Epigenetic regulation of inflammation by microRNAs in post-infectious bronchiolitis obliterans

Inflammation; MicroRNA; Post‐infectious bronchiolitis obliteransInflamación; MicroARN; Bronquiolitis obliterante posinfecciosaInflamació; MicroARN; Bronquiolitis obliterant postinfecciosaObjectives Post-infectious bronchiolitis obliterans (PiBO) is a rare, chronic disease initiated by severe infection and followed by perpetuating inflammation and obliteration of the small airways. MicroRNAs (miRNAs) have been proposed to play a central role as epigenetic regulators, which control resolution and prevent the uncontrolled progress of inflammation. The aim of this study was to define biomarkers on the level of post-transcriptional gene regulation in order to characterise PiBO. Methods A total of 39 patients with well-defined PiBO and 31 controls from two centres, Barcelona, Spain, and Frankfurt, Germany, were analysed by next-generation sequencing (NGS). The evaluation of the biological targets of the miRNAs was performed by pathway enrichment analysis and protein–protein interaction network analysis respectively. Results Patients with PiBO had significantly lower lung function values and increased airway inflammation in induced sputum as indicated by total cell counts, neutrophils, IL-1β, IL-6, IL-8 and TGF-β compared to controls. Next-generation sequencing analysis revealed a total of 22 dysregulated miRNAs, which passed significance threshold for Padj ≤ 0.001 with 17 being upregulated and 5 being downregulated. Of these dysregulated miRNAs, miR-335-5p, miR-186-5p, miR-30b-5p and miR-30c-5p were further validated using qRT-PCR. Interestingly, these miRNAs are functionally implicated in cytokine–cytokine receptor interaction, TGF-β signalling and FoxO signalling pathway and significantly correlated with lung function values (FEV1). Conclusion Our results demonstrate an aberrant miRNA expression profile in PiBO, which impacts pathways responsible for the regulation of inflammation and fibrosis. The defined miRNAs are useful biomarkers and should be assessed as potential target in the field of miRNA therapeutics.Starke Lunge Foundation. Grant Number: I 1325d 04/11(6)-7

Measurement properties of the EQ-5D-Y administered through a smartphone app in children with asthma: a longitudinal questionnaire study

Calidad de vida relacionada con la salud; Asma; Aplicación para teléfonos inteligentesQualitat de vida relacionada amb la salut; Asma; Aplicació per a telèfons intel·ligentsHealth-related quality of life; Asthma; Smartphone appBackground Asthma impacts children’s physical, emotional, and psychosocial Health-Related Quality of Life (HRQL). The EQ-5D-Y is a generic econometric instrument developed to measure HRQL in children. Objective Evaluation of feasibility, validity, reliability, and responsiveness of EQ-5D-Y descriptive system and utility index to allow the assessment of HRQL in children with asthma, aged 8–11 years (self-response version) or under 8 years old (proxy-response version). Methods We used data from baseline to 10 months of follow-up of an observational, prospective study of children with persistent asthma recruited by pediatricians in Spain (2018–2020). HRQL instruments were administered through a smartphone application: ARCA app. The EQ-5D-Y is composed of a 5-dimension descriptive system, a utility index ranging from 1 to − 0.5392, and a general health visual analogue scale (EQ-VAS). The Pediatric Asthma Impact Scale (PROMIS-PAIS) includes 8 items, providing a raw score. Construct validity hypotheses were stated a priori, and evaluated following two approaches, multitrait–multimethod matrix and known groups’ comparisons. Reliability and responsiveness subsamples were defined by stability or change in EQ-VAS and the Asthma Control Questionnaire (ACQ), to estimate the intraclass correlation coefficient (ICC) and the magnitude of change over time. Results The EQ-5D-Y was completed at baseline for 119 children (81 self-responded and 38 through proxy response), with a mean age of 9.1 (1.7) years. Mean (SD) of the EQ-5D-Y utility index was 0.93 (0.11), with ceiling and floor effects of 60.3% and 0%, respectively. Multitrait–multimethod matrix confirmed the associations previously hypothesized for the EQ-5D-Y utility index [moderate with PROMIS-PAIS (0.38) and weak with ACQ (0.28)], and for the EQ-5D-Y dimension “problems doing usual activities” [moderate with the ACQ item (0.35) and weak with the PROMIS-PAIS item (0.17)]. Statistically significant differences were found in the EQ-5D-Y between groups defined by asthma control, reliever inhalers use, and second-hand smoke exposure, with mostly moderate effect sizes (0.45–0.75). The ICC of the EQ-5D-Y utility index in the stable subsamples was high (0.81 and 0.79); and responsiveness subsamples presented a moderate to large magnitude of change (0.68 and 0.78), though without statistical significance. Conclusions These results support the use of the EQ-5D-Y as a feasible, valid, and reliable instrument for evaluating HRQL in children with persistent asthma. Further studies are needed on the responsiveness of the EQ-5D-Y in this population.Financial support for this study was provided through grants by the Instituto de Salud Carlos III FEDER: Fondo Europeo de Desarrollo Regional (PI15/00449 and FI16/00071), University of Costa Rica (OAICE-85-2019), and Generalitat de Catalunya (2017 SGR 452). The funding agreements ensure the authors’ independence in designing the study, interpreting the data, and writing and publishing the report

Epigenetic regulation of inflammation by microRNAs in post-infectious bronchiolitis obliterans

Post-infectious bronchiolitis obliterans (PiBO) is a rare, chronic disease initiated by severe infection and followed by perpetuating inflammation and obliteration of the small airways. MicroRNAs (miRNAs) have been proposed to play a central role as epigenetic regulators, which control resolution and prevent the uncontrolled progress of inflammation. The aim of this study was to define biomarkers on the level of post-transcriptional gene regulation in order to characterise PiBO. A total of 39 patients with well-defined PiBO and 31 controls from two centres, Barcelona, Spain, and Frankfurt, Germany, were analysed by next-generation sequencing (NGS). The evaluation of the biological targets of the miRNAs was performed by pathway enrichment analysis and protein-protein interaction network analysis respectively. Patients with PiBO had significantly lower lung function values and increased airway inflammation in induced sputum as indicated by total cell counts, neutrophils, IL-1β, IL-6, IL-8 and TGF-β compared to controls. Next-generation sequencing analysis revealed a total of 22 dysregulated miRNAs, which passed significance threshold for P adj ≤ 0.001 with 17 being upregulated and 5 being downregulated. Of these dysregulated miRNAs, miR-335-5p, miR-186-5p, miR-30b-5p and miR-30c-5p were further validated using qRT-PCR. Interestingly, these miRNAs are functionally implicated in cytokine-cytokine receptor interaction, TGF-β signalling and FoxO signalling pathway and significantly correlated with lung function values (FEV1). Our results demonstrate an aberrant miRNA expression profile in PiBO, which impacts pathways responsible for the regulation of inflammation and fibrosis. The defined miRNAs are useful biomarkers and should be assessed as potential target in the field of miRNA therapeutics. We identified dysregulated miRNAs, which impact pathways for inflammatory cytokines and TGF-β signalling in post-infectious bronchiolitis obliterans. The miRNAs reflect bronchial inflammation and fibrosis and could be considered as novel biomarkers supporting diagnosis and treatment options

Epigenetic regulation of inflammation by microRNAs in post-infectious bronchiolitis obliterans

Post-infectious bronchiolitis obliterans (PiBO) is a rare, chronic disease initiated by severe infection and followed by perpetuating inflammation and obliteration of the small airways. MicroRNAs (miRNAs) have been proposed to play a central role as epigenetic regulators, which control resolution and prevent the uncontrolled progress of inflammation. The aim of this study was to define biomarkers on the level of post-transcriptional gene regulation in order to characterise PiBO. A total of 39 patients with well-defined PiBO and 31 controls from two centres, Barcelona, Spain, and Frankfurt, Germany, were analysed by next-generation sequencing (NGS). The evaluation of the biological targets of the miRNAs was performed by pathway enrichment analysis and protein-protein interaction network analysis respectively. Patients with PiBO had significantly lower lung function values and increased airway inflammation in induced sputum as indicated by total cell counts, neutrophils, IL-1β, IL-6, IL-8 and TGF-β compared to controls. Next-generation sequencing analysis revealed a total of 22 dysregulated miRNAs, which passed significance threshold for P adj ≤ 0.001 with 17 being upregulated and 5 being downregulated. Of these dysregulated miRNAs, miR-335-5p, miR-186-5p, miR-30b-5p and miR-30c-5p were further validated using qRT-PCR. Interestingly, these miRNAs are functionally implicated in cytokine-cytokine receptor interaction, TGF-β signalling and FoxO signalling pathway and significantly correlated with lung function values (FEV1). Our results demonstrate an aberrant miRNA expression profile in PiBO, which impacts pathways responsible for the regulation of inflammation and fibrosis. The defined miRNAs are useful biomarkers and should be assessed as potential target in the field of miRNA therapeutics. We identified dysregulated miRNAs, which impact pathways for inflammatory cytokines and TGF-β signalling in post-infectious bronchiolitis obliterans. The miRNAs reflect bronchial inflammation and fibrosis and could be considered as novel biomarkers supporting diagnosis and treatment options

Epigenetic regulation of inflammation by microRNAs in post-infectious bronchiolitis obliterans

Post-infectious bronchiolitis obliterans (PiBO) is a rare, chronic disease initiated by severe infection and followed by perpetuating inflammation and obliteration of the small airways. MicroRNAs (miRNAs) have been proposed to play a central role as epigenetic regulators, which control resolution and prevent the uncontrolled progress of inflammation. The aim of this study was to define biomarkers on the level of post-transcriptional gene regulation in order to characterise PiBO. A total of 39 patients with well-defined PiBO and 31 controls from two centres, Barcelona, Spain, and Frankfurt, Germany, were analysed by next-generation sequencing (NGS). The evaluation of the biological targets of the miRNAs was performed by pathway enrichment analysis and protein-protein interaction network analysis respectively. Patients with PiBO had significantly lower lung function values and increased airway inflammation in induced sputum as indicated by total cell counts, neutrophils, IL-1β, IL-6, IL-8 and TGF-β compared to controls. Next-generation sequencing analysis revealed a total of 22 dysregulated miRNAs, which passed significance threshold for P adj ≤ 0.001 with 17 being upregulated and 5 being downregulated. Of these dysregulated miRNAs, miR-335-5p, miR-186-5p, miR-30b-5p and miR-30c-5p were further validated using qRT-PCR. Interestingly, these miRNAs are functionally implicated in cytokine-cytokine receptor interaction, TGF-β signalling and FoxO signalling pathway and significantly correlated with lung function values (FEV1). Our results demonstrate an aberrant miRNA expression profile in PiBO, which impacts pathways responsible for the regulation of inflammation and fibrosis. The defined miRNAs are useful biomarkers and should be assessed as potential target in the field of miRNA therapeutics. We identified dysregulated miRNAs, which impact pathways for inflammatory cytokines and TGF-β signalling in post-infectious bronchiolitis obliterans. The miRNAs reflect bronchial inflammation and fibrosis and could be considered as novel biomarkers supporting diagnosis and treatment options

Epigenetic regulation of inflammation by microRNAs in post-infectious bronchiolitis obliterans

Post-infectious bronchiolitis obliterans (PiBO) is a rare, chronic disease initiated by severe infection and followed by perpetuating inflammation and obliteration of the small airways. MicroRNAs (miRNAs) have been proposed to play a central role as epigenetic regulators, which control resolution and prevent the uncontrolled progress of inflammation. The aim of this study was to define biomarkers on the level of post-transcriptional gene regulation in order to characterise PiBO. A total of 39 patients with well-defined PiBO and 31 controls from two centres, Barcelona, Spain, and Frankfurt, Germany, were analysed by next-generation sequencing (NGS). The evaluation of the biological targets of the miRNAs was performed by pathway enrichment analysis and protein-protein interaction network analysis respectively. Patients with PiBO had significantly lower lung function values and increased airway inflammation in induced sputum as indicated by total cell counts, neutrophils, IL-1β, IL-6, IL-8 and TGF-β compared to controls. Next-generation sequencing analysis revealed a total of 22 dysregulated miRNAs, which passed significance threshold for P adj ≤ 0.001 with 17 being upregulated and 5 being downregulated. Of these dysregulated miRNAs, miR-335-5p, miR-186-5p, miR-30b-5p and miR-30c-5p were further validated using qRT-PCR. Interestingly, these miRNAs are functionally implicated in cytokine-cytokine receptor interaction, TGF-β signalling and FoxO signalling pathway and significantly correlated with lung function values (FEV1). Our results demonstrate an aberrant miRNA expression profile in PiBO, which impacts pathways responsible for the regulation of inflammation and fibrosis. The defined miRNAs are useful biomarkers and should be assessed as potential target in the field of miRNA therapeutics. We identified dysregulated miRNAs, which impact pathways for inflammatory cytokines and TGF-β signalling in post-infectious bronchiolitis obliterans. The miRNAs reflect bronchial inflammation and fibrosis and could be considered as novel biomarkers supporting diagnosis and treatment options

Estudio de la hiperrespuesta bronquial a la metacolina y de la inflamación bronquial valorada mediante el óxido nítrico exhalado, en niños menores de cuatro años con bronquitis sibilantes de repetición

Consultable des del TDXTítol obtingut de la portada digitalitzadaAntecedentes y objetivos: Las bronquitis sibilantes de repetición en niños menores de 4 años constituyen una patología muy frecuente. En un 60% de ellos las bronquitis serán transitorias, y desaparecerán antes de los 3 años y en un 40% persistirán más allá. Dentro de este último grupo, solo la mitad serán atópicos, y los no atópicos, generalmente cederán antes de a la pubertad. Clínicamente los niños de estos 3 grupos son indistinguibles en edades tempranas. El fenotipo asmático se caracteriza por la triada: obstrucción bronquial reversible, hiperrespuesta e inflamación bronquial. La medida de estos parámetros en niños no colaboradores requiere habitualmente técnicas complejas con sedación. Objetivos: Determinar la respuesta bronquial normal a la metacolina en niños sanos menores de 4 años de edad, mediante el método de la auscultación traqueal modificado (Springer, et al; AJRCCM 2000;162:857-860), que no requiere sedación, analizando la eficacia y seguridad del método. Valorar la presencia de hiperrespuesta bronquial en niños de este grupo de edad con bronquitis de repetición. Analizar las variables que puedan afectar esta hiperrespuesta bronquial. Asimismo, se pretende determinar los valores normales de óxido nítrico exhalado en niños sanos 400/mm3), presentaban FENO más elevados. Probablemente ello refleje que el FENO es un marcador de inflamación eosinofílica Hubo una tendencia estadísticamente no significativa de que los niños con IgE >100 UI/ml, presentasen como grupo, FENO más elevadas. En cambio, no existió relación entre el FENO y los niños con PPB positiva a metacolina ni con el nº de episodios de bronquitis presentadas por los niños en el año previo Conclusiones: El método de la auscultación traqueal modificado es efectivo y seguro para valorar la hiperrespuesta bronquial en niños menores de 4 años de edad, y no requiere sedación. Un porcentaje elevado de ellos presentan hiperrespuesta bronquial; 68% reaccionan a concentraciones inferiores respecto a los niños sanos. La medición del óxido nítrico exhalado mediante la recogida off-line a volumen corriente es sencilla y no precisa sedación ni colaboración activa de los niños Los niños menores de 4 años afectos de bronquitis sibilantes de repetición en fase asintomática, presentan inflamación bronquial, reflejada por un incremento en la concentración de FENO Sin embargo, el resultado no discrimina adecuadamente los niños sanos de los niños con bronquitis, existiendo una amplia zona de superposición Los pacientes que recibían tratamiento corticoides inhalados presentaban un valor de FENO igual a los niños sanos, mientras que los que no lo recibían presentaban un aumento del FENO Son necesarios estudios longitudinales para valorar si el FENO ayuda a discriminar asma de sibilantes transitorios.Recuurently wheezy bronchitis is a very common illness in infancy. We require complex techniques and sedation to evaluate bronchial responsiveness and bronchial inflammation at this age. Aims: To determine the efficacy and safety of the chest auscultation method. To assess bronchial reactivity to inhaled metacholine in young children and to evaluate its prevalence in children under 4 years of age with recurrent bronchitis. To determine the normal values of FENO in such young children using the tidal breathing method (off line). To assess bronchial inflammation in children under 4 years old, with recurrent bronchitis, without crisis at the time of the exploration, through the FENO determination. Methods: 63 wheezy children (6 months to 4 years old) with ≥3 wheezing episodes over the last year and age matched healthy control children (n=16) were studied. A metacholine bronchial challenge test was performed with a two minute dosing protocol and the chest auscultation method (ATS;AJRCCM 2000;161:309;162:857). End point (PCw) was defined as wheezing heard over trachea , oxygen desaturation of ≥5% from baseline or an increase in respiratory rate of ≥50% from baseline. Data were compared using the non parametric U Mann-Whitney test , assuming a PCw of 16 mg/ml for negative tests. We also measured the FENO in 80 infants. We followed the tidal breathing method (off line)(ATS-ERS Task Force-AJRCCM 2002). Infant tidal breaths were collected into an inert gas sampling bag , via a nonrebreathing valve attached to a special face mask with nasal dettachment. ENO was measured using a chemoanalyser. Results: Out of the healthy children, 10 had a negative test and 10 showed a PCw= 8 mg/ml (the maximum concentration). Among the wheezy group, 53 had a positive test, 43 had a PCw ≤4 mg/ml (68,2%). Mean PCw for wheezy children was lower than that in the control group. (5,8 versus 13,3 mg/ml)(p88%), but it was reversed inmediately after the inhalation of salbutamol. The only factor studied that showed any influence on the PCw was the age of the fist bronchitis. The main results show that the wheezy group has a greater FENO than the control group (p=0,0406), although there is some overlap between results from both groups. The only factor that showed any influence on FENO was the eosinophilia (>400/mm³), there was a direct relationship between both factors. Probably this would mean that FENO is a marker of eosinophilic inflammation. There was also a possible relationship (statistically not significant) between high IgE levels and higher FENO levels. There was no relationship between FENO and bronchial hyperresponsiveness. Conclusions: The auscultation method is effective and safe in the assessment of bronchial reactivity in young children ant it requires no sedation. Airway responsiveness to metacholine was increased in the majority of our recurrently wheezy children. The measurement of FENO through the tidal breathing (off line ) method is easy and does not require sedation neither active cooperation.. Wheezy assympthomatic children under 4 years old, show some degree of bronchial inflammation demonstrated through an elevation of the FENO levels when compared with the healthy control group, although there is some overlap between both groups. The patients who received IGC showed similar values to those of the healthy group. Further longitudinal studies are needed to assess the value of FENO in distinguishing asthma fron transitory wheezing

Estudio de la hiperrespuesta bronquial a la metacolina y de la inflamación bronquial valorada mediante el óxido nítrico exhalado, en niños menores de cuatro años con bronquitis sibilantes de repetición

Antecedentes y objetivos: Las bronquitis sibilantes de repetición en niños menores de 4 años constituyen una patología muy frecuente. En un 60% de ellos las bronquitis serán transitorias, y desaparecerán antes de los 3 años y en un 40% persistirán más allá. Dentro de este último grupo, solo la mitad serán atópicos, y los no atópicos, generalmente cederán antes de a la pubertad. Clínicamente los niños de estos 3 grupos son indistinguibles en edades tempranas. El fenotipo asmático se caracteriza por la triada: obstrucción bronquial reversible, hiperrespuesta e inflamación bronquial. La medida de estos parámetros en niños no colaboradores requiere habitualmente técnicas complejas con sedación.Objetivos: Determinar la respuesta bronquial normal a la metacolina en niños sanos menores de 4 años de edad, mediante el método de la auscultación traqueal modificado (Springer, et al; AJRCCM 2000;162:857-860), que no requiere sedación, analizando la eficacia y seguridad del método. Valorar la presencia de hiperrespuesta bronquial en niños de este grupo de edad con bronquitis de repetición. Analizar las variables que puedan afectar esta hiperrespuesta bronquial. Asimismo, se pretende determinar los valores normales de óxido nítrico exhalado en niños sanos Métodos: Se incluyeron 63 niños de 6 meses a Se realizó una prueba de provocación bronquial (PPB) con metacolina (Provocholine®) mediante el protocolo de inhalación a volumen corriente durante 2 minutos (ATS; AJRCCM 2000; 161:309), usando una variedad acortada. Se consideró positiva la prueba a una determinada concentración de metacolina (PCw) si se auscultaban sibilantes en tráquea, disminuía la SaO2  5% o aumentaba la frecuencia respiratoria más del 50%. Se compararon los grupos mediante el test no paramétrico de la U de Mann Whitney, asumiendo un valor de 16 mg/ml en los casos de prueba negativa. Asimismo se determinó el óxido nítrico exhalado mediante la técnica de recogida off- line, con respiración espontánea a volumen corriente (ERS-ATS Task Force - AJRCCM 2002) con mascarilla con tabique nasal y un sistema de recogida en bolsa de Mylar, efectuándose la medición posterior de en un aparato de quimioluminiscencia. Resultados: De los niños sanos, 10 no reaccionaron a la metacolina y 6 lo hicieron a las concentraciones máximas de 8 mg/ml. De los del grupo de bronquitis hubo 10 que no respondieron, 10 que reaccionaron a la concentración máxima y 43 que reaccionaron a concentraciones inferiores a la del grupo control. La diferencia entre los 2 grupos fue estadísticamente significativa (5,8 versus 13,3 mg/ml) (pEn cuanto a las variables que podían influir en el grupo de bronquitis sobre la PCw, se observó que sólo la edad a la que habían presentado la 1ª bronquitis era estadísticamente-significativa No influía la edad a la que se había realizado la PPBLos resultados del estudio del óxido nítrico exhalado muestran que el grupo con bronquitis presenta como media una FENO más elevada que el grupo control, aunque hay superposición de datos con el grupo control.Por otro lado si distinguimos dentro del grupo de pacientes entre los que llevan tratamiento y los que no, observamos que también hay diferencias significativas entre el grupo no tratado y el control, pero no entre el grupo tratado con corticoides inhalados y el control.Asimismo dentro del grupo de pacientes con bronquitis sibilantes de repetición analizamos la influencia de las diferentes variables sobre el FENO. Hubo relación con el nº de eosinófilos en sangre de forma que los que tenían un mayor nivel de eosinófilos en sangre (> 400/mm3), presentaban FENO más elevados. Probablemente ello refleje que el FENO es un marcador de inflamación eosinofílicaHubo una tendencia estadísticamente no significativa de que los niños con IgE >100 UI/ml, presentasen como grupo, FENO más elevadas. En cambio, no existió relación entre el FENO y los niños con PPB positiva a metacolina ni con el nº de episodios de bronquitis presentadas por los niños en el año previoConclusiones:El método de la auscultación traqueal modificado es efectivo y seguro para valorar la hiperrespuesta bronquial en niños menores de 4 años de edad, y no requiere sedación. Un porcentaje elevado de ellos presentan hiperrespuesta bronquial; 68% reaccionan a concentraciones inferiores respecto a los niños sanos.La medición del óxido nítrico exhalado mediante la recogida off-line a volumen corriente es sencilla y no precisa sedación ni colaboración activa de los niñosLos niños menores de 4 años afectos de bronquitis sibilantes de repetición en fase asintomática, presentan inflamación bronquial, reflejada por un incremento en la concentración de FENO Sin embargo, el resultado no discrimina adecuadamente los niños sanos de los niños con bronquitis, existiendo una amplia zona de superposiciónLos pacientes que recibían tratamiento corticoides inhalados presentaban un valor de FENO igual a los niños sanos, mientras que los que no lo recibían presentaban un aumento del FENOSon necesarios estudios longitudinales para valorar si el FENO ayuda a discriminar asma de sibilantes transitorios.Recuurently wheezy bronchitis is a very common illness in infancy. We require complex techniques and sedation to evaluate bronchial responsiveness and bronchial inflammation at this age.Aims: To determine the efficacy and safety of the chest auscultation method. To assess bronchial reactivity to inhaled metacholine in young children and to evaluate its prevalence in children under 4 years of age with recurrent bronchitis. To determine the normal values of FENO in such young children using the tidal breathing method (off line). To assess bronchial inflammation in children under 4 years old, with recurrent bronchitis, without crisis at the time of the exploration, through the FENO determination.Methods: 63 wheezy children (6 months to 4 years old) with ≥3 wheezing episodes over the last year and age matched healthy control children (n=16) were studied. A metacholine bronchial challenge test was performed with a two minute dosing protocol and the chest auscultation method (ATS;AJRCCM 2000;161:309;162:857). End point (PCw) was defined as wheezing heard over trachea , oxygen desaturation of ≥5% from baseline or an increase in respiratory rate of ≥50% from baseline. Data were compared using the non parametric U Mann-Whitney test , assuming a PCw of 16 mg/ml for negative tests.We also measured the FENO in 80 infants. We followed the tidal breathing method (off line)(ATS-ERS Task Force-AJRCCM 2002). Infant tidal breaths were collected into an inert gas sampling bag , via a nonrebreathing valve attached to a special face mask with nasal dettachment. ENO was measured using a chemoanalyser.Results: Out of the healthy children, 10 had a negative test and 10 showed a PCw= 8 mg/ml (the maximum concentration). Among the wheezy group, 53 had a positive test, 43 had a PCw ≤4 mg/ml (68,2%). Mean PCw for wheezy children was lower than that in the control group. (5,8 versus 13,3 mg/ml)(p88%), but it was reversed inmediately after the inhalation of salbutamol. The only factor studied that showed any influence on the PCw was the age of the fist bronchitis.The main results show that the wheezy group has a greater FENO than the control group (p=0,0406), although there is some overlap between results from both groups. The only factor that showed any influence on FENO was the eosinophilia (>400/mm³), there was a direct relationship between both factors. Probably this would mean that FENO is a marker of eosinophilic inflammation.There was also a possible relationship (statistically not significant) between high IgE levels and higher FENO levels. There was no relationship between FENO and bronchial hyperresponsiveness.Conclusions: The auscultation method is effective and safe in the assessment of bronchial reactivity in young children ant it requires no sedation. Airway responsiveness to metacholine was increased in the majority of our recurrently wheezy children. The measurement of FENO through the tidal breathing (off line ) method is easy and does not require sedation neither active cooperation.. Wheezy assympthomatic children under 4 years old, show some degree of bronchial inflammation demonstrated through an elevation of the FENO levels when compared with the healthy control group, although there is some overlap between both groups. The patients who received IGC showed similar values to those of the healthy group.Further longitudinal studies are needed to assess the value of FENO in distinguishing asthma fron transitory wheezing