Alterations in nasal airflow and air conditioning after endoscopic nasopharyngectomy for recurrent nasopharyngeal carcinoma: a pilot computational fluid dynamics study

Endoscopic nasopharyngectomy represents a significant intervention for recurrent nasopharyngeal carcinoma (NPC). Various surgical techniques, including transnasal and transoral approaches, are employed. However, the impact of these procedures on nasal airflow dynamics is not well understood. This computational fluid dynamics (CFD) study aimed to investigate alterations in nasal airflow and air conditioning following endoscopic nasopharyngectomy. A 55-year-old male patient with recurrent NPC was selected, whose CT data were utilized for image reconstruction. A preoperative model and two postoperative models, including the transnasal and transoral approach models, were established. The airflow patterns and various CFD parameters were analyzed. In the postoperative models, the high-speed airflow went along the soft palate and into the nasopharyngeal outlet, and there was the low-speed turbulence in the expanded nasopharyngeal cavity. Compared to the preoperative model, the postoperative models exhibited reductions in surface-to-volume ratio, nasal resistance, airflow velocity and proportion of high wall shear stress regions in nasopharynx. The changing trends of nasopharyngeal air temperature and humidity in the preoperative and transoral models were consistent. The heating and humidification efficiency decreased in the transnasal model compared to the transoral model. The endoscopic nasopharyngectomy for recurrent NPC affects the nasal airflow and warming and humidification function. The transoral approach has less influence on aerodynamics of the upper airway compared to the transnasal approach. From a CFD perspective, the endoscopic nasopharyngectomy does not increase the risk of postoperative complications, including the empty nose syndrome and the carotid blowout syndrome.

内镜下鼻咽切除术(Endoscopic nasopharyngectomy)是治疗复发性鼻咽癌(nasopharyngeal carcinoma, NPC)的重要干预手段。目前临床已采用经鼻入路、经口入路等多种手术技术，但此类操作对鼻腔气流动力学的影响尚未得到充分阐明。本项计算流体力学(computational fluid dynamics, CFD)研究旨在探讨内镜下鼻咽切除术后鼻腔气流与空气调温调湿功能的变化。研究选取1例55岁复发性NPC男性患者，利用其CT影像数据完成三维图像重建，分别构建术前模型以及经鼻、经口入路两种术后模型，并对气流模式与多项CFD参数进行分析。结果显示，术后模型中高速气流沿软腭走行并进入鼻咽出口，扩张的鼻咽腔内可见低速湍流区域；与术前模型相比，两种术后模型的比表面积、鼻阻力、气流速度以及鼻咽部高壁面切应力区域占比均有所降低。术前模型与经口入路术后模型的鼻咽气温、湿度变化趋势保持一致，经鼻入路术后模型的加温加湿效率相较于经口入路模型有所下降。内镜下鼻咽切除术治疗复发性NPC会对鼻腔气流以及加温加湿功能产生影响，且经口入路相较经鼻入路对上气道气流动力学的影响更为轻微。从CFD分析视角来看，内镜下鼻咽切除术并不会增加术后并发症风险，包括空鼻综合征(empty nose syndrome)与颈动脉破裂综合征(carotid blowout syndrome)。