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PURPOSE: To investigate the nasal cycle (NC) during sleep in healthy individuals without nasal obstruction or obstructive sleep apnoea via a flexible wearable respiratory monitoring system in a continuous and real-time manner. METHODS: NC during sleep was continuously measured in 30 healthy individuals (15 women, 15 men) via long-term sleep respiratory monitoring system, while sleep stage and body position were simultaneously recorded via polysomnography (PSG). The number of NC transitions and positional changes were documented each night. Additionally, time intervals between NC transitions and their closest positional changes during sleep were meticulously recorded to investigate potential correlations between them. RESULTS: A total of 86.7% of the participants displayed the classic NC, with a mean duration of 6.43 ± 2.33 h. Nightly observations revealed an average occurrence of 2.19 ± 0.40 NC transitions, predominantly occurring during REM stage (68.4%), and 9.15 ± 7.77 postural changes. Analysis of the intervals between NC transitions and positional changes revealed an average absolute value of 27.72 ± 10.85 min, with a substantial 56.4% exceeding 30 min, indicating a non-obvious sequence order among them. CONCLUSION: NC can be measured in a continuous and real-time manner, the transitions occur mainly during the REM stage. However, we have not identified a clear correlation between NC transition and positional change.

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Background: Traditional yoga texts describe "cross nostril breathing," with inhalation and exhalation through different nostrils. Previous research reported no clear differences in oxygen consumption during uninostril breathing (i.e., inhalation and exhalation through the same nostril), hence not supporting right and left uninostril breathing as activating or relaxing, respectively, with no research on oxygen consumed in "cross nostril breathing." Methods: Oxygen consumed during "cross nostril breathing" was measured in healthy participants (n = 47, males, 26.3 ± 6.4 years). Five sessions (viz., right nostril inspiration yoga breathing [RNIYB], left nostril inspiration yoga breathing [LNIYB], alternate nostril yoga breathing [ANYB], breath awareness (BAW), and quiet rest (QR) were conducted on separate days in random order. Sessions were 33 min in duration with pre, during, and post states. Results: Volume of oxygen consumed (VO2) and carbon dioxide eliminated (VCO2) increased during RNIYB (9.60% in VO2 and 23.52% in VCO2), LNIYB (9.42% in VO2 and 21.20% in VCO2) and ANYB (10.25% in VO2 and 22.72% in VCO2) with no significant change in BAW and QR. Diastolic blood pressure decreased during BAW and QR and after all five sessions (P < 0.05; in all cases). All comparisons were with the respective preceding state. Conclusion: During the three yoga breathing practices, the volume of oxygen consumed increased irrespective of the nostril breathed through, possibly associated with (i) conscious regulation of the breath; (ii) attention directed to the breath, and (iii) "respiration-locked cortical activation." Restriction of the study to males reduces the generalizability of the findings.

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To study the characteristics of nasal airflow in the presence of nasal cycle by computational fluid dynamics. CT scan data of a healthy Chinese individual was used to construct a three-dimensional model of the nasal cavity to be used as simulation domain. A sinusoidal airflow velocity is set at the nasal cavity entrance to reproduce the breathing pattern of a healthy human. There was a significant difference in the cross-sectional area between the two sides of the nasal cavity. Particularly, the decongested side is characterized by a larger cross-section area, and consequently, by a larger volume with respect to the congested side. The airflow velocity, pressure, and nasal resistance were higher on the congested narrow side. The temperature regulation ability on the congested narrow side was stronger than that on the decongested wider side. During the nasal cycle, there are differences in the nasal cavity function between the congested and decongested sides. Therefore, when evaluating the impact of various factors on nasal cavity function, the nasal cycle should be considered.

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Obstructive sleep apnea (OSA) patients who use continuous positive airway pressure (CPAP) often complain of nasal dryness and nasal obstruction as side effects of CPAP. The physiological mechanisms by which CPAP may cause nasal dryness and nasal obstruction remain poorly understood. It has been hypothesized that CPAP interferes with the nasal cycle, abolishing the resting phase of the cycle and leading to nasal dryness. We performed rhinomanometry measurements in 31 OSA patients sitting, laid supine, and supine after 10 min of CPAP at 10 cmH2O. A posture change from sitting to supine led to more symmetric airflow partitioning between the left and right nostrils in the supine position. CPAP did not have a significant impact on nasal resistance, unilateral airflows, or airflow partitioning. Our results suggest that airflow partitioning becomes more symmetric immediately after changing to a supine position, while CPAP had no effect on nasal airflow, thus preserving the nearly symmetric airflow partitioning achieved after the posture change.

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Nasal cycle (NC) is a rhythmic change of lateralised nasal airflow mediated by the autonomous nervous system. Previous studies reported the dependence of NC dominance or more patent side on handedness and hemispheric cerebral activity. We aimed to investigate firstly the possible lateralised effect of NC on olfactory bulb volume and secondly the association of NC with the lateralised cerebral dominance in terms of olfactory processing. Thirty-five subjects (22 women and 13 men, mean age 26 ± 3 years) participated in the study. NC was ascertained using a portable rhino-flowmeter. Structural and functional brain measurements were assessed using a 3T MR scanner. Vanillin odorant was presented during functional scans using a computer-controlled olfactometer. NC was found to be independent of the olfactory bulb volumes. Also, cerebral activations were found independent of the NC during odorant perception. NC potency is not associated with lateralised structural or functional differences in the cerebral olfactory system.

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This study investigated the intricate dynamics of intranasal spray deposition within nasal models, considering variations in head orientation and stages of the nasal cycle. Employing controlled delivery conditions, we compared the deposition patterns of saline nasal sprays in models representing congestion (N1), normal (N0), and decongestion (P1, P2) during one nasal cycle. The results highlighted the impact of the nasal cycle on spray distribution, with congestion leading to confined deposition and decongestion allowing for broader dispersion of spray droplets and increased sedimentation towards the posterior turbinate. In particular, the progressive nasal dilation from N1 to P2 decreased the spray deposition in the middle turbinate. The head angle, in conjunction with the nasal cycle, significantly influenced the nasal spray deposition distribution, affecting targeted drug delivery within the nasal cavity. Despite controlled parameters, a notable variance in deposition was observed, emphasizing the complex interplay of gravity, flow shear, nasal cycle, and nasal morphology. The magnitude of variance increased as the head tilt angle increased backward from upright to 22.5° to 45° due to increasing gravity and liquid film destabilization, especially under decongestion conditions (P1, P2). This study's findings underscore the importance of considering both natural physiological variations and head orientation in optimizing intranasal drug delivery.

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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.

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OBJECTIVE: To explore whether the different phases of the nasal cycle have a significant effect on nasal temperature, the nasal mucosal clearance rate, and levels of nasal nitric oxide (nNO) and to investigate the correlation between these nasal conditions. METHODS: The study participants were divided into 2 groups: the control group and the rhinitis group. The participants' nasal temperature, cilia clearance rate, and nNO levels were measured during different phases of the nasal cycle (the congestion phase and decongestion phase) in the control group and before and after undergoing inferior turbinate ablation in the rhinitis group. RESULTS: The temperature of the nasal cavity in the control group was significantly higher in the congestion phase than in the decongestion phase (P = .0025), while in the rhinitis group, the temperature of the nasal cavity decreased significantly after inferior turbinate ablation (P = .001). In the control group, the nasal mucosa clearance time was significantly shorter in the congestion phase than in the decongestion phase (P = .001), and in the rhinitis group, the clearance time of the nasal mucosa was significantly shortened after the operation (P = .0025). In the control group, the levels of nNO were significantly higher in the congestion phase than in the decongestion phase (P = .025), while in the rhinitis group, nNO levels decreased significantly after the operation (P = .005). CONCLUSION: The function of the nasal cavity changes in different phases of the nasal cycle. Therefore, when evaluating the impact of various factors on nasal function, factors associated with the nasal cycle should also be considered. Inferior turbinate plasma ablation can improve the ciliary function of the nasal mucosa, reduce the temperature of the nasal cavity, and reduce nNO levels.

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The yogic pranayama technique of unilateral nostril breathing (UNB) has previously demonstrated improvements in language and anxiety in stroke sufferers, as well as reduced blood pressure and increased heart rate in normal healthy adults. The nose typically passes different amounts of air through each nostril with the greater amount of air passing through the 'patent' side, and a lesser amount through the 'congested' side. Each side of the nose periodically takes turns at carrying the dominant tidal air flow in what is termed the' nasal cycle'. The nasal sinuses are a rich source of inhaled nitric oxide, a colourless and odourless gas that acts as a bronchodilator, vasodilator, and neurotransmitter. Nasal derived nitric oxide (NO) may contribute to the benefits attributed to UNB. This investigation seeks to assess the influence the nasal cycle has on inhaled nasopharyngeal NO concentrations during UNB by comparing unobstructed bilateral nostril breathing to patent-side and congested-side UNB in healthy individuals demonstrating a nasal cycle. After determining the patent and congested nasal sides in healthy adult volunteers, and sampling air at both nostrils, nasopharyngeal inhaled NO concentrations were then assessed during normal nasal at-rest tidal breathing during three different nasal breathing states: first both nostrils, then allocated in randomised order, patent side only, and congested side with only UNB. Nasopharyngeal NO concentrations were found to be consistently higher on both exhalation and inhalation during congested side UNB, when compared with either unilateral patent side UNB or breathing through both nostrils.

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BACKGROUND: The nasal cycle is one of the many cyclic events in a human being. Nasal airflow is greater in one nostril at any given point in time and this alternates between right and left nostrils over time. Its periodicity ranges from 25 min to 8 h. This alteration has been known to be controlled by the autonomic nervous system. The current study was designed to assess the effect of nasal dominance during rest on pulmonary function parameters and heart rate. MATERIALS AND METHODS: A cross-sectional study was done on 35 apparently healthy individuals of the age group of 18-30 years. Based on a cold mirror test, the participants were categorized into two groups of right nasal dominance (RND) and left nasal dominance (LND). The parameters recorded were forced expiratory volume in the first sec (FEV1), forced vital capacity (FVC), FEV1/FVC, peak expiratory flow rate, forced expiratory flow between 25%-75%, SpO2, and pulse rate. Data were expressed as mean ± standard deviation and were analyzed using SPSS version 20. RESULTS: All pulmonary function parameters exhibited higher values in RND participants compared to LND participants and the difference was found to be statistically significant (P < 0.05). CONCLUSION: Nasal dominance has a measurable effect on pulmonary functions and heart rate hence emphasizing the role of autonomic control of airways. This influence can be used as adjuvant therapy for certain disorders.

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OBJECTIVES/HYPOTHESIS: Demonstrate that the Nasal Obstruction Balance Index (NOBI) model fulfils the unmet need of improving unilateral correlation between subjective and objective nasal obstruction outcome measures and identifying the more obstructed side. Improve correlation between unilateral objective nasal airway measurements (nasal inspiratory peak flow [NIPF] and acoustic rhinometry [AR]) and subjective Visual Analogue Scale for nasal obstruction (VAS-NO) scores. Improve assessment of nasal airway asymmetry by evaluating unilateral measurements both before and after the application of nasal decongestant; which the patient could better understand. NOBI represents a ratio calculated by taking the difference between left and right nasal airway measurements and divided by the maximum unilateral measurement. It is based on Poiseuille's law and aims to reduce the confounding variables which challenge nasal airway measurement. STUDY DESIGN: Prospective cohort study. METHODS: Forty-three controls and 34 patients with nasal obstruction underwent both unilateral and bilateral NIPF, AR and VAS-NO measurements; these were repeated after the application of nasal decongestant. The NOBI values for unilateral NIPF, AR, and VAS-NO were calculated both before and after decongestant. RESULTS: The correlation between unilateral NIPF and AR measurements was enhanced considerably (r = 0.57, P < .01) when NOBI was applied. The NOBI metric significantly increased the correlation between unilateral NIPF, AR, and VAS-NO scores. Postdecongestant NOBI for NIPF and AR measurements correctly identified the more obstructed side in 82.4% and 94.1% of the deviated nasal septum (DNS) cases, respectively. CONCLUSION: The NOBI model provides a better correlation between unilateral subjective and objective measurements and identifies the more obstructed side. LEVEL OF EVIDENCE: 3 Laryngoscope, 131:E2833-E2840, 2021.

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INTRODUCTION: This review discusses how nasal congestion may have benefits as a mechanism of defence against respiratory viruses. METHODS: A literature research was conducted on respiratory viruses and nasal congestion, following a recently published review on how temperature sensitivity is important for the success of common respiratory viruses. RESULTS: The literature reported that common respiratory viruses are temperature sensitive and replicate well at the cooler temperatures of the upper airways (32°C), but replication is restricted at body temperature (37°C). The amplitude of the phases of congestion and decongestion associated with the nasal cycle was increased on infection with respiratory viruses and this caused unilateral nasal congestion and obstruction. Nasal congestion and obstruction increase nasal mucosal temperature towards 37°C and therefore restricted the replication of respiratory viruses. CONCLUSION: Nasal congestion associated with the nasal cycle may act as a mechanism of respiratory defence against infection with respiratory viruses.

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Nasal saline irrigation is frequently utilised in rhinosinusitis management, and after nasal and sinus surgery. Nasal saline irrigation improves mucociliary transport and assists inflammatory mediator and post-surgical debris removal. The aim of this study was to assess the influence different head positions, irrigation inflow nostril, and the nasal cycle have on Neti pot nasal saline volume filling within the nasal passages and maxillary sinuses. Computational fluid dynamics modelling using anatomically correct nasal geometry found only minor difference in nasal cavity volume filling with inflow from either side of the nose however both head position and inflow direction were both found to have a major influence on maxillary sinus volume filling. Computational modelling flow velocity results at the nasopharynx were validated using particle image velocimetry. It was also found that directing irrigation inflow into the patent side of the nose while in the head-back position achieved the highest volume filling of both maxillary sinuses.

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Anatomically accurate 3D models of 10 healthy nasal cavities are developed from computerized tomography (CT) scan images. Considering anatomical and physiological importance of different parts of the nasal cavity, the surface of each nasal passage is divided to eleven anatomical surfaces. Also the coronal cross sections in the nasal passage are divided to six sub-sections that share the total nasal passage airflow. The details of the flow field, heat transfer and water-vapor transport are numerically investigated for resting and low activity conditions. The mean and standard deviation of the different anatomical and air conditioning parameters such as: surface area, wall shear stress, heat and moisture transfer on different parts of the nasal passage surfaces and volume flow rates through different sections are presented. Results show that the percentages of airflow for inferior, middle and superior meatuses are 11.3 ± 6.4, 36.5 ± 9.5, 1.9 ± 0.81 % respectively and 4.1 ± 2.1 % of air passes through olfactory area. The inhaled air passing from the remaining surface (main passage) is 46.2 ± 10 %. Heat and moisture fluxes are highest in the anterior part of the nasal cavity, turbinates and lower part of the septum respectively. The percentage of the heat transfer from turbinates is 25.7 ± 3.9 % of total nasal heat transfer.

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Nasal saline irrigation is frequently utilised in allergic rhinitis and rhinosinusitis management, and after nasal and sinus surgery. Anatomical modelling, clinical and computational studies guide treatment optimisation. This review offers a comprehensive summary of the modelling methodologies used in previous nasal irrigation studies by undertaking a systematic analysis of anatomical, clinical and computational investigations that assessed nasal saline irrigation using Medline, EMBASE, and Cochrane Review databases. Both procedural and assessment methods were reviewed. It was found that all twenty-four publications reviewed did not discuss the influence of the nasal cycle on internasal geometry and nasal resistance. Cadaver studies misrepresent in vivo nasal geometry. Irrigation pressure and shear forces, which could influence mucociliary transport and postoperative cleaning, were not evaluated. Previous studies focus on irrigation coverage and have not considered the nasal cycle which influences unilateral nasal resistance and thus pressure/ flow relationships and may also increase nasal air-locking. New computational fluid dynamic models could better inform nasal irrigation clinical practice.

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The air-conditioning characteristics in nasal cavity models obtained from two subjects exhibiting different degrees of the nasal cycle states in terms of the airflow partition were investigated using computational fluid dynamics. A constant inspiratory flow rate of approximately 250 mL/s was considered, and the air temperature and relative humidity at the inlet were assumed to be 25 °C and 35%, respectively. The air-conditioning capacities of the congested and decongested sides were assessed by the amounts of epithelial heat and water vapor transferred to the inhaled air through the airway from the nostrils to the end of the septum. The results revealed that the air temperature and relative humidity near the end of the septum, respectively, reached approximately 31.4-32.5 °C and 81.4-88.0% in the decongested sides and 34.0-35.9 °C and 95.3-100% in the congested sides. The differences seen in the air temperatures and relative humidity between the congested and decongested sides were found to be larger in the cavity model that showed a larger degree of reciprocal change in the airflow rate. From a fluid mechanics perspective, while the congested side is in a rest period during the nasal cycle such that a lower amount of airflow is transported through it, this side, in effect, works to provide assistive air-conditioning capacity to the nasal cavity and aids when insufficiently conditioned airflow passes through the decongested side so that the inhaled air merging after the septum can approach the alveolar condition favorably through the nasopharynx.

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We can benefit from various services with context recognition using wearable sensors. In this study, we focus on the contexts acquired from sensor data in the nostrils. Nostrils can provide various contexts on breathing, nasal congestion, and higher level contexts including psychological and health states. In this paper, we propose a context recognition method using the information in the nostril. We develop a system to acquire the temperature in the nostrils using small temperature sensors connected to glasses. As a result of the evaluations, the proposed system can detect breathing correctly, workload at an accuracy of 96.4%, six behaviors at an accuracy of 54%, and eight behaviors in daily life at an accuracy of 86%. Moreover, the proposed system can detect nasal congestion, therefore, it can log nasal cycles that are considered to have a relationship with the autonomic nerves and/or biological states.

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OBJECTIVE: To plot the nasal cycle using unilateral peak nasal inspiratory flow (UPNIF) and unilateral minimal cross-sectional area (UMCA) readings demonstrating a linear relationship in normal nasal function. Additionally, to determine how this changes in abnormal nasal function. DESIGN: A cross-sectional study measuring UPNIF and UMCA in controls demonstrating normal nasal function and in patients with nasal obstruction. SETTING: Royal National Throat Nose and Ear Hospital, London. PARTICIPANTS: A total of 39 participants, 26 controls and 13 patients, were recruited. Controls exhibited normal nasal function with SNOT-22 <5. Patients nasal obstruction symptoms secondary to inflammation or structural abnormality with SNOT-22 >9. MAIN OUTCOME MEASURES AND RESULTS: Airflow rates and resistance values were derived from UPNIF and UMCA measurements respectively based on Poiseuille's laws. Ratios between right and left UPNIF and UMCA values were taken to adjust for confounding factors. The relationship of 1/Resistance Ratio and Airflow Rate Ratio demonstrated a linear of direct proportionality of strong correlation and statistical significance (correlation coefficient = 0.76, P « 0.01). This suggests that data points from controls with a normal nasal cycle lie closely along the regressed line, whilst those lying significantly away were shown to belong to patients with nasal dysfunction. Olfactory dysfunction appears to be a sensitive discriminator in predicting this. CONCLUSION: This study demonstrates the directly proportional relationship of 1/Resistance Ratio and Airflow Rate Ratio in normal nasal function. Furthermore, nasal pathology can be predicted if data points lie significantly outside these normal limits. Further studies are needed to validate exact normal and abnormal thresholds.

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The inferior turbinate has well-recognized respiratory and immune functions to provide the airway with appropriate warmth, humidification, and filtration of the inspired air while sampling the environment for pathogens. Normal functioning of the inferior turbinate relies on an intact autonomic system to maintain homeostasis within the nasal cavity. The autonomic nervous system innervates the submucosal glands and the vasculature within the inferior turbinate, resulting in control of major turbinate functions: nasal secretions, nasal patency, warmth, and humidification. This review will summarize the autonomic innervations of the turbinates, both the normal and abnormal autonomic processes that contribute to the turbinate functions, and the clinical considerations regarding optimal functioning of the turbinate autonomic system.

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