上呼吸道模型微粒沉積特性研究：CT掃瞄模型與真人比對測試

Characteristics of Aerosol Deposition in Human Upper Airway Casts Based on Computed Tomography: an in vivo Validation

了解微粒在呼吸道的沉積特性，不但有助於粒狀汙染物的暴露評估，對於呼吸道疾病的藥 物輸送效率設計也能提供有用的建議。上呼吸道模型是研究呼吸道微粒沉積效率常見的方法， 已被沿用多年，但是過去的研究證明上呼吸道模型能有效代表真人實際沉積情形的方式，均為 收集文獻中人體實驗的資料來互相比較，至今仍未有研究嘗試比較同一受試者之上呼吸道模型 與真人測試資料的差異。為了探討上呼吸道模型的研究結果是否能有效代表真人的沉積情形， 本研究找一名非吸菸的健康成年男性當受試者，以其電腦斷層掃描 (computed tomography, CT) 影像為基礎製作上呼吸道模型。CT影像諮詢專業的耳鼻喉科醫 師協助判斷，避免混淆鼻道與 鼻竇的範圍。使用超音波霧化器與定量輸出霧化器產生微米級與次微米級微粒。微粒經過射源 (25 mCi Am241)，使整個氣膠團帶電呈波茲曼平衡。使用氣動微粒分徑器（偵測粒徑範圍大於 0.7μm）和微粒電移動度掃瞄分徑器（偵測粒徑範圍小於 0.7μm）來量測上下游的微粒分佈與 濃度。真人量測鼻入口出沉積率時，次微米級微粒改用快速微粒電移動度粒徑分析儀量測。實 驗結果發現真人測試時，暫停呼吸的方式會顯著影響沉積率。上呼吸道模型的鼻入口出壓降與 沉積率均與真人測試的結果很相似。隨著抽氣流率增加，微米級微粒的沉積率也會增加，代表 微米級微粒的沉積機制是慣性衝擊。

Aerosol deposition efficiency in airway is useful for particle matter exposure assessment and inhaled drug delivery industry. Upper airway cast is a conventional method for airway deposition studies. The object of this study is to characterize the artificial cast deposition efficiency by comparing with in vivo measurements of the same subject. This study recruited a Taiwanese healthy male adult volunteer to take computed tomography (CT) scan, and the dimensions of the cast were referred to the CT scan images. For aerosol deposition test, a TSI constant output and an ultrasonic atomizing nozzle were used to generate submicro-meter-sized and micrometer-sized aerosols, respectively. The aerosol output was then neutralized by a radioactive source, 25 mCi Am241, to the Boltzmann charge equilibrium. A Scanning Mobility Particle Sizer (for particle < 0.7 μm) and an Aerosol Particle Sizer (for particles > 0.7 μm) were used to measure the aerosol concentration and size distribution upstream and downstream of the casts. A Fast Mobility Paticle Sizer was used to measure the aerosol deposition in the nasal cavity while the subjects held breaths. The breath holding maneuvers of the subject would affect aerosol depositions significantly. The nasal-in-mouth-out aerosol deposition through the cast correlated reasonably well with that through the same human subject. However, the CT scan image takes a well trained ENT doctor to correctly interpret. Otherwise, some of the sinus cavity might be treated as the air pathways. For micrometer-sized aerosols, the deposition efficiency in the casts increased with increasing sampling flow, indicating that inertial impaction was the dominating mechanism.