Chronic respiratory morbidity following premature delivery--prediction by prolonged respiratory support requirement?

Physiologic findings in children previously ventilator dependent at home due to bronchopulmonary dysplasia

INTRODUCTION

Bronchopulmonary dysplasia (BPD) is the primary respiratory complication of premature birth. Some preterm newborns develop chronic respiratory failure, requiring home ventilator support. While physiologic measures have been described for prematurely born children, little is known about spirometric indices in patients with severe BPD who were previously ventilator dependent at home.

METHODS

We retrospectively reviewed medical charts of patients with severe BPD who were ventilator dependent at home. We excluded patients with other comorbidities that could contribute to the severity of BPD. Spirometry was performed when the patient was able to follow commands.

RESULTS

Between 1984 and 2012, within our severe BPD cohort who previously required home ventilator support, 19 patients were able to perform reproducible spirometry meeting ATS/ERS acceptability criteria. Ten (52.6%) were females, 13 (68.4%) were Caucasians. Mean age at liberation from ventilation was 2.4 years (C.I. 2.0, 2.9) and at decannulation was 3.5 years (C.I. 2.9, 4.0); median age at first reproducible spirometry measurement was 6.6 years (IQR: 4.9, 8.3). Spirometry results revealed significant airway obstruction, as demonstrated by Z-scores values of -1.5 (C.I. -2.5, -0.4) for FVC, -2.7 (C.I. -3.3, -1.9) for FEV1 , and -3.6 (C.I. -4.3, -2.9) for FEF25-75 . More so, serial spirometric measurements' slopes revealed that the airway obstruction remained static over time (FEV1 slope: -0.07, P-value: 0.2624; FVC slope: -0.01, P-value: 0.9064; and FEF25-75 : 0.0, P-value: 0.8532).

CONCLUSIONS

Extreme prematurity associated with severe BPD requiring home ventilator support carries significant risks of morbidity. These patients had substantially diminished respiratory function reflecting airflow abnormalities that remained static over time.

Prediction of respiratory outcome in extremely low gestational age infants

BACKGROUND

Bronchopulmonary dysplasia (BPD) is a commonly used outcome for randomized neonatal trials.

OBJECTIVES

The aim of the present study was to determine whether a diagnosis of BPD or respiratory morbidity (RM1 or RM2) at 12 months corrected age better predicted subsequent RM in extremely low gestational age infants (23-28 weeks of gestation).

METHODS

Initial analysis was undertaken in a development cohort of 76 infants who underwent pulmonary function tests (PFTs) at 12 months corrected age. Parents completed infant respiratory diaries 2 weeks before the PFTs. Analysis was then undertaken in a validation cohort of 227 infants whose parents completed a 4-week respiratory diary when their infant was 12 months corrected age. BPD at 28 days (BPD28d) and 36 weeks post-menstrual age (BPD36w), RM1 (≥3 days and/or nights of cough, wheeze, and/or medicine use) and RM2 (≥4 days and/or nights of cough, wheeze, and/or respiratory medicine use) each week for 2 weeks at 12 months corrected age were assessed with regard to prediction of respiratory outcomes at 24 months documented by respiratory health questionnaires.

RESULTS

BPD28d and BPD36w were not significantly associated with any respiratory outcome. Areas under the receiver operating characteristic curves were significantly better for either definition of RM than BPD28d or BPD36w for all outcomes.

CONCLUSIONS

RM documented by parental completed diaries at 12 months corrected age better predicted respiratory outcome at 24 months corrected age than BPD regardless of diagnostic criteria.

Respiratory morbidity at follow-up of small-for-gestational-age infants born very prematurely

BACKGROUND

The aim of this study was to determine whether small-for-gestational-age (SGA) infants born very prematurely had increased respiratory morbidity in the neonatal period and at follow-up.

METHODS

Data were examined from infants recruited into the United Kingdom Oscillation Study (UKOS). Of the 797 infants who were born at <29 wk of gestational age, 174 infants were SGA. Overall, 92% were exposed to antenatal corticosteroids and 97% received surfactant; follow-up data at 22-28 mo were available for 367 infants.

RESULTS

After adjustment for gestational age and sex, SGA infants had higher rates of supplementary oxygen dependency at 36 wk postmenstrual age (odds ratio (OR): 3.23; 95% confidence interval: 2.03, 5.13), pulmonary hemorrhage (OR: 3.07; 95% CI: 1.82, 5.18), death (OR: 3.32; 95% CI: 2.13, 5.17), and postnatal corticosteroid requirement (OR: 2.09; 95% CI: 1.35, 3.23). After adjustment for infant and respiratory morbidity risk factors, a lower mean birth weight z-score was associated with a higher prevalence of respiratory admissions (OR: 1.40; 95% CI: 1.03, 1.88 for 1 SD change in z-score), cough (OR: 1.28; 95% CI: 1.00, 1.65), and use of chest medicines (OR: 1.32; 95% CI: 1.01, 1.73).

CONCLUSION

SGA infants who were born very prematurely, despite routine use of antenatal corticosteroids and postnatal surfactant, had increased respiratory morbidity at follow-up, which was not due to poor neonatal outcome.

Postnatal corticosteroids to treat or prevent chronic lung disease in preterm infants

This statement is intended for health care professionals caring for neonates and young infants. The objectives of this statement are to review the short and long term effects of systemic and inhaled postnatal corticosteroids for the prevention or treatment of evolving or established chronic lung disease, and to make recommendations for the use of corticosteroids in infants with very low birth weight. The routine use of systemic dexamethasone for the prevention or treatment of chronic lung disease in infants with very low birth weight is not recommended.

Fatores associados à morbidade respiratória entre 12 e 36 meses de vida de crianças nascidas de muito baixo peso oriundas de uma UTI neonatal pública

O objetivo do estudo foi estimar a morbidade respiratória entre 12 e 36 meses em crianças prematuras e identificar os fatores associados. A população compreendeu 84 crianças de uma coorte de prematuros de muito baixo peso. O desfecho foi a taxa de incidência de morbidade respiratória. A associação entre as variáveis independentes e morbidade respiratória foi verificada por modelo linear generalizado. Entre 12 e 24 meses, 56,3% das crianças apresentaram morbidade respiratória. Entre 24 e 36 meses, 38,1% das crianças foram acometidas. As variáveis associadas à morbidade respiratória foram: displasia broncopulmonar (RT = 1,9; IC95%: 1,2-2,9), complacência pulmonar alterada (RT = 1,6; IC95%: 1,1-2,2), pneumonia neonatal (RT = 2,8; IC95%: 2,0-4,0), persistência do canal arterial (RT = 1,6; IC95%: 1,1-2,4) e morbidade respiratória no primeiro ano de vida (RT = 1,8; IC95%: 1,3-2,6). A incidência de morbidade respiratória entre 12 e 36 meses se manteve elevada neste grupo de crianças de alto risco, o que reforça a necessidade de acompanhamento e de intervenções efetivas na prevenção do adoecimento e na melhora da qualidade de vida destas crianças e suas famílias.

A scoring system to predict chronic oxygen dependency

INTRODUCTION

Chronic oxygen dependency (COD) is a common adverse outcome of very premature birth. It is, therefore, important to develop an accurate and simple predictive test to facilitate targeting of interventions to prevent COD. Our aim was to determine if a simple score based on respiratory support requirements predicted COD development.

METHODS

A retrospective study of 136 infants, median gestation age (GA) 28 weeks (range: 23-33 weeks) and a prospective study of 75 infants, median GA 30 weeks (range: 23-32 weeks), were performed. The score was calculated by multiplying the inspired oxygen concentration by the level of respiratory support (mechanical ventilation: 2.5; continuous positive airway pressure: 1.5; nasal cannula or head box oxygen or air: 1.0). Scores were calculated on data from days 2 and 7, and their predictive ability compared to that of the maximum inspired oxygen concentration at those ages and (retrospective study) the results of lung volume measurement.

RESULTS

Infants that were oxygen dependent at 28 days and 36 weeks post-menstrual age (PMA) had higher scores on days 2 (p<0.0001, p<0.0001, respectively) and 7 (p<0.0001, p<0.0001, respectively) than the non-oxygen dependent infants in both the retrospective and prospective cohorts. Construction of receiver operator characteristic curves demonstrated the score performed better than the inspired oxygen level and lung volume measurement results. A score on day 7 >0.323 had 95% specificity and 78% sensitivity in predicting COD at 28 days, and 80% specificity and 73% sensitivity in predicting COD at 36 weeks PMA.

CONCLUSION

Chronic oxygen dependency can be predicted using a simple scoring system.

Bronchopulmonary dysplasia--long term follow up

Fifty percent of BPD infants require readmission to hospital during infancy, particularly if they suffer an RSV infection. Many BPD infants require supplementary oxygen at home, early discharge can be achieved if those still requiring nasogastric feeding are given appropriate community support. Troublesome respiratory symptoms are common in children who had BPD, as are lung function abnormalities even in adolescents and young adults.

Lung-function tests in neonates and infants with chronic lung disease: tidal breathing and respiratory control

This paper is the fourth in a series of reviews that will summarize available data and critically discuss the potential role of lung-function testing in infants with acute neonatal respiratory disorders and chronic lung disease of infancy. The current paper addresses information derived from tidal breathing measurements within the framework outlined in the introductory paper of this series, with particular reference to how these measurements inform on control of breathing. Infants with acute and chronic respiratory illness demonstrate differences in tidal breathing and its control that are of clinical consequence and can be measured objectively. The increased incidence of significant apnea in preterm infants and infants with chronic lung disease, together with the reportedly increased risk of sudden unexplained death within the latter group, suggests that control of breathing is affected by both maturation and disease. Clinical observations are supported by formal comparison of tidal breathing parameters and control of breathing indices in the research setting.

Lung volumes in infants who had mild to moderate bronchopulmonary dysplasia

"New" bronchopulmonary dysplasia (BPD) has been suggested to be a maldevelopment sequence with reduced alveolarisation of the lungs; affected infants then would be predicted to have low lung volumes. The aim of this study was to test that hypothesis by comparing the lung volumes of infants who had had mild-moderate BPD with those without BPD of similar postmenstrual age. Lung volumes of 17 infants who had mild-moderate BPD (oxygen dependent beyond 28 days, but not past term) (BPD infants) were compared to those of 17 infants without BPD (non-BPD infants). All were born at less than 33 weeks of gestation and studied at postmenstrual ages of 33 to 39 weeks. Lung volume was assessed by measurement of functional residual capacity (FRC). The BPD infants had lower lung volumes (median 19.1 ml/kg) than the non-BPD infants (median 26.5 ml/kg) (p = 0.0001). The BPD compared to the non-BPD infants were of greater postnatal age (p = 0.0003), born at a lower gestational age (p = 0.0001) and of lighter birthweight (p = 0.0001). Regression analysis, however, demonstrated that lung volume was significantly related to BPD status (p = 0.005), independently of postnatal age, birthweight and gestational age. It is concluded that the lower lung volumes of the infants who had had mild-moderate BPD support the hypothesis that new BPD is associated with poor alveolarisation.

Discharge and aftercare in chronic lung disease of the newborn

This article deals with the discharge planning and continuing care of babies with chronic lung disease of the newborn (CLD), especially those with a continuing oxygen requirement, with some reference to longer term outcome. The pattern of CLD has changed since early descriptions, and the most useful definition for persisting morbidity in a baby with lung disease is a continuing oxygen requirement beyond 36 weeks post-menstrual age. Long-term oxygen therapy to maintain oxygen saturation at a mean of 95% or more and prevent levels below 90% is the cornerstone of management, and with adequate oxygen therapy the excess mortality previously reported in CLD can largely be avoided. Care must be given to the method of assessing oxygen saturation: overnight monitoring using appropriate recording devices is recommended. Exposure to respiratory viruses should be minimized where possible. Metabolic requirements are increased, but if efforts are made to maintain adequate energy input the long-term outlook for catch-up growth in height is good. Respiratory morbidity is increased in early life, but this improves in later childhood, along with lung function and exercise tolerance. Although respiratory symptoms should be treated as they arise, there is no evidence for long-term benefit from any pharmacological intervention in CLD.

Postnatal corticosteroids to treat or prevent chronic lung disease in preterm infants

This statement is intended for health care professionals caring for neonates and young infants. The objectives of this statement are to review the short- and long-term effects of systemic and inhaled postnatal corticosteroids for the prevention or treatment of evolving or established chronic lung disease and to make recommendations for the use of corticosteroids in infants with very low birth weight. The routine use of systemic dexamethasone for the prevention or treatment of chronic lung disease in infants with very low birth weight is not recommended.

Home oxygen status and rehospitalisation and primary care requirements of infants with chronic lung disease

OBJECTIVES

To determine whether the rehospitalisation and primary care requirements of infants with chronic lung disease (CLD) during the first two years after birth were influenced by a requirement for supplementary oxygen after discharge from the neonatal intensive care unit.

METHODS

Review of records from both the hospital and general practitioner.

PATIENTS

235 infants, median gestational age 27 (range 22-31) weeks, 88 of whom were receiving supplementary oxygen when discharged home.

RESULTS

Overall, the infants required a median of 2 (range 0-20) admissions per patient, 8 (0-41) outpatient attendances, 13 (0-76) contacts with the general practitioner, and 17 (0-169) consultations with other primary healthcare professionals. The home oxygen patients required significantly more and longer admissions (p < 0.01) and more outpatient attendances (p < 0.05). The total cost of care per infant of the home oxygen group was greater (p < 0.001); this reflected higher costs for hospital stay (p < 0.01), total inpatient care (p < 0.01), and primary care drugs (p < 0.01).

CONCLUSION

Despite routine use of antenatal steroids and postnatal surfactant, certain patients with CLD, particularly those who receive home oxygen treatment, show high rates of utilisation of health service resources after discharge from the neonatal care unit.

Health care utilisation of infants with chronic lung disease, related to hospitalisation for RSV infection

AIMS

To compare the use of health care resources and associated costs between infants with chronic lung disease (CLD) who had or had not an admission with a proven respiratory syncytial virus (RSV) infection.

METHODS

Review of community care, outpatient attendances, and readmissions in the first two years after birth.

PATIENTS

235 infants (median gestational age 27 weeks) evaluated in four groups: 45 infants with a proven RSV admission (RSV proven); 24 with a probable bronchiolitis admission; 60 with other respiratory admissions; and 106 with non-respiratory or no admissions.

RESULTS

The RSV proven compared to the other groups required more frequent and longer admissions to general paediatric wards and intensive care units, more outpatient attendances and GP consultations for respiratory related disorders, and had a higher total cost of care.

CONCLUSION

RSV hospitalisation in patients with CLD is associated with increased health service utilisation and costs in the first two years after birth.

Randomised trial of fluid restriction in ventilated very low birthweight infants

BACKGROUND

Fluid restriction has been reported to improve survival of infants without chronic lung disease (CLD), but it remains unknown whether it reduces CLD in a population at high risk of CLD routinely exposed to antenatal steroids and postnatal surfactant without increasing other adverse outcomes.

AIM

To investigate the impact of fluid restriction on the outcome of ventilated, very low birthweight infants.

STUDY DESIGN

A randomised trial of two fluid input levels in the perinatal period was performed. A total of 168 ventilated infants (median gestational age 27 weeks (range 23-33)) were randomly assigned to receive standard volumes of fluid (60 ml/kg on day 1 progressing to 150 ml/kg on day 7) or be restricted to about 80% of standard input.

RESULTS

Similar proportions of infants on the two regimens had CLD beyond 28 days (56% v 51%) and 36 weeks post conceptional age (26% v 25%), survived without oxygen dependency at 28 days (31% v 27%) and 36 weeks post conceptional age (58% v 52%), and developed acute renal failure. There were no statistically significant differences between other outcomes, except that fewer of the restricted group (19% v 43%) required postnatal steroids (p < 0.01). In the trial population overall, duration of oxygen dependency related significantly to the colloid (p < 0.01), but not crystalloid, input level; after adjustment for specified covariates, the hazard ratio was 1.07 (95% confidence interval 1.02 to 1.13).

CONCLUSIONS

In ventilated, very low birthweight infants, fluid restriction in the perinatal period neither reduces CLD nor increases other adverse outcomes. Colloid infusion, however, is associated with increased duration of oxygen dependency.

Measuring respiratory outcome

Chronic respiratory morbidity is a common outcome of very premature birth. Infants who are chronically oxygen dependent with an abnormal chest radiograph are described as suffering from chronic lung disease (CLD), and those with the worst abnormalities diagnosed as having bronchopulmonary dysplasia. CLD infants are very likely to be readmitted to hospital during infancy, particularly during a respiratory syncytial virus (RSV) epidemic. Very low birthweight, prematurity and CLD are associated with recurrent respiratory symptoms and lung function abnormalities during the preschool years. These problems are detected even in adolescents who were chronically oxygen dependent after premature birth. Further research to identify effective preventative strategies is urgently required.

The chest radiograph appearances of very premature infants at 36 weeks post-conceptional age

The chest radiograph of very premature infants at 36 weeks post-conceptional age (PCA) was evaluated with regard to the degree of hyperinflation and cardiomegaly, and the presence of fibrosis/interstitial shadowing, cystic elements, air bronchograms and opacification. The evolution of abnormalities was assessed by comparing the radiograph appearance at 36 weeks PCA with that at 28 days post-natal age (PNA). Three scoring systems were used to determine how any abnormalities present could be best quantified to reflect disease severity as determined by chronic dependency upon supplementary oxygen status. Chest radiographs at 36 weeks PCA from 60 infants (median gestational age 26 weeks (range 24-28)) were studied. 47 infants also had radiographs at 28 days PNA. Only three infants had no chest radiograph abnormalities at 36 weeks PCA, although 24 infants were not dependent upon supplementary oxygen. The most common abnormalities were interstitial shadowing and hyperinflation, while cystic elements and cardiomegaly were rare. The radiographic appearance had deteriorated from 28 days PNA to 36 weeks PCA (p < 0.05); more infants at 36 weeks PCA were hyperinflated (p < 0.01). The chest radiograph appearances of infants who were dependent upon supplementary oxygen scored higher than those who were not (p < 0.01) using all three scoring systems. The system that assessed only the presence of interstitial shadowing, cystic elements and hyperinflation had the highest specificity in identifying oxygen dependency beyond 36 weeks PCA and had the highest area under the respective receiver operator characteristic curve. In conclusion, the majority of very immature infants have an abnormal chest radiograph appearance at 36 weeks PCA. The appearance can, however, be meaningfully scored by evaluating only three abnormalities.

Early prediction of chronic oxygen dependency by lung function test results

Chronic oxygen dependency (COD) is a common sequela to very premature birth. Steroid therapy may reduce COD if given within the first 2 weeks, but has important side effects. It is, therefore, crucial to identify an accurate predictor of COD and hence only expose high-risk infants to intervention therapy. The aim of this study was to determine if, within 48 hr of birth, abnormal lung function predicted COD and whether such results performed better than readily available clinical data. Results from 100 consecutive, very low birth-weight infants, median gestation age 28 weeks (range, 24-33), who were ventilated within 6 hr of birth and survived beyond 36 weeks postconceptional age (PCA), were analyzed. Lung volume was assessed by measurement of functional residual capacity (FRC) using a helium gas dilution technique, and compliance was measured using either a passive inflation or an occlusion technique. The maximum peak inflating pressure and inspired oxygen concentration within the first 48 hr were recorded. The infants who remained oxygen-dependent beyond 28 days (n = 58) and 36 weeks PCA (n = 24) differed from the rest in being more immature (P < 0.001), more had a patent ductus arteriosus, and they had both a lower median lung volume (P < 0.001) and lower compliance (P < 0.01) on day 2. An FRC <19 mL/kg and a low gestational age were the most accurate predictors of COD at 28 days. An FRC <19 mL/kg on day 2 remained the best predictor of COD beyond 28 days if only the 50 infants whose gestational age was < or = 28 weeks were considered. We conclude that demonstration of a low lung volume in the first 48 hr helps to identify infants who might benefit from therapy aimed at preventing COD.