Jiang Jianbo, Zhao Kai
Monell Chemical Senses Center, Philadelphia, PA 19104.
J Aerosol Sci. 2010 Nov 1;41(11):1030-1043. doi: 10.1016/j.jaerosci.2010.06.005.
Accurate prediction of nanoparticle (1100 nm) deposition in the rat nasal cavity is important for assessing the toxicological impact of inhaled nanoparticles as well as for potential therapeutic applications. A quasi-steady assumption has been widely adopted in the past investigations on this topic, yet the validity of such simplification under various breathing and sniffing conditions has not been carefully examined. In this study, both steady and unsteady computational fluid dynamics (CFD) simulations were conducted in a published rat nasal model under various physiologically realistic breathing and sniffing flow rates. The transient airflow structures, nanoparticle transport and deposition patterns in the whole nasal cavity and the olfactory region were investigated and compared with steady state simulation of equivalent flow rate. The results showed that (1) the quasi-steady flow assumption for cyclic flow was valid for over 70% of the cycle period during all simulated breathing and sniffing conditions in the rat nasal cavity, or the unsteady effect was only significant during the transition between the respiratory phases; (2) yet the quasi-steady assumption for nanoparticle transport was not valid, except in the vicinity of peak respiration. In general, the total deposition efficiency of nanoparticle during cyclic breathing would be lower than that of steady state due to the unsteady effect on particle transport and deposition, and further decreased with the increase of particle size, sniffing frequency, and flow rate. In the contrary, previous study indicated that for micro-scale particles (0.54μm), the unsteady effect would increase deposition efficiencies in rat nasal cavity. Combined, these results suggest that the quasi-steady assumption of nasal particle transport during cycling breathing should be used with caution for an accurate assessment of the toxicological and therapeutic impact of particle inhalation. Empirical equations and effective steady state approximation derived in this study are thus valuable to estimate such unsteady effects in future applications.
准确预测纳米颗粒（1100纳米）在大鼠鼻腔中的沉积，对于评估吸入纳米颗粒的毒理学影响以及潜在的治疗应用至关重要。过去关于该主题的研究广泛采用了准稳态假设，但尚未仔细研究这种简化在各种呼吸和嗅吸条件下的有效性。在本研究中，在已发表的大鼠鼻腔模型中，针对各种生理现实的呼吸和嗅吸流速进行了稳态和非稳态计算流体动力学（CFD）模拟。研究了整个鼻腔和嗅觉区域的瞬态气流结构、纳米颗粒传输和沉积模式，并与等效流速的稳态模拟进行了比较。结果表明：（1）在大鼠鼻腔所有模拟的呼吸和嗅吸条件下，循环气流的准稳态流动假设在超过70%的周期内是有效的，或者非稳态效应仅在呼吸阶段之间的过渡期间显著；（2）然而，纳米颗粒传输的准稳态假设无效，除了在呼吸峰值附近。一般来说，由于对颗粒传输和沉积的非稳态影响，循环呼吸期间纳米颗粒的总沉积效率将低于稳态，并且随着颗粒尺寸、嗅吸频率和流速的增加而进一步降低。相反，先前的研究表明，对于微米级颗粒（0.54μm），非稳态效应会增加大鼠鼻腔中的沉积效率。综合来看，这些结果表明，在循环呼吸期间，对于鼻腔颗粒传输的准稳态假设应谨慎使用，以准确评估颗粒吸入的毒理学和治疗影响。因此，本研究中推导的经验方程和有效的稳态近似对于估计未来应用中的这种非稳态效应具有重要价值。
