwIjoxNzIzNzIyMDUxfQ.bXWgMuEWDZeFZvAPesR3knrpaLtMY7i4LP_SLRVFcG3aPddesCYQDTJsQFjYClAzuiZf1z1gFr_Q0b_NrSRdjl9Cv0UfEKG-ez16lioUc5RKd3_GNtlUwU8bcuyVn-3WfSgJeF2Ghj7o-bn7LyP7mtQE_UEa1oSxULzCpXJFSuZLepYy6anYYJHCzZpKNSeZYkBL9eCi9he6iZwosJOomRpd82ENlltPBWTDxGoN-0RPaozKwWbXq295MOhewRQYzgpqUWM-HTO7RH1i9MGSlUVbOTo6FzgQBxv07CTqd-niYS3EV6IVFa7iAraF7hEDp4VN-qTqPc8YZb8CA1J2SQ Download .mp4 (4.67 MB) Help with .mp4 files Supplemental VideoVisualization of the flow of water vapor and simulated cough aerosols using a laser beam. The airflow within the red box in the left image was visualized by laser scattering. (A) The direction of airflow around the examination bed toward the exhaust port was confirmed by observing the movement of water vapor. (B) Simulated aerosols generated by the mannequin's cough were also observed moving toward the exhaust port. (C) Velocity vector image illustrates the trajectory of titanium particles simulating aerosols dispersed at high velocity through coughing.1