A model for the central control of airflow patterns within the human nasal cycle

Real-time observation of nasal cycle during sleep with polysomnography

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.

Nasal Patency Measurement: State of the Art of Acoustic Rhinometry

Nasal obstruction is one of the main symptoms of different nasal pathologies. Many physiological and pathological conditions can produce nasal airflow impairment causing nasal obstruction and affecting patients' quality of life. There are different methods for the measurement of nasal obstruction, but in clinical practice the most common used are acoustic rhinometry, rhinomanometry, and peak nasal inspiratory flow. This review describes the fundamentals of acoustic rhinometry, its normal values, the different physiological and pathological conditions that can modify nasal patency, and the utility of this instrument for the measurement of nasal obstruction in clinical practice. Acoustic rhinometry is a simple test, so it is suitable for measurements in the pediatric population, i.e., for evaluating adenoid hypertrophy. Acoustic rhinometry normal values are available, unilaterally and bilaterally for pediatric and adult populations. Acoustic rhinometry has been demonstrated to be reproducible and even superior to rhinomanometry when measuring nasal modifications during challenges. It is possible to use acoustic rhinometry before and after nasal surgery. Measuring nasal cavities volume and cross-sectional area, acoustic rhinometry is particularly indicated in rhinosurgery, especially for the evaluation of spreader grafts. Brief considerations about the correlation between nasal symptoms, in particular the subjective sensation of nasal obstruction, and the acoustic rhinometry results as well as the correlation of acoustic rhinometry with other methods for the measurement of nasal obstruction are also reported. Objective and subjective evaluation of nasal obstruction gives different information that together optimizes the diagnosis and the treatment of rhinologic patients. Acoustic rhinometry alone or in combination of other instruments for the measurement of nasal obstruction or patency should be used regularly in every outpatient clinic that treats patients with nasal obstruction as there is an increasing need of evidence-based therapies.

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.

Inferior nasal turbinate mucosa shrinkage prior to surgery under local anaesthesia

INTRODUCTION AND OBJECTIVES

Chronic rhinitis-related complaints may result from isolated hypertrophy of the inferior nasal turbinates. If the symptoms persist despite conservative management, turbinoplasty is indicated. However, the nasal mucosa lining the inferior turbinates seems decongested immediately before the surgery performed under local anaesthesia, compared to the examination when the patients were entered for surgery. The study aimed to confirm this observation and to hypothesize as to the reasons for its occurrence.

PATIENTS AND METHODS

The measurements of the longest distances between the medial rim of the inferior nasal turbinate mucosa and nasal septum and the shortest distances between the lower rim of the turbinate and floor of the nasal cavity in the inferior part of both common nasal meatus, were carried out on photos taken during endoscopic examinations: the one entering the patient for turbinoplasty, and the other immediately before the procedure. The results in this group were compared to those obtained from patients operated on under general anaesthesia.

RESULTS

In 130 patients aged 18-60 (mean=40.7) years, operated on under local anaesthesia, the sum of the mean distances between the nasal septum and the medial rim of the lower turbinate in both nasal cavities, was 3.4mm during the first examination, and 4.5mm (p=.0008) during the second one. In the group of 42 participants aged 26-47, mean=36.8 years operated on under general anaesthesia, the values were: 4.8mm and 3.6mm (p=.02), respectively. The differences were significantly smaller in the smokers (.3) compared to non-smokers (1.3; p=.04) mm.

CONCLUSIONS

Records of the entering examination must be considered before turbinoplasty under local anaesthesia.

Side asymmetry in nasal resistance correlate with nasal obstruction severity in patients with septal deformities: Computational fluid dynamics study

OBJECTIVES

The objective of this study was to investigate the relationship between side asymmetry in nasal resistance (NR) and severity of the nasal airway obstruction (NAO) in patients with different types of nasal septal deformity (NSD).

DESIGN

Computational fluid dynamics (CFD) study.

SETTING

The study was conducted in a tertiary medical centre.

PARTICIPANTS

The study included 232 patients, who were referred to the CT examination of the paranasal sinuses. Exclusion criteria were sinonasal and respiratory diseases that may interfere with the nasal obstruction. The presence and the type of NSD were recorded according to the Mladina's classification.

MAIN OUTCOME MEASURES

The presence and severity of NAO in each patient were assessed by NOSE questionnaire. Eight computational models of the nasal cavity were created from CT scans. Models represented seven Mladina's NSD types and a straight septum of a symptomless patient. CFD calculated airflow partitioning and NR for each nasal passage. Side differences in NR were calculated by the equation ∆NR = NR_left  - NR_right . The relationship between NOSE scores, airflow partitioning and side differences in NR was explored using Spearman's correlation analysis.

RESULTS

Mladina's types of NSD showed differences in airflow partitioning and the degree of side asymmetry in NR. A significant positive correlation was detected between side differences in NR and NOSE scores (R = .762, P = .028). A significant negative correlation was found between the per cent of unilateral airflow and NR (R = -.524, P = .037).

CONCLUSIONS

Our results demonstrated that side asymmetry in NR could explain differences in NAO severity related to the NSD type.

Characterization of the Airflow within an Average Geometry of the Healthy Human Nasal Cavity

This study's objective was the generation of a standardized geometry of the healthy nasal cavity. An average geometry of the healthy nasal cavity was generated using a statistical shape model based on 25 symptom-free subjects. Airflow within the average geometry and these geometries was calculated using fluid simulations. Integral measures of the nasal resistance, wall shear stresses (WSS) and velocities were calculated as well as cross-sectional areas (CSA). Furthermore, individual WSS and static pressure distributions were mapped onto the average geometry. The average geometry featured an overall more regular shape that resulted in less resistance, reduced WSS and velocities compared to the median of the 25 geometries. Spatial distributions of WSS and pressure of the average geometry agreed well compared to the average distributions of all individual geometries. The minimal CSA of the average geometry was larger than the median of all individual geometries (83.4 vs. 74.7 mm²). The airflow observed within the average geometry of the healthy nasal cavity did not equal the average airflow of the individual geometries. While differences observed for integral measures were notable, the calculated values for the average geometry lay within the distributions of the individual parameters. Spatially resolved parameters differed less prominently.

Relationship Between Nasal Cycle, Nasal Symptoms and Nasal Cytology

Background

The nasal cycle is the spontaneous congestion and decongestion of nasal mucosa that happens during the day. Classically, 4 types of nasal cycle patterns have been described: (1) classic, (2) parallel, (3) irregular, and (4) acyclic. Hypothalamus has been considered as the central regulator even if several external factors may influence its activity.

Objective

The aim of the study was to evaluate the presence of a correlation between nasal cycle pattern, nasal cytology and nasal symptoms.

Methods

Thirty healthy volunteers have been enrolled in the study. All subjects completed a Sino-Nasal Outcome Test-22 questionnaire and a Visual Analog Scale (VAS) for nasal obstruction. The nasal cycle was studied by means of peak nasal inspiratory flow. Nasal cytology has been used to evaluate the presence of local nasal inflammation.

Results

Nineteen subjects showed a parallel nasal cycle pattern, while 11 showed a regular one. A parallel pattern was present in 60% of asymptomatic subjects and in 67% of the symptomatic one ( P = 1). VAS for nasal obstruction did not show a significant difference between the 2 patterns of the nasal cycle ( P = .398). Seventeen subjects had a normal rhinocytogram, while 13 volunteers showed a neutrophilic rhinitis; 53.8% of the subjects with a neutrophilic rhinitis showed a parallel pattern, while the remaining 46.2% had a regular one. In the case of a normal cytology, 70.6% of the volunteers had a parallel pattern and 29.4% had a regular one. Differences between the 2 groups were not statistically significant ( P = .575).

Conclusion

Rhinitis with neutrophils seems to not influence the nasal cycle pattern. Based on the present results, the pattern of nasal cycle does not influence subjective nasal obstruction sensation.

A Case of Synchronised Pupillary and Nasal Cycling: Evidence for a Central Autonomic Pendulum?

We previously reported that some healthy individuals show alternating anisocoria. We now describe one such individual who also exhibits a classic nasal cycle (alternating periods of nasal congestion and decongestion). We made measurements of his pupil asymmetry and nasal asymmetry at 21 different time points and found that these variables were always synchronised such that greater nasal airflow was invariably found on the same side as the larger pupil. We hypothesise that a common central oscillator may be responsible for co-modulating the sympathetic outflow to both nasal vessels and iris dilator muscles in some healthy individuals.

Is there any relationship between right and left hand dominance and right and left nasal airflow dominance?

BACKGROUND

Left- or right-handedness is a common human trait, and it has been previously reported that human nasal airflow dominance correlates with hand dominance. Any relationship between hand dominance and nasal airflow dominance would be unusual. This study aimed to measure nasal airflow and look for any relationship to handedness.

METHODS

The modified Glatzel mirror was used to record the dominant nasal passage at 15-minute intervals over a 6-hour period in 29 healthy participants consisting of 15 left-handers and 14 right-handers.

RESULTS

In left-handers, the percentage of time that the left nasal passage was dominant ranged from 0 to 100 per cent. In right-handers, the percentage of time that the right nasal passage was dominant ranged from 4.2 to 95.8 per cent. No correlation between nasal airflow dominance and hand dominance was identified.

CONCLUSION

The results do not support the hypothesis that nasal airflow and handedness are related.

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.

Nasal airflow and brain activity: is there a link?

BACKGROUND

Over the past few decades, evidence has emerged suggesting that nasal airflow asymmetry and brain asymmetry are linked. The nose exhibits asymmetrical airflow, with the dominant airflow alternating from one nasal passage to the other over a period of hours. Some authors have suggested a correlation between cerebral hemisphere dominance and nostril dominance. Others have proposed an association between rhythmic fluctuations in nasal airflow and corresponding fluctuations in cerebral hemisphere activity. Based on ancient yoga breathing techniques, newer evidence suggests that altering nasal airflow can influence brain activity, with reports of improved cognitive function caused by unilateral forced nostril breathing. It seems that a nasal airflow stimulus may have an activating effect on the brain, as it has also been shown to trigger seizure activity in epileptic patients.

OBJECTIVES

This article explores these theories in detail, reviews the evidence, and presents new models linking nasal airflow and brain activity.