Paranasal sinus ventilation by humming

The impact of geometrical parameters on acoustically driven drug delivery to maxillary sinuses

Acoustically driven nebulized drug delivery (acoustic aerosol delivery) is the most efficient noninvasive technique for drug delivery to maxillary sinuses (MS). This method is based on the oscillation of the air plug inside the ostium to transport drug particles from the nasal cavity (NC) to the MS. The larger the wavelength of the air plug oscillation in the ostium, the greater the penetration of drug particles to the MS. However, using this technique, the maximum drug delivery efficiency achieved to date is 5%, which means 95% of the aerosolized drugs do not enter the MS and are wasted. Since the largest amplitude of the air plug oscillation occurs at its resonance frequency, to achieve an improved MS drug delivery efficiency, it is important to determine the resonance frequency of the nose-sinus combination accurately. This paper aims to investigate the impact of geometrical parameters on the resonance frequency of the nose-sinus model. Both experimental and computational acoustic models, along with the theoretical analysis, were conducted to determine the resonance frequency of an idealized nose-sinus model. The computational modeling was carried out using computational fluid dynamics (CFD) and finite element analysis (FEA), whereas in the analytical solution, the mathematical relationships developed for a conventional Helmholtz resonator were employed. A series of experiments were also conducted to measure the resonance frequency of a realistic NC-MS combination. The results demonstrated a good agreement between the experimental and CFD modeling, while the FEA and theoretical analysis showed a significant deviation from the experimental data. Also, it was shown that the resonance frequency of the idealized nose-sinus model increases by up to twofold with increasing the ostium diameter from 3 to 9 mm; however, it has an inverse relationship with the ostium length and sinus volume. It was also reported that the resonance frequency of the nose-sinus model is independent of the NC width and MS shape.

Toward smart Nebulization: Engineering acoustic airflow to penetrate maxillary sinuses in chronic rhinosinusitis

Treating chronic rhinosinusitis (CRS) by nebulization requires an airflow capable to deliver medication to deep target sites beyond the nasal valve. Fixed frequency acoustic airflow technology is currently available, mainly as post-surgical therapy, but still have not been able to realize the full potential of direct nose to paranasal sinuses delivery. Reported herein are the application of frequency sweep acoustic airflow and the optimization of its frequency range, sweep cycle duration and intensity. The resonant frequencies of the model's maxillary sinuses can be estimated using the Helmholtz resonator theory. Results indicated a resonant frequency of 479 Hz for the right maxillary sinus and one of 849 Hz for the left maxillary sinus. The highest intrasinus deposition within the experiments are from sweep cycle duration of 1 s, intensity of 80 dB, and frequency range of 100-850 Hz. The optimal range of frequency determined from experiments is in good agreement with the corresponding frequency range obtained from the Helmholtz resonator theory. Results reveal a significantly enhanced maxillary sinus drug deposition. This technique affords the potential of treating CRS.

Eliminating paranasal sinus resonance and its effects on acoustic properties of the nasal tract

The significance of nasal resonance and anti-resonance to voice production is a classical issue in vocal pedagogy and voice research. The complex structure of the nasal tract produces a complex frequency response. This complexity must be heavily influenced by the morphology of the paranasal cavities, but their contributions are far from being entirely understood. Detailed analyses of these cavities are difficult because of their limited accessibility. Here we test different methods aiming at documenting the acoustical properties of the paranasal tract. The first set of experiments was performed under in vivo conditions, where the middle meatus was occluded by means of targeted application of a maltodextrin mass under endoscopic control. The efficiency of this occlusion method was verified by measuring the nasal nitric oxide (NO) output during humming. In another experiment the frequency responses to sine sweep excitation of an epoxy mould of a nasal cavity were measured, with and without elimination of paranasal sinuses. The third experiment was conducted in a cadaveric situs, with and without maltodextrin occlusion of the middle meatus and the sphenoidal ostia. The results show that some nasal tract resonances were unaffected by the manipulation of the paranasal cavities. Providing access to a maxillary sinus resulted in marked dips in the response curve while access to the sphenoidal ostium caused only minor effects.

Effect of accessory ostia on maxillary sinus ventilation: a computational fluid dynamics (CFD) study

We evaluated, by CFD simulation, effects of accessory ostium (AO) on maxillary sinus ventilation. A three-dimensional nasal model was constructed from an adult CT scan with two left maxillary AOs (sinus I) and one right AO (sinus II), then compared to an identical control model with all AOs sealed (sinuses III and IV). Transient simulations of quiet inspiration and expiration at 15 L/min, and nasal blow at 48 L/min, were calculated for both models using low-Reynolds-number turbulent analysis. At low flows, ventilation rates in sinuses with AOs (I ≈ 0.46 L/min, II ≈ 0.54 L/min), were both more than a magnitude higher than sinuses without AOs (II I ≈ 0.019 L/min, IV ≈ 0.020 L/min). Absence of AO almost completely prevented sinus ventilation. Increased ventilation of sinuses with AOs is complex. Under high flow conditions mimicking nose blowing, in sinuses II, III, and IV, the sinus flow rate increased. In contrast, the airflow direction through sinus I reversed between inspiration and expiration, while it remained almost constant throughout the respiration cycle in sinus II. CFD simulation demonstrated that AOs markedly increase maxillary sinus airflow rates and alter sinus air circulation patterns. Whether these airflow changes impact maxillary sinus physiology or pathophysiology is unknown.

Computational modeling of flow and gas exchange in models of the human maxillary sinus

The present study uses numerical modeling to increase the understanding of sinus gas exchange, which is thought to be a factor in sinus disease. Order-of-magnitude estimates and computational fluid dynamics simulations were used to investigate convective and diffusive transport between the nose and the sinus in a range of simplified geometries. The interaction between mucociliary transport and gas exchange was modeled and found to be negligible. Diffusion was the dominant transport mechanism for small ostia and large concentration differences between the sinus and the nose, whereas convection was important for larger ostia or smaller concentration differences. The presence of one or more accessory ostia can increase the sinus ventilation rate by several orders of magnitude, because it allows a net flow through the sinus. Estimates of nitric oxide (NO) transport through the ostium based on measured sinus and nasal NO concentrations suggest that the sinuses cannot supply all the NO in nasally exhaled air.

Nitric oxide in the airways

PURPOSE OF REVIEW

This review briefly explains the basic facts about nitric oxide, which is entering clinical practice as a measure of lower airways inflammation and is likely also to be employed in otorhinolaryngological practice.

RECENT FINDINGS

These include the validity of nasal nitric oxide in diagnosing primary ciliary dyskinesia and in monitoring the response to chronic rhinosinusitis therapy. The nasal nitric oxide value combined with a humming manoeuvre, which increases the passage of nitric oxide from the sinuses to the nose if the ostiomeatal complex is patent, could reduce the need for computed tomography scans. The link between nitric oxide production and ciliary beating requires further exploration. Therapeutic adjustments to nitric oxide production are under investigation.

SUMMARY

Nitric oxide is likely to prove highly relevant to airways defence, as well as being an inflammatory mediator. Nasal nitric oxide probably explains some of the benefit of nasal rather than mouth breathing.