Airway Resistance In Children Research Articles

Outcomes of heliox use in children with respiratory compromise: A 10-year single institution experience.

Heliox, a mixture of helium and oxygen, has been shown to improve laminar airflow and decrease airway resistance in children. This study aims to describe the outcomes of heliox use in children with respiratory compromise and to identify variables associated with a need for airway surgical intervention. A retrospective cohort study of patients who received heliox between 2012 and 2022 at a tertiary care children's hospital. A hundred and thirty-eight heliox treatments were recorded in 119 children. Twelve patients were excluded. Most (n = 100, 84%) patients had significant comorbidities. On average, patients spent a cumulative mean of 94 ± 187 h on heliox therapy per hospital admission. Patients with croup or asthma without known airway pathology presented at an older age than patients with other indications for heliox therapy (4.0 ± 4.7 vs. 2.2 ± 3.6 years, p = 0.04) and were significantly less likely to have background diseases (n = 14, 52% vs. n = 74, 93%, p < 0.0001). Overall, 51 (47.7%) patients were recommended tracheostomy placement, airway reconstruction, or palliative care. Cumulative use of heliox for more than 47 h was associated with an increased risk of needing tracheostomy or airway reconstruction (odds ratio 6.2, 95% confidence intervals 2.56-14.13, p < 0.0001). In multivariable regression analysis, neuromuscular disease, intracranial neuropathology, and cumulative time of heliox were associated with a need for definitive airway intervention. Heliox may be used as a temporizing agent in children with upper airway obstruction. The effectiveness of heliox use for more than 47 h in children, especially in the presence of neuromuscular disease and intracranial neuropathology should be reconsidered.Level of evidence: 4.

The influence of body mass index on airway resistance in children with sickle cell disease: A longitudinal study based on impulse oscillometry

BackgroundImpulse oscillometry (IOS) is an effective tool for assessing airway mechanics and diagnosing obstructive airway disease (OAD) in children with sickle cell disease (C-SCD). Obesity is known to be associated with OAD, and untreated OAD often leads to hypoxia-related complications in C-SCD. Considering the increasing prevalence of obesity in C-SCD, it is important to explore the influence of body mass index (BMI) on OAD in this disease population. MethodsA longitudinal retrospective chart review was conducted on 55 C-SCD (161 IOS observations) and 35 non-SCD asthmatic children (C-Asthma) (58 observations), primarily to investigate the association between BMI and airway resistance in C-SCD and C-Asthma. We conducted generalized linear mixed models (GLMM), adjusted for pharmacotherapies, to demonstrate the influence of BMI on total (R5), central (R20), and peripheral (R5-20) airway resistance and reactance (X5, resonant frequency (Fres)). We further compared age, BMI, and IOS indices between C-SCD and C-Asthma using the Mann-Whitney test. ResultsAge and BMI were not statistically different between the two groups. In C-SCD, BMI was associated with R5 (GLMM t-statistics:3.75, 95%CI:1.01,3.27, p-value<0.001*) and R20 (t-statistics:4.01, 95%CI:1.04,1.15, p-value<0.001*), but not with R5-20 or airway reactance. In asthmatics, BMI was not associated with IOS estimates except Fres (t-statistics: 3.93, 95%CI: −0.06, −0.02, p-value<0.001*). C-SCD demonstrated higher airway resistances (R5 and R20) and reactance (Fres) compared to C-Asthma (Mann-Whitney: p-values<0.05). ConclusionBMI significantly influenced total and central airway resistance in C-SCD. While higher airway resistances reflected increased OAD in C-SCD than asthmatics, higher Fres perhaps indicated progressive pulmonary involvement in C-SCD.

Impulse oscillometry system for assessing small airway dysfunction in pediatric bronchiolitis obliterans; association with conventional pulmonary function tests.

Impulse oscillometry system (IOS) is a simple, and less invasive method for assessing small to total airway resistance in children. We analyzed the correlation between IOS, spirometry, and plethysmographic parameters performed for the diagnosis of pediatric BO patients. A total of 89 IOS assessments of pediatric BO patients or children without lung disease were included, and the relationship between pulmonary function tests (PFTs) and diagnostic performance was analyzed. R5, R5-20, X5, and AX were statistically significantly worse in the BO group. In general linear correlation analysis, R5% (adjusted β [aβ], -0.59; p < 0.001) and AX % (aβ, -0.9; p < 0.001) showed the strongest correlation with conventional PFT parameters. R5% and AX % also showed the highest correlation with FEF25-75% (aβ, -0.48; p < 0.001 and aβ, -0.83; p < 0.001), and sRaw % (aβ, -0.73; p = 0.003 and aβ, -0.59; p = 0.008, respectively). Multivariate logistic regression analysis showed that R5 Z-score showed the highest ORs with FEV1 (OR = 3.94, p = 0.006), FEF25-75% (OR = 5.96, p = 0.005), and sRaw % (OR = 4.85, p = 0.022). Receiver operating curve analysis suggested AX % and R5% as the most optimal IOS parameters for BO diagnostic performance with the area under the curve of 0.915 and 0.882, respectively. In conclusion, R5 and AX are the parameters that can independently identify the severity of airway obstruction in pediatric BO patients without conventional lung function tests. IOS is an easy-to-perform, and reliable diagnostic method capable of detecting pathological obliteration of the small airways in children with BO.

The Relevance of Airway Resistance in Children Requiring Mechanical Ventilatory Support.

To describe pulmonary resistance in children undergoing invasive mechanical ventilation (MV) for different causes. A cross-sectional study. Two PICUs in the South region of Brazil. Children 1 month to 15 years old undergoing MV for more than 24 hours were included. We recorded ventilator variables and measured pulmonary mechanics (inspiratory and expiratory resistance, auto positive end-expiratory pressure [PEEP], and dynamic and static compliance) in the first 48 hours of MV. Measurements of the respiratory mechanics variables during neuromuscular blockade. A total of 113 children were included, 5 months (median [interquartile range (IQR) [2.0-21.5 mo]) old, and median (IQR) weight 6.5 kg (4.5-11.0 kg), with 60% male. Median (IQR) peak inspiratory pressure (PIP) was 30 cm H 2 O (26-35 cm H 2 O), and median (IQR) PEEP was 5 cm H 2 O (5-7 cm H 2 O). The median (IQR) duration of MV was 7 days (5-9 d), and mortality was nine of 113 (8%). The median (IQR) inspiratory and expiratory resistances were 94.0 cm H 2 O/L/s (52.5-155.5 cm H 2 O/L/s) and 117 cm H 2 O/L/s (71-162 cm H 2 O/L/s), with negative association with weight and age (Spearman -0.850). When we assess weight, in smaller children (&lt; 10 kg) had increased pulmonary resistance, with mean values over 100 mH 2 O/L/s, which were higher than larger children ( p &lt; 0.001). Increased pulmonary resistance is prevalent in the pediatric population undergoing invasive MV. Especially in children less than 1 year old, this variable should be considered when defining a ventilatory strategy.

Impulse Oscillometry System for the Diagnosis of Wheezing Episode in Children in Office Practice.

Background and ObjectiveObjectively differentiating between wheezing episodes and other respiratory disorders will be helpful in treatment in office practice. The impulse oscillometry system has been useful in assessing airway resistance in children 3–6 years old. As the reference values are different in geographical regions the use of the impulse oscillometry is still limited. Comparison between the percent change in IOS parameters as compared to reference standards and changes in actual IOS parameters was done to diagnose wheezing episodes.MethodologyThree to six years old children with a history of fever, cough, cold, and/or breathlessness with noisy breathing and who were not on any regular medications, whose parents gave consent were recruited in the study. The children underwent an impulse oscillometry system examination as per the guidelines. The test was repeated after they were given nebulization by salbutamol (2.5 mg) (before COVID 19 pandemic). Final diagnosis was done by following patients for 7 days.ResultsAbout 106 children were recruited in the study. Five children could not perform the IOS test. Eighteen children did not complete the follow-up. Hence, 83 children were analyzed. There were 47 males and 36 female patients. The change in actual values of AX, R5, and X20 showed statistically significant difference in wheezing episode group (p-value<0.001). The percentage change as compared to predicted values of R5 and X20 also showed a statistically significant difference in the wheezing episode group and the others group (p-value<0.001).ConclusionThe change in actual values of AX, R5, X20, and resonant frequency may help to differentiate wheezing episode from other respiratory diseases.

From the pages of AllergyWatch®: December 2020

For this month’s edition of “From the Pages of AllergyWatch,” I have chosen reviews of articles from one of the recent issues. The first article, reviewed by Dr Lee, suggests that a quarter of our patients with asthma also have laryngeal dysfunction. Next, Dr Joshi points out that the study he reviewed revealed improvement in small airway resistance in children with asthma after high-efficiency particular air filters were used in their bedrooms. The final, also by Dr Joshi, reviews a study investigating the reasons why adults diagnosed as having food allergy who tolerated oral food challenges still tend to avoid those foods.

Impulse Oscillometry Discerns the Peripheral Airway Response to an Inhaled Bronchodilator between Obese and Nonobese Children

IntroductionImpulse oscillometry (iOS) is a useful tool to distinguish between central and peripheral airway resistance. For example, iOS has shown that peripheral airway resistance is greater in children with versus those without obesity, despite no difference in FEV1. Considering the added peripheral airway resistance in children with obesity, we sought to determine if iOS can detect potential differences in the peripheral airway response to an inhaled bronchodilator (BD) between children with and those without obesity.MethodsTwenty‐four children with and eleven without obesity, ages 8–12yrs, completed iOS and spirometry testing before and 15mins after the administration of four puffs of an inhaled BD (Ventolin®, 90μg). A mixed models ANOVA (group by pre‐to‐post‐BD) was used to determine differences in FEV1, plethysmographic airway resistance (Raw) and specific Raw (sRaw), and iOS parameters associated with airway resistance. These parameters include resistance at 5 Hz, 10 Hz (R5 and R10: total airway resistance), 20 Hz (R20: large airway resistance), and the difference between R5 and R20 (R5–20: peripheral airway resistance). Reactance at 5 Hz (X5: total airway elastic recoil) and the area under the reactance‐frequency curve (AX: index of small airway patency) were also measured using iOS.ResultsThere was no difference in FEV1 (% pred) or FEV1/FVC between groups and none of our participants showed a positive BD response based on the conventional method of a ≥12% increase in FEV1. Compared with children without obesity, children with obesity presented a greater baseline R5 (7.28 ± 1.20 vs. 5.42 ± 1.44 cmH2O·L−1·s−1; p=0.001), R10 (6.04 ± 1.12 vs. 4.58 ± 1.07 cmH2O·L−1·s−1; p=0.002), R20 (4.76 ± 0.95 vs. 3.94 ± 0.79 cmH2O·L−1·s−1; p=0.025), R5–20 (2.52 ± 0.64 vs. 1.49 ± 0.75 cmH2O·L−1·s−1; p&lt;0.001), and AX (7.65 ± 5.59 vs. 3.75 ± 1.97 cmH2O·L−1; p=0.008), with no difference in X5 (−1.19 ± 0.77 vs. −1.19 ± 0.33 cmH2O·L−1; p=0.667). A group by pre‐to‐post‐BD interaction was found for R5 (p=0.033) and R10 (p=0.024). Both R5 and R10 decreased to a greater extent with BD in children with obesity versus children without obesity (R5: −20.8 ± 9.5% vs. −12.8 ± 15.2%; R10: −21.6 ± 8.6% vs. −14.5 ± 13.1%). In all children (n=35), Raw, sRaw, and all iOS parameters, except for X5, decreased with the BD (p&lt;0.05).ConclusionIn addition to greater central and peripheral airway resistance in children with obesity, iOS also detected a greater peripheral airway response to a BD in children with obesity. Although no established criteria exist for children ages 8–12yrs, the American Thoracic Society defines an airway response in preschool children as a 20–40% decrease in R5 and a 15–30% decrease in R10. Based on these criteria, our finding that R5 and R10 dropped by 20.8% and 21.6% in children with obesity indicates potential peripheral airway hyperresponsiveness in children with obesity. However, further research is warranted to establish the meaning of, or normal criteria for, peripheral airway responsiveness in prepubescent children.Support or Funding InformationNIH R01 HL136643, Texas Health Presbyterian Hospital Dallas, King Charitable Foundation Trust, and Dr. Pepper Snapple.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Effects of non-surgical rapid maxillary expansion on nasal structures and breathing: A systematic review

This systematic review aims to determine the effects of non-surgical rapid maxillary expansion (RME) on breathing and upper airway structures. An electronic search of the scientific literature from January 2005 to June 2016 was done using Web of Science, Dentistry & Oral Sciences Source and PubMed databases. A combination of search terms "rapid maxillary expansion", "nasal", "airway" and "breathing" were used. Studies that involved surgical or combined RME-surgical treatments and patients with craniofacial anomalies were excluded. The initial screening yielded a total of 183 articles. After evaluation of the titles, abstracts and accessing the full text, a total of 20 articles fulfilled both inclusion/exclusion criteria and possessed adequate evidence to be incorporated into this review. Non-surgical RME was found to improve breathing, increase nasal cavity geometry and decrease nasal airway resistance in children and adolescents.

The association of nasal patency with small airway resistance in children with allergic and nonallergic rhinitis.

Allergic rhinitis (AR) is immunologically and morphologically related to disorders in the lower airway. We investigated the relationship between the anatomy of the intranasal cavity and small airway resistance in subjects with nonallergic rhinitis (NAR). We enrolled 226 children who were 7 years old and participated in the Seongnam Atopy Project 2016. We evaluated nasal patency using acoustic rhinometry to measure the volume of the nasal cavity at 0-5 cm, and measured lung function of the lower airway using an impulse oscillometry system (IOS) and spirometry. We also performed skin prick tests for 18 aero-allergens, and measured blood total eosinophil counts (TEC) and rhinitis symptom scores for the previous month using a visual analog scale (VAS, range: 0-10). We examined 226 children, 71 (31.7%) with AR, and 62 (27.7%) with NAR. Nasal patency in children with AR (median: 8.28 mm3 , IQR: 7.07-9.83) was lower than that of healthy children (median: 9.3 mm3 , IQR: 7.69-10.64, P = 0.011). Multivariate regression analysis showed that nasal patency was inversely associated with IOS resistance at 5 Hz after adjustment for compounding factors (B = -0.005, SE = 0.0032, P = 0.041). Analysis of NAR subjects, according to quartiles of nasal patency and quartiles of small airway resistance (Rrs5), indicated that nasal patency decreased as Rrs5 increased (linear trend: P = 0.020). Nasal symptoms and TEC negatively correlated with nasal patency. Children with AR and NAR who had poor nasal patency had increased small airway resistance.

Airway Resistance in Children with Obstructive Sleep Apnea Syndrome.

Enlarged tonsils and adenoids, the main cause of obstructive sleep apnea syndrome (OSAS) in children, results in upper airway (UA) loading. This contributes to the imbalance between structural and neuromotor factors ultimately leading to UA collapse during sleep. However, it is unknown whether this UA loading can cause elevated airway resistance (AR) during wakefulness. We hypothesized that children with OSAS have elevated AR compared to controls and that this improves after OSAS treatment. Case control study performed at an academic hospital. Children with OSAS and nonsnoring healthy controls underwent baseline polysomnography and spirometry, and AR measurement by body plethysmography while breathing via an orofacial mask. Children with OSAS repeated the previously mentioned tests after adenotonsillectomy. 31 OSAS participants (mean age ± SD = 9.7 ± 3.0 y, obstructive apnea-hypopnea index (OAHI) median [range] = 14.9 [2-58.7] events/h, body mass index [BMI] z = 1.5 ± 1) and 31 controls (age = 10.5 ± 2.5 y, P = 0.24; OAHI = 0.4 [0-1.4], P < 0.001; BMI z = 0.9 ± 1, P = 0.01) were tested. OSAS AR at baseline was 3.9 [1.5-10.3] cmH2O/L/sec and controls 2.8 [1.4 - 6.2] (P = 0.027). Both groups had similar spirometry results. 20 patients with OSAS were tested 6.4 ± 6.6 mo after adenotonsillectomy. OAHI decreased from 15.2 [2.1-58.7] to 0.5 [0 - 5.1] events/h postoperatively (P < 0.001), and AR decreased from 4.3 [1.5 - 10.3] to 2.8 [1.7 - 4.7] cmH2O/L/sec (P = 0.009). Children with OSAS have elevated AR that decreases after treatment. This is likely because of upper airway loading secondary to adenotonsillar hypertrophy and may contribute to the increased frequency of respiratory diseases in untreated children with OSAS.

Evaluation of Airway Resistance in Children with Juvenile Idiopathic Arthritis.

Background: Pneumonitis, pleuritis, and pulmonary interstitial infiltration have been described in patients with juvenile idiopathic arthritis (JIA). However, the pulmonary involvement of JIA is not often clinically apparent. There are few studies based on pulmonary function in children having only a diagnosis of JIA. The aim of the present study is to determine whether children with JIA have airway resistance and flow impairments measured by easily applied interrupter technique. Method: We performed interrupter resistance (Rint) measurements in children with JIA and in healthy control subjects who had no respiratory symptoms or diseases. Results: Fifty-eight children with the diagnosis of JIA (Mean age=12.5±2.75 years; range 7-17 years) and 33 healthy subjects (Mean age=11.8±2.62 years; range 6-16 years) were included in the study. The mean value of tidal peak flow during expiration measured by the interrupter technique was significantly lower in the JIA study group (0.73±0.11 L/s) compared to the healthy control group (0.79±0.08 L/s; p=0.01). Rint values measured during inspiration (Rintinsp) and during expiration (Rintexp) were higher in the JIA study group (Rintinsp=0.28±0.16 Kpa/L/s; Rintexp=0.30±0.50 Kpa/L/s) compared to the healthy control group (Rintinsp=0.26±0.11 Kpa/L/s; Rintexp=0.23±0.08 Kpa/L/s; p>0.05). There was also a positive correlation between C-reactive protein level and median expiratory interrupter resistance (Rintexp; r=0.50, p=0.005). Conclusion: The interrupter technique is a noninvasive and feasible technique and can be used to assess airway abnormalities in children with JIA who cannot successfully complete spirometry.

Specific airway resistance in children: Panting or tidal breathing?

The measurement of specific airway resistance during tidal breathing (sRaw(tb)) has gained popularity in children, but methodological concerns have been raised regarding the electronic compensation for the thermal artifact. The panting method (sRaw(p)) is efficient in minimizing the latter, but may be associated with a change in end expiratory lung volume if the effort is not properly balanced. The aim of the study was to compare sRaw(tb) with sRaw(p) in children. Fifty-five children aged 6.5-11.5 years were studied. sRaw(tb) was measured in a commercial plethysmograph. sRaw(p) was measured with a home made equipment that allowed breath by breath analysis (sRaw(p1)) as well as with the commercial body box (sRaw(p2)). sRaw(tb) was significantly larger than either sRaw(p1) or sRaw(p2) (P < 0.0001). The mean (95% CI) difference sRaw(p1) - sRaw(tb) was -0.374 (-0.835 to 0.088) kPa s. The difference between sRaw(p1) and sRaw(p2) was significant (P < 0.005) but not clinically relevant, and mean (95% CI) difference sRaw(p1) - sRaw(p2) was 0.115 (-0.094 to 0.324) kPa s. The breath by breath analysis showed small but significant increase in sRaw(p1) throughout the maneuver (P < 0.001), whatever the pattern of end expiratory level. Tidal breathing is associated with an overestimation of sRaw compared with panting in children. Although the latter results in small increase throughout the panting maneuver, sRaw(p) is probably more trustful than sRaw(tb).

Vitamin A deficiency alters airway resistance in children with acute upper respiratory infection

ObjectiveTo assess whether vitamin A deficiency alters the recovery of total respiratory resistance (TRR) following acute upper respiratory tract infection (URI).MethodsThis is a case control study of children, age 4–6 years and grouped as: URI, (n = 74), URI and wheezing, (URI‐wheezing, n = 52), and healthy controls (n = 51). Vitamin A and total respiratory resistance (TRR) were assessed using the modified relative dose response (MRDR) and forced oscillometry, respectively.ResultsChildren with URI and URI‐wheezing had lower retinol, 32.4 ± 13.12 and 18.3 ± 6.83 µg/dl respectively, compared to controls, 56.9 ± 29.82 µg/dl (ANOVA, P < 0.001). The MRDR was elevated in children in the URI or URI‐wheezing groups 0.066 ± 0.045 and 0.021 ± 0.021, respectively, compared to controls 0.007 ± 0.006 (ANOVA, P < 0.0001). The TRR in the URI and URI‐wheezing groups differed from controls. During convalescence, the TRR failed to decline in the URI‐group only when the MRDR was >0.06. In the URI‐wheezing group, TRR declined independently of retinol and MRDR.ConclusionVitamin A contributes to preservation of airway function during and in recovery after upper respiratory infection in children. Pediatr Pulmonol. 2013; 48:481–489. © 2012 Wiley Periodicals, Inc.

The Use of Impulse Oscillometry Percent of Predicted Value to Determine Abnormal Lung Function in Pediatric Patients

PURPOSE: Lung function is considered abnormal via impulse oscillometry (IOS) if the airway resistance (AR) is greater than 150 percent of the predicted value. The purpose of our study was to determine if new percent of predicted values needed to be set for airway resistance in children.

Effect of addition of salmeterol versus doubling the dose of fluticasone propionate on specific airway resistance in children with asthma

Based primarily on extrapolation from adult studies, current pediatric asthma guidelines advise the addition of long-acting beta₂-agonists for children symptomatic on low/moderate-dose inhaled corticosteroids before increasing the corticosteroid dose. This study was designed to compare the effect of combination salmeterol/fluticasone propionate (SFC) with doubling the dose of fluticasone propionate (FP) on specific airway resistance (sR(aw)) in moderate/severe persistent asthmatic children. A double-blind, randomized, controlled study was performed; children with asthma (4-11 years old; sR(aw) > 1.3 kPa·s) were randomized after a 2-week run-in (FP, 100 μg, b.i.d.) to either SFC (50 μg/100 μg b.i.d.) or FP (200 μg b.i.d.) via Diskus (GlaxoSmithKline, Stockley Park, U.K.) for 6 weeks. Lung function (sR(aw)-plethysmography and forced expiratory volume in 1 second [FEV₁]) was measured before run-in, at randomization, after 3 weeks, at the end of 6-week treatment, and after 48-hour washout. Symptom scores and rescue medication use were recorded throughout. Thirty-five children entered run-in and 24 were randomized (mean age, 7.3 ± 2.2 years; 50% boys). All children showed an improvement in sR(aw). After adjusting for age, gender, and baseline sR(aw,) children receiving SFC had a significantly greater improvement in sR(aw) compared with those receiving FP (adjusted means ratio [95% confidence interval {CI}], 0.81 [0.68-0.97]; p = 0.021). There was a significant interaction between treatment and gender (sR(aw), adjusted geometric mean [95% CI ]kPa·s, SFC versus FP: boys, 1.25 [1.10-1.41] [n = 7] versus 1.87 [1.61-2.17] [n = 5]; girls, 1.29 [1.10-1.52] [n = 5] versus 1.29 [1.13-1.47] [n = 7]; p = 0.008). There were no differences in FEV₁, symptoms, or rescue medication use between the groups. Addition of salmeterol provides greater improvement in sR(aw) than doubling the dose of FP in children with moderate/severe persistent asthma.

Reference equations for specific airway resistance in children: the Asthma UK initiative

Plethysmographic specific airway resistance (sR(aw)) is a useful research method for discriminating lung disease in young children. Its use in clinical management has, however, been limited by lack of consensus regarding equipment, methodology and reference data. The aim of our study was to collate reference data from healthy children (3-10 yrs), document methodological differences, explore the impact of these differences and construct reference equations from the collated dataset. Centres were approached to contribute sR(aw) data as part of the Asthma UK initiative. A random selection of pressure-flow plots were assessed for quality and site visits elucidated data collection and analysis protocols. Five centres contributed 2,872 measurements. Marked variation in methodology and analysis excluded two centres. sR(aw) over-read sheets were developed for quality control. Reference equations and recommendations for recording and reporting both specific effective and total airway resistance (sR(eff) and sR(tot), respectively) were developed for White European children from 1,908 measurements made under similar conditions. Reference sR(aw) data collected from a single centre may be misleading, as methodological differences exist between centres. These preliminary reference equations can only be applied under similar measurement conditions. Given the potential clinical usefulness of sR(aw), particularly with respect to sR(eff), methodological guidelines need to be established and used in prospective data collection.

Lung function assessment using the interrupter technique in infants and preschool children

There are numerous problems regarding lung function assessment in infants and preschool children despite the great interest to this field worldwide. Therefore, investigations of the interrupter technique in infants and preschool children are of great importance. This article contains results of measurement of airway resistance in children with asthma, atopic dermatitis, acute bronchitis and croup and in healthy children using the interrupter technique. Results of mathematic modeling have also been discussed in the article.

Variability analysis of oscillatory airway resistance in children

Testing pulmonary function in preschool children is problematic since individual cooperation is often insufficient to yield adequate results. This is especially the case when repetitive measurements are carried out, e.g., during provocation tests in order to diagnose bronchial hyperresponsiveness. We therefore sought to determine whether the variability of the oscillatory airway resistance, which can be measured with minimal patient cooperation, might serve as an approach to separate asymptomatic children with asthma from age-matched healthy controls. Monofrequent forced oscillation technique was used to measure the oscillatory resistance (Ros) continuously at a repetition rate of 10 Hz. Forty consecutive values of Ros at the end of expiration (Ros(pe)) and at the end of inspiration (Ros(pi)) were used to calculate variability measures [standard deviation (SD), averaged deviation (LD), root mean square successive differences (RMSSD)] known from heart rate variability analysis to describe the airway diameter variability in 36 asthmatics and 21 healthy controls. Airway diameter variability of Ros(pi) and Ros(pe) as expressed by SD from the mean (P = 0.01 and 0.05, respectively), from LD (P = 0.01 and 0.21, respectively) and from the RMSSD (P = 0.006 and 0.03, respectively) was greater in patients with asthma. Mean values of Ros(pi) and Ros(pe) were not different between groups. Airway diameter variability is higher in asymptomatic children with asthma than in healthy controls. Future research should evaluate whether the measurement of the variability of Ros(pi), which does not require the patient's cooperation, can give similar information as challenge tests with respect to bronchial hyperresponsiveness.

Assessment of inspiratory flow limitation in children with sleep‐disordered breathing by a nasal cannula pressure transducer system

A nasal cannula pressure transducer system identifies inspiratory flow limitation and increased upper airway resistance in adults with sleep-disordered breathing (SDB). The purpose of this study was to evaluate whether nasal cannula pressure (NCP) detects apneas and hypopneas as well as additional flow-limited events associated with increased airway resistance in children. We studied NCP in 47 patients (ages 2-14 years) referred for SDB to a university-based sleep disorders program during nocturnal polysomnography (NPSG). During NPSG, airflow was assessed simultaneously by thermistor and NCP. There was a high correlation between apneas assessed by thermistor (T) and NCP (r = 0.90, P < 0.0001), and for hypopneas using these two methods (r = 0.94, P = 0.0001). Respiratory driving pressure was indirectly measured with an esophageal pressure catheter. Flow-limited (flattened) NCP waves were associated with significantly higher driving pressure, indicating elevated upper airway resistance, compared to nonflow-limited (rounded) waves during nonrapid eye movement (NREM) (P = 0.05) and rapid eye movement (REM) (P = 0.01) sleep. Patients were classified as either having obstructive sleep apnea syndrome (OSAS) or primary snoring, based on standard NPSG criteria. NCP identified additional respiratory events with a flattened contour (FC) not detected by thermistor. NCP is a noninvasive device that identifies obstructive apneas and hypopneas as well as additional respiratory events associated with flow limitation in children.

Stress and airway resistance in children with asthma

Objective: The present study implements an experimental paradigm to examine airway reactivity to stress in children with asthma and controls. Method: 114 children with asthma and 30 controls (ages 9–15) participated. The protocol involved 5 min of baseline physiological measurements followed by a 5-min stressful task. Skin conductance (EDG), skin temperature, and heart rate were measured continuously. Airway resistance was measured at baseline and after the task. Results: 110 children (76% of the sample) were significantly “stressed” as shown by physiological changes. Asthmatics and controls differed on overall airway resistance, F(1,108)=12.3, P<.001. The entire sample demonstrated a trend toward increased airway resistance in response to stress, F(1,108)=3.1, P<.08. A portion of asthmatics (22%) had increases of greater than 20% of baseline airway resistance. Changes in airway resistance in response to stress were unrelated to asthma severity, F(2,78)=2.0, ns. Conclusion: Children with asthma and controls demonstrate variation in airway function in response to stress, although increases are likely more meaningful for children with asthma. Further research is needed to examine the mechanisms underlying this response.