Nasal cycle in children

Nasal Disorders

Nasal obstruction, rhinorrhea, and epistaxis are common presenting concerns in primary care clinics. Nasal disorders affect the quality of life for many children and families. Rarely, these complaints may represent a life-threatening condition among infant obligate nasal breathers or cases of unusual pathology. The most common causes of rhinorrhea and nasal obstruction vary by age and include physiologic, infectious, allergic, foreign body, irritant, and traumatic causes. Less commonly, children may have congenital malformations, sinonasal masses, or autoimmune disease. The most common causes of epistaxis are inflammatory, environmental, and traumatic causes and medication misuse, but rarely, children may have predisposing anatomic, hematologic, or vascular abnormalities or even sinonasal tumors. In this article, we provide a thorough review of the common nasal disorders treated every day in primary care clinics and mention briefly some of the rare but serious cases that may be overlooked without considering a full differential diagnosis.

Assessing Nasal Epithelial Dynamics: Impact of the Natural Nasal Cycle on Intranasal Spray Deposition

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.

[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.

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.

Circuits for social learning: A unified model and application to Autism Spectrum Disorder

Early life social experiences shape neural pathways in infants to develop lifelong social skills. This review presents the first unified circuit-based model of social learning that can be applied to early life social development, drawing together unique human developmental milestones, sensitive learning periods, and behavioral and neural scaffolds. Circuit domains for social learning are identified governing Activation, Integration, Discrimination, Response and Reward (AIDRR) to sculpt and drive human social learning. This unified model can be used to identify social delays earlier in development. We propose social impairments observed in Autism Spectrum Disorder are underpinned by early mistimed sensitive periods in brain development and alterations in amygdala development to disrupt the AIDRR circuits. This model directs how interventions can target neural circuits for social development and be applied early in life. To illustrate, the role of oxytocin and its use as an intervention is explored. The AIDRR model shifts focus away from delivering broad treatments based only on diagnostic classifications, to specifying and targeting the relevant circuits, at the right time of development, to optimize social learning.

The Effect of the Nasal Cycle on the Interpretation of Rhinomanometric Results in a Nasal Provocation Test

A nasal provocation test was carried out in two groups of adults: patients with birch pollen allergy (n = 25) and a group of healthy volunteers with no nasal allergy (n = 25). An endonasal provocation test was performed using increasing concentrations of birch pollen extract. The maximal duration of the test was 1 hour. The physiologic changes in the nasal patency in both groups were studied at a separate session at 10-minute intervals during 1 hour. The nasal patency was recorded with a computerized rhinomanometer using the anterior active method. The statistical analysis of the results shows that modern rhinomanometry is a reliable method of objectively evaluating the alternations in nasal obstruction during a nasal provocation test. The rhinomanometric findings correlate well with the rhinoscopic findings and the subjective symptoms of the patients. The changes in the nasal resistance values during the provocation were significantly larger than the physiologic ones. The individual biologic rhythmicity of nasal airway patency cannot hide the real positive result of a rhinomanometric provocation test, but it must be considered as an important factor in interpreting the results in nasal challenge.

Airflow and the Nasal Cycle: Nasal Patency Fluctuations after Laryngectomy

A periodic fluctuation in nasal patency or “nasal cycle” is observed in the majority of adults but has not hitherto been demonstrated in individuals after diversion of nasal airflow. Acoustic rhinometry, a highly sensitive technique which does not require airflow, provided the opportunity to evaluate this situation in patients who had undergone laryngectomy. We examined 21 postoperative individuals (mean postoperative time 4 years) and 14 control subjects matched for age (including 2 patients prelaryngectomy). Acoustic rhinometry was performed serially over 3–8 hours to determine minimum cross-sectional area and nasal cavity volume as indices of nasal patency. Fluctuations in nasal patency were observed in all laryngectomees and controls. These were classified as classical (reciprocal alternating), in concert (parallel) or irregular. The distribution of the control and laryngectomy subjects between the cycle categories was not statistically significant (Fisher's exact test: P > 0.05). The mean periodicity of the cycle was similar in the two groups (controls: 180 minutes, laryngectomees: 176 minutes), but the mean amplitude was significantly less in the laryngectomy group (68 versus 96 cm3; P < 0.07 Mann-Whitney U test). The nasal cycle can continue after cessation of airflow, but it is diminished in amplitude. Therefore, afferent input from nasal airflow receptors may continue to play a role in modulating the cycle's periodicity and amplitude, but are not responsible for generating the underlying cycle phenomenon.

A Review of the Safety, Efficacy and Mechanisms of Delivery of Nasal Oxytocin in Children: Therapeutic Potential for Autism and Prader-Willi Syndrome, and Recommendations for Future Research

In this article, we conduct a comprehensive review of existing evidence for the safety and therapeutic potential of intranasal oxytocin in pediatric populations. Unique considerations for dosing and delivery of oxytocin to the nasal passageway in pediatric populations and methods to promote adherence are reviewed. Intranasal oxytocin has been administered to 261 children in three open-label studies and eight randomized controlled trials. To date, the only published results in pediatric populations have focused on autism spectrum disorder (ASD) and Prader-Willi syndrome (PWS). Results regarding efficacy for improving social impairment in ASD are equivocal, partially due to mixed methodological designs, dosing regimens, and outcome measures. At present, there is no randomized controlled evidence that oxytocin provides benefit to individuals with PWS. There is no clear evidence of a link between oxytocin administration and any specific adverse event. Adverse events have been assessed using medical interviews, open reports, checklists, and physiological assessments. Adverse events reports have been largely classified as mild (n = 93), with few moderate (n = 9) or severe (n = 3) events reported. There were 35 additional adverse events reported, without severity ratings. Severe events, hyperactivity and irritability, occurred at first administration in both placebo and oxytocin groups, and subsided subsequent to discontinuation. We note that adverse event monitoring is inconsistent and often lacking, and reporting of its relationship to the study drug is poor. Only one study reported adherence data to suggest high adherence. Recommendations are then provided for the delivery of nasal sprays to the nasal passageway, monitoring, and reporting of efficacy, safety, and adherence for oxytocin nasal spray trials in pediatric populations.

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.

Asymmetric nasal mucosal thickening in healthy dogs consistent with the nasal cycle as demonstrated by MRI and CT

The nasal cycle is a physiological phenomenon that causes regular cyclical congestion and decongestion of the venous sinusoids lining the nasal mucosa. The purpose of this prospective study was to describe magnetic resonance imaging (MRI) and computed tomographic (CT) features of the normal nasal cycle in a group of dogs. Five dogs were recruited that met the following criteria: 8 to 15 months old, nonbrachiocephalic breed, no clinical signs or history of nasal disease, and undergoing anesthesia for problems unrelated to the nasal cavity. Nasal MRI (n = 5) and CT scans (pre- and postcontrast, n = 5) were acquired. Images were evaluated subjectively by two board-certified radiologists and objectively by a diagnostic imaging intern using regions of interest placed on each side of the nasal cavity. Findings were compared using Cohen's kappa coefficient and Students t-test on log-transformed data. All dogs showed diffuse unilateral mucosal thickening of the rostral part of the nasal cavity in both MRI and CT studies. This mucosal thickening shifted sides between examinations in three dogs. Changes appeared most marked on T2-weighted scans. No asymmetric mucosal changes were seen in the mucosa of the ethmoturbinates, vomer-nasal septum, hard palate or the frontal sinuses in any patient on MRI or CT. Computed tomographic contrast enhancement of the thickened mucosa was not statistically significant (P-value < 0.08). In conclusion, the normal nasal cycle may cause asymmetrical mucosal changes in the rostral part of the nasal cavity that mimic MRI and CT characteristics previously reported for inflammatory disease in dogs.

Nasal resistance in Japanese elementary schoolchildren: determination of normal value

CONCLUSION

Rhinomanometry is a useful method for evaluating nasal airway patency in schoolchildren, and we could confirm the validity of the results it produces.

OBJECTIVE

Our purpose was to assess the validity nasal resistance measurements produced using anterior active rhinomanometry by comparing the results with those of our previous study and to determine a normal value of the nasal resistance.

METHODS

Nasal resistance was measured by rhinomanometry in 852 children using the active anterior method.

RESULTS

Mean nasal resistance was 0.45 ± 0.70 Pa/cm(3)/s. Nasal diseases were noted in 358 (42%) children, and nasal condition was normal (the normal group) in 494 (58%) children. Nasal resistance was 0.57 ± 1.05 Pa/cm(3)/s in the nasal disease group and 0.35 ± 0.16 Pa/cm(3)/s in the normal group, showing that resistance was significantly higher in the nasal disease group. In the normal nasal groups, nasal resistance tended to be lower in the children in higher grades (first grade, 0.44 ± 0.17 Pa/cm(3)/s; second grade, 0.37 ± 0.11 Pa/cm(3)/s; third grade, 0.36 ± 0.23 Pa/cm(3)/s; fourth grade, 0.36 ± 0.14 Pa/cm(3)/s; fifth grade, 0.30 ± 0.08 Pa/cm(3)/s; sixth grade, 0.29 ± 0.11 Pa/cm(3)/s), and taller groups (<120 cm, 0.43 ± 0.16 Pa/cm(3)/s; 120-130 cm, 0.37 ± 0.19 Pa/cm(3)/s; 130-140 cm, 0.34 ± 0.12 Pa/cm(3)/s; >140 cm, 0.28 ± 0.09 Pa/cm(3)/s). Results similar to those seen in our previous study were obtained in each group.

Measurement of nasal resistance by rhinomanometry in 892 Japanese elementary school children

OBJECTIVE

The normal value of nasal resistance in adults has been reported (0.25 Pa/cm³/s), but that in children has not. In this study, we measured nasal resistance in Japanese school children by employing rhinomanometry.

METHODS

An otolaryngologist examined 939 Japanese school children with regard to the presence or absence of nasal diseases and tonsil size. Nasal resistance was measured by rhinomanometry employing the active anterior method in 892 children. A questionnaire concerning the condition during sleep, such as the presence or absence of snoring and sleep apnea syndrome, was performed.

RESULTS

The mean nasal resistance was 0.43 ± 0.50 Pa/cm³/s: 0.46 ± 0.65 and 0.39 ± 0.22 Pa/cm³/s in boys and girls, respectively. Of the 892 children, Grade 3 and 4 tonsil hypertrophy was noted in 84 (9%), but the presence of tonsil hypertrophy did not influence nasal resistance. Nasal diseases were noted in 335 children (38%) and the nasal condition was normal (the normal group) in 557 (62%). Nasal resistance was 0.56 ± 0.75 Pa/cm³/s in the nasal disease group and 0.36 ± 0.21 Pa/cm³/s in the normal group, showing that the resistance was significantly higher in the nasal disease group. The resistance tended to decrease as the school grade increased. In the normal group, 290 children (33%) experienced no problem regarding the upper airway, such as snoring and sleep apnea syndrome, based on a questionnaire, and nasal resistance was 0.35 ± 0.17 Pa/cm³/s.

CONCLUSION

This normal nasal resistance value may be adopted for the objective evaluation of nasal obstruction and effects of treatment in pediatric nasal diseases.

Acoustic rhinometry assessment of the nasal cycle in neonates

In this study the nasal cycle in newborns was assessed using acoustic rhinometry with miniprobe (RHIN 2100). Enrolled in the study were 67 newborns aged 2 to 4 days. Each subject was assessed for 3 h, examinations taking place every 30 min. At least six measurements, three from each nostril, were taken at each examination. The miniprobe RHIN 2100 (SR Electronics ApS) was used for evaluation of nasal geometry. The minimal cross-sectional area (MCA) and the total volume of the anterior 45 mm (VOL45) were calculated and used for statistical analysis. The mean volume of MCA and VOL45 in the examined group of children was 0.08 cm3 and 1.19 cm3 respectively. Nasal cycle was assessed by constructing the plots of acoustic rhinometry parameters MCA or VOL45 for time and statistically using Pearson's correlation coefficients. Most of the examined infants (70-85%) showed no significant fluctuations in nasal patency.

Nasal cycle in patients with septal deviation: evaluation by acoustic rhinometry

The nasal cycle in patients with septal deviation was studied by acoustic rhinometric techniques. This study included 24 patients with anteriorly located septal deviations (mean age = 23.5), and 26 normal controls (mean age = 24.7). Data of MCA (minimum cross-sectional area) and NV (nasal volume), collected in 20-minute intervals, were plotted for each subject during 8 hours. Twenty of 24 patients (83%) with septal deviation and 20 of 26 normal subjects (77%) showed at least one complete cycle. Duration of the nasal cycle, which ranged from 100 minutes to 400 minutes, had no statistical difference between the septal deviation group (mean duration of 216 minutes) and the normal control group (mean duration of 227 minutes). The degrees of variation of MCA and NV, defined as Degree of Variation of MCA (%) = 100 (MCAmax - MCAmin)/MCAmax, Degree of Variation of NV (%) = 100 (NVmax - NVmin)/NVmax, which represent the percent change of MCA and NV throughout the study, showed no difference between the wide side and the narrow side, or between the septal deviation group and the normal control group. These findings suggest that the nasal cycle is relatively independent of peripheral anatomic factors for its generation. However, the amplitude of changes of MCA was greater in the wide side, and the sum of both MCAs tended to fluctuate in accordance with the fluctuation of MCA of the wide side. Thus, the nasal cycle seemed to be affected by septal deviation.

The effects of adenoid hypertrophy and subsequent adenoidectomy on pediatric nasal airway resistance

To investigate how adenoid hypertrophy and subsequent adenoidectomy affect pediatric airway resistance, we developed a prospective controlled study. Fifty children, aged 3 to 12 years, diagnosed with adenoid hypertrophy and selected for adenoidectomy, preoperatively had their nasal airway resistance assessed by active anterior rhinomanometry. Twenty-five of these children were subsequently followed up postoperatively, undergoing nasal resistance evaluations at 1 month, 3 months, 6 months, and 12 months. Another 25 children, without chronic upper airway obstruction symptoms, were enrolled as a control group, and their airway resistance was assessed in the same fashion. We concluded that the children selected for adenoidectomy, compared to the control group and before surgery, had mean resistance values up to two- to threefold higher, in both untreated and decongested nose states. Surgery was found to dramatically reduce airway resistance, but only in children under the age of seven. However, the postoperative values still tended to remain higher than the control subjects results. If in a significant number of children the operation failed in completely resolving their complaints, no pre-operative rhinomanometric pattern could be found to specifically relate to a complete surgical success.

Influence of age on the 'nasal cycle'

The nasal cycle is classicially defined as a side-to-side fluctuation in nasal engorgement and airflow, with period lengths ranging from approximately 1 to 5 hours. This cycle, as well as its variants (e.g., cyclic changes on one side of the nose only), is produced by alterations in autonomic tone of the nasal vasculature and reportedly correlates with a number of ultradian rhythms, including asymmetries in left:right cerebral electroencephalographic (EEG) activity and differential performance on visual/spatial psychological tasks. Since the pacemaker for the nasal cycle is believed to lie within the suprachiasmatic nucleus of the hypothalamus, and this nucleus evidences degeneration in later life, we sought to determine whether the nasal cycle or its variants changes with age. To achieve this end, we used a liquid crystal thermography exhalation monitor to measure relative airflow of the two nasal chambers at 15-minute intervals for 6 hours in 60 people representing four age categories: 18 to 29 years (n=12); 30 to 49 years (n=15); 50 to 69 years (n=13); and 70 to 85 years (n=20). Overall, the proportion of subjects exhibiting the alternating rhythmicity associated with the classic nasal cycle decreased with age. No association was present between nasal cycle parameters and scores on the Mini-Mental State Examination (MMSE). The results suggest that the classic nasal cycle may be a marker for age-related central nervous system changes.

Monitoring fluctuations in nasal patency in children: acoustic rhinometry versus rhinohygrometry

Simple rhinohygrometry and passive rhinomanometry studies have suggested that the 'nasal cycle' in children is often different in pattern of that of adults and experimental animals. We aimed to establish whether this assertion was correct, using a reliable and sensitive method, acoustic rhinometry (AR), and to compare results with those of simple rhinohygrometry (RH). Healthy children with no evidence of nasal disease were examined (n = 15; age range three to 10 years; mean age six years). Simultaneous recordings using AR and RH were made on each child every 10-15 minutes over two to four hour periods. Six children underwent nine additional AR studies on separate occasions. 'Classical' reciprocal alternating patterns were evident in 80 per cent (12/15) AR and 53 per cent (8/15) RH studies, 'in concert' patterns in seven per cent (1/15) AR and 20 per cent (3/15) RH studies and 'irregular' patterns in 13 per cent (2/15) AR and 27 per cent (4/15) RH studies. The agreement between the two methods was 47 per cent, with a kappa (kappa) value of -0.17 (poor agreement compared to chance). Agreements between the acoustic rhinometry parameters were 'fair' for all data (kappa = 0.34) and excellent (kappa = 1.0) if irregular patterns were ignored. Repeated studies showed that the pattern of fluctuation varies within any particular individual. The nasal cycle is similar in pattern in children and adults, and acoustic rhinometry is currently the method of choice to further investigate and clarify this phenomenon.

The adenoid as a key factor in upper airway infections

The adenoids (and the nasopharynx) play a key role in the normal functioning and in various pathologies of the upper respiratory tract. In this paper the role of adenoidal pathology and the beneficial effect of adenoidectomy in some upper respiratory tract and facial anomalies and diseases are discussed; otitis media with effusion, recurrent acute otitis media, sinusitis, snoring and sleep apnea and abnormal patterns in the midface growth and development.

Assessment of an abbreviated odorant identification task for children: a rapid screening device for schools and clinics

To validate the level of olfactory performance of children, we tested 825 volunteers, aged 4-17 years, with an abbreviated form of our pediatric odorant identification task. The test consisted of sniffing and identifying five odorants (baby powder, bubble gum, candy cane, licorice and peach). Mean olfactory scores increased as a function of age, reaching a plateau of about 94-95% correct at 8 years of age. In general, girls out-performed boys. Physicians require a test instrument such as the one we have devised to allow them to diagnose olfactory dysfunction in children. The present task is particularly applicable in screening large numbers of children in clinics or schools because it can be administered easily and rapidly. Adult subjects with olfactory dysfunction also performed poorly on this odorant identification task designed for children. Therefore, we expect that our odorant identification task will also detect children with severe olfactory dysfunction.

The nasal cycle after deprivation of airflow: a study of laryngectomy patients using acoustic rhinometry

Previous studies of the nasal cycle in laryngectomy patients using rhinomanometric techniques concluded that the cycle was abolished as a result of the cessation of airflow after laryngectomy. This study was performed with 20 postoperative laryngectomy patients (mean time after surgery 4 years, range: 2 weeks to 10 years) and 10 control subjects matched for age and sex (including 2 preoperative patients). Acoustic rhinometry was used to determine minimum nasal cross-sectional area and nasal cavity volume as the indices of nasal patency. Testing was repeated at intervals of 15-30 min over a period of 3-8 h. Fluctuations in nasal patency were observed in all laryngectomees and controls. The fluctuations were classified as 'classical' (reciprocal alternating) in 5 (25%) laryngectomees and 5 (50%) controls. An 'irregular' pattern of fluctuation was seen in 8 (40%) laryngectomees and 2 (20%) controls. An 'in concert' cyclical pattern was seen in 7 (35%) laryngectomees and 3 (30%) controls. This is the first demonstration of retention of the nasal cycle after airflow deprivation. Whilst the cycle may in some instances be modified after operation, it is not abolished. The central generation of the cycle is confirmed, although afferent input from airflow receptors may play a role in modulating the cycle's pattern and amplitude.

Acoustic Rhinometry in Rhinological Practice: Discussion Paper

Acoustic rhinometry is a new technique which evaluates nasal obstruction by analysing reflections of a sound pulse introduced via the nostrils. The technique is rapid, reproducible, non-invasive and requires minimal cooperation from the subject. Unlike rhinomanometry it does not require airflow. A graph of nasal cross-sectional area as a function of distance from the nostril is produced, from which several area and volume estimates of the nasal cavity can be derived. The reliability of the method is greatest in the anterior nasal cavity, which is the site of the nasal valve.

We have applied the technique to the study of normal nasal physiology in adults and children and to a range of pathological conditions. The role of acoustic rhinometry in diagnosis is somewhat limited compared to nasal endoscopy, but it is useful for nasal challenge and for quantifying nasal obstruction. Monitoring of medical and surgical therapy is a more promising application.

In future, acoustic rhinometry is likely to be of particular help in evaluating childhood nasal obstruction, as it is well tolerated by children as young as 3 years old - a group of patients to whom objective tests have hitherto been difficult to apply.

Developmental changes in nasal airflow patterns

Airflow through each nasal passage was measured every 10 min throughout a 5-h period in 48 subjects whose ages ranged from 3 to 17 years. The data were subjected to statistical techniques that characterize and quantify periodicities in a time series. Such analyses revealed that for the majority of children younger than 7 years of age, the airflow through the two nostrils changed either randomly (50%) or in parallel (31%). Between the ages of 7 and 10 years, however, the distribution of airflow patterns characteristic of adults emerged, such that the incidence of reciprocity increased to 63%, and the incidence of random and parallel patterns decreased to 31% and 6%, respectively. A similar distribution was evidenced in the 11- to 17-year-old subjects (56% reciprocal, 38% random, 6% parallel). Although the total airflow through the nose also increased with age, the increased inspiratory flow rates could not account for the developmental changes evidenced in airflow patterns.

The management of neonatal rhinitis

Life-threatening upper airway obstruction secondary to neonatal rhinitis is a rare and poorly understood condition. Despite potential lethal effects, there has been no basic scientific research investigating the nature of this curious condition. This paper retrospectively reviews 8 patients suffering from neonatal rhinitis. Both the medical and surgical management of neonatal rhinitis and possible aetiological factors involved are discussed. Increasing clinical awareness of this condition may, therefore, serve as inspiration for future research of both an epidemiological and basic scientific nature.

Evaluation of nasal impedance using the forced oscillation technique in infants

By applying oscillations to the respiratory system through a rigid face mask, the infant-adapted Lándsér forced oscillation technique measures impedance of the total respiratory system including the nose, at frequencies from 4 to 52 Hz. The present study was aimed at evaluating nasal impedance in infants from consecutive forced oscillation measurements through both nostrils and each nostril separately, using a simple electrical model. In 30 asthmatic infants with varying degrees of nasal obstruction, aged 1-16 months, calculated nasal resistance (Rn) at 24 Hz ranged from 1 to 16 cm H2O.L-1.s. The ratio of Rn to total respiratory system resistance varied between 1 and 48% (mean: 16%). In seven non-asthmatic infants, aged 0-12 months, Rn was between 1 and 11 cm H2O.L-1.s. Nasal patency (evaluated clinically) was correlated with the calculated Rn (P less than 0.05). Rn showed almost no frequency dependence between 24 and 48 Hz as demonstrated by a mean slope of -0.09 +/- 0.08 cm H2O.s2/L for the asthmatic and of -0.08 +/- 0.07 for the non-asthmatic infants. In seven of the asthmatic infants the differences between two Rn determinations at a 45 min interval ranged from -1.7 to 3.8 cm H2O.L-1.s-1 at 24 Hz and from -3.6 to 1.0 at 48 Hz. Changes in Rn did not correlate with changes in total respiratory system resistance (P greater than 0.05). In conclusion, nasal impedance can be approximated from three consecutive measurements through both nostrils and through each nostril separately.

Limbic autonomic arousal: its physiological classification and review of the literature

The object of this article is to present a novel physiological classification of Limbic-Autonomic (LA) arousal on the basis of human physiological data, specifically the oro-nasal breathing patterns in man. It is proposed that the multidimensional LA arousal can be classified into five grades: Grade I: Non-nasal (NN) or oral breathing with bilateral nasal congestion, and nonactive behavior, Grade II: Left Nasal (LN) breathing and quiet behavior, Grade III: Right Nasal (RN) breathing and active behavior, Grade IV: Bilateral Nasal (BN) breathing and very active behavior, and Grade V: Oral and Bilateral Nasal (ON) breathing with maximal behavioral activation. The data from polygraphic electroencephalographic recordings from five healthy volunteers, before, during and after exercise are presented in support of this physiological classification of LA arousal. On the basis of Limbic-Autonomic asymmetry a novel concept of "Visceral Dominance" is also proposed.

Effect of head position on distribution of nasal airflow in preterm infants

Supine preterm infants characteristically adopt a lateral head position; however, it is not known whether this influences the distribution of nasal airflow. Ventilation was measured in 12 healthy preterm infants (postconceptional age 34 +/- 2 weeks) by employing a nasal mask pneumotachygraph that separated airflow between the left and right nasal passages. In the midline supine position, the percent of total tidal volume (%VT) through the right nasal passage ranged from 31% to 64% and varied by less than 5% between active and quiet sleep in any infant. Lateral positioning of the head caused %VT to increase on the dependent side and decrease through the upper nasal passage. When the right side was dependent, mean %VT on that side increased from 52 +/- 9% to 67 +/- 14% (P less than 0.01) and decreased to 43 +/- 10% (P less than 0.05) when the right side was up. In the midline position, the presence of a nasogastric tube caused %VT through the nasal passage with the tube to fall from 54 +/- 8% to 39 +/- 8% (P less than 0.01). The %VT fell farther, to 25 +/- 10% (P less than 0.01), when the nasal passage with the nasogastric tube was up. Despite these changes in VT distribution, total VT remained constant during these maneuvers. We speculate that when supine preterm infants adopt a lateral head position, the decrease in airflow through the upper nasal passage results from partial obstruction of the oropharyngeal or nasopharyngeal airway on that side.

Biological rhythmicity of nasal airway patency: a re-examination of the 'nasal cycle'

Rhinomanometric observations of nasal airway patency were obtained for each nasal passage every 10 min throughout an uninterrupted 8-h session. The 49 airflow observations for each nasal passage were subjected to autocorrelation analysis, a statistical technique for quantifying periodicities in a temporal sequence of observations. No significant periodicities were found in any of the 16 subjects when the autocorrelation functions were interpreted by conventional statistical criteria. However, when less stringent criteria were applied, we found suggestive evidence for rhythmicity in one (7 subjects) or both nasal passages (2 subjects). The relationship in patency between the two sides of the nose was characterized with correlation coefficients. These correlations were significantly negative in 7 subjects, indicating bilateral reciprocity of patency. In addition, the correlations were significantly positive in one, and nonsignificant in 8 subjects. Only a minority of subjects (13%) displayed the classical nasal cycle, i.e., rhythmicity in both nasal passages as well as reciprocity of patency between passages.

A non-invasive method of demonstrating the nasal cycle using flexible liquid crystal thermography

The relationship between air flow at 38 degrees C and area colour change on a flexible liquid crystal film was found to be virtually linear between the values of 1 and 31 min-1 cm-2. This value of flow per unit area corresponded to values expected at the level of the nostril during quiet breathing. A series of 6 subjects were asked to breathe over a flexible liquid crystal film regularly during the day and the area of colour change produced by flow from each nostril was examined. Four subjects showed a regular change in relative flow through each nostril whilst 2 subjects showed a constant flow through each nostril. This simple and non-invasive technique provides a method of examining the nasal cycle in adults and children in health and disease.

Mucociliary function and nasal resistance evaluation before and after adenoidectomy

Thirty-four children with clinically and radiologically confirmed adenoid hypertrophy underwent otoscopy, impedance tests, active anterior rhinomanometry and nasal mucociliary clearance evaluation before and 6 months after adenoidectomy. Mucociliary clearance velocity increased significantly while binasal resistances decreased after surgery. The authors conclude that mucociliary evaluation and objective measurements of nasal resistances should be added to impedance tests as indicators to adenoidectomy.

Clinical use of rhinomanometry in children

To investigate Passive Anterior Rhinomanometry (PAR), several clinical experiments were set up to explore in children aged 3-6 years the nasal resistance in various normal and pathological situations, in order to determine the role of rhinomanometry in clinical situations in young children. It was shown that the nasal cycle in children differs greatly from that in adults, showing a regular undulating pattern of nasal resistance, but without alternating phenomena. There are also quite regular fluctuations with a short period of about 90 s. Physical exercise and changes in body position have also, in children, a definite influence on nasal resistance. PAR in various pathological situations of the nasal cavity gave a wide range of individual results. It was, however, found that children with a nasal septum deviation, with a pronounced nasal edema, and with serous and purulent nasal secretions had a higher nasal resistance than children without nasal pathology. Because of the spontaneous and evoked changes in nasal resistance in children and because of the large standard deviations of nasal resistance values in pathological situations, clinicians should interpret the results of a one-time rhinomanometrical measurement very carefully.