WP1 will provide excised soft tissue of soft palate and throat to be examined for its structural properties in WP2. Furthermore, WP1 will produce necessary input data for patient specific mathematical models being developed in WP3 and WP4. This includes generic data on the geometry, volume flow rate and pressure for typical patients suffering from OSAS. Moreover, WP1 will provide WP4 with patient specific data on the geometry, volume flow rate and pressure for one patient where nasal surgery has successfully treated OSAS, and for another patient where nasal surgery has failed. The clinical material can readily be adapted for use as input and calibration for mathematical models, and it is opportune to use the clinical research that has already been conducted by St. Olavs hospital and DMF as a basis for this research. The main tasks of WP1 are:
A combined high resolution 1mm CT scan and 3mm MRI will be provided by the radiologic department at St. Olav Hospital to create a 3D model of the upper airway. The combination of the two modalities will supply the geometry of the upper airways. CT is the better choice for bony structures (the nasal cavity and hard palate) and MRI is superior for the soft tissues (soft palate, tongue and pharyngeal walls). Patients for the image creation will be recruited from an ongoing study population described under Task 1.3. From our own study (in line with comparable studies) two thirds of the patients experience an improvement of their OSAS from nasal surgery while one third are unchanged or worsened. From these figures we estimate that we need to do CT/MRI scans on 20 patients with OSAS and nasal stenosis prior to nasal surgery, in order to obtain both surgical failures and success. The CT and MRI scans will be repeated postoperatively for two patients the one with most improvement and the one with failure or most pronounced worsening. The geometry obtained from these patients will form a basis for the planned CFD modeling in WP4.
The elasticity has to be determined for the soft tissues of interest. Tissue samples will be obtained from fresh cadavers from palate, tongue and pharyngeal wall. The samples will be analyzed in WP2 to establish material models that can be employed in WP3 and WP4.
There is ongoing clinical research at St. Olavs Hospital, NTNU, on the effects of nasal stenosis on OSAS. These studies include:
Study 1 results (submitted for publication) show that a combination of septoplasty and volume reductive surgery had a better outcome regarding apneas than septal surgery alone. In studies 2 and 3 there is extensive registration of patient data: Acoustic rhinometry (AR) measures the cross-sectional area of the nasal cavity relative to the distance from the nasal tip;Peak nasal inspiratory flow (PNIF) measures the maximum combined nasal flow; Clinical interpretation of anatomical parameters. It is natural to compare AR and the clinical dimensional evaluations to CT/MRI dimensions and flow models to PNIF.
The combined effort of clinical studies and mathematical modeling will form the basis for a database that enables us to do a better selection of patients to specific treatment options, which remains the most important objective within this field. The results may lead to a conclusion that MRI imaging is necessary to predict outcome from surgery, or that special characteristics on imaging are recognizable on clinical evaluation and associated tests. If it is so, it may be convenient to construct a graded classification system based on these data to predict the outcome from surgery.