Evaluation of interrupter resistance in methacholine challenge testing in children

Breastfeeding and asthma outcomes at the age of 6 years: The Generation R Study

BACKGROUND

Breastfeeding is associated with a lower risk of asthma symptoms in early childhood, but its effect at older ages remains unclear. We examined the associations of duration and exclusiveness of breastfeeding with asthma outcomes in children aged 6 years, and whether these associations were explained by atopic or infectious mechanisms.

METHODS

We performed a population-based prospective cohort study among 5675 children. Information about breastfeeding was collected by questionnaires. At age 6 years, we measured interrupter resistance (Rint) and fractional exhaled nitric oxide (FeNO). Information about wheezing patterns (early (≤3 years only), late (>3 years only), persistent (≤3 and >3 years)), and current asthma at 6 years was derived from repeated questionnaires.

RESULTS

Compared to children who were ever breastfed, those who were never breastfed had lower FeNO levels (sympercent (95% CI): -16.0 (-24.5, -7.5)) and increased risks of late and persistent wheezing (OR(95% CI): 1.69 (1.06, 2.69) and 1.44 (1.00, 2.07), respectively). Shorter duration of breastfeeding was associated with early wheezing and current asthma (1.40 (1.14, 1.73) and 2.19 (1.29, 3.71), respectively). Less exclusive breastfeeding was associated with early wheezing (1.28 (1.08, 1.53)). Breastfeeding duration and exclusiveness were not associated with FeNO or Rint. The associations were not explained by inhalant allergies, partly by lower respiratory tract infections in early life, and to a lesser extent by lower respiratory tract infections in later life.

CONCLUSIONS

Breastfeeding patterns may influence wheezing and asthma in childhood, which seems to be partly explained by infectious mechanisms.

Foetal and infant growth patterns, airway resistance and school-age asthma

BACKGROUND AND OBJECTIVE

Preterm birth, low birth weight and rapid infant weight gain are associated with increased risks of asthma symptoms in childhood. The underlying mechanism may include persistently higher airway resistance (Rint). The aim of our study was to examine the associations of longitudinally measured foetal and infant growth characteristics with Rint and asthma outcomes in school-age children.

METHODS

This study was embedded in a population-based prospective cohort study in Rotterdam, The Netherlands. Foetal growth was estimated by ultrasound in the second and third trimesters. Infant growth was measured at birth, 3, 6 and 12 months. At age 6 years, Rint was measured, and information about wheezing and asthma was obtained by questionnaires. The number of subjects per analysis differed per available outcome (3954-5066 subjects).

RESULTS

Longitudinal growth analyses showed that school-age children with increased Rint had lower foetal length growth and weight gain, and lower infant length growth. Children with persistent wheezing until age 6 years and physician-diagnosed asthma had a higher Rint compared with children who never wheezed or without asthma (difference z-scores Rint: 0.58 (0.19, 0.97) and 0.55 (0.15, 0.95), respectively).

CONCLUSION

Rint in school-age children is influenced by foetal growth restriction and is associated with asthma outcomes. See article, page 574.

Methacholine-Induced Variations in Airway Volume and the Slope of the Alveolar Capnogram Are Distinctly Associated with Airflow Limitation and Airway Closure

Mechanisms driving alteration of lung function in response to inhalation of a methacholine aerosol are incompletely understood. To explore to what extent large and small airways contribute to airflow limitation and airway closure in this context, volumetric capnography was performed before (n = 93) and after (n = 78) methacholine provocation in subjects with an intermediate clinical probability of asthma. Anatomical dead space (VDaw), reflecting large airway volume, and the slope of the alveolar capnogram (slope3), an index of ventilation heterogeneity linked to small airway dysfunction, were determined. At baseline, VDaw was positively correlated with lung volumes, FEV₁ and peak expiratory flow, while slope3 was not correlated with any lung function index. Variations in VDaw and slope3 following methacholine stimulation were correlated to a small degree (R² = -0.20). Multivariate regression analysis identified independent associations between variation in FEV₁ and variations in both VDaw (Standardized Coefficient-SC = 0.66) and Slope3 (SC = 0.35). By contrast, variation in FVC was strongly associated with variations in VDaw (SC = 0.8) but not Slope3. Thus, alterations in the geometry and/or function of large and small airways were weakly correlated and contributed distinctly to airflow limitation. While both large and small airways contributed to airflow limitation as assessed by FEV1, airway closure as assessed by FVC reduction mostly involved the large airways.

Total specific airway resistance vs spirometry in asthma evaluation in children in a large real-life population

BACKGROUND

Total specific airway resistance (sRtot) has been introduced as an alternative technique to assess lung function with a particular application to younger children with asthma.

OBJECTIVE

To establish a diagnostic value of the body plethysmographic parameter (sRtot) in asthma diagnosis in young children.

METHODS

This was a prospective, noninterventional study. Children 4 to 18 year old with symptoms suggestive of asthma were included (n = 885). Subjects underwent body plethysmography and spirometry (when capable) with reversibility tests. Of 788 subjects who could perform spirometry in addition to body plethysmography, 578 were diagnosed with asthma. Subjects with asthma were treated for minimum of 6 months and then their asthma was confirmed or refuted.

RESULTS

In 471 patients, asthma diagnosis was confirmed after 6 months of antiasthmatic treatment; 142 patients were 4 to 6 years old and 329 were 7 to 18 years old. Change in response to bronchodilator in children with asthma was significant for sRtot (P = .02) but not for forced expiration volume in 1 second (P = .21); sRtot was more sensitive and specific in identifying children with reversible obstruction than spirometry. There was a significant association between sRtot and asthma diagnosis in patients 4 to 6 years old (odds ratio 1.02, 95% confidence interval 1.01-1.03, P = .001); to differentiate subjects with asthma from those without asthma, the optimal cutoff point for sRtot was 174.5%. A sRtot value higher than 174.5% was associated with a positive prediction of an asthma diagnosis in patients 4 to 6 years old. A ratio of forced expiration volume in 1 second to forced vital capacity below 80% was not significantly associated with asthma.

CONCLUSION

These data support the recommendation of performing sRtot rather than spirometry in young children as a fairly sensitive marker of asthma.

TRIAL REGISTRATION

www.ClinicalTrials.gov (NCT01805635).

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 (Rint_insp) and during expiration (Rint_exp) were higher in the JIA study group (Rint_insp=0.28±0.16 Kpa/L/s; Rint_exp=0.30±0.50 Kpa/L/s) compared to the healthy control group (Rint_insp=0.26±0.11 Kpa/L/s; Rint_exp=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 (Rint_exp; 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.

Diagnostic value of lung function parameters and FeNO for asthma in schoolchildren in large, real-life population

BACKGROUND AND OBJECTIVE

To establish a diagnostic value of fractional exhaled nitric oxide (FeNO), interrupter resistance measurement (Rint), specific resistance of the airways (sRaw), spirometric parameters in asthma diagnosis in schoolchildren.

METHODS

It was a retrospective, cross-sectional study. We evaluated data from medical documentation of 6,439 children (aged 6-18) with symptoms suggestive of asthma, who attended our Pediatric Allergic Outpatient Clinic. Medical documentation of the patients was analyzed with special attention to the first ever obtained results (before the introduction of controller medication) of: FeNO, Rint, sRaw, spirometry, diagnoses of allergic diseases, and allergen sensitization (specific IgE results).

RESULTS

We included 3,612 children in the analysis. Older age, male gender, the presence of allergic rhinitis, sensitization to perennial and seasonal allergens, higher FeNO and Rint, and FEV1 /FVC <80% were significantly associated with asthma. We observed a significant association between FeNO and Rint in the prediction of asthma diagnosis. Optimal cutoff points to differentiate asthmatics from non-asthmatics were established. Thus, Rint >175.4% was defined as asthma-predicting Rint, and FeNO >15.8 ppb was defined as asthma-predicting FeNO. In all study subgroups, sensitivity for asthma-predicting Rint was significantly higher than for asthma-predicting FeNO with an inverse trend in specificity value.

CONCLUSION

Our results suggest that asthma-predicting Rint and, to a lesser extent, asthma-predicting FeNO, defined in the present study, could serve as a reliable tool to exclude asthma in schoolchildren. However, our results also indicate a clinically important fact that all lung function parameters or FeNO should be interpreted in the context of age, gender, allergy profile, and the presence of co-morbidities in schoolchildren. Pediatr Pulmonol. 2014; 49:632-640. © 2013 Wiley Periodicals, Inc.