Postoperative Characteristics Of Structure And Airflow Field In Nasopharyngeal Airway Of Children With Adenoidectomy

Objective: To study the morphological changes and airflow changes in postoperative nasopharyngeal airway of children with adenoidectomy we applied acoustic rhinometry(AR), medical imaging and biological fluid dynamics technology.Methods: Sixteen children were evaluated by AR to measure the nasopharyngeal volume (NPV) before adenoidectomy, evaluated again after adenoidectomy three months later. We used the SPSS statistical software to test the preoperative and postoperative data by paired t test. We used multi-slice spiral CT to scan the nasopharyngeal continuously for analyzing the preoperative nasal and nasopharyngeal imaging features. Postoperative CT images, which were scanned three months after adenoidectomy, were compared with the corresponding preoperative CT images in order to study the changes in nasopharyngeal airway. With this couple of preoperative and postoperative CT images, we used the finite element software to reconstruct the upper airway to study the airflow changes after the adenoidectomy.Results:1. Nasopharyngeal volume measurement results. Preoperative NPV is 17.61±3.89 cm3, postoperative NPV is 31.34±7.11 cm3. The results show that postoperative nasopharyngeal NPV increase after adenoidectomy. After paired-samples t test, we can see significant differences (P <0.01).2. CT scanning results. Preoperative CT scanning results: The nasopharyngeal airway is narrow because of the hyperplasia of adenoid which shows soft tissue density shadow on the CT image. Adenoid of nine children grows into the posterior naris. In seven patients (43.75%), the CT images of the pharyngeal recess and pharyngeal opening of pharyngo- tympanic tube is unclear. The CT images show that five patients(31.25%) are sinusitis and three patients ( 18.75 % ) are secretory otitis media. Differences between preoperative and postoperative CT images: The pre-operative CT images show that the nasopharyngeal airway is narrow because of the hyperplasia of adenoid while postoperative CT images show that the airway becomes unobstructed after the adenoidectomy and the sinusitis is cured.3. Numerical simulation results. Structural features of geometric model: From the three-dimensional geometric model of preoperative upper airway, we can see that adenoid hypertrophy results in the nasopharyngeal stenosis, while the nasopharyngeal stenosis disappears after adenoidectomy. The overall pressure distribution: At the moment of maximum inspiratory flow rates, the pressure is gradually reduced from anterior naris to the glottis[0] and the total pressure drop is about 162 Pa in preoperative model ,while 40 Pa in postoperative model. At the moment of maximum expiratory flow rates the pressure is gradually increased and the total pressure increase is about 146 Pa in preoperative model, while 50 Pa in postoperative model. In the preoperative model, we can see that there is an obvious pressure drop for about 105 Pa in nasopharynx, while there is no significant change of pressure in postoperative model. Velocity distribution: In the preoperative model, the main airflow flows through the inferior meatus with high-speed flow in limen nasi and nasopharynx. In the postoperative model, the main airflow flows through the middle meatus and the high-speed airflow still exist in limen nasi, but the high-speed airflow in nasopharynx disappears. Nasopharyngeal airflow patterns: The velocity vector profile of naso- pharyngeal airflow shows that in preoperative model the nasopharyngeal airflow pattern is mainly turbulent flow but postoperative model is laminar flow.Conclusions:1. There is a narrow plane in nasopharyngeal airway in children with adenoidal hypertrophy, but the narrow plane disappear after adenoidectomy.2. After adenoidectomy, the upper airway airflow field is changed on the overall pressure, airflow velocity distribution and nasopharyngeal airflow patterns. 3. It can be interpreted by the principle of biological fluid dynamics technology why the clinical symptoms disappear after adenoidectomy.4. The finite element numerical model can be used to simulate the real operation before clinical adenoidectomy in order to predict postoperative effect.5. Acoustic rhinometry is accurate for investigating the geometry of the nasopharyngeal airway. It is helpful for adenoidectomy in preoperative diagnosis and postoperative evaluation.Nasopharyngeal CT scanning is benefit for diagnosis of adenoidal hypertrophy and its complications, comprehensive assessment of the patient's condition and preoperative surgical decision-making.