Jung Won Yoon

Reference values for respiratory system impedance using impulse oscillometry in healthy preschool children

Purpose The normal values for lung resistance and lung capacity of children, as determined by impulse oscillometry (IOS), are different for children of different ethnicities. However, reference values there is no available reference value for Korean preschool children have yet to be determined. The aim of the present study was to determine the normal ranges of IOS parameters in Korean preschool children. Methods A total of 133 healthy Korean preschool children were selected from 639 children (aged 3 to 6 years) who attended kindergarten in Seongnam, Gyeonggi province, Korea. Healthy children were defined according to the European Respiratory Society (ERS) criteria. All subjects underwent lung function tests using IOS. The relationships between IOS value (respiratory resistance (Rrs) and reactance (Xrs) at 5 and 10 Hz and resonance frequency (RF)) and age, height, and weight were analyzed by simple linear and multiple linear regression analyses. Results The IOS success rate was 89.5%, yielding data on 119 children. Linear regression identified height as the best predictor of Rrs and Xrs. Using stepwise multiple linear regressions based on age, height, and weight, we determined regression equations and coefficients of determination (R2) for boys (Rrs5=1.934-0.009×Height, R2=12.1%; Xrs5=0.774+0.006×Height-0.002×Age, R2=20.2% and for girls (Rrs5=2.201-0.012×Height, R2=18.2%; Xrs5=-0.674+0.004×Height, R2=10.5%). Conclusion This study provides reference values for IOS measurements of normal Korean preschool children. These provide a basis for the diagnosis and monitoring of preschool children with a variety of respiratory diseases.

Oscillometric and spirometric bronchodilator response in preschool children with and without asthma

BACKGROUND Bronchodilator responses (BDR) are routinely used in the diagnosis and management of asthma; however, their acceptability and repeatability have not been evaluated using quality control criteria for preschool children. OBJECTIVES To compare conventional spirometry with an impulse oscillometry system (IOS) in healthy and asthmatic preschool children. METHODS Data from 30 asthmatic children and 29 controls (two to six years of age) who underwent IOS and spirometry before and after salbutamol administration were analyzed. RESULTS Stable asthmatic subjects significantly differed versus controls in their spirometry-assessed BDR (forced expiratory volume in 1 s [FEV1], forced vital capacity and forced expiratory flow at 25% to 75% of forced vital capacity) as well as their IOS-assessed BDR (respiratory resistance at 5 Hz [Rrs5], respiratory reactance at 5 Hz and area under the reactance curve). However, comparisons based on the area under the ROC curve for ΔFEV1 %initial versus ΔRrs5 % initial were 0.82 (95% CI 0.71 to 0.93) and 0.75 (95% CI 0.62 to 0.87), respectively. Moreover, the sensitivity and specificity for ΔFEV1 >=9% were 0.53 and 0.93, respectively. Importantly, sensitivity increased to 0.63 when either ΔFEV1 >=9% or ΔRrs5 >=29% was considered as an additional criterion for the diagnosis of asthma. CONCLUSION The accuracy of asthma diagnosis in preschool children may be increased by combining spirometry with IOS when measuring BDR.

Patterns of sensitisation to common food and inhalant allergens and allergic symptoms in pre‐school children

Sensitisation to allergens and allergy symptoms depends on age, but this relationship is poorly understood. We therefore investigated the effect of age on allergen sensitisation and allergy symptoms in pre‐school children.

Useful marker of oscillatory lung function in methacholine challenge test-comparison of reactance and resistance with dose-response slope.

There are few studies focusing on the comparison of resistance (Rrs) and reactance (Xrs) in impulse oscillometry system (IOS) in the bronchial challenge test using dose–response slope (DRS), a quantitative index of bronchial hyperresponsiveness.

Use of impulse oscillometry system in assessment of asthma severity for preschool children.

Objective. The National Asthma Education and Prevention Program/Expert Panel Report (NAEPP/EPR)-3 Guidelines for asthma treatment categorize asthma severity based on impairment and risks and on medications administered. The objective of this study was to determine whether impulse oscillometry system (IOS) measures in preschool children are consistent with asthma severity as defined by NAEPP/EPR-3 Guidelines. Methods. Asthma severity of the 162 subjects (aged 2–5 years) was classified by impairment and risks for exacerbations requiring oral systemic corticosteroids, by medication usage, and by combination classification (higher severity of impairment and risks or medication usage). An experienced pediatrician determined the appropriate medications for each child and parents completed structured questionnaires regarding day and night symptoms and interference with normal activity over the preceding 4 weeks. All children were tested by IOS. Results. The mean age was 3.7 ± 0.9 years and 91 (56%) of the total patients were males. When asthma severity was based on (1) impairment and risks and (2) medication usage, asthma was “intermittent” in 17.9% and 11.1% of the total patients, “mild persistent” in 42.0% and 50.6% of total patients, and “moderate–severe persistent” in 40.1% and 38.3% of total patients, respectively. The agreement between severity based on impairment and risks and medication usage was not significant. Xrs5 z-scores differed between intermittent asthma and mild/moderate–severe persistent asthma, as determined by medication usage and combination classification, but not by impairment and risks. As asthma severity (assessed by medication usage) increased, the duration of asthma increased. Conclusions. Xrs5 can be used to discriminate intermittent and persistent asthma in preschool children. Further studies with larger sample sizes are warranted to confirm this finding and to determine the underlying mechanism.

Clinical risk factors associated with the development of wheezing in children less than 2 years of age who required hospitalization for viral lower respiratory tract infections

Purpose Wheezing following viral lower respiratory tract infections (LRTIs) in children <2 years of age is an important risk factor for the development of asthma later in life; however, not all children with viral LRTIs develop wheezing. This study investigated risk factors for the development of wheezing during viral LRTIs requiring hospitalization. Methods The study included 142 children <2 years of age hospitalized for LRTIs with at least one virus identified as the cause and classified them into children diagnosed with LRTIs with wheezing (n=70) and those diagnosed with LRTIs without wheezing (n=72). Results There were no significant differences in the viruses detected between the two groups. Multivariate logistic regression analysis showed that, after adjusting for potentially confounding variables including sex and age, the development of wheezing was strongly associated with parental history of allergic diseases (adjusted odds ratio [aOR], 20.19; 95% confidence interval [CI], 3.22-126.48), past history of allergic diseases (aOR, 13.95; 95% CI, 1.34-145.06), past history of hospitalization for respiratory illnesses (aOR, 21.36; 95% CI, 3.77-120.88), exposure to secondhand smoke at home (aOR, 14.45; 95% CI, 4.74-44.07), and total eosinophil count (aOR, 1.01; 95% CI, 1.01-1.02). Conclusion Past and parental history of allergic diseases, past history of hospitalization for respiratory illnesses, exposure to secondhand smoke at home, and total eosinophil count were closely associated with the development of wheezing in children <2 years of age who required hospitalization for viral LRTIs. Clinicians should take these factors into consideration when treating, counseling, and monitoring young children admitted for viral LRTIs.

Food allergen sensitization in young children with typical signs and symptoms of immediate-type food allergies: a comparison between monosensitized and polysensitized children

Purpose The clinical interpretation of children sensitized to allergens is challenging, particularly in children with food allergies. We aimed to examine clinical differences between children with monosensitization and those with polysensitization to common food allergens and to determine risk factors for polysensitization in young children <10 years of age with immediate-type food allergies. Methods The study included children <10 years of age with signs and symptoms indicative of immediate-type food allergies. Serum total IgE level was measured, and ImmunoCAP analysis for food allergens was performed. Results The mean age of the study subjects was 1.6±1.6 years (75 boys and 51 girls). Thirty-eight children (30.2%) were monosensitized and 88 children (69.8%) were polysensitized. Multivariate logistic regression analysis showed that the development of polysensitization to common food allergens was positively associated with a parental history of allergic rhinitis (adjusted odds ratio [aOR], 6.28; 95% confidence interval [CI], 1.78-22.13; P=0.004), season of birth (summer/fall) (aOR, 3.10; 95% CI, 1.10-8.79; P=0.033), and exclusive breastfeeding in the first 6 months of age (aOR, 3.51; 95% CI, 1.20-10.25; P=0.022). Conclusion We found significant clinical differences between children with monosensitization and those with polysensitization to common food allergens and identified risk factors for the development of polysensitization in young children with immediate-type food allergies. Clinicians should consider these clinical risk factors when evaluating, counseling, treating, and monitoring young children with food allergies.

Clinical Implications of Oscillatory Lung Function during Methacholine Bronchoprovocation Testing of Preschool Children

OBJECTIVE To investigate the repeatability and safety of measuring impulse oscillation system (IOS) parameters and the point of wheezing during bronchoprovocation testing of preschool children. METHODS Two sets of methacholine challenge were conducted in 36 asthma children. The test was discontinued if there was a significant change in reactance (Xrs5) and resistance (Rrs5) at 5 Hz (Condition 1) or respiratory distress due to airway obstruction (Condition 2). The repeatability of PC80_Xrs5, PC30_Rrs5, and wheezing (PCw) was assessed. The changes in Z-scores and SD-indexes from prebaseline (before testing) to postbaseline (after bronchodilator) were determined. RESULTS For PC30_Rrs5, PC80_Xrs5, and PCw for subjects, PC80_Xrs5 showed the highest repeatability. Fifteen of 70 tests met Condition 2. The changes from pre- and postbaseline values varied significantly for Rrs5 and Xrs5. Excluding subjects with Z-scores higher than 2SD, we were able to detect 97.1% of bronchial hyperresponsiveness during methacholine challenge based on the change in Rrs5 or Xrs5. A change in IOS parameters was associated with wheezing at all frequencies. CONCLUSION Xrs5 and Rrs5 have repeatability comparable with FEV1, and Xrs5 is more reliable than Rrs5. Clinicians can safely perform a challenge test by measuring the changes in Rrs5, Xrs5, and Z-scores from the prebaseline values.

Exhaled nitric oxide and mannitol test to predict exercise‐induced bronchoconstriction

Exercise‐induced bronchoconstriction (EIB) is diagnosed via exercise challenge on a treadmill, but such testing requires complex equipment and sufficient health‐care resources. The fraction of exhaled nitric oxide (FeNO) test and mannitol bronchial provocation test (BPT) may serve as a surrogate for exercise testing.

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).