Nasal flow limitation in children

Extracting signature responses from respiratory flows: Low-dimensional analyses on Direct Numerical Simulation-predicted wakes of a flapping uvula

Uvula-induced snoring and associated obstructive sleep apnea is a complex phenomenon characterized by vibrating structures and highly transient vortex dynamics. This study aimed to extract signature features of uvula wake flows of different pathological origins and develop a linear reduced-order surrogate model for flow control. Six airway models were developed with two uvula kinematics and three pharynx constriction levels. A direct numerical simulation (DNS) flow solver based on the immersed boundary method was utilized to resolve the wake flows induced by the flapping uvula. Key spatial and temporal responses of the flow to uvula kinematics and pharynx constriction were investigated using continuous wavelet transform (CWT), proper orthogonal decomposition (POD), and dynamic mode decomposition (DMD). Results showed highly complex patterns in flow topologies. CWT analysis revealed multiscale correlations in both time and space between the flapping uvular and wake flows. POD analysis successfully separated the flows among the six models by projecting the datasets in the vector space spanned by the first three eigenmodes. Perceivable differences were also captured in the time evolution of the DMD modes among the six models. A linear reduced-order surrogate model was constructed from the predominant eigenmodes obtained from the DMD analysis and predicted vortex patterns from this surrogate model agreed well with the corresponding DNS simulations. The computational and analytical platform presented in this study could bring a variety of applications in breathing-related disorders and beyond. The computational efficiency of surrogate modeling makes it well suited for flow control, forecasting, and uncertainty analyses.

Impact of physicochemical properties of nasal spray products on drug deposition and transport in the pediatric nasal cavity model

The study is focused on the analysis of physicochemical properties of selected nasal sprays of mometasone furoate, and the influence of these properties on aerosol quality and penetration in the pediatric nose. After the determination of drugs surface tension and viscosity, spray geometry and size distribution of aerosol droplets, the topical delivery of each drug to different parts of the pediatric model of the nose with the flexible vestibule was evaluated by colorimetric visualization. All tested drugs are pseudo-plastic liquids, showing some differences in flow consistency constant k (range 714-1422) and flow behavior index n (range 0.16-0.31). At no-flow conditions, all sprays are deposited mainly in the anterior of the nasal cavity and the septum (2-3 cm from the nostril), as a result of inertial impaction of large droplets. The deposition range is slightly influenced by the geometry of the aerosol cloud, which, in turn, depends both on drug properties and the type of the spraying nozzle. Deposition experiments accompanied by the airflow show an enhancement of drug transport to deeper parts of the nasal cavity (up 4-6 cm from the vestibule), and this effect can be attributed to the secondary effects of spreading of the deposited liquid layer along the narrow air passages in the nose. Plume geometry, dose volume and rheological properties of the drug were shown to be important factors in the spray penetration pattern in the pediatric nose. The deepest delivery can be expected for drugs of low viscosity and short aerosol plumes.

Numerical study of dynamic glottis and tidal breathing on respiratory sounds in a human upper airway model

BACKGROUND

Human snores are caused by vibrating anatomical structures in the upper airway. The glottis is a highly variable structure and a critical organ regulating inhaled flows. However, the effects of the glottis motion on airflow and breathing sound are not well understood, while static glottises have been implemented in most previous in silico studies. The objective of this study is to develop a computational acoustic model of human airways with a dynamic glottis and quantify the effects of glottis motion and tidal breathing on airflow and sound generation.

METHODS

Large eddy simulation and FW-H models were adopted to compute airflows and respiratory sounds in an image-based mouth-lung model. User-defined functions were developed that governed the glottis kinematics. Varying breathing scenarios (static vs. dynamic glottis; constant vs. sinusoidal inhalations) were simulated to understand the effects of glottis motion and inhalation pattern on sound generation. Pressure distributions were measured in airway casts with different glottal openings for model validation purpose.

RESULTS

Significant flow fluctuations were predicted in the upper airways at peak inhalation rates or during glottal constriction. The inhalation speed through the glottis was the predominating factor in the sound generation while the transient effects were less important. For all frequencies considered (20-2500 Hz), the static glottis substantially underestimated the intensity of the generated sounds, which was most pronounced in the range of 100-500 Hz. Adopting an equivalent steady flow rather than a tidal breathing further underestimated the sound intensity. An increase of 25 dB in average was observed for the life condition (sine-dynamic) compared to the idealized condition (constant-rigid) for the broadband frequencies, with the largest increase of approximately 40 dB at the frequency around 250 Hz.

CONCLUSION

Results show that a severely narrowing glottis during inhalation, as well as flow fluctuations in the downstream trachea, can generate audible sound levels.

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.

Hygroscopic aerosol deposition in the human upper respiratory tract under various thermo-humidity conditions

The deposition of hygroscopic aerosols is highly complex in nature, which results from a cumulative effect of dynamic particle growth and the real-time size-specific deposition mechanisms. The objective of this study is to evaluate hygroscopic effects on the particle growth, transport, and deposition of nasally inhaled aerosols across a range of 0.2-2.5 μm in an adult image-based nose-throat model. Temperature and relative humidity fields were simulated using the LRN k-ω turbulence model and species transport model under a spectrum of thermo-humidity conditions. Particle growth and transport were simulated using a well validated Lagrangian tracking model coupled with a user-defined hygroscopic growth module. Results of this study indicate that the saturation level and initial particle size are the two major factors that determine the particle growth rate (d/d0), while the effect of inhalation flow rate is found to be not significant. An empirical correlation of condensation growth of nasally inhaled hygroscopic aerosols in adults has been developed based on a variety of thermo-humidity inhalation conditions. Significant elevated nasal depositions of hygroscopic aerosols could be induced by condensation growth for both sub-micrometer and small micrometer particulates. In particular, the deposition of initially 2.5 μm hygroscopic aerosols was observed to be 5-8 times that of inert particles under warm to hot saturated conditions. Results of this study have important implications in exposure assessment in hot humid environments, where much higher risks may be expected compared to normal conditions.

Dynamic growth and deposition of hygroscopic aerosols in the nasal airway of a 5-year-old child

Hygroscopic growth within the human respiratory tract can be significant, which may notably alter the behavior and fate of the inhaled aerosols. The objective of this study is to evaluate the hygroscopic effects upon the transport and deposition of nasally inhaled fine-regime aerosols in children. A physiologically realistic nasal-laryngeal airway model was developed based on magnetic resonance imaging of a 5-year-old boy. Temperature and relative humidity field were simulated using the low Reynolds number k - ε turbulence model and chemical specie transport model under a spectrum of four thermo-humidity conditions. Particle growth and transport were simulated using a well validated Lagrangian tracking model coupled with a user-defined hygroscopic growth module. The subsequent aerosol depositions for the four inhalation scenarios were evaluated on a multiscale basis such as total, subregional, and cellular-level depositions. Results of this study show that a supersaturated humid environment is possible in the nasal turbinate region and can lead to significant condensation growth (d / d(0)  > 10) of nasally inhaled aerosols. Depositions in the nasal airway can also be greatly enhanced by condensation growth with appropriate inhalation temperature and humidity. For subsaturated and mild inhalation conditions, the hygroscopic effects were found to be nonsignificant for total depositions, while exerting a large impact upon localized depositions.

Nasal versus oronasal raised volume forced expirations in infants--a real physiologic challenge

Raised volume rapid thoracoabdominal compression (RTC) generates forced expiration (FE) in infants typically from an airway opening pressure of 30 cm H(2)O (V(30)). We hypothesized that the higher nasal than pulmonary airway resistance limits forced expiratory flows (FEF(%)) during (nasal) FE(n), which an opened mouth, (oronasal) FE(o), would resolve. Measurements were performed during a brief post-hyperventilation apnea on 12 healthy infants aged 6.9-104 weeks. In two infants, forced expiratory (FEFV) flow volume (FV) curves were generated using a facemask that covered the nose and a closed mouth, then again with a larger mask with the mouth opened. In other infants (n = 10), the mouth closed spontaneously during FE. Oronasal passive expiration from V(30) generated either the inspiratory capacity (IC) or by activating RTC before end-expiration, the slow vital capacity ((j) SVC). Peak flow (PF), FEF(25), FEF(50), FEF(25-75), FEV(0.4), and FEV(0.5) were lower via FE(n) than FE(o) (P < 0.05), but the ratio of expired volume at PF and forced vital capacity (FVC) as percent was higher (P < 0.05). FEF(75), FEF(85), FEF(90), FVC as well as the applied jacket pressures were not different (P > 0.05). FEFV curves generated via FE(o) exhibited higher PF than FV curves of IC (P < 0.05); PF of those produced via FE(n) were not different from FV curves of IC (P > 0.05) but lower than those of (j) SVC (P < 0.05). In conclusion, the higher nasal than pulmonary airways resistance unequivocally affects the FEFV curves by consistently reducing PF and decreases mid-expiratory flows. A monitored slightly opened mouth and a gentle anterior jaw thrust are physiologically integral for raised volume RTC in order to maximize the oral and minimize nasal airways contribution to FE so that flow limitation would be in the pulmonary not nasal airways.

Restricting cough and cold medicines in children

AIMS

Based on concerns about safety and efficacy, international authorities have either advised against the use of cough and cold medication or considering such action. We aimed to systematically review the evidence for the effectiveness and safety of cough and cold medicines in children.

METHODS

We conducted a systematic review to identify studies relating to the use of products to treat symptoms of the common cold, influenza or allergic rhinitis, and relating to poisoning or toxicity from unintentional ingestion or overdose in children (<12 years). Medline, Embase and the Cochrane database were searched. No meta-analysis was undertaken because of the paucity of evidence, multiple medicines available, and the need to consider both effectiveness and safety.

RESULTS

Seventy two relevant studies or clinical reports were identified. There was little support for the effectiveness of these medicines for acute cough or the common cold in children. However, the majority of these medicines do not appear to be highly toxic in children and are not a major cause of severe effects following unintentional poisoning. The common use of these agents does not appear to be responsible for increased deaths in young children. Many cases of toxicity from cough and cold medications in young children are a result of therapeutic error. Particular medications, including diphenhydramine and codeine, appear to be associated with a high frequency of severe adverse effects and toxicity.

CONCLUSION

Restriction of cough and cold medicines in children is supported by currently available evidence.

Effects of intranasal xylometazoline, alone or in combination with ipratropium, in patients with common cold

BACKGROUND

Common cold is one of the most prevalent conditions that family doctors encounter. One of the first symptoms to occur is nasal congestion, which can have a negative impact on daily life and prompts many patients to seek treatment for relief. Xylometazoline nasal spray (Otrivin*) is a topical decongestant that has been used successfully for many years and is generally recognized as an effective and safe therapy. However, most studies have investigated its clinical efficacy in healthy patients and few have included patients with common cold.

SCOPE

To review the published clinical efficacy and safety of xylometazoline alone and in combination in the management of nasal congestion in patients with common cold. Literature searches of PubMed and the Cochrane Library were conducted to obtain published open or blinded, randomized, placebo- or active-controlled studies on the use of xylometazoline hydrochloride for the symptomatic relief of nasal congestion in patients with common cold. Searches included papers published in English only, up to September 2009.

FINDINGS

Despite the small number of studies identified in common cold (n = 4), as per search criteria defined, intranasal xylometazoline quickly and effectively relieved nasal congestion. When used alone, xylometazoline had a clinically relevant decongestant effect that was significantly superior for up to 10 hours compared with placebo. The superior decongestant effect with xylometazoline led to high patient satisfaction with treatment. When used in combination with ipratropium bromide, nasal congestion and rhinorrhoea were treated simultaneously, leading to significantly higher patient general impression scores compared with either agent used alone. Xylometazoline was well tolerated, with generally mild to moderate nasal-related side effects (e.g. epistaxis in 3.4% of patients, and blood-tinged mucus in 10-26% of patients) that were easily resolved; the most frequently reported non-nasal AEs were headache (3.4%) and period pain (10.3%); no cases of sedation were reported. As expected, no rhinitis medicamentosa or rebound congestion was noted with short-term use (<10 days). No clinically important differences in ciliary motility and mucociliary clearance were observed. Xylometazoline does not result in sympathomimetic systemic side effects seen with oral decongestants (e.g. pseudoephedrine, phenylephrine).

CONCLUSIONS

The few studies available in common cold suggest that intranasal xylometazoline provides fast and effective relief of nasal congestion and is well tolerated. When xylometazoline is used in combination with ipratropium, patients with common cold experience the additive benefit of nasal congestion and rhinorrhoea being treated simultaneously.

Efficacy and safety of intranasal xylometazoline and ipratropium in patients with common cold

BACKGROUND

Many over-the-counter medications are available to treat common cold nasal symptoms, but patients may be unsure which one to use.

METHODS

This review assesses two widely used intranasal treatments for nasal congestion and rhinorrhea in the common cold: xylometazoline hydrochloride and ipratropium bromide.

RESULTS

Xylometazoline quickly and effectively relieves nasal congestion, while ipratropium is effective at reducing rhinorrhea. When used in combination, a novel approach to treatment, nasal congestion and rhinorrhea are treated simultaneously, providing effective relief from two of the most troublesome symptoms of the common cold Both drugs are well tolerated, with only mild to moderate, nasal-related side effects.

CONCLUSIONS

The efficacy and safety of the combination product suggest that it should be used first-line in the symptomatic relief of nasal congestion and rhinorrhea, before the use of oral treatments.

Does inhaling menthol affect nasal patency or cough?

OBJECTIVE

There is widespread use of menthol in over-the-counter medications, despite scant information on any beneficial effects. Our aim was to assess the effect of menthol on nasal air flow, perception of nasal patency and cough challenge testing.

MATERIALS AND METHODS

Subjects comprised 42 healthy children aged 10 and 11 in a school setting. We used a single-blind pseudo-randomized cross-over trial to compare the effect of an inhalation of either menthol or placebo(eucalyptus oil). Baseline and post-intervention measurements were made on each of 2 consecutive days. Main outcome measures were (i) nasal expiratory and inspiratory flows and volumes, measured by spirometer, (ii) perception of nasal patency, assessed with a visual analogue scale (VAS), and (iii) the number of coughs in response to nebulized citric acid.

RESULTS

There was no effect of menthol on any of the spirometric measurements. Following menthol, there was a significant increase in the perception of nasal patency (mean difference in log VAS (menthol-placebo) = -0.207, 95%CI -0.329, -0.085). The cough count after menthol inhalation was reduced when compared to baseline but the change was not different from that after placebo (mean difference in cough count (menthol-placebo) = -1.71, 95%CI -4.11, 0.69).

CONCLUSION

Menthol has no effect on objective measures of flow but significantly increases the perception of nasal patency. It may not be possible to extrapolate these findings to younger children and those with rhinitis. Extending the study of menthol to these groups, including investigations of the efficacy and safety profiles, will provide further valuable evidence for its common use.

The response to β-agonists in wheezy infants: three methods compared

BACKGROUND

Studies into the effects of salbutamol in the treatment of wheeze in infancy have been conflicting, possibly due to differences in outcome variables. We aimed to assess the response to salbutamol using indices derived from passive and forced expiration.

METHODS

We recruited 39 infants who had a history of wheezing (mean age 43 weeks) and measured maximum flow at functional residual capacity (V'(max FRC)) by rapid thoracoabdominal compression (RTC), and forced expired volume at 0.4s (FEV0.4) using the raised-volume RTC technique (RV-RTC). We calculated passive compliance (C(rs)), resistance (R(rs)) and time constant (tau) from relaxed expirations that followed the augmented inspirations delivered during RV-RTC. Measurements were repeated after aerosol salbutamol (800 mcg).

RESULTS

Data were obtained in 32 infants for V'(max FRC), 22 for FEV0.4 and 19 for passive mechanics. There were no mean changes in any index of forced expiration after salbutamol. Some individuals showed significant changes (improvement or worsening) in one or other index. Overall, there was a small increase in C(rs) after salbutamol but no change in R(rs) or tau.

CONCLUSIONS

We found no consistent pattern of response in either index of forced expiration. Validated clinical scores or alternative physiological techniques may be preferable to respiratory mechanics in assessing bronchodilator response.

Budesonide aqueous nasal spray is an effective treatment in children with perennial allergic rhinitis, with an onset of action within 12 hours

BACKGROUND

Budesonide aqueous nasal spray is a topical corticosteroid which at doses of 64 to 256 microg once daily has been found to be effective in the treatment of seasonal allergic rhinitis in adults and children.

OBJECTIVE

This study was conducted to determine the efficacy of budesonide aqueous nasal spray, 128 microg once daily, in children with perennial allergic rhinitis.

METHODS

This double-blind, randomized, placebo-controlled, parallel-group, multicenter study compared the efficacy and safety of budesonide aqueous nasal spray, 128 microg once daily intranasally, with placebo in 202 patients (aged 6 to 16 years) with perennial allergic rhinitis. Efficacy was evaluated daily by measurement of peak nasal inspiratory flow (PNIF), nasal symptom scores over 12 hours, and an overall evaluation of treatment efficacy. In a subset of patients (n = 76), quality of life was measured by validated questionnaires.

RESULTS

Budesonide, 128 microg once daily, was significantly more effective than placebo in improving the PNIF, combined and individual nasal symptom scores, and the overall evaluation of treatment efficacy. The onset of action was found to occur within the first 12-hour time interval evaluated for combined nasal symptoms and within 48 hours for PNIF. Budesonide was associated with reduced percentage of eosinophils in brush samples and reduced intake of rescue medication in comparison with placebo. Quality of life scores were reduced, but the differences did not reach significance.

CONCLUSIONS

Budesonide aqueous nasal spray, 128 microg once daily, is effective in children with perennial allergic rhinitis. Efficacy was demonstrated within 12 hours.

Effect of airway opening manoeuvres on thoraco-abdominal asynchrony in anaesthetized children

Thoraco-abdominal asynchrony is frequently encountered during inhalation anaesthesia in children with adenotonsillar hypertrophy causing an upper airway obstruction. The study goal was to evaluate the impact of different airway opening manoeuvres on thoraco-abdominal asynchrony as a measure of airway obstruction. Thirty anaesthetized children (aged 2-8 yrs; sevoflurane 3% in 50% oxygen/nitrous oxide) were studied prior to elective adenotonsillectomy using respiratory inductance plethysmography to record ribeage and abdominal wave forms as a basis for calculation of the phase angle. Five airway situations were compared: 1) baseline (unsupported mandible); 2) chin lift; 3) chin lift combined with continuous positive airway pressure of 10 cmH2O; 4) jaw thrust; and 5) jaw thrust combined with continuous positive airway pressure of 10 cmH2O. Three children had complete upper airway obstruction at baseline and were excluded from the study. With chin lift, thoraco-abdominal asynchrony improved in three patients, worsened in three patients and was unchanged in 21 patients. Additional continuous positive airway pressure during chin lift did not markedly reduce thoraco-abdominal asynchrony (phase angle 89 +/- 43 , p = 0.33). Jaw thrust resulted in a significant decrease of the phase angle (from 106 +/- 53 at baseline to 65 +/- 49 , p < 0.01); when combined with continuous positive airway pressure, no further effect on thoraco-abdominal asynchrony was found (72 +/- 44). In anaesthetized children with adenotonsillar hypertrophy, airway opening manoeuvres have distinct effects on thoraco-abdominal asynchrony. Delivery of continuous positive airway pressure and jaw thrust can be the first airway opening manoeuvres to improve breathing patterns. Chin lift without additional continuous positive airway pressure should be used with caution in these patients because it may convert partial into almost complete airway obstruction.

Effect of common airway manoeuvres on upper airway dimensions and clinical signs in anaesthetized, spontaneously breathing children

Chin lift, jaw thrust and these manoeuvres combined with continuous positive airway pressure (CPAP) can be used to improve the patency of the upper airway during general anaesthesia. We used video endoscopy and measurement of stridor to compare the efficacy of these manoeuvres in 24 children (3-10 yr) with adenotonsillar hyperplasia. A bronchofibrescope was passed via the nose while the children were breathing spontaneously, to identify (i) the shortest transverse distance between the tonsils during inspiration and during expiration and (ii) the distance from the tip of the epiglottis to the posterior pharyngeal wall. Chin lift or jaw thrust lifted the epiglottis and, when combined with CPAP (10 cm H2O), there was a significant lateral displacement of the tonsils. Both chin lift plus CPAP and jaw thrust plus CPAP reduced stridor significantly compared with the unsupported condition. In conclusion, in spontaneously breathing children with large tonsils, chin lift plus CPAP is recommended, whereas jaw thrust plus CPAP is no better and may cause post-operative discomfort.