Prematurity, the diagnosis of bronchopulmonary dysplasia, and maturation of ventilatory control

Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is a chronic lung disease, associated with premature birth, that arises during the infantile period. It is an evolving disease process with an unchanged incidence due to advancements in neonatal care which allow for the survival of premature infants of lower gestational ages and birth weights. Currently, there are few effective interventions to prevent BPD. However, careful attention to BPD phenotypes and comprehensive care provided by an interdisciplinary team have improved care. Interventions early in the disease course hold promise for improving long-term survival and outcomes in adulthood for this high-risk population.

Hyperoxia-induced airflow restriction and Renin-Angiotensin System expression in a bronchopulmonary dysplasia mouse model

Mechanisms underlying hyperoxia-induced airflow restriction in the pediatric lung disease Bronchopulmonary dysplasia (BPD) are unclear. We hypothesized a role for Renin-Angiotensin System (RAS) activity in BPD. RAS is comprised of a pro-developmental pathway consisting of angiotensin converting enzyme-2 (ACE2) and angiotensin II receptor type 2 (AT2), and a pro-fibrotic pathway mediated by angiotensin II receptor type 1 (AT1). We investigated associations between neonatal hyperoxia, airflow restriction, and RAS activity in a BPD mouse model. C57 mouse pups were randomized to normoxic (FiO2  = 0.21) or hyperoxic (FiO2  = 0.75) conditions for 15 days (P1-P15). At P15, P20, and P30, we measured airflow restriction using plethysmography and ACE2, AT1, and AT2 mRNA and protein expression via polymerase chain reaction and Western Blot. Hyperoxia increased airflow restriction P15 and P20, decreased ACE2 and AT2 mRNA, decreased AT2 protein, and increased AT1 protein expression. ACE2 mRNA and protein remained suppressed at P20. By P30, airflow restriction and RAS expression did not differ between groups. Hyperoxia caused high airflow restriction, increased pulmonary expression of the pro-fibrotic RAS pathway, and decreased expression of the pro-developmental in our BPD mouse model. These associated findings may point to a causal role for RAS in hyperoxia-induced airflow restriction.

Assessment of Skin Maturity by LED Light at Birth and Its Association With Lung Maturity: Clinical Trial Secondary Outcomes

BACKGROUND

Clinicians face barriers when assessing lung maturity at birth due to global inequalities. Still, strategies for testing based solely on gestational age to predict the likelihood of respiratory distress syndrome (RDS) do not offer a comprehensive approach to addressing the challenge of uncertain outcomes. We hypothesize that a noninvasive assessment of skin maturity may indicate lung maturity.

OBJECTIVE

This study aimed to assess the association between a newborn's skin maturity and RDS occurrence.

METHODS

We conducted a case-control nested in a prospective cohort study, a secondary endpoint of a multicenter clinical trial. The study was carried out in 5 Brazilian urban reference centers for highly complex perinatal care. Of 781 newborns from the cohort study, 640 were selected for the case-control analysis. Newborns with RDS formed the case group and newborns without RDS were the controls. All newborns with other diseases exhibiting respiratory manifestations were excluded. Skin maturity was assessed from the newborn's skin over the sole by an optical device that acquired a reflection signal through an LED sensor. The device, previously validated, measured and recorded skin reflectance. Clinical data related to respiratory outcomes were gathered from medical records during the 72-hour follow-up of the newborn, or until discharge or death, whichever occurred first. The main outcome measure was the association between skin reflectance and RDS using univariate and multivariate binary logistic regression. Additionally, we assessed the connection between skin reflectance and factors such as neonatal intensive care unit (NICU) admission and the need for ventilatory support.

RESULTS

Out of 604 newborns, 470 (73.4%) were from the RDS group and 170 (26.6%) were from the control group. According to comparisons between the groups, newborns with RDS had a younger gestational age (31.6 vs 39.1 weeks, P<.001) and birth weight (1491 vs 3121 grams, P<.001) than controls. Skin reflectance was associated with RDS (odds ratio [OR] 0.982, 95% CI 0.979-0.985, R2=0.632, P<.001). This relationship remained significant when adjusted by the cofactors antenatal corticosteroid and birth weight (OR 0.994, 95% CI 0.990-0.998, R2=0.843, P<.001). Secondary outcomes also showed differences in skin reflectance. The mean difference was 0.219 (95% CI 0.200-0.238) between newborns that required ventilatory support versus those that did not and 0.223 (95% CI 0.205-0.241) between newborns that required NICU admission versus those that did not. Skin reflectance was associated with ventilatory support (OR 0.996, 95% CI 0.992-0.999, R2=0.814, P=.01) and with NICU admission (OR 0.994, 95% CI 0.990-0.998, R2=0.867, P=.004).

CONCLUSIONS

Our findings present a potential marker of lung immaturity at birth using the indirect method of skin assessment. Using the RDS clinical condition and a medical device, this study demonstrated the synchrony between lung and skin maturity.

TRIAL REGISTRATION

Registro Brasileiro de Ensaios Clínicos (ReBEC) RBR-3f5bm5; https://tinyurl.com/9fb7zrdb.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

RR2-10.1136/bmjopen-2018-027442.

Oxidative Stress Levels and Dynamic Thiol-Disulfide Balance in Preterm Newborns with Bronchopulmonary Dysplasia

OBJECTIVE

The aim of this study was to assess the oxidative stress (OS) levels and dynamic thiol-disulfide balance in preterm newborns with bronchopulmonary dysplasia (BPD).

METHODS

This prospective study included newborns separated into 2 groups, those with BPD (case) or without BPD (control). The 2 groups were compared by clinical and laboratory findings. The OS parameters total oxidant status (TOS), total antioxidant status (TAS), OS index (OSI), native thiol (NT), and total thiol were measured within the first day after birth. Oxygen requirements were measured using the fraction of inspired oxygen (FIO2) recorded in the first hour after birth/admission and the average FIO2 within 28 days of the birth.

RESULTS

Infants diagnosed with BPD had a significantly lower gestational age and birth weight and a lower 5-min Apgar score (P < .05). Infants with BPD also had a higher rate of respiratory distress syndrome, rate of use of surfactant therapy, duration of ventilation therapy, and duration of hospital stay compared with control (P = .001, P = .001, P = .001, and P = .001, respectively). Plasma TAS and NT levels of newborns with BPD were significantly lower than newborns without BPD (P < .05). In the BPD group, plasma TOS and OSI levels were significantly higher than in the control group.

CONCLUSION

We found that OS was increased in newborns with BPD. The clinical significance of this study will provide the clinician with a different perspective on BPD by determining the dynamic thiol disulfide balance.

Required biological time for lung maturation and duration of invasive ventilation: a Korean cohort study of very low birth weight infants

Background

We investigated the duration of invasive ventilation among very low birth weight (VLBW) infants to evaluate the current minimum time required for lung maturation to breathe without ventilator assistance after preterm birth.

Methods

A total of 14,658 VLBW infants born at ≤32⁺⁶ weeks between 2013 and 2020 were enrolled. Clinical data were collected from the Korean Neonatal Network, a national prospective cohort registry of VLBW infants from 70 neonatal intensive care units. Differences in the duration of invasive ventilation according to gestational age and birth weight were investigated. Recent trends and changes in assisted ventilation duration and associated perinatal factors between 2017-20 and 2013-16 were compared. Risk factors related to the duration of assisted ventilation were also identified.

Results

The overall duration of invasive ventilation was 16.3 days and the estimated minimum time required corresponded to 30⁺⁴ weeks of gestation. The median duration of invasive ventilation was 28.0, 13.0, 3.0, and 1.0 days at <26, 26-27, 28-29, and 30-32 weeks of gestation, respectively. In each gestational age group, the estimated minimum weaning points from the assisted ventilator were 29⁺⁵, 30⁺², 30⁺², and 31⁺⁵ weeks of gestation. The duration of non-invasive ventilation (17.9 vs. 22.5 days) and the incidence of bronchopulmonary dysplasia (28.1% vs. 31.9%) increased in 2017-20 (n = 7,221) than in 2013-16 (n = 7,437). In contrast, the duration of invasive ventilation and overall survival rate did not change during the periods 2017-20 and 2013-16. Surfactant treatment and air leaks were associated with increased duration of invasive ventilation (inverse hazard ratio 1.50, 95% CI, 1.04-2.15; inverse hazard ratio 1.62, 95% CI, 1.29-2.04). We expressed the incidence proportion of ventilator weaning according to the invasive ventilation duration using Kaplan-Meier survival curves. The slope of the curve slowly decreased as gestational age and birth weight were low and risk factors were present.

Conclusions

This population-based data on invasive ventilation duration among VLBW infants suggest the present limitation of postnatal lung maturation under specific perinatal conditions after preterm birth. Furthermore, this study provides detailed references for designing and/or assessing earlier ventilator weaning protocols and lung protection strategies by comparing populations or neonatal networks.

The ventilatory response to hypoxia is blunted in some preterm infants during the second year of life

BACKGROUND

Preterm birth and subsequent neonatal ventilatory treatment disrupts development of the hypoxic ventilatory response (HVR). An attenuated HVR has been identified in preterm neonates, however it is unknown whether the attenuation persists into the second year of life. We investigated the HVR at 12-15 months corrected postnatal age and assessed predictors of a blunted HVR in those born very preterm (<32 weeks gestation).

METHODS

HVR was measured in infants born very preterm. Hypoxia was induced with a three-step reduction in their fraction of inspired oxygen (F_IO₂) from 0.21 to 0.14. Respiratory frequency (f), tidal volume (V _T), minute ventilation (V _E), inspiratory time (t _I), expiratory time (t _E), V _T/t _I, t_I/t _TOT, V _T/t _TOT, area under the low-volume loop and peak tidal expiratory flow (PTEF) were measured at the first and third minute of each F_IO₂. The change in respiratory variables over time was assessed using a repeated measures ANOVA with Greenhouse-Geisser correction. A blunted HVR was defined as a <10% rise in V _E, from normoxia. The relationship between neonatal factors and the magnitude of HVR was assessed using Spearman correlation.

RESULTS

Thirty nine infants born very preterm demonstrated a mean (SD) HVR of 11.4 (10.1)% (increase in V _E) in response to decreasing F_IO₂ from 0.21 to 0.14. However, 17 infants (44%) failed to increase V _E by ≥10% (range -14% to 9%) and were considered to have a blunted response to hypoxia. Males had a smaller HVR than females [ΔV _E (-9.1%; -15.4, -2.8; p = 0.007)].

CONCLUSION

Infants surviving very preterm birth have an attenuated ventilatory response to hypoxia that persists into the second year of life, especially in males.