Computational fluid dynamics calculations in inferior turbinate surgery: a cohort study.

PURPOSE: To investigate how the results of nasal computational fluid dynamics (CFD) simulations change due to inferior turbinate surgery and how the results correlate with patient specific subjective assessment and volumetric results in the nasal cavities. METHODS: The steady inspiratory airflow of 25 patients was studied pre- and postoperatively with heat transfer from the mucous membrane by performing CFD calculations to patient-specific nasal cone beam computed tomography images. These results were then compared to the severity of the patients' nasal obstruction Visual Analogue Scale (VAS) and Glasgow Health Status Inventory assessments, and acoustic rhinometry measurements. RESULTS: Total wall shear forces decreased statistically significantly (p < 0.01) in the operated parts of the inferior turbinates. Patients' subjective nasal obstruction VAS assessment changes between the pre- and postoperative conditions correlated statistically significantly (p = 0.04) with the wall shear force results. CONCLUSION: Inferior turbinate surgery lead to decreased total wall shear force values postoperatively. Changes in subjective nasal obstruction VAS results against total wall shear force changes between the pre- and postoperative conditions were statistically significant. CFD data have a potential to be used for the evaluation of nasal airflow.

Association between nasal airway minimal cross-sectional areas and obstructive sleep apnoea.

BACKGROUND/OBJECTIVES: Patients with obstructive sleep apnoea (OSA) frequently present with some form of upper airway anatomical impairment. Considerable research has been conducted on the role of the structures of the jaw and pharynx in the pathogenesis of OSA; however, the significance of the nose is somewhat unclear. Computed tomography is a widely used imaging modality for assessing the nasal cavity and paranasal sinuses, but only a small amount of the acquired data is used. Our aim was to ascertain whether the size of the cross-sectional areas of the nasal airway, measured from cone beam computed tomography (CBCT) images, is associated with OSA severity. MATERIALS/METHODS: A total of 58 patients with OSA, without any major paranasal sinus inflammatory pathology, were included in this register-based study. Patients had previously undergone ambulatory polysomnography and CBCT. The cross-sectional areas of the nasal cavity were measured in CBCT coronal sections. Statistical analyses were performed to determine any correlation between the cross-sectional area measurements and apnoea-hypopnoea index (AHI) or any significant difference in cross-sectional areas between AHI severity groups. RESULTS: No correlation was found between AHI and the smallest, total, or sum of the anterior cross-sectional areas of the nasal airway. Furthermore, there was no statistically significant difference in the cross-sectional areas between patients with the highest and lowest AHI. CONCLUSIONS/IMPLICATIONS: The small cross-sectional area of the anterior nasal cavity in patients without any major nasal pathology does not appear to be associated with OSA severity.

Computational fluid dynamics assessed changes of nasal airflow after inferior turbinate surgery.

OBJECTIVE: To demonstrate how Computational Fluid Dynamics (CFD) simulations can reveal important airflow changes in the nasal cavities due to surgical interventions. MATERIAL AND METHODS: The steady inspiratory airflow of eight patients was studied pre- and postoperatively with heat transfer from the mucous membrane by performing CFD calculations to patient specific cone beam computed tomography (CBCT) images. Eight patients with the largest distance from pre- and postoperative mean changes in inferior turbinate volumetry and Visual Analogue Scale (VAS) results were selected. RESULTS: Calculated CFD heat transfer results from the anterior parts of the inferior turbinates, where surgical interventions were performed, decreased significantly. The heat transfer results were in line with VAS changes. CONCLUSION: Surgical interventions reduced heat transfer in the operated parts of the inferior turbinates and were in line with VAS changes. CFD is an option in assessing patient well-being as a function of airflow parameters from mucous membrane with larger data sets. The limitations of the study were the small sample size and the preliminary nature of the study.

Three-Dimensional Measurements in Assessing the Results of Inferior Turbinate Surgery.

OBJECTIVES: Acoustic rhinometry is widely used in evaluating patients with nasal congestion, but it only has a partial correlation with patient symptoms. The use and focus of cone beam computed tomography (CBCT) scans are mainly on the paranasal sinuses and less on the nasal cavities. Therefore, information acquired from CBCT scans is not used to its full extent. In our present study, we have studied patients with enlarged inferior turbinates. Our aim was to investigate and compare the use of 3D volumetric measurements and cross-sectional area measurements taken from CBCT scans to results obtained from acoustic rhinometry. MATERIAL AND METHODS: In total, 25 patients with enlarged inferior turbinates were studied. CBCT scans were obtained preoperatively and at twelve months postoperatively. 3D volumetric and cross-sectional area measurements were compared to results from acoustic rhinometry, the visual analogue scale (VAS) and Glasgow Health Status Inventory (GHSI) questionnaires. RESULTS: A statistically significant change in 3D volume and cross-sectional area was measured in the anterior part of the inferior turbinate and surrounding air space after inferior turbinate surgery. VAS and GHSI results had mild correlations with the 3D volume and cross-sectional area measurements of the anterior part of the inferior turbinate. Acoustic rhinometry correlated with the air space 3D volume measurements in the anterior part. CONCLUSIONS: Fully utilized CBCT scans provide more comprehensive and accurate information. Furthermore, 3D analysis of the inferior turbinates provides valuable information and more precise measurements compared to acoustic rhinometry.

Differentiation of aspirated nasal air from room air using analysis with a differential mobility spectrometry-based electronic nose: a proof-of-concept study.

Over the last few decades, breath analysis using electronic nose (eNose) technology has become a topic of intense research, as it is both non-invasive and painless, and is suitable for point-of-care use. To date, however, only a few studies have examined nasal air. As the air in the oral cavity and the lungs differs from the air in the nasal cavity, it is unknown whether aspirated nasal air could be exploited with eNose technology. Compared to traditional eNoses, differential mobility spectrometry uses an alternating electrical field to discriminate the different molecules of gas mixtures, providing analogous information. This study reports the collection of nasal air by aspiration and the subsequent analysis of the collected air using a differential mobility spectrometer. We collected nasal air from ten volunteers into breath collecting bags and compared them to bags of room air and the air aspirated through the device. Distance and dissimilarity metrics between the sample types were calculated and statistical significance evaluated with Kolmogorov-Smirnov test. After leave-one-day-out cross-validation, a shrinkage linear discriminant classifier was able to correctly classify 100% of the samples. The nasal air differed (p< 0.05) from the other sample types. The results show the feasibility of collecting nasal air by aspiration and subsequent analysis using differential mobility spectrometry, and thus increases the potential of the method to be used in disease detection studies.

Assessment of PIV performance in validating CFD models from nasal cavity CBCT scans.

OBJECTIVE: The aim of our study was to investigate how well Particle Image Velocimetry (PIV) measurements could serve Computational Fluid Dynamics (CFD) model validation for nasal airflow. MATERIAL AND METHODS: For the PIV measurements, a silicone model of the nose based on cone beam computed tomography (CBCT) scans of a patient was made. Corresponding CFD calculations were conducted with laminar and two turbulent models (k-ω and k-ω SST). RESULTS: CFD and PIV results corresponded well in our study. Especially, the correspondence of CFD calculations between the laminar and turbulent models was found to be even stronger. When comparing CFD with PIV, we found that the results were most convergent in the wider parts of the nasal cavities. CONCLUSION: PIV measurements in realistically modelled nasal cavities succeed acceptably and CFD calculations produce corresponding results with PIV measurements. Greater model scaling is, however, necessary for better validations with PIV and comparisons of competing CFD models.

Three-Dimensional Printing of the Nasal Cavities for Clinical Experiments.

3D printing has produced many beneficial applications for surgery. The technique´s applicability in replicating nasal cavity anatomy for clinical use has not been studied. Our aim was to determine whether 3D printing could realistically replicate the nasal cavities and the airflow passing through them from a clinical point of view. We included Cone Beam Computed Tomography (CBCT) scans of five patients with symptoms of chronic nasal congestion. These CBCT scans were used to print plastic 3D prints of the nasal cavities, which were also CBCT scanned and the measurements were compared. The results in vivo were higher than the results in vitro in maxillary sinus volumes with a ratio of 1.05 ± 0.01 (mean ± SD) and in the nasal cavities with a ratio of 1.20 ± 0.1 (mean ± SD). Linear measurements in vitro were very close to those in vivo. Rhinomanometric results showed some differences, but rhinomanometric graphs in vitro were close to the graphs in vivo. 3D printing proved to be a suitable and fast method for replicating nasal cavity structures and for the experimental testing of nasal function. It can be used as a complementary examination tool for rhinomanometry.