Unravelling the respiratory health path across the lifespan for survivors of preterm birth

Physiologic Pulmonary Phenotyping of Infants Born Preterm and Post-Discharge Respiratory Morbidity

OBJECTIVE

To determine whether airway and parenchymal function identifies subgroups of infants born preterm according to the predominant pulmonary pathophysiology, and whether these subgroups have different risks for respiratory disease during infancy.

STUDY DESIGN

We prospectively enrolled a cohort of 125 infants born preterm with planned clinical follow-up after neonatal intensive care unit discharge. The study included monthly questionnaires for wheeze and visits to a physician or care provider for any respiratory illness. In addition, infant lung function testing near 5 months corrected-age included measures of airways and parenchymal function using forced expiratory flows, alveolar volume (VA), and the carbon monoxide transfer constant (diffusion capacity of lung [DL]/VA). Phenotypes were defined using 2 approaches: an a priori defined phenotypes based on forced expiratory flow 75% and DL/VA z-scores, and an unbiased approach to classifying infants using k-means clustering.

RESULTS

We identified 4 pulmonary physiologic phenotypes that distinguished participants with predominantly decreased airway and/or parenchymal function. Although the worst physiologic phenotypes were associated with a lower gestational age at birth, these phenotypes had a better predictive value than gestational age, sex, and diagnosis of bronchopulmonary dysplasia for increased respiratory morbidity during infancy (area under the curve = 0.71 vs 0.63 for respiratory illness and 0.69 vs 0.63 for wheeze).

CONCLUSIONS

Physiologic pulmonary phenotypes of infants born preterm were associated with differential risks for respiratory morbidities as infants, which may identify heterogeneous risks for long-term respiratory sequelae to individualize therapeutic strategies.

Long-term respiratory consequences of prematurity

Approximately 10% of all children worldwide are born preterm and respiratory consequences are amongst the most common sequelae of preterm birth. Except for a higher prevalence of respiratory symptoms and hospital admissions, preterm birth is associated with lower lung function that may track into adulthood. Lung function impairment is not restricted to extreme or very preterm-born subjects as also children born moderate-late preterm have lower Z-scores for lung function. Given the heterogeneity of prematurity-associated lung disease, phenotype-based, multidisciplinary management is needed to improve respiratory health in preterm-born subjects.

Research priorities for preterm lung health research across the lifespan: a community priority setting partnership

BACKGROUND

It is essential to embed patient and public perspectives into every stage of the research journey, including setting the future research agenda. The substantial gaps in our understanding of prematurity-associated lung disease presented a timely opportunity to determine the community's research priorities.

OBJECTIVE

To conduct a priority setting partnership (PSP) to determine the top 10 research priorities for preterm lung health.

DESIGN

We undertook a modified James Lind Alliance methodology comprising three main stages: (1) an idea generating survey with open questions to ascertain the community's most important ideas for future preterm lung health research, (2) prioritisation survey to distill the main themes into a shortlist of 20 and (3) consensus workshop where participants were tasked with ranking their final top 10. This PSP is reflective of the view of preterm-born individuals, parents of preterm children and healthcare professionals in an Australian healthcare setting.

RESULTS

We collated 144 submissions from the idea generating survey from which 27 prioritisation themes were developed. From the 150 prioritisation survey responses, the 20 themes receiving the most votes were taken to the consensus workshop. Participants identified the following top 10: (1) lifelong impacts; (2) interventions, treatments or supports; (3) ongoing lung health follow-up; (4) diagnostic tools, resources and education for primary healthcare providers; (5) resources to inform and empower families; (6) relationship to physical health and developmental issues; (7) preventing and/or treating lung infections; (8) additional supports, resources and research for minority groups; (9) impact on mental well-being; and (10) likelihood of asthma diagnosis.

CONCLUSION

Priorities identified through the PSP will be invaluable in informing future research into prematurity-associated lung disease.

Similarities of metabolomic disturbances in prematurity-associated obstructive lung disease to chronic obstructive pulmonary disease

Prematurity-associated lung disease (PLD) is a long-term consequence of preterm-birth. Since the underlying mechanisms of PLD remain poorly characterised, we compared the urinary metabolome between recently described spirometry phenotypes of PLD. Preterm- and term-born children aged 7-12 years, from the Respiratory Health Outcomes in Neonates (RHiNO) cohort, underwent spirometry and urine collection. The urinary metabolome was analysed by gas chromatography time-of-flight mass spectrometry. Preterm-born children were classified into phenotypes of prematurity-associated obstructive lung disease (POLD, Forced expiratory volume in 1 s (FEV1) < lower limit of normal (LLN), FEV1/Forced Vital Capacity (FVC) < LLN), prematurity-associated preserved ratio impaired spirometry (pPRISm, FEV1 < LLN, FEV1/FVC ≥ LLN) and Preterm/Term controls (FEV1 ≥ LLN). Metabolite set enrichment analysis was used to link significantly altered metabolites between the groups with metabolic pathways. Univariable and multivariable linear regression models examined associations between early and current life factors and significantly altered metabolites of interest. Urine from 197 preterm- and 94 term-born children was analysed. 23 and 25 were classified into POLD and pPRISm groups respectively. Of 242 identified metabolites, 49 metabolites were significantly altered in the POLD group compared with Preterm controls. Decreased capric acid (log2 fold change - 0.23; p = 0.003), caprylic acid (- 0.18; 0.003) and ceratinic acid (- 0.64; 0.014) in the POLD group, when compared to preterm controls, were linked with reduced β-oxidation of very long chain fatty acids (p = 0.004). Reduced alanine (log2 fold change - 0.21; p = 0.046), glutamic acid (- 0.24; 0.023), and pyroglutamic acid (- 0.17; 0.035) were linked with decreased glutathione metabolism (p = 0.008). These metabolites remained significantly associated with POLD in multivariable models adjusting for early/current life factors. The pPRISm urinary metabolome was minimally changed when compared with preterm-born controls. When compared to term-born subjects, alterations in tryptophan metabolism were implicated (p = 0.01). The urinary metabolome in POLD showed significantly altered β-oxidation of fatty acids and glutathione metabolism, implying alterations in cellular metabolism and oxidative stress. Similar findings have been noted in adults with chronic obstructive pulmonary disease. Given the similarity of findings between the POLD group and those reported for COPD, the POLD group should be considered at future risk of developing COPD.

The respiratory consequences of preterm birth: from infancy to adulthood

Survival of preterm-born infants, especially at extremes of prematurity (less than 28 weeks gestation), is now common, particularly in the developed world. Despite advances in neonatal care, short-term respiratory morbidity, termed bronchopulmonary dysplasia (also called chronic lung disease of prematurity), remains an important clinical outcome. As survival during the neonatal period has improved, preterm-born individuals are now entering childhood, adolescence and adulthood in far greater numbers, and adverse longer-term respiratory outcomes following birth at an immature stage of lung development are becoming increasingly apparent. In this article, we shall review the background of the major respiratory complications in the neonatal period, bronchopulmonary dysplasia, and the current evidence regarding its prevention and management. In addition, we shall review the emerging literature on the respiratory morbidity experienced in childhood, adolescence, and adulthood by preterm-born survivors, with reduced lung function and a risk of developing chronic obstructive pulmonary disease in early adult life. As this population of preterm-born individuals increases, an understanding of the respiratory consequences of preterm birth will become increasingly important not only for neonatologists, paediatricians and paediatric pulmonologists but also for physicians and healthcare professionals involved in the care of adults who were born preterm.

Azithromycin therapy for prevention of chronic lung disease of prematurity (AZTEC): a multicentre, double-blind, randomised, placebo-controlled trial

BACKGROUND

Systematic reviews have reported conflicting evidence on whether macrolide antibiotics reduce rates of chronic lung disease of prematurity (CLD) in at-risk preterm infants born at less than 30 weeks' gestation, including in those colonised with pulmonary Ureaplasma spp. Since an adequately powered trial has been lacking, we aimed to assess if the macrolide azithromycin improved survival without the development of physiologically defined moderate or severe CLD in preterm infants.

METHODS

AZTEC was a multicentre, double-blind, randomised, placebo-controlled trial conducted in 28 tertiary neonatal intensive care units in the UK. Infants were eligible if they were born at less than 30 weeks' gestation and had received at least 2 h of either non-invasive (continuous positive airway pressure or humidified high flow nasal cannula therapy) or invasive respiratory support (via endotracheal tube) within 72 h of birth. Eligible infants were randomly allocated in a 1:1 ratio using random permuted blocks of four to receive either intravenous azithromycin at 20 mg/kg per day for 3 days followed by 10 mg/kg for 7 days, or to placebo. Allocation was stratified by centre and gestational age at birth (<28 weeks vs ≥28 weeks). Azithromycin and placebo vials were encased in tamper-evident custom cardboard cartons to ensure masking for clinicians, parents, and the research team. The primary outcome was survival without development of physiologically defined moderate or severe CLD at 36 weeks' postmenstrual age. Outcomes and safety were analysed on an intention-to-treat basis (all randomly allocated infants, regardless of any post-randomisation events). The study was registered with ISRCRN (11650227) and is closed.

FINDINGS

Infants were recruited between Oct 9, 2019, and March 22, 2022. 799 (53·1%) of 1505 eligible infants underwent random allocation; three infants were withdrawn, including consent to use their data, leaving 796 infants for analysis. Survival without moderate or severe CLD occurred in 166 (42%) of 394 infants in the intervention group and 179 (45%) of 402 in the placebo group (three-level adjusted OR [aOR] 0·84, 95% CI 0·55-1·29, p=0·43). Pulmonary Ureaplasma spp colonisation did not influence treatment effect. Overall, seven serious adverse events were reported for the azithromycin group (five graded as severe, two as moderate), and six serious adverse events were reported in the placebo group (two severe, two moderate, and two mild), as assessed by the local principal investigators.

INTERPRETATION

Since prophylactic use of azithromycin did not improve survival without development of physiologically-defined CLD, regardless of Ureaplasma spp colonisation, it cannot be recommended in clinical practice.

FUNDING

UK National Institute for Health and Care Research.

BPD: Latest Strategies of Prevention and Treatment

BACKGROUND

Bronchopulmonary dysplasia (BPD) is the most common long-term complication of extreme preterm birth. It is associated with lifelong multisystemic consequences. Advances in neonatal care have not reduced the incidence of BPD and no new breakthrough therapy has been successfully translated into the clinic in recent decades.

SUMMARY

Current evidence demonstrates benefit of new modalities of first-line noninvasive positive pressure ventilation, selected strategies of postnatal corticosteroid administration, alternative surfactant delivery methods, and caffeine. Promising emerging therapies that are being translated from bench to bedside include mesenchymal stromal cells (MSCs), insulin-like growth factor 1/binding protein-3 (IGF-1/IGFBP-3), and interleukin 1 receptor (IL-1R) antagonist (anakinra). Strong preclinical data support efficacy of MSCs in attenuating neonatal lung injury. Early-phase clinical trials have already demonstrated safety and feasibility in preterm infants. Phase II studies that aimed at demonstrating efficacy are currently underway. Both IGF-1/IGFBP-3 and IL-1R antagonist present with biological plausibility and animal data of efficacy. Phase I/II clinical trials are currently recruiting patients.

KEY MESSAGES

Early noninvasive respiratory support, late systemic dexamethasone, less invasive surfactant administration, and caffeine are proven strategies in reducing the risk of BPD. Potentially disruptive therapies - MSCs, IGF-1/IGFBP-3, and anakinra - are being advanced to clinical trials and their efficacy in remains to be demonstrated. Continued research efforts are needed in the growing population of extremely preterm infants at risk of developing BPD.

To burn or not to burn: similar effects of different types of prenatal tobacco exposure on infant lung function

The first study to describe the harmful effects of snus on the unborn infant provides evidence to help clinicians and mothers collectively to make an informed choice about quitting the use of snus before planning pregnancies https://bit.ly/3vJnBxW.

Prematurity-associated lung disease: is it asthma?

Not all wheeze is "asthma" in those born very preterm. Further work is needed to better understand the aetiology of prematurity-associated lung disease and the best treatments for this population. https://bit.ly/3Tko3vi.