Beyond skeletal studies: A computational analysis of nasal airway function in climate adaptation

OBJECTIVES

Ecogeographic variation in human nasal anatomy has historically been analyzed on skeletal morphology and interpreted in the context of climatic adaptations to respiratory air-conditioning. Only a few studies have analyzed nasal soft tissue morphology, actively involved in air-conditioning physiology.

MATERIALS AND METHODS

We used in vivo computer tomographic scans of (N = 146) adult individuals from Cambodia, Chile, Russia, and Spain. We conducted (N = 438) airflow simulations during inspiration using computational fluid dynamics to analyze the air-conditioning capacities of the nasal soft tissue in the inflow, functional, and outflow tract, under three different environmental conditions: cold-dry; hot-dry; and hot-humid. We performed statistical comparisons between populations and sexes.

RESULTS

Subjects from hot-humid regions showed significantly lower air-conditioning capacities than subjects from colder regions in all the three conditions, specifically within the isthmus region in the inflow tract, and the anterior part of the internal functional tract. Posterior to the functional tract, no differences were detected. No differences between sexes were found in any of the tracts and under any of the conditions.

DISCUSSION

Our statistical analyses support models of climatic adaptations of anterior nasal soft tissue morphology that fit with, and complement, previous research on dry skulls. However, our results challenge a morpho-functional model that attributes air-conditioning capacities exclusively to the functional tract located within the nasal cavity. Instead, our findings support studies that have suggested that both, the external nose and the intra-facial soft tissue airways contribute to efficiently warming and humidifying air during inspiration. This supports functional interpretations in modern midfacial variation and evolution.

The nasal cycle before and after nasal septoplasty

PURPOSE

Septoplasty is one of the most frequently performed operations in patients with septal deviation of the nose. The aim of this surgical intervention is to reduce nasal obstruction and to achieve a physiological nasal breathing. The nasal cycle plays a crucial role in this. The aim of this study was to investigate nasal breathing and the nasal cycle after septoplasty over a long period of time and under everyday conditions.

METHODS

We examined 22 healthy subjects and 19 patients with nasal septal deviation. They participated in two sessions separated by an interval of three months. Shortly after the first session patients received nasal septoplasty. Testing included multiple questionnaires regarding nasal breathing and olfactory function, anterior rhinoscopy, rhinomanometry, acoustic rhinometry, and long-term rhinoflowmetry over 24 h.

RESULTS

Nasal septoplasty was associated with subjectively improved nasal breathing and nasal patency comparable to that in healthy subjects. The severity of nasal obstruction was reduced. Nasal airflow and the hydraulic diameter increased on the deviated side of the nose while the inspiratory resistance did not significantly change. In addition, the number of phases of the nasal cycle decreased on the nondeviated side. Hence, the surgery was associated with a more even distribution of phases on both sides of the nose.

CONCLUSION

Nasal septoplasty leads to a subjectively satisfactory result in patients with pathological septal deviation of the nose. In particular, septoplasty appears to be accompanied by a more even distribution of the nasal cycle across the two nasal cavities.

[Definition and illustration of the different types of nasal cycle using long-term rhinometry]

BACKGROUND

A reciprocal swelling of the nasal mucosa is often referred to as the classical nasal cycle; however, reports in the literature suggest a more complex picture. Most of the research on the nasal cycle is based on individual measurements. The long-term rhinometry (LRM) now makes it possible to continuously examine the cyclic swelling of the nasal mucosa over 24 h. The aim of this study was therefore to evaluate the nasal cycle with LRM over 24 h.

MATERIAL AND METHODS

An LRM was performed in 55 rhinologically healthy subjects over 24 h using the portable measuring system Rhino-Move© (Happersberger Otopront; Hohenstein, Germany).

RESULTS

In addition to the expected strictly reciprocal swelling of the nasal mucosa in the sense of the classical nasal cycle, the following cycle types were detected: in-concert type with simultaneous rise and drop of the air flow on both sides of the nose, the one-sided type with significant congestion and decongestion of the mucous membrane only on one side and no detectable changes on the other side of the nose and the non-cycle type without any change in airflow on both sides. Most subjects showed a complex picture with multiple cycle types within the 24 h measurement (mixed nasal cycle). The types often differed during the day and night.

CONCLUSION

This study confirms the assumption that the nasal cycle measured over 24 h is much more complex than often described in the literature. Most subjects showed several of the 5 cycle types described here. The LRM has proven to be an easy to- use and reliable measurement method. The relationship between cycle type and physical activity as well as other factors remains to be investigated.

EEG signatures change during unilateral Yogi nasal breathing

Airflow through the left-and-right nostrils is said to be entrained by an endogenous nasal cycle paced by both poles of the hypothalamus. Yogic practices suggest, and scientific evidence demonstrates, that right-nostril breathing is involved with relatively higher sympathetic activity (arousal states), while left-nostril breathing is associated with a relatively more parasympathetic activity (stress alleviating state). The objective of this study was to further explore this laterality by controlling nasal airflow and observing patterns of cortical activity through encephalographic (EEG) recordings. Thirty subjects participated in this crossover study. The experimental session consisted of a resting phase (baseline), then a period of unilateral nostril breathing (UNB) using the dominant nasal airway, followed by UNB using the non-dominant nasal airway. A 64-channel EEG was recorded throughout the whole session. The effects of nostril-dominance, and nostril-lateralization were assessed using the power spectral density of the neural activity. The differences in power-spectra and source localization were calculated between EEG recorded during UNB and baseline for delta, theta, alpha, beta and gamma bands. Cluster-based permutation tests showed that compared to baseline, EEG spectral power was significantly (1) decreased in all frequency bands for non-dominant nostril UNB, (2) decreased in alpha, beta and gamma bands for dominant nostril UNB, (3) decreased in all bands for left nostril UNB, and (4) decreased in all bands except delta for right nostril UNB. The beta band showed the most widely distributed changes across the scalp. our source localisation results show that breathing with the dominant nostril breathing increases EEG power in the left inferior frontal (alpha band) and left parietal lobule (beta band), whereas non-dominant nostril breathing is related to more diffuse and bilateral effects in posterior areas of the brain.These preliminary findings may stimulate further research in the area, with potential applications to tailored treatment of brain disorders associated with disruption of sympathetic and parasympathetic activity.

Re-evaluating the nasal cycle by long-term rhinoflowmetry: most individuals demonstrate a 'mixed' nasal cycle

BACKGROUND

The nasal cycle seems to be more complex than a strictly alternating swelling of the nasal mucosa. Long-term rhinoflowmetry (LRFM) allows continuous investigation of changes in nasal airflow over 24 hours (24h). We evaluated the various types of nasal cycle with LRFM over 24 hours and investigated the influence of age and gender.

METHODS

LRFM was continuously performed over 24h in 55 rhinologically healthy subjects (36 female, 19 male). The LRFM flow curves were examined for phases of the 'classical' 'in-concert' 'one-side' and'no-cycle' cycle types. Subjects were divided into 4 age subgroups (19-29; 30-49; 50-69; >70 years). Correlations of age and gender with the individual cycle forms were analyzed.

RESULTS

85.5% of the subjects presented a 'mixed' nasal cycle within 24h. 'classical' nasal cycle was seen most often (92.7% vs. 'in-concert' 56.4% vs. 'one-sided' 18.2% vs. 'no-cycle' 5.5%). Older age groups significantly more often presented the 'no-cycle' type. A tendency was seen towards a mixed nasal cycle with increasing age. The mixed nasal cycle was significantly more often seen in the female subjects.

CONCLUSIONS

LRFM is an easy-to-use measurement tool. The 'mixed' nasal cycle predominates. However, all 4 different cycle types can be detected, alternating over 24h in each subject. Moreover, the cycle type varies with age.

[Relevance of nasal provocation testing in house dust mite allergy]

Patients with house dust mite allergies frequently exhibit very different symptoms to those allergic to other inhalant allergens. The frequency of comorbid allergic asthma in these patients is increased. Therefore, diagnosing patients with suspected house dust mite allergies can be difficult. It is important to distinguish between sensitization to an allergen and a clinically relevant allergy. Nasal provocation testing (NPT) is a reliable method to identify patients suitable for a causal treatment (specific immunotherapy). Position papers on methodology and interpretation of NPT data are available. Skin prick and allergen-specific IgE tests reveal a reasonable correlation with NPT results, although this is inexact to some extent. Performance of NPT in patients with suspected house dust mite allergy is important in individuals with questionable symptoms and unclear skin and blood test results, particularly prior to initiation of allergen immunotherapy.

Estimates of nasal airflow at the nasal cycle mid-point improve the correlation between objective and subjective measures of nasal patency

INTRODUCTION

The nasal cycle represents a significant challenge when comparing pre- and post-surgery objective measures of nasal airflow.

METHODS

Computational fluid dynamics (CFD) simulations of nasal airflow were conducted in 12 nasal airway obstruction patients showing significant nasal cycling between pre- and post-surgery computed tomography scans. To correct for the nasal cycle, mid-cycle models were created virtually. Subjective scores of nasal patency were obtained via the Nasal Obstruction Symptom Evaluation (NOSE) and unilateral visual analog scale (VAS).

RESULTS

The correlation between objective and subjective measures of nasal patency increased after correcting for the nasal cycle. In contrast to biophysical variables in individual patients, cohort averages were not significantly affected by the nasal cycle correction.

CONCLUSIONS

The ability to correct for the confounding effect of the nasal cycle is a key element that future virtual surgery planning software for nasal airway obstruction will need to account for when using anatomic models based on single instantaneous imaging.

Measuring and Characterizing the Human Nasal Cycle

Nasal airflow is greater in one nostril than in the other because of transient asymmetric nasal passage obstruction by erectile tissue. The extent of obstruction alternates across nostrils with periodicity referred to as the nasal cycle. The nasal cycle is related to autonomic arousal and is indicative of asymmetry in brain function. Moreover, alterations in nasal cycle periodicity have been linked to various diseases. There is therefore need for a tool allowing continuous accurate measurement and recording of airflow in each nostril separately. Here we provide detailed instructions for constructing such a tool at minimal cost and effort. We demonstrate application of the tool in 33 right-handed healthy subjects, and derive several statistical measures for nasal cycle characterization. Using these measures applied to 24-hour recordings we observed that: 1: subjects spent slightly longer in left over right nostril dominance (left = 2.63 ± 0.89 hours, right = 2.17 ± 0.89 hours, t(32) = 2.07, p < 0.05), 2: cycle duration was shorter in wake than in sleep (wake = 2.02 ± 1.7 hours, sleep = 4.5 ± 1.7 hours, (t(30) = 5.73, p < 0.0001). 3: slower breathing was associated with a more powerful cycle (the extent of difference across nostrils) (r = 0.4, p < 0.0001), and 4: the cycle was influenced by body posture such that lying on one side was associated with greater flow in the contralateral nostril (p < 0.002). Finally, we provide evidence for an airflow cycle in each nostril alone. These results provide characterization of an easily obtained measure that may have diagnostic implications for neurological disease and cognitive state.

Simulating the nasal cycle with computational fluid dynamics

OBJECTIVES

(1) To develop a method to account for the confounding effect of the nasal cycle when comparing preoperative and postoperative objective measures of nasal patency. (2) To illustrate this method by reporting objective measures derived from computational fluid dynamics (CFD) models spanning the full range of mucosal engorgement associated with the nasal cycle in 2 subjects.

STUDY DESIGN

Retrospective.

SETTING

Academic tertiary medical center.

SUBJECTS AND METHODS

A cohort of 24 patients with nasal airway obstruction was reviewed to select the 2 patients with the greatest reciprocal change in mucosal engorgement between preoperative and postoperative computed tomography (CT) scans. Three-dimensional anatomic models were created based on the preoperative and postoperative CT scans. Nasal cycling models were also created by gradually changing the thickness of the inferior turbinate, middle turbinate, and septal swell body. Moreover, CFD was used to simulate airflow and to calculate nasal resistance and the average heat flux.

RESULTS

Before accounting for the nasal cycle, patient A appeared to have a paradoxical worsening nasal obstruction in the right cavity postoperatively. After accounting for the nasal cycle, patient A had small improvements in objective measures postoperatively. The magnitude of the surgical effect also differed in patient B after accounting for the nasal cycle.

CONCLUSION

By simulating the nasal cycle and comparing models in similar congestive states, surgical changes in nasal patency can be distinguished from physiological changes associated with the nasal cycle. This ability can lead to more precise comparisons of preoperative and postoperative objective measures and potentially more accurate virtual surgery planning.

[CT rhinometry : a correlation of rhinomanometry and multiplanar computer tomography of the nasal cavity]

BACKGROUND

Otorhinolaryngologists require new diagnostic methods to give further insight into the physiology of nasal breathing. The functional aspects of radiological data in the field of ENT have rarely been examined. This study compares computed tomography (CT) scan area measurements of the paranasal sinuses with physiological data from rhinomanometry.

PATIENTS AND METHODS

In a retrospective study, paranasal CT scans from 36 patients were analysed for volume, width and hydraulic diameter of the five key regions of the nasal cavity (CT rhinometry) and compared to the active anterior rhinomanometric (RMM) results representing the gold standard in nasal flow description.

RESULTS

The highest correlation between the rhinomanometric results and CT rhinometry was found at the internal ostium, followed by the diffuser region. The structures important for regulating nasal flow could thus be identified in the CT area data.

CONCLUSION

CT rhinometry revealed structures important for nasal breathing, in addition to providing anatomical and topographical data. CT rhinometry measured volumes, width and hydraulic diameters of the nasal cavity correlated with measurements of transnasal flow.

Septal injection of botulinum neurotoxin A for idiopathic rhinitis: a pilot study

PURPOSE

Botulinum neurotoxin A (BTA) is a promising therapeutic option in the treatment of idiopathic rhinitis (IR), a disease characterized by nasal obstruction and hydrous rhinorrhea. The conventional localization for the injection of BTA in IR is the nasal turbinates. In our own clinical experience, submucoperichondrial injection of BTA in the nasal septum is an alternative that is easy to perform for the therapist and also well tolerated by the patient.

MATERIAL AND METHODS

Five patients received an injection of in total 80 mouse units Dysport (Ipsen Pharma, Ettlingen, Germany) in the nasal septum. The unpleasantness of the nasal injection of BTA was measured on a visual analogue scale. Over the course of 14 days, nasal symptoms (rhinorrhea, nasal obstruction, urge to sneeze, nasal pruritus), the number of facial tissues used daily, and possible complications were evaluated.

RESULTS

The unpleasantness of the injection of BTA into the nasal septum after local anesthesia was rated low (visual analogue scale, 0.76 on average). A good subjective symptom control was achieved in 3 patients concerning rhinorrhea and in all patients concerning nasal obstruction. The number of facial tissues used daily as a parameter for rhinorrhea was on average 21.0 before the injection of BTA, decreased in 4 patients over the course of time, and was on average 5.8 after 14 days. No patient reported any adverse effects after the injection of BTA.

CONCLUSIONS

This pilot study demonstrates that septal injection of BTA in patients with IR can achieve good symptom control and patient comfort and should be compared in further studies to the conventional turbinal injection technique.

[Nasal-air conditioning]

INTRODUCTION

We present a review of nasal-air conditioning, a process essential to undisturbed gas exchange and cleansing of the respiratory mucosa in the nose.

METHODS

A selective literature review was made on the basis of in vivo measurements and computer simulation of the upper airways as well as the authors' own clinical and experimental data.

RESULTS AND DISCUSSION

Healthy subjects normally breathe through the nose, although the nasal airways have significantly higher airway resistance compared to the oral cavity, which is opened for breathing during exercise, in the case of nasal airway blockage, or in allergic rhinitis. In addition to olfaction, the main tasks of nasal breathing include: cleansing, defense, and conditioning (i.e., humidification and heating). The current knowledge of nasal conditioning processes will be discussed. In addition, research activities of particular relevance for diagnosis and intervention in various pathologies of the upper airways will be presented.

[Diagnostic methods of nasal respiratory function]

Objective assessment of nasal obstruction may help with preoperative planning for rhinosurgery and indicate different aspects of endonasal pathology. To improve quality control, preoperative and postoperative objective assessment is desirable. This review presents objective functional diagnostic tools and explains their appropriate uses, the information obtained, and their limitations. An algorithm is presented for analysing nasal obstruction by means of objective functional assessment. Examples illustrate how to use this information for preoperative planning in rhinosurgery.

Paradoxical nasal obstruction: analysis of characteristics using acoustic rhinometry

BACKGROUND

The aim of this study was to determine the characteristics of acoustic rhinometric parameters in patients with paradoxical nasal obstruction.

METHODS

The medical records of 1844 patients who had nasal septal deviation between 1998 and 2004 at our institute were assessed retrospectively. The authors selected 31 subjects for the experimental group and 256 subjects for the control group. Minimal cross-sectional area (MCA), volume, and degree of mucosal change at baseline and decongested phase were analyzed.

RESULTS

MCA of the convex side in the baseline state for the experimental (paradoxical) group is wider than that for the control group (p = 0.005). Degree of mucosal change of the experimental group is smaller than that of the control group in the convex side (p = 0.001). Other parameters are similar for the two groups.

CONCLUSION

Patients with paradoxical nasal obstruction might be explained by less degree of mucosal change in the concave side of the nasal cavity during nasal cycle than the control group.

Expiratory nasal sound analysis as a new method for evaluation of nasal obstruction in patients with nasal septal deviation: comparison of expiratory nasal sounds from both deviated and normal nasal cavity

BACKGROUND

The reliability of nasal obstruction measurements could be improved, and several new techniques are being developed. Our objective was to investigate the use of a new software program, Odiosoft-Rhino, in the assessment of nasal obstruction via analysis of the sounds of nasal expiration.

METHODS

We compared the nasal symptom scores and Odiosoft-Rhino and acoustic rhinometry test results for 61 patients with known nasal septal deviation.

RESULTS

We found a significant difference, and a correlation, between Odiosoft-Rhino results at 2000-4000 Hz and 4000-6000 Hz intervals, and the minimal cross-sectional area 2.2 cm from the nostril, in the right nasal cavity in patients with right-sided deviations. Similar results were observed for the left nasal cavity in patients with left-sided deviations.

CONCLUSIONS

The Odiosoft-Rhino software test is noninvasive, requires minimal cooperation and experience, and provides results that can be saved as digital data. Additionally, data from the Odiosoft-Rhino test are strongly correlated with acoustic rhinometry results and visual analogue scores of nasal obstruction. It seems that sound intensity within the 2000-4000 Hz and 4000-6000 Hz intervals is more sensitive than other sound intensity intervals. Thus, we speculate that Odiosoft-Rhino testing could be used as a new diagnostic method in order to evaluate nasal airflow in clinical practice.

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.