呼吸回饋式個人呼出微粒捕集氣罩研發與測試

Abstract

氣膠傳播(Aerosol transmission)為呼吸道傳染疾病包含嚴重特殊傳染性肺炎(COVID-19)主要之傳播途徑。病毒附著於氣膠微粒表面，隨染疫者之呼吸活動如呼吸、咳嗽、打噴嚏等傳播至環境中。健康個體因吸入或接觸後食入含有病毒之氣膠微粒而被感染。目前針對氣膠微粒的危害控制方式主要為將染疫者隔離、拉長社交距離以及佩戴個人防護具。分別為源頭控制、傳播途徑控制及接收者控制。其中又以源頭控制效益最大，因微粒剛生成濃度較高，須處理的體積較小，移除效益最高。而目前源頭控制最常使用的方式為佩戴口罩，佩戴口罩雖對粒徑大之微粒捕集效能佳。然而，一般情形下口罩多被用於保護健康個體，此時口罩須過濾之微粒粒徑較小，此情形下口罩與臉部之密合度將成關鍵，且隨佩戴過濾級數越高尤其重要。在2022年已有研究團隊研發出一款個人呼出微粒捕集器(Personal Exhaled Breath Aerosol Receiver, PEBAR)，透過風扇及濾材，將人體呼出微粒過濾後排回環境中，在一定的使用範圍內能不受面體佩戴密合度之影響。然而PEBAR實際運作時可能使佩戴者吸氣負擔、眼睛黏膜乾澀或是濾材及電池使用週期短等問題可進行改善。因此，本研究將以PEBAR作為雛形，加入呼吸回饋功能，使風扇之抽氣流量能隨佩戴者不同呼吸型態而變動，風扇於佩戴者吸氣時減少抽氣量、於呼氣時增加抽氣量，且以維持面體內最小負壓值為最終目標。如此不僅能減輕佩戴者吸氣負擔，延長濾材及電池的使用週期。

呼吸回饋功能之個人呼出微粒捕集氣罩(Breath-Responsive Personal Exhaled Breath Aerosol Receiver, BR-PEBAR)之運作受各元件影響，因此研究中針對壓力感測元件、抽氣管、濾材、抽氣扇及回饋程式等建立量測系統，評估各元件及參數之性能對BR-PEBAR帶來的影響，並挑選最能發揮BR-PEBAR運作效能之種類及參數。經過各項參數測試後，針對BR-PEBAR之捕集效率、能源消耗及噪音產生量進行評估。在進氣孔面積為1 cm2的情形下，BR-PEBAR最大能於呼吸流量每分鐘32 L情形下，維持捕集效率大於99.99%。此外，於一般成人呼吸流量12-15 L/min下BR-PEBAR所耗能量為100 watt/min。噪音峰值落在65-70 dB間。另外經測試瞭解，設有預存空間之面體能用於更高之呼吸流量。在未來，若想增加BR-PEBAR使用範圍，除擴大預存空間增加氣體滯留空間，增加抽氣流量如改變風扇扇葉構型及降低系統阻抗如移除抽氣管等方式亦能有效提高抽氣流量。使用時間則可藉由增加電池組數或挑選容量較大之種類，以延長BR-PEBAR運作時間。

最後是BR-PEBAR的輕量化設計，本研究所研發之BR-PEBAR為風機與濾材整合為一透過腰帶固定，並以抽氣管連接至面體。對需要長時間佩戴之個體將成負擔，可能導致其行動受限，因此未來可參考市面上直結式呼吸防護具設計，將面體、風扇及濾材三者合而為一，並盡可能減輕重量，透過頭帶固定，使BR-PEBAR應用之情境更加靈活，如無塵室、空間較狹窄之環境等。

Aerosol transmission has emerged as a primary mode of respiratory infectious disease, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In this situation, viruses attach to aerosol particles expelled during respiratory activities such as breathing, coughing, and sneezing, spreading into the environment. Healthy individuals are susceptible to infection through inhalation or ingestion of virus-containing aerosol particles after exposure. Currently, strategies for aerosol particle control involve a negative pressure isolation ward, maintaining social distancing, using personal protective equipment, focusing on source control, transmission pathway control, and recipient control. Source control, particularly through the timely removal of generated particles, has proven most effective in minimizing exposure.

To address this problem, face masks are commonly used for source control, effectively capturing larger particles (environmental protection). However, in scenarios where masks are worn for personal protection, the filtration of smaller particle sizes becomes critical, emphasizing the importance of a secure mask fit, especially with higher filtration levels. A recent development, the Personal Exhaled Breath Aerosol Receiver (PEBAR), utilizes a constant suction flow rate and filter to capture exhaled particles, demonstrating effectiveness within a specific range and regardless of the face seal. Nevertheless, operational challenges such as increased respiratory burden, dry eyes, and short filter and battery lifespans.

This study introduces the concept of a Breath-Responsive Personal Exhaled Breath Aerosol Receiver (BR-PEBAR) by breath-responsive feedback system. This innovation allows the fan''s suction flow rate to adjust based on the wearer''s different breathing patterns, reducing suction during inhalation and increasing it during exhalation to maintain minimal negative pressure within the mask that we set. This not only reduce the wearer''s respiratory burden but also extends the lifespan of filters and batteries.

The operation of BR-PEBAR is influenced by various components, including pressure sensors, connecting tubes, filters, suction fans, and a breath-responsive feedback system. A comprehensive measurement system was established to assess the performance of each component and parameter, selecting those that optimize the operation of BR-PEBAR. Performance testing included capture efficiency, energy consumption, and noise level. Under conditions of a 1 cm² intake area, BR-PEBAR achieved a capture efficiency exceeding 99.99% when breathing flow rate under 32 L/min. Energy consumption was measured at 100 watts/min for adult breathing flow rates of 12-15 L/min, with a noise peak ranging from 65-70 dB. Additionally, the addition of reservoir space in the facepiece was found to broaden the BR-PEBAR usage range.

For future enhancements and expanded usability, increasing the storage space, increasing suction flow rates by altering fan blade configurations, and reducing system requirements by removing the connecting tube are recommended. The use time can be extended by installing more batteries or selecting higher-capacity batteries.

Finally, a conceptual lightweight design for BR-PEBAR is proposed. Recognizing the potential burden for prolonged wear, future designs may draw inspiration from direct-connected respiratory protective devices available in the market, combining the face mask, fan, and filter into a single unit, minimizing weight and offering flexibility through headband fixation. This design could find more applications in environments, such as cleanrooms or narrow spaces.