Numerical Simulation of Airflow Patterns and Air Temperature Distribution during Inspiration in a Nose Model with Septal Perforation

Background

The most typical symptoms of patients with nasal septal perforation (SP) are crusting and recurrent nosebleed. The objective of the study was to determine the influence of SP on intranasal temperature profile and airflow patterns during inspiration by means of numerical simulation.

Methods

Two realistic bilateral models of the human nose with and without SP were reconstructed based on computed tomography (CT). A numerical simulation was performed. The intranasal air temperature distribution and airflow patterns during inspiration were displayed, analyzed, and compared.

Results

SP causes a highly disturbed airflow in the area of perforation. A spacious vortex within the perforation including various localized vortices was detected. A disturbed intranasal temperature distribution between the right and left nasal cavities developed.

Conclusions

The numerical simulation demonstrates the interaction between airflow patterns and heating of respiratory air. The disturbed airflow causes reduced air conditioning. This fact may contribute to crusting and recurrent nosebleed.

Evaluation of Protective and Therapeutic Effects of Dexpanthenol on Nasal Decongestants and Preservatives: Results of Cytotoxic Studies in Vitro

Background

More than 600 million units of nasal decongestants are sold worldwide annually. The cytotoxic and ciliary toxic potential of decongestants, as well as the preservatives of these products, in particular benzalkonium chloride (BKC), is well established. Recently, a beneficial effect of dexpanthenol on the tolerability of the ά-sympathomimetic xylometazoline and BKC has been described; however, it was unclear if this effect, resulting in significantly higher cell counts in a cytotoxicity study and an increase in ciliary beat frequency in a ciliary toxicity study was of protective or therapeutic nature. The objective of this study was (a) to evaluate whether dexpanthenol would be a useful additive to nasal decongestants to counter the cytotoxic and ciliary toxic effects of the active ingredient and the preservative and (b) to find out whether this beneficial effect is of protective or therapeutic nature.

Methods

Systematic cytotoxic in vitro tests were performed. After exposure to xylometazoline (0.1%), the effect of dexpanthenol (5%) and BKC (0.01%) was determined by placebo-controlled assessment of cell growth in a human amniotic cell line.

Results

Dexpanthenol significantly reduces the toxic effects of xylometazoline regarding cell growth (p < 0.001) when applied in advance. When BKC is eliminated from the nasal sprays, a further significant increase of cell growth was found (p < 0.001). When dexpanthenol is therapeutically applied after xylometazoline, effects on cell growth are only one-half of those of the protective approach.

Conclusion

The additive application of dexpanthenol (5%) given before nasal decongestants or preserved nasal sprays is able to improve the tolerability of these substances and to counteract the toxic effects. (American Journal of Rhinology 18, 315–320, 2004)

Dynamic nasal infrared thermography in patients with nasal septal perforations

BACKGROUND

Nasal obstruction is a typical symptom in patients with nasal septal perforations. Rhinomanometry and acoustic rhinometry are not reliable in these cases because the perforations generate incorrect results. Infrared thermography camera (ITC) systems allow contact-free intranasal recordings of the nasal surface temperature and the semiquantification of nasal airflow. The aim of this study was to perform contact-free temperature measurements of the nasal vestibular surface by application of ITC systems in patients with septal perforations to investigate the disturbed intranasal heat exchange and nasal airflow.

METHODS

The surface temperature profiles within the nasal vestibules of healthy volunteers (n=10) and patients with septal perforations (n=3) were recorded with an ITC during several breathing cycles. Thermal images were taken (60/s) displaying the surface temperature in degrees centigrade corresponding to a color scale.

RESULTS

The temperature recordings showed a disturbed intranasal heat exchange during inspiration and expiration in patients with septal perforations in comparison with healthy subjects. A reduced and irregular inspiratory cooling of the entire surface within the nasal vestibules visualizes a reduced and disturbed airflow volume.

CONCLUSION

The study was able to prove the feasibility of intranasal temperature recordings of the surface with an ITC system in patients with septal perforations. Contrary to rhinomanometry and acoustic rhinometry, thermography cameras can be applied to examine airflow in patients with septal perforations. The detected reduced cooling of the surface during inspiration might be a possible explanation for the patients' feelings of nasal obstruction.

Influence of the turbinate volumes as measured by magnetic resonance imaging on nasal air conditioning

BACKGROUND

Changes in nasal airflow caused by varying intranasal volumes and cross-sectional areas affect the contact between air and surrounding mucosa entailing alterations in nasal air conditioning. This study evaluates the correlation between nasal air conditioning and the volumes of the inferior and middle turbinates as measured by magnetic resonance imaging (MRI).

METHODS

Fourteen healthy volunteers were enrolled. Each volunteer had been examined by rhinomanometry, acoustic rhinometry, intranasal air temperature, and humidity measurements at defined intranasal sites as well as MRI of the nasal cavity and the paranasal sinuses. The volumetric data of the turbinates was based on the volumetric software Amira.

RESULTS

Comparable results were obtained regarding absolute humidity values and temperature values within the nasal valve area and middle turbinate area for both the right and the left side of the nasal cavity. No statistically significant differences were found in the rhinomanometric values and the acoustic rhinometry results of both sides (p > 0.05). No statistical correlations were found between the volumes of the inferior (mean, 6.1 cm3) and middle turbinate (mean, 1.8 cm3) and the corresponding humidity and temperature values. Additionally, the air temperature and humidity values did not correlate with the rhinometrical endonasal volumes (0-20 mm and 20-50 mm from the nasal entrance).

CONCLUSION

The normal range of volumes of the inferior and middle turbinate does not seem to have a significant impact on intranasal air conditioning in healthy subjects. The exact limits where alterations of the turbinate volume negatively affect nasal air conditioning are still unknown.

Impact of Menthol Inhalation on Nasal Mucosal Temperature and Nasal Patency

Background

Menthol is a natural herbal compound. Its isomer L-menthol presents the characteristic peppermint scent and is also responsible for the cooling sensation when applied to nasal mucosal surfaces because of stimulation of trigeminal cold receptors. The aim of this study was to assess the effect of menthol inhalation on end-inspiratory nasal mucosa temperature and nasal patency.

Methods

Eighteen healthy volunteers with a mean age of 30 years were enrolled in this study. Objective measurements included the septal mucosal temperature within the nasal valve area by using a miniaturized thermocouple as well as active anterior rhinomanometry before and after inhalation of l-menthol vapor. All subjects completed a visual analog scale (VAS; range, 1–10) evaluating nasal patency before and after menthol.

Results

The mean end-inspiratory mucosal temperature ranged from 27.7°C (±4.0) before menthol inhalation to 28.5°C (±3.5) after menthol inhalation. There were no statistically significant differences between the temperature values before and after menthol inhalation (p > 0.05). In addition, no statistically significant differences between the rhinomanometric values before and after menthol inhalation were observed. Sixteen of the 18 subjects reported an improvement of nasal breathing after menthol inhalation by means of the VAS.

Conclusion

Menthol inhalation does not have an effect on nasal mucosal temperature and nasal airflow. The subjective impression of an improved nasal airflow supports the fact that menthol leads to a direct stimulation of cold receptors modulating the cool sensation, entailing the subjective feeling of a clear and wide nose.

Nasal mucosal temperature in relation to nasal airflow as measured by rhinomanometry

BACKGROUND

The aim of this study was to measure in vivo nasal mucosal temperature and assess its relationship to nasal patency.

METHODS

Nasal mucosal temperature of 30 nasal cavities was measured by means of a miniaturized thermocouple within the anterior turbinate area during respiration. Temperature values were compared with corresponding rhinomanometrical data.

RESULTS

The median mucosal temperature ranged from 30.2 degrees C (range, 28.9-31.7 degrees C) after inspiration to 32.2 degrees C (range, 31.0-33.9 degrees C) after expiration. The end-inspiratory (r = -0.85) and end-expiratory mucosal temperature values (r = -0.88) negatively correlated with the rhinomanometrical data.

CONCLUSION

This study supports the fact that there is a negative correlation between nasal mucosal temperature and nasal resistance. Changes in nasal patency seem to influence nasal mucosal temperature. Within this context, nasal thermoreceptors might play an important role concerning the perception of nasal patency.

Simultaneous in vivo measurements of intranasal air and mucosal temperature

Nasal cavity volume and blood temperature along the nasal airways, reflecting the mucosal temperature, are considered to be the most important predictors of nasal air conditioning. The purpose of this study was to simultaneously in vivo measure intranasal air as well as mucosal temperature for the first time. Fifteen healthy subjects were enrolled into the study. Two combined miniaturized thermocouples were used for simultaneous recording of intranasal air and mucosal temperature within the anterior turbinate area close to the head of the middle turbinate without interruption of nasal breathing. The highest air and mucosal temperature values were detected at the end of expiration, the lowest values at the end of inspiration. The difference was statistically significant (P < 0.05). The mean mucosal temperature ranged from 30.2 +/- 0.9 to 32.2 +/- 0.8 degrees C. The mean air temperature ranged from 28.5 +/- 1.2 to 34.1 +/- 0.7 degrees C. The mean differences between air and mucosal temperature were 1.7 +/- 0.5 degrees C after inspiration and 1.9 +/- 0.7 degrees C after expiration. Simultaneous measurements of intranasal air and mucosal temperature are practicable. The detected temperature gradient between air and mucosa confirm a relevant heat exchange during inspiration and expiration. This gradient between air and mucosa is obligatory for heat and water exchange to ensure adequate nasal air conditioning.

Numerical simulation of air temperature and airflow patterns in the human nose during expiration

Recovery of heat and water during expiration is an important but not yet fully understood function of the nose. The presented study investigated cooling of the expiratory air for heat recovery within the human nose applying numerical simulation. A numerical simulation in a bilateral three-dimensional model of the human nose based on computed tomography was employed. Temperature distribution and airflow patterns during expiration were displayed. Cooling of the expiratory air primarily takes place in the areas of inferior and middle turbinate. Areas of the highest decrease in temperature are characterized by turbulent airflow with vortices of low velocity. Numerical results showed good concordance with experimental in vivo temperature measurements. Heating of inspired air not only depends on inspiration but also on expiration. Cooling the warm expiratory air may be regarded as an important factor for heat recovery. Furthermore, the results demonstrate the close relation between heat exchange and airflow patterns.

Immediate effect of benzalkonium chloride in decongestant nasal spray on the human nasal mucosal temperature

Benzalkonium chloride is a preservative commonly used in nasal decongestant sprays. It has been suggested that benzalkonium chloride may be harmful to the nasal mucosa. Decongestion with the vasoconstrictor xylometazoline containing benzalkonium chloride has been shown to cause a significant reduction of the nasal mucosal temperature. The purpose of the present study was to determine the short-term influence of xylometazoline nasal spray with and without benzalkonium chloride on the nasal mucosal temperature. Healthy volunteers (30) were included in the study. Fifteen volunteers received xylometazoline nasal spray (1.0 mg/mL) containing benzalkonium chloride (0.1 mg/mL) and 15 age-matched subjects, received xylometazoline nasal spray without benzalkonium chloride. Using a miniaturized thermocouple the septal mucosal temperature was continuously measured at defined intranasal detection sites before and after application of the nasal spray. The mucosal temperature values did not significantly differ between the group receiving xylometazoline containing benzalkonium chloride and the group receiving xylometazoline spray without benzalkonium chloride before and after decongestion (P > 0.05). In both study groups septal mucosal temperatures significantly decreased after decongestion (P < 0.05) because of a reduction of the nasal mucosal blood flow following vasoconstriction. This study indicates that benzalkonium chloride itself does not seem to influence nasal blood flow and nasal mucosal temperature in topical nasal decongestants.

A numerical simulation of intranasal air temperature during inspiration

OBJECTIVES/HYPOTHESIS

In vivo measurements of the intranasal air temperature are feasible. The present study was designed to reproduce temperature distributions within the human nasal cavity by means of numerical simulation.

STUDY DESIGN

Numerical simulation.

METHODS

Based on computed tomography (CT), a steady-state computational fluid dynamics (CFD) simulation was performed displaying the temperature distribution throughout the human nasal cavity during inspiration. The results of the numerical simulation were compared with in vivo temperature measurements.

RESULTS

The numerical simulation demonstrated that the major increase of the inspiratory air temperature can be found in the anterior nasal segment, especially within the nasal valve area, which is comparable to in vivo measurements. Intranasal areas of high temperature were characterized by turbulent airflow with vortices of low velocity. The results of numerical simulation showed an excellent comparability to the results of previous in vivo measurements in the entire nasal cavity.

CONCLUSION

The anterior nasal segment is the most effective part of the nose in heating of the ambient air. The findings demonstrated the complexity of the relationship between airflow patterns and heating of inspired air. A numerical simulation of the temperature distribution using CFD is practicable.

Techniques of intranasal steroid use

OBJECTIVE

The effectiveness of topical intranasal steroids (INS) sprays for the treatment of allergic and nonallergic rhinitis may be limited by lack of instruction in the optimal spray technique. To determine whether the technique used affects the efficacy and safety of the product, this review of evidence had the goal of identifying and establishing a preferred method of applying INS sprays.

STUDY DESIGN

A MEDLINE search of pertinent literature on 7 INS and 1 intranasal antihistamine spray preparations conducted with the use of appropriate search terms, yielded an initial 121 articles, 29 of which were identified as appropriate for review and grading for quality of evidence.

RESULTS

The analysis provided no definitive evidence regarding how best to instruct patients to use INS or antihistamine spray devices.

CONCLUSIONS

On the basis of a lack of clear evidence regarding instructions to maximize efficacy and safety of these drugs, the panel recommended a 7-step standard technique.