Aero-acoustic Simulation of Patient-specific Breathing Sounds in Obstructive Sleep Apnea Versus Healthy Airways
Bibliographic record
Abstract
Abstract Rationale: This study numerically simulates tracheal breathing sounds (TBS) within the upper airway for healthy and obstructive sleep apnea (OSA) individuals using a hybrid aeroacoustics approach. The primary objective is to examine how anatomical features of the upper airway influence TBS, with potential application in OSA diagnosis and treatment. Methods: CT scans were utilized to develop patient-specific 3D CAD models of the airway, constructed through segmentation software (ITK-Snap). The numerical simulation is performed by separating aeroacoustics source generation and its propagation. Initially, incompressible, low Reynolds number flow is discretized using the finite volume CFD method (ANSYS Fluent). Large Eddy Simulation is then employed to conduct transient simulations, capturing turbulence scales down to the mesh size. A pressure difference of 3 cmH₂O is applied between the inlet (nostrils) and the outlet (trachea) as boundary conditions, with a time step of 10-4 s specified for the transient simulation. The instantaneous velocity field across the airway domain, obtained in the first stage, is used as input for the second stage, where the aeroacoustic noise sources are calculated using Lighthill's acoustic analogy. The computed sources are then transformed into the frequency domain using Fast Fourier Transform and subsequently mapped onto a new finite element mesh (ACTRAN software). The propagation of acoustic waves is then simulated using finite element method to calculate the sound pressure level at specified microphone locations. Validation is conducted by comparing simulated breathing sounds with recordings of actual TBS from the healthy participant. Further, CFD results are analyzed to compare healthy and OSA participants, and finally the effect of constriction at the velopharyngeal region on TBS is evaluated by manually modifying the healthy participant's model (Blender Software). Results: Simulated sounds closely matched recorded sounds, with an error of less than 3% in the resonating frequencies detected and less than 8% in amplitude. Additionally, the OSA participant exhibits higher turbulent kinetic energy and wall shear stress in the velopharynx region. Variations in the velopharyngeal constriction level also induce a frequency shift in the [1000-1600] Hz range, indicating a strong correlation between TBS and airway constriction. Conclusion: Numerical simulations can effectively model the impact of airway anatomy on TBS, offering a non-invasive approach to OSA diagnosis. The results highlight the potential of TBS analysis for personalized treatment strategies and for assessing the level of airway constriction in OSA patients.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".