Elevated Carbon Dioxide Tension as a Predictor of Subsequent Adverse Events in Infants with Bronchopulmonary Dysplasia

Managing established bronchopulmonary dysplasia without using routine blood gas measurements

OBJECTIVE

Routine blood gas measurements are common in infants with severe bronchopulmonary dysplasia (sBPD) and are a noxious stimulus. We developed a guideline-driven approach to evaluate the care of infants with sBPD without routine blood gas sampling in the chronic phase of NICU care (after diagnosis at 36 weeks PMA).

STUDY DESIGN

We examined blood gas utilization and outcomes in our sBPD inpatient care unit using data collected between 2014 and 2020.

RESULTS

485 sBPD infants met inclusion criteria, and 303 (62%) never had a blood gas obtained after 36 weeks PMA. In infants who had blood gas measurements, the median number of total blood gases per patient was only 4 (IQR 1-10). We did not identify adverse effects on hospital outcomes in patients without routine blood gas measurements.

CONCLUSIONS

We found that patients with established BPD could be managed without routine blood gas analyses after 36 weeks PMA.

Early Changes and Indicators Characterizing Lung Aging in Neonatal Chronic Lung Disease

Infants suffering from neonatal chronic lung disease, i.e., bronchopulmonary dysplasia, are facing long-term consequences determined by individual genetic background, presence of infections, and postnatal treatment strategies such as mechanical ventilation and oxygen toxicity. The adverse effects provoked by these measures include inflammatory processes, oxidative stress, altered growth factor signaling, and remodeling of the extracellular matrix. Both, acute and long-term consequences are determined by the capacity of the immature lung to respond to the challenges outlined above. The subsequent impairment of lung growth translates into an altered trajectory of lung function later in life. Here, knowledge about second and third hit events provoked through environmental insults are of specific importance when advocating lifestyle recommendations to this patient population. A profound exchange between the different health care professionals involved is urgently needed and needs to consider disease origin while future monitoring and treatment strategies are developed.

Using a home oxygen weaning protocol and pCO2 to evaluate outcomes for infants with bronchopulmonary dysplasia discharged on home oxygen

BACKGROUND

Predischarge capillary blood gas partial pressure of carbon dioxide (pCO₂ ) has been associated with increased adverse events including readmission. This study aimed to determine if predischarge pCO₂ or 36-week pCO₂ was associated with increased respiratory readmissions or other pulmonary healthcare utilization in the year after neonatal intensive care unit (NICU) discharge for infants with bronchopulmonary dysplasia (BPD) discharged with home oxygen, using a standardized outpatient oxygen weaning protocol.

METHODS

This was a secondary cohort analysis of infants born <32 weeks gestational age with BPD, referred to our clinic for home oxygen therapy from either from our level IV NICU or local level III NICUs between 2015 and 2017. Infants with major nonrespiratory comorbidities were excluded. Subject information was obtained from electronic health records.

RESULTS

Of 125 infants, 120 had complete 1-year follow-up. Twenty-three percent of infants experienced a respiratory readmission after NICU discharge. There was no significant association between predischarge or 36-week pCO₂ and respiratory readmissions, emergency room visits, new or increased bronchodilators, or diuretics. Higher 36-week pCO₂ was associated with a later corrected age when oxygen was discontinued (<6 months; median, 54 mmHg; interquartile range [IQR], 51-61; 6-11 months; median, 62 mmHg; IQR, 57-65; ≥12 months, median, 66 mmHg; IQR, 58-73; p = .006).

CONCLUSIONS

Neither predischarge pCO₂ nor 36-week pCO₂ was associated with 1-year respiratory readmissions. However higher pCO₂ at 36 weeks was associated with a longer duration of home oxygen. Neonatal illness measures like 36-week pCO₂ may be useful in communicating expectations for home oxygen therapy to families.

Utility of echocardiography in predicting mortality in infants with severe bronchopulmonary dysplasia

OBJECTIVE

To determine the relationship between interventricular septal position (SP) and right ventricular systolic pressure (RVSP) and mortality in infants with severe BPD (sBPD).

STUDY DESIGN

Infants with sBPD in the Children's Hospitals Neonatal Database who had echocardiograms 34-44 weeks' postmenstrual age (PMA) were included. SP and RVSP were categorized normal, abnormal (flattened/bowed SP or RVSP > 40 mmHg) or missing.

RESULTS

Of 1157 infants, 115 infants (10%) died. Abnormal SP or RVSP increased mortality (SP 19% vs. 8% normal/missing, RVSP 20% vs. 9% normal/missing, both p < 0.01) in unadjusted and multivariable models, adjusted for significant covariates (SP OR 1.9, 95% CI 1.2-3.0; RVSP OR 2.2, 95% CI 1.1-4.7). Abnormal parameters had high specificity (SP 82%; RVSP 94%), and negative predictive value (SP 94%, NPV 91%) for mortality.

CONCLUSIONS

Abnormal SP or RVSP is independently associated with mortality in sBPD infants. Negative predictive values distinguish infants most likely to survive.

A modified physiologic test for bronchopulmonary dysplasia: a clinical tool for weaning from CPAP and/or oxygen-therapy the premature babies?

Background

A physiologic test for estimating BPD rate has been developed by Walsh and collaborators. Actually there are not standard criteria for weaning from CPAP and/or oxygen therapy the premature babies. Aim of this study was to verify if a physiologic test, modified respect to that developed by Walsh and collaborators for estimating BPD rate, can be used as a clinical tool for weaning the premature babies from CPAP and/or oxygen therapy.

Methods

Neonates with BW 500–1250 g and GA ≤ 32 weeks, receiving FiO₂ ≤ 0.30 by hood or CPAP, were prospectively studied at 28 days of life and at 36 weeks of postmestrual age. The test was performed in 3 steps: baseline, challenge (FiO₂ and CPAP reduction to room air) and post test (room air). Monitoring of transcutaneous CO₂ was added to SpO₂ and the newborns passing the test were left in room air.

Results

Six of 23 tested babies (26%) passed the challenge at 28 days of life, 4 of 10 tested babies (40%) passed the challenge at 36 weeks. Median values of SpO₂ were significantly higher in the neonates passing the test, respect to the failing patients. At the same time median values of TcPCO₂ were significantly higher in the latter babies.

Conclusion

TcPCO₂ monitoring appeared to be a new useful parameter for failure prediction of weaning. The test represented a clinical guide because the newborns passing it were left in room air.

CO2-evoked release of PGE2 modulates sighs and inspiration as demonstrated in brainstem organotypic culture

Inflammation-induced release of prostaglandin E₂ (PGE₂) changes breathing patterns and the response to CO₂ levels. This may have fatal consequences in newborn babies and result in sudden infant death. To elucidate the underlying mechanisms, we present a novel breathing brainstem organotypic culture that generates rhythmic neural network and motor activity for 3 weeks. We show that increased CO₂ elicits a gap junction-dependent release of PGE₂. This alters neural network activity in the preBötzinger rhythm-generating complex and in the chemosensitive brainstem respiratory regions, thereby increasing sigh frequency and the depth of inspiration. We used mice lacking eicosanoid prostanoid 3 receptors (EP3R), breathing brainstem organotypic slices and optogenetic inhibition of EP3R^+/+ cells to demonstrate that the EP3R is important for the ventilatory response to hypercapnia. Our study identifies a novel pathway linking the inflammatory and respiratory systems, with implications for inspiration and sighs throughout life, and the ability to autoresuscitate when breathing fails.

DOI:http://dx.doi.org/10.7554/eLife.14170.001

Humans and other mammals breathe air to absorb oxygen into the body and to remove carbon dioxide. We know that in a part of the brain called the brainstem, several regions work together to create breaths, but it is not clear precisely how this works. These regions adjust our breathing to the demands placed on the body by different activities, such as sleeping or exercising. Sometimes, especially in newborn babies, the brainstem’s monitoring of oxygen and carbon dioxide does not work properly, which can lead to abnormal breathing and possibly death.

In the brain, cells called neurons form networks that can rapidly transfer information via electrical signals. Here, Forsberg et al. investigated the neural networks in the brainstem that generate and control breathing in mice. They used slices of mouse brainstem that had been kept alive in a dish in the laboratory. The slice contained an arrangement of neurons and supporting cells that allowed it to continue to produce patterns of electrical activity that are associated with breathing. Over a three-week period, Forsberg et al. monitored the activity of the cells and calculated how they were connected to each other. The experiments show that the neurons responsible for breathing were organized in a “small-world” network, in which the neurons are connected to each other directly or via small numbers of other neurons.

Further experiments tested how various factors affect the behavior of the network. For example, carbon dioxide triggered the release of a small molecule called prostaglandin E2 from cells. This molecule is known to play a role in inflammation and fever. However, in the carbon dioxide sensing region of the brainstem it acted as a signaling molecule that increased activity. Therefore, inflammation could interfere with the body’s normal response to carbon dioxide and lead to potentially life-threatening breathing problems. Furthermore, prostaglandin E2 induced deeper breaths known as sighs, which may be vital for newborn babies to be able to take their first deep breaths of life. Future challenges include understanding how the brainstem neural networks generate breathing and translate this knowledge to improve the treatment of breathing difficulties in babies.

DOI:http://dx.doi.org/10.7554/eLife.14170.002

Pediatric Pulmonary Hypertension: Guidelines From the American Heart Association and American Thoracic Society

Pulmonary hypertension is associated with diverse cardiac, pulmonary, and systemic diseases in neonates, infants, and older children and contributes to significant morbidity and mortality. However, current approaches to caring for pediatric patients with pulmonary hypertension have been limited by the lack of consensus guidelines from experts in the field. In a joint effort from the American Heart Association and American Thoracic Society, a panel of experienced clinicians and clinician-scientists was assembled to review the current literature and to make recommendations on the diagnosis, evaluation, and treatment of pediatric pulmonary hypertension. This publication presents the results of extensive literature reviews, discussions, and formal scoring of recommendations for the care of children with pulmonary hypertension.

Etiology, diagnosis, and pharmacologic treatment of pediatric pulmonary hypertension

Major advances have been made in the understanding and treatment of pulmonary hypertension in the last few years. Without treatment (medication) for idiopathic pulmonary arterial hypertension, which is a rare and potentially fatal condition, the survival time is only about 3 years after diagnosis. However, if pulmonary hypertension is secondary to other causes such as congenital heart disease, it is possible to survive for 30 years or more without treatment. The condition can affect children at any age, from fetal life to adulthood. Patients with pulmonary hypertension can present to the respiratory pediatrician with unresponsive asthma, to the neurologist with faints, or to the general pediatrician with failure to thrive. Over the last few years there have been significant developments in the available therapy for managing this complicated disease. There is now a generally recognized ladder of long-term therapy for chronic pulmonary hypertension. Treatment can start with oxygen at home at night or even during the day. Next is the use of oral phosphodiesterase inhibitors, mostly type V, such as sildenafil, which enhance endogenous nitric oxide. More potent are the endothelin receptor antagonists and the most potent are the prostanoids, especially epoprostenol, which is given by constant intravenous infusion. In addition to interventional catheterization with atrial septostomy, these agents have improved the prognostic outlook. This article reviews the current knowledge about the etiology, investigation, and treatment of children with pulmonary hypertension in the clinical setting.

Effects of chronic hypercapnia in the neonatal mouse lung and brain

BACKGROUND

Permissive hypercapnia is increasingly utilized in the care of premature infants to prevent bronchopulmonary dysplasia. In a previous investigation, we described gene expression changes in the neonatal mouse lung exposed to chronic hypercapnia that might contribute to lung protection and accelerated maturation. However, it is unknown whether chronic hypercapnia increases alveolar formation, nor if it has detrimental effects in other developing organs such as the brain.

OBJECTIVE

To determine whether chronic hypercapnia accelerates early alveolar formation and increases neuronal cell injury in the developing mouse lung and brain, respectively.

DESIGN

Mouse pups were exposed to 8% CO(2) + 21% O(2) starting at postnatal day (P) 2 until P7. Control animals were maintained in room air. Animals were sacrificed at P4 or P7, and lungs and brains were excised and analyzed.

RESULTS

Exposure to 8% CO(2) resulted in an increased expression of alpha-smooth muscle actin (alpha-sma) which localized to the tips of developing alveolar buds, and also an increased number of alveolar buds at P7. Importantly, hypercapnic animals also demonstrated evidence of increased TUNEL-positive cells in the brain.

CONCLUSIONS

Exposure to chronic hypercapnia may lead to early initiation of alveolar budding in the neonatal mouse, but may also lead to increased TUNEL-positive cells in the developing brain.

Effect of a short course of prednisolone in infants with oxygen-dependent bronchopulmonary dysplasia

OBJECTIVE

The purpose of this work was to determine whether oral prednisolone is effective in weaning infants with bronchopulmonary dysplasia, after 36 weeks' postmenstrual age, off supplemental oxygen and to identify factors associated with successful weaning.

METHODS

Data were abstracted from a standardized prospectively collected database at the John Dempsey Hospital NICU. Logistic regression and receiver operating curve analyses were used.

RESULTS

Of 385 infants, 131 (34%) received oral prednisolone and 254 (66%) did not. There was no significant difference in race, gender, birth weight, or gestational age between the groups receiving and not receiving oral prednisolone. Infants in the oral prednisolone group were more likely to have received previous dexamethasone therapy, had longer duration of mechanical ventilation, had longer length of hospital stay, and were more likely to be discharged from the hospital on oxygen. Of those in the oral prednisolone group, 63% responded to treatment. Pulmonary acuity score and PCO2 were the only parameters that remained significant on multiple logistic regression analyses. The oral prednisolone-responsive group had a lower pulmonary acuity score compared with the oral prednisolone-nonresponsive group. A pulmonary acuity score value of < or = 0.5 had a sensitivity of 20% and specificity of 97.4%, with positive and negative predictive values of 94.1% and 42.1%, respectively. Capillary PCO2 values were significantly lower in the oral prednisolone-responsive group compared with the oral prednisolone-nonresponsive group. In predicting a successful response to oral prednisolone, a capillary PCO2 value of < 48.5 mmHg had a sensitivity of 50% and specificity of 89.7%, with positive and negative predictive values of 89.1% and 51.8%, respectively.

CONCLUSIONS

Oral prednisolone therapy is effective in weaning off supplemental oxygen in a postterm infant with oxygen-dependent bronchopulmonary dysplasia who has a pulmonary acuity score of < 0.5 and PCO2 of < 48.5 mmHg. In addition, if a single course of prednisolone fails, there is no clear benefit of using multiple courses.

PCO2 and room air saturation values in premature infants at risk for bronchopulmonary dysplasia

OBJECTIVE

To determine the capillary partial pressure of carbon dioxide (PCO(2)) and room air transcutaneous hemoglobin saturation (RA SAT) at 36 weeks' postmenstrual age (PMA) in infants born with weight between 501 and 1250 g.

STUDY DESIGN

Multicenter, prospective investigation with primary data collection within 72 h of 36 weeks PMA or discharge, whichever first. PCO(2) and RA SAT determinations were done at rest on infants not requiring mechanical ventilation or nasal continuous positive airway pressure (NCPAP).

RESULT

A total of 220 infants were enrolled (mean gestational age 27.7 weeks, mean birthweight 951 g). In infants with traditionally defined chronic lung disease (CLD) compared to those without CLD, the mean PCO(2) was significantly higher (54 versus 45 mm Hg) and the median RA SAT significantly lower (<80 versus 97%). In infants with the new classification of bronchopulmonary dysplasia (BPD), there was a significant linear trend toward increasing PCO(2) with increasing severity of BPD (45, 47, 54 and 62 mm Hg in No, Mild, Moderate and Severe BPD). There was a significant linear trend toward decreasing RA SAT with increasing severity of BPD (97, 95 <80, <80% in No, Mild, Moderate and Severe BPD).

CONCLUSION

Defining CLD as BPD based upon a RA SAT test is a more discriminate, objective method to categorize lung injury. PCO(2) is an objective measure of lung function that inversely correlates with RA SAT. These determinations done together at 36 weeks PMA may provide more precise and accurate estimates of lung injury that might allow for better understanding of pulmonary therapies and clearer comparison of BPD rates and severities among NICUs.