High TSLP responses in the human infant airways are associated with pre-activated airway epithelial IFN antiviral immunity.

Thymic stromal lymphopoietin (TSLP) is a primarily epithelial-derived cytokine that drives type 2 allergic immune responses. Early life viral respiratory infections elicit high TSLP production, which leads to the development of type 2 inflammation and airway hyperreactivity. The goal of this study was to examine in vivo and in vitro the human airway epithelial responses leading to high TSLP production during viral respiratory infections in early infancy. A total of 129 infants (<1-24 m, median age 10 m) with severe viral respiratory infections were enrolled for in vivo (n = 113), and in vitro studies (n = 16). Infants were classified as 'high TSLP' or 'low TSLP' for values above or below the 50th percentile. High versus low TSLP groups were compared in terms of type I-III IFN responses and production of chemokines promoting antiviral (CXCL10), neutrophilic (CXCL1, CXCL5, CXCL8), and type 2 responses (CCL11, CCL17, CCL22). Human infant airway epithelial cell (AEC) cultures were used to define the transcriptomic (RNAseq) profile leading to high versus low TSLP responses in vitro in the absence (baseline) or presence (stimulated) of a viral mimic (poly I:C). Infants in the high TSLP group had greater in vivo type III IFN airway production (median type III IFN in high TSLP 183.2 pg/mL vs. 63.4 pg/mL in low TSLP group, p = 0.007) and increased in vitro type I-III IFN AEC responses after stimulation with a viral mimic (poly I:C). At baseline, our RNAseq data showed that infants in the high TSLP group had significant upregulation of IFN signature genes (e.g., IFIT2, IFI6, MX1) and pro-inflammatory chemokine genes before stimulation. Infants in the high TSLP group also showed a baseline AEC pro-inflammatory state characterized by increased production of all the chemokines assayed (e.g., CXCL10, CXCL8). High TSLP responses in the human infant airways are associated with pre-activated airway epithelial IFN antiviral immunity and increased baseline AEC production of pro-inflammatory chemokines. These findings present a new paradigm underlying the production of TSLP in the human infant airway epithelium following early life viral exposure and shed light on the long-term impact of viral respiratory illnesses during early infancy and beyond childhood.

Asthma Cases Treated With Inhaled Anesthetics or Extracorporeal Membrane Oxygenation: A Virtual Pediatric Systems Database Study of Outcomes.

OBJECTIVES: Extracorporeal membrane oxygenation (ECMO) and/or inhaled anesthetics (IAs) are considered in the management of asthma when refractory to conventional therapy. We aimed to compare the outcomes of these two modalities in asthma PICU care and determine associated survival to hospital discharge among patients in a United States database. DESIGN: Retrospective analysis using the Virtual Pediatric Systems (VPS, LLC) database. SETTING: PICUs participating in the VPS database. PATIENTS: Patients less than 18 years old with diagnosis of asthma treated with IA and/or ECMO from January 2010 to December 2020. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: A total of 221 patients were included; 149 (67%) received ECMO, 62 (28%) received IA, and 10 (5%) received both interventions. We failed to identify any difference between the ECMO and IA groups in demographics, Pediatric Index of Mortality 2 percentage, Pediatric Risk of Mortality 3 score, Pediatric Logistic Organ Dysfunction score, or pre-intervention pH and Pa co2 levels. Use of ECMO versus IA was associated with lower pre-intervention Pa o2 (60 torr [7.99 kPa] vs 78 torr [10.39 kPa]; p < 0.001) and higher utilization of high-frequency oscillatory ventilation. We failed to identify an association between type of intervention (IA vs ECMO) and greater odds of survival (57/62 [92%] vs 128/149 [86%]; odds ratio [OR], 1.87; 95% CI, 0.67-5.21; p = 0.23). However, these data do not exclude the possibility that IA use is associated with more than five-fold greater odds of survival. ECMO use was associated with longer duration of intervention (5 vs 1.3 d; p < 0.001) and PICU length of stay (LOS) (13 vs 7 d; p < 0.001). As expected, ECMO versus IA was also associated with greater odds of undergoing bronchoscopy (34% vs 11%; OR, 3.7; 95% CI, 1.5-9.4; p = 0.004). CONCLUSIONS: In the VPS database of asthma management cases, we failed to identify an association between ECMO versus IA use and survival to hospital discharge. However, ECMO was associated with longer duration of intervention and PICU LOS.

Dynamic PEEP Study: A Non-invasive Diagnostic Exam to Assess for Effective PEEP in Children with Severe BPD.

OBJECTIVE: Tracheobronchomalacia (TBM) is common in neonates with bronchopulmonary dysplasia (BPD) and is associated with higher morbidity. This study evaluates the value of a CT protocol to assess the degree of TBM and gauge the adequacy of prescribed PEEP. STUDY DESIGN: Four infants with severe BPD on invasive mechanical ventilation underwent a chest CT protocol, including limited reduced-dose expiratory scans with varying PEEP levels. RESULTS: Baseline PEEP was adjusted in all subjects after performing the Dynamic PEEP CT. In two infants, the PEEP was increased due to significant TBM and in the other two without signs of TBM PEEP was decreased. The clinical course improved in all patients after adjusting PEEP. CONCLUSION: A "Dynamic PEEP" study may be reliable and non-invasive imaging modality for the evaluation of adequate ventilator settings in infants with severe BPD who are not optimal candidates for bronchoscopy.

Innate IFN-lambda responses to dsRNA in the human infant airway epithelium and clinical regulatory factors during viral respiratory infections in early life.

INTRODUCTION: IFN lambda (type III-IFN-λ1) is a molecule primarily produced by epithelial cells that provides an important first-line defence against viral respiratory infections and has been linked to the pathogenesis of viral-induced wheezing in early life. The goal of this study was to better understand the regulation of innate IFN-lambda responses in vitro in primary human infant airway epithelial cells (AECs) and in vivo using nasal aspirates during viral respiratory infections. METHODS: IFN-lambda protein levels were quantified: (a) in human infant AECs exposed to (poly(I:C) dsRNA) under different experimental conditions (n = 8 donors); and (b) in nasal aspirates of young children (≤3 years) hospitalized with viral respiratory infection (n = 138) and in uninfected controls (n = 74). In vivo IFN-lambda airway levels during viral infections were correlated with individual characteristics and respiratory disease parameters. RESULTS: Our in vitro experiments showed that the poly(I:C)-induced innate production of IFN lambda in human infant AECs is regulated by (a) p38-MAPK/NF-kB dependent mechanism; and (b) exposure to pro-inflammatory signals such as IL1ß. Our in vivo studies demonstrated that (a) infants (<18 months) had higher virus-induced IFN-lambda airway secretion; (b) subjects with RSV infection showed the highest IFN-lambda airway levels; and (c) individuals with the highest virus-induced IFN-lambda levels (>90th percentile) had higher viral loads and were more likely to have respiratory sick visits within 12 months of discharge (OR = 5.8). CONCLUSION: IFN-lambda responses to dsRNA in the human infant airway epithelium are regulated by p38-MAPK and NF-kB signalling. High in vivo IFN-lambda production is influenced by virus type and associated with recurrent respiratory sick visits in young children.

Peak Cough Flow in Children with Neuromuscular Disorders.

PURPOSE: Patients with neuromuscular disease (NMD) experience weakened cough due to progressive respiratory muscle weakness. Peak cough flow (PCF) measurements derived from adult populations are used to recommend initiation of assisted cough therapies. The objective of this study was to characterize PCF values among pediatric patients with NMD. METHODS: Retrospective chart review was performed for patients seen in the multidisciplinary pediatric muscular dystrophy clinic from 2010 to 2016. Clinical and demographic variables included age, gender, ambulation status, and PCF measurements. RESULTS: 366 patients with an established diagnosis of NMD (median age 11.8 years) were included in this study. 102 (27.8%) out of the 366 patients were affected by Duchenne muscular dystrophy (DMD), 42 (11.5%) by congenital muscular dystrophy (CMD), 42 (11.5%) by Charcot Marie Tooth disease (CMT) and 24 (6.5%) by Becker's muscular dystrophy (BMD). The mean PCF values in DMD (255.8 L/min) and CMD (249.1 L/min) were lower than CMT (321.5 L/min) with p-values of 0.007 and 0.02, respectively. The mean PCF of BMD (333.3 L/min) was higher than that of DMD and CMD but the difference was not statistically significant. PCFs were not statistically different between ambulatory and non-ambulatory status (263.0 L/min versus 290.8 L/min, p = 0.12). Children under 10 years of age had lower PCF relative to older subjects (179.5 L/min versus 300.9 L/min, p < 0.0001). CONCLUSION: Baseline PCF values in young children are below the adult-specific values suggested for starting assisted cough techniques. Further longitudinal trials are required to derive pediatric-specific reference values for PCF in patients with NMD.

Clinical, genetic and microbiological characterization of pediatric patients with cystic fibrosis in a public Hospital in Ecuador.

BACKGROUND: To carry out a complete clinical, pathological, genetic and microbiological characterization of pediatric patients with molecular confirmed cystic fibrosis (CF) attending the Carlos Andrade Marín Hospital (HCAM) within the study period. METHODS: A cross-sectional analysis of the pediatric population with a confirmed diagnosis of CF disease who attended HCAM, one of the largest tertiary-level hospitals in Ecuador, between 2017 and 2018 was performed. All demographic, clinical and genetic variables were obtained from the electronic medical records (EMR) stored by the hospital. RESULTS: Forty seven patients with CF were included in the study. Gender distribution was similar between male (48.9%, n = 23) and female patients (51.1%, n = 24). The Tiffeneau-Pinelli index (FEV1/FVC) changed significantly after nine months post-diagnosis (85.55 ± 13.26; p < 0.05). The most common pathogenic genetic variants were F508del, found in 52.78% of the cohort (n = 19); H609R, found in 36.11% (n = 13); g.204099A > C, found in 14.1% (n = 7), followed by G85E and the N1303K with 11.11% (n = 3) each. CONCLUSIONS: To our best knowledge, this is the first study exploring the clinical, genetic and bacteriological profile of CF's patients in Ecuador. Within the cohort of patients, an important and unique genetic feature was characterized by the presence of the g.204099A > C and the c.206359C > A homozygous polymorphism as well as the presence of the H609R variant, a mutation only reported among Ecuadorians.

Premature infants have impaired airway antiviral IFNγ responses to human metapneumovirus compared to respiratory syncytial virus.

BACKGROUND: It is unknown why human metapneumovirus (HMPV) and respiratory syncytial virus (RSV) cause severe respiratory infection in children, particularly in premature infants. Our aim was to investigate if there are defective airway antiviral responses to these viruses in young children with history of prematurity. METHODS: Nasal airway secretions were collected from 140 children ≤ 3 y old without detectable virus (n = 80) or with PCR-confirmed HMPV or RSV infection (n = 60). Nasal protein levels of IFNγ, CCL5/RANTES, IL-10, IL-4, and IL-17 were determined using a multiplex magnetic bead immunoassay. RESULTS: Full-term children with HMPV and RSV infection had increased levels of nasal airway IFNγ, CCL5, and IL-10 along with an elevation in Th1 (IFNγ)/Th2 (IL-4) ratios, which is expected during antiviral responses. In contrast, HMPV-infected premature children (< 32 wk gestation) did not exhibit increased Th1/Th2 ratios or elevated nasal airway secretion of IFNγ, CCL5, and IL-10 relative to uninfected controls. CONCLUSION: Our study is the first to demonstrate that premature infants have defective IFNγ, CCL5/RANTES, and IL-10 airway responses during HMPV infection and provides novel insights about the potential reason why HMPV causes severe respiratory disease in children with history of prematurity.

Rhinovirus-induced airway cytokines and respiratory morbidity in severely premature children.

BACKGROUND: Rhinovirus (RV) has been linked to the pathogenesis of asthma. Prematurity is a risk factor for severe RV infection in early life, but is unknown if RV elicits enhanced pro-asthmatic airway cytokine responses in premature infants. This study investigated whether young children born severely premature (<32 wks gestation) exhibit airway secretion of Th2 and Th17 cytokines during natural RV infections and whether RV-induced Th2-Th17 responses are linked to more respiratory morbidity in premature children during the first 2 yrs of life. METHODS: We measured Th2 and Th17 nasal airway cytokines in a retrospective cohort of young children aged 0-2 yrs with PCR-confirmed RV infection or non-detectable virus. Protein levels of IL-4, IL-13, TSLP, and IL-17 were determined with multiplex immunoassays. Demographic and clinical variables were obtained by electronic medical record (EMR) review. RESULTS: The study comprised 214 children born full term (n = 108), preterm (n = 44) or severely premature (n = 62). Natural RV infection in severely premature children was associated with elevated airway secretion of Th2 (IL-4 and IL-13) and Th17 (IL-17) cytokines, particularly in subjects with history of bronchopulmonary dysplasia. Severely premature children with high RV-induced airway IL-4 had recurrent respiratory hospitalizations (median 3.65 hosp/yr; IQR 2.8-4.8) and were more likely to have at least one pediatric intensive care unit admission during the first 2 yrs of life (OR 8.72; 95% CI 1.3-58.7; p = 0.02). CONCLUSIONS: Severely premature children have increased airway secretion of Th2 and Th17 cytokines during RV infections, which is associated with more respiratory morbidity in the first 2 yrs of life.

Airway clearance therapy in the school environment: Retrospective analysis of a cohort of pediatric patients with cystic fibrosis.

BACKGROUND: Adherence to airway clearance therapy (ACT) in pediatric cystic fibrosis (CF) patients is reported to be below 50% and inability to sustain daily care is linked to poor health outcomes7,8,9. Through a collaboration between a CF care center and several schools, we hypothesized that ACT completed at school by pediatric CF patients will improve lung function while decreasing pulmonary exacerbations (PEx), days of antibiotics (abx) and hospitalizations. METHODS: This was a retrospective case-control study at a single CF care center consisting of 50 CF patients age < 18 at time when data was recorded (2012-2020). The case group used high-frequency chest wall oscillation or positive expiratory pressure devices at school for at least 1 year after self-reported or physician identified inadequate use at home. Lung function and measures of healthcare utilization were collected. RESULTS: In the case group (n = 14), paired t-tests showed that after initiation of ACT at school, there were significant reductions in PEx requiring IV or PO abx (P = 0.010), total days of abx (P = 0.032), and visits to the CF care center (P = 0.037). There was no change in these outcomes in the matched control group (n = 36). CONCLUSIONS: This is the first known study to highlight an initiative between a CF care center and schools which utilized airway clearance devices at school to ensure pediatric CF patients completed ACT. Through increased adherence, this relationship was associated with improved health outcomes. Use of alternative strategies may help patients with CF sustain adequate airway clearance.

Measuring the impact of an empiric antibiotic algorithm for pulmonary exacerbation in children and young adults with cystic fibrosis.

BACKGROUND: Antimicrobial stewardship is a systematic effort to change prescribing attitudes that can provide benefit in the provision of care to persons with cystic fibrosis (CF). Our objective was to decrease the unwarranted use of broad-spectrum antibiotics and assess the impact of an empiric antibiotic algorithm using quality improvement methodology. METHODS: We assembled a multidisciplinary team with expertise in CF. We assessed baseline antibiotic use for treatment of pulmonary exacerbation (PEx) and developed an algorithm to guide empiric antibiotic therapy. We included persons with CF admitted to Children's National Hospital for treatment of PEx between January 2017 and March 2020. Our primary outcome measure was reducing unnecessary broad-spectrum antibiotic use, measured by use consistent with the empiric antibiotic algorithm. The primary intervention was the initiation of the algorithm. Secondary outcomes included documentation of justification for broad-spectrum antibiotic use and use of infectious disease (ID) consult. RESULTS: Data were collected from 56 persons with CF who had a total of 226 PEx events. The mean age at first PEx was 12 (SD 6.7) years; 55% were female, 80% were white, and 29% were Hispanic. After initiation of the algorithm, the proportion of PEx with antibiotic use consistent with the algorithm increased from 46.2% to 79.5%. Documentation of justification for broad-spectrum antibiotics increased from 56% to 85%. Use of ID consults increased from 17% to 54%. CONCLUSION: Antimicrobial stewardship initiatives are beneficial in standardizing care and fostering positive working relationships between CF pulmonologists, ID physicians, and pharmacists.

Genes, environment, and developmental timing: New insights from translational approaches to understand early origins of respiratory diseases.

Over the past decade, "omics" approaches have advanced our understanding of the molecular programming of the airways in humans. Several studies have identified potential molecular mechanisms that contribute to early life epigenetic reprogramming, including DNA methylation, histone modifications, microRNAs, and the homeostasis of the respiratory mucosa (epithelial function and microbiota). Current evidence supports the notion that early infancy is characterized by heightened susceptibility to airway genetic reprogramming in response to the first exposures in life, some of which can have life-long consequences. Here, we summarize and analyze the latest insights from studies that support a novel epigenetic paradigm centered on human maturational and developmental programs including three cardinal elements: genes, environment, and developmental timing. The combination of these factors is likely responsible for the functional trajectory of the respiratory system at the molecular, functional, and clinical levels.

Cost-effectiveness analysis of phenotypic-guided versus guidelines-guided bronchodilator therapy in viral bronchiolitis.

OBJECTIVES: Although recent evidence suggests that management of viral bronchiolitis requires something other than guidelines-guided therapy, there is a lack of evidence supporting the economic benefits of phenotypic-guided bronchodilator therapy for treating this disease. The aim of the present study was to compare the cost-effectiveness of phenotypic-guided versus guidelines-guided bronchodilator therapy in infants with viral bronchiolitis. METHODS: A decision analysis model was developed to compare the cost-effectiveness of phenotypic-guided versus guidelines-guided bronchodilator therapy in infants with viral bronchiolitis. Phenotypic-guided bronchodilator therapy was defined as the administration of albuterol in infants exhibiting a profile of increased likelihood of response to bronchodilators. The effectiveness parameters and costs of the model were obtained from systematic reviews of the literature with meta-analyses and electronic medical records. The main outcome was the avoidance of hospital admission after initial care in the emergency department. RESULTS: Compared to guidelines-guided strategy, treating patients with viral bronchiolitis with the phenotypic-guided bronchodilator therapy strategy was associated with lower total costs (US$250.99; 95% uncertainty interval [UI]: US$184.37 to $336.51 vs. US$263.46; 95% UI: US$189.81 to $349.19 average cost per patient) and a higher probability of avoidance of hospital admission (0.7902; 95% UI: 0.7315-0.8356 vs. 0.7638; 95% UI: 0.7062-0.8201), thus leading to dominance. Results were robust to deterministic and probabilistic sensitivity analyses. CONCLUSIONS: Compared to guidelines-guided strategy, treating infants with viral bronchiolitis using the phenotypic-guided bronchodilator therapy strategy is a more cost-effective strategy, because it involves a lower probability of hospital admission at lower total treatment costs.

Airway Remodeling Factors During Early-Life Rhinovirus Infection and the Effect of Premature Birth.

Background: Early rhinovirus (RV) infection is a strong risk factor for asthma development. Airway remodeling factors play a key role in the progression of the asthmatic condition. We hypothesized that RV infection in young children elicits the secretion of growth factors implicated in airway remodeling and asthma progression. Methods: We examined the nasal airway production of remodeling factors in children ( ≤ 2 years old) hospitalized due to PCR-confirmed RV infection. Airway remodeling proteins included: MMP-1, MMP-2, MMP-7, MMP-9, MMP-10, TIMP-1, TIMP-2, EGF, Angiopoietin-2, G-CSF, BMP-9, Endoglin, Endothelin-1, Leptin, FGF-1, Follistatin, HGF, HB-EGF, PLGF, VEGF-A, VEGF-C, VEGF-D, FGF-2, TGF-ß1, TGF-ß2, TGF-ß3, PDGF AA, PDGF BB, SPARC, Periostin, OPN, and TGF-α. Results: A total of 43 young children comprising RV cases (n = 26) and uninfected controls (n = 17) were included. Early RV infection was linked to (1) enhanced production of several remodeling factors (e.g., HGF, TGFα), (2) lower MMP-9/TIMP-2 and MMP-2/TIMP-2 ratios, and (3) increased MMP-10/TIMP-1 ratios. We also found that relative to term infants, severely premature children had reduced MMP-9/TIMP-2 ratios at baseline. Conclusion: RV infection in young children elicits the airway secretion of growth factors implicated in angiogenesis, fibrosis, and extracellular matrix deposition. Our results highlight the potential of investigating virus-induced airway remodeling growth factors during early infancy to monitor and potentially prevent chronic progression of respiratory disorders in all ages.

Author Correction: Characterization of Sex-Based Dna Methylation Signatures in the Airways During Early Life.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Bedside clinical assessment predicts recurrence after hospitalization due to viral lower respiratory tract infection in young children.

Infants requiring hospitalization due to a viral lower respiratory tract infection (LRTI) have a high risk of developing recurrent respiratory illnesses in early life and asthma beyond childhood. Notably, all validated clinical scales for viral LRTI have focused on predicting acute severity instead of recurrence. We present a novel clinical approach combining individual risk factors with bedside clinical parameters to predict recurrence after viral LRTI hospitalization in young children. A retrospective longitudinal cohort of young children (≤3 years) designed to define clinical predictive factors of recurrent respiratory illnesses within 12 months after hospitalization due to PCR-confirmed viral LRTI. Data collection was through electronic medical record. We included 138 children hospitalized with viral LRTI. Using automatic stepwise logistic model selection, we found that the strongest predictors of recurrence in infants hospitalized for the first time were severe prematurity (≤32 weeks' gestational age, OR=5.19; 95% CI 1.76 to 15.32; p=0.002) and a clinical score that weighted hypoxemia, subcostal retractions and wheezing (OR=3.33; 95% CI 1.59 to 6.98; p<0.001). After the first hospitalization, the strongest predictors of subsequent episodes were wheezing (OR=5.62; 95% CI 1.03 to 30.62; p=0.04) and family history of asthma (OR=5.39; 95% CI 1.04 to 27.96; p=0.04). We found that integrating individual risk factors (eg, prematurity or family history of asthma) with bedside clinical assessment (eg, wheezing, subcostal retractions or hypoxemia) can predict the risk of recurrence after viral LRTI hospitalization in infants. This strategy may enable clinically oriented subsetting of infants with viral LRTI based on individual predictors for recurrent respiratory illnesses during early life.

Phenotypical Sub-setting of the First Episode of Severe Viral Respiratory Infection Based on Clinical Assessment and Underlying Airway Disease: A Pilot Study.

Introduction: Viral bronchiolitis is a term often used to group all infants with the first episode of severe viral respiratory infection. However, this term encompasses a collection of different clinical and biological processes. We hypothesized that the first episode of severe viral respiratory infection in infants can be subset into clinical phenotypes with distinct outcomes and underlying airway disease patterns. Methods: We included children (≤2 years old) hospitalized for the first time due to PCR-confirmed viral respiratory infection. All cases were categorized based on primary manifestations (wheezing, sub-costal retractions and hypoxemia) into mild, hypoxemia or wheezing phenotypes. We characterized these phenotypes using lung-X-rays, respiratory outcomes and nasal protein levels of antiviral and type 2 cytokines (IFNγ, IL-10, IL-4, IL-13, IL-1ß, and TNFα). Results: A total of 50 young children comprising viral respiratory infection cases (n = 41) and uninfected controls (n = 9) were included. We found that 22% of viral respiratory infection cases were classified as mild (n = 9), 39% as hypoxemia phenotype (n = 16) and 39% as wheezing phenotype (n = 16). Individuals in the hypoxemia phenotype had more lung opacities, higher probability of PICU admission and prolonged hospitalizations. Subjects in the wheezing phenotype had higher probability of recurrent sick visits. Nasal cytokine profiles showed that individuals with recurrent sick visits in the wheezing phenotype had increased nasal airway levels of type 2 cytokines (IL-13/IL-4). Conclusion: Clinically-based classification of the first episode of severe viral respiratory infection into mild, hypoxemia or wheezing phenotypes provides critical information about respiratory outcomes, lung disease patterns and underlying airway immunobiology.

Validation of a new predictive model to improve risk stratification in bronchopulmonary dysplasia.

We need a better risk stratification system for the increasing number of survivors of extreme prematurity suffering the most severe forms of bronchopulmonary dysplasia (BPD). However, there is still a paucity of studies providing scientific evidence to guide future updates of BPD severity definitions. Our goal was to validate a new predictive model for BPD severity that incorporates respiratory assessments beyond 36 weeks postmenstrual age (PMA). We hypothesized that this approach improves BPD risk assessment, particularly in extremely premature infants. This is a longitudinal cohort of premature infants (≤32 weeks PMA, n = 188; Washington D.C). We performed receiver operating characteristic analysis to define optimal BPD severity levels using the duration of supplementary O2 as predictor and respiratory hospitalization after discharge as outcome. Internal validation included lung X-ray imaging and phenotypical characterization of BPD severity levels. External validation was conducted in an independent longitudinal cohort of premature infants (≤36 weeks PMA, n = 130; Bogota). We found that incorporating the total number of days requiring O2 (without restricting at 36 weeks PMA) improved the prediction of respiratory outcomes according to BPD severity. In addition, we defined a new severity category (level IV) with prolonged exposure to supplemental O2 (≥120 days) that has the highest risk of respiratory hospitalizations after discharge. We confirmed these findings in our validation cohort using ambulatory determination of O2 requirements. In conclusion, a new predictive model for BPD severity that incorporates respiratory assessments beyond 36 weeks improves risk stratification and should be considered when updating current BPD severity definitions.