title: [Sneezing as a mechanical defence - a numerical simulation and analysis of the nasal flow].
abstract: BACKGROUND
  The nose is responsible for humidification, heating and cleaning of the inhaled air. The sneeze reflex leads to a shock-like cleaning of the nose in strong particle exposure. The aim of this study was the simulation of intranasal air flow of sneezing in a realistic computer model.
  
  
  METHODS
  Based on the CT scan of a 40 year old man a three-dimensional computer model of the nasal cavity and the ethmoid sinuses was created. Flow simulations were performed for different inspiratory and expiratory velocities (± 2 m/s to ± 45 m/s) in order to simulate sneezing. RESULTS were visualized and analyzed by video simulation.
  
  
  RESULTS
  During inspiration the main airflow takes place along the middle turbinate. During expiration, the flow is located more cranially. This effect is caused by the shape of the nasopharynx and the posterior portions of the nasal turbinates. During very high speeds (sneezing) also adjacent ethmoid sinuses and the olfactory region are covered by the shock-like expiratory flow. A large vortex formation in the nasopharynx is responsible for a uniform distribution of the airflow also on lower nasal areas.
  
  
  CONCLUSIONS
  Sneezing is a protective reflex that provides for cleaning of the nose. From a flow rate of 10 m/s, the cranial nasal areas as well as adjacent ethmoid sinuses are covered by the -airflow. Compared to the inspiratory airflow the exhalation is not just vice versa. Particles that deposed in the cranial nasal areas during quiet breathing are removed.
authors.affiliation: Universitätsklinik für Hals-Nasen-Ohrenheilkunde, Kopf- und Halschirurgie, Universitätsklinikum Ulm.
authors.forename: F
authors.initials: F
authors.lastname: Sommer
authors.affiliation: Universitätsklinik für Hals-Nasen-Ohrenheilkunde, Kopf- und Halschirurgie, Universitätsklinikum Ulm.
authors.forename: M
authors.initials: M
authors.lastname: Scheithauer
authors.affiliation: ANSYS Germany, Darmstadt.
authors.forename: R
authors.initials: R
authors.lastname: Kröger
authors.affiliation: Universitätsklinik für Hals-Nasen-Ohrenheilkunde, Kopf- und Halschirurgie, Universitätsklinikum Ulm.
authors.forename: G
authors.initials: G
authors.lastname: Rettinger
authors.affiliation: Universitätsklinik für Hals-Nasen-Ohrenheilkunde, Kopf- und Halschirurgie, Universitätsklinikum Ulm.
authors.forename: J
authors.initials: J
authors.lastname: Lindemann
mesh_terms: D000328:Adult; D003198:Computer Simulation; D005005:Ethmoid Sinus / Q000502:physiology*; D045853:Exhalation / Q000502:physiology; D006801:Humans; D021621:Imaging, Three-Dimensional; D001239:Inhalation / Q000502:physiology; D008297:Male; D009296:Nasal Cavity / Q000502:physiology*; D009297:Nasal Mucosa / Q000502:physiology; D009305:Nasopharynx / Q000502:physiology; D012123:Pulmonary Ventilation / Q000502:physiology*; D012912:Sneezing / Q000502:physiology*; D014057:Tomography, X-Ray Computed; D014420:Turbinates / Q000502:physiology; D014741:Video Recording