Bronchopulmonary dysplasia: early diagnosis, prophylaxis, and treatment

An epidemiological analysis of retinopathy of prematurity over 10 years

PURPOSE

To analyze the incidence of retinopathy of prematurity (ROP) in a single neonatal intensive care unit over 10 years to clarify its ROP profile and how it was modified by advances in neonatal care.

METHODS

Epidemiological data related to incidence and severity of ROP were collected over 10 years. Premature infants with a birth weight of less than 1,500 g underwent a screening fundus examination and ROP was defined according to the International Classification of Retinopathy of Prematurity. The survival rates and incidence of ROP were calculated and compared for two consecutive time periods (1995-1999 vs 2000-2004), dividing the study population into subgroups according to their birth weights and gestational age.

RESULTS

Data of 607 preterm infants were collected. Survival rate significantly improved in the later time period (from 76.6% to 88.6%). The incidence of total, severe, and surgical ROP did not differ overall in the two time periods despite changes in survival rate, although some changes occurred in the most immature infants over time.

CONCLUSION

Increased survival of immature infants seemed to correlate with an increased risk for severe ROP and need for retinal ablation therapy, even if the incidence did not reach statistical significance.

Adrenocortical function and chronic lung disease of pre-maturity: an unresolved problem?

The aim of this study was to investigate the relationship between adrenocortical function and chronic lung disease (CLD) of pre-term infants. Plasma F and ACTH were measured at 7, 14, 21 and 28 days of life in 25 pre-term infants with gestational age < or = 32 weeks and birth weight < or = 1,250 g. Fourteen infants developed CLD (CLD group) and 11 recovered without CLD (NOCLD group). Response to ACTH stimulation was tested on days 7 and 28. The results show that at the 7th day of life plasma F and ACTH levels were similar in the NOCLD and CLD group. CLD group had significantly higher plasma F and ACTH concentrations at the 14th (p=0.006 for F and p=0.020 for ACTH) and at the 21st (p=0.008 for F and p=0.024 for ACTH) day of life, while no significant differences were detected at the 28th day of life. The response to ACTH stimulation test was similar between the NOCLD and CLD group. These data demonstrate the lack of any significant association between adrenal insufficiency and CLD and discourage the use of baseline or stimulated plasma F levels to predict the development of CLD in pre-term infants.

Cardiac adverse effects of early dexamethasone treatment in preterm infants: a randomized clinical trial

This study evaluates the effects of early administration of dexamethasone on left ventricle dimensions and their clinical significance in preterm infants. Fifty preterm infants with birth weight < or = 1250 g and gestational age < or = 30 weeks were randomly assigned after 72 hours of life to the dexamethasone group (n = 25) or to the control group (n = 25). The treated infants received dexamethasone intravenously from the 4th day of life for 7 days (0.5 mg/kg/day for the first 3 days, 0.25 mg/kg/day for the next 3 days, and 0.125 mg/kg/day for the 7th day). Serial echocardiographic measurements of end systolic interventricular septum thickness, end diastolic interventricular septum thickness, end systolic left ventricle posterior wall thickness, end diastolic left ventricle posterior wall thickness, left ventricle end diastolic diameter, and left ventricle end systolic diameter were taken before starting dexamethasone, on days 3 and 7 of treatment, 7 days after the interruption of treatment, and at the 28th day of life. Five infants of each group were excluded by the final analysis because of the lack of a complete cardiac evaluation, leaving 20 treated and 20 control infants. Infants receiving dexamethasone had a significantly larger increase in mean septal and left posterior wall thickness during the treatment and 7 days after the dexamethasone weaning. The mean left ventricle diameter of treated infants was significantly lower than that of control infants from the 7th day of treatment to the 28th day of life. Four neonates (20%) in the dexamethasone group developed left ventricular myocardial hypertrophy without left ventricle outflow tract obstruction, showing signs of decreased cardiac output and ischemic changes on ECG. The daily fluid intake was increased to 200 ml/kg to ensure an adequate preload volume, and the complete resolution of left ventricle hypertrophy was obtained within the 2nd to 3rd week after dexamethasone weaning. Preterm infants receiving an early (< 96 hours of life) short course of dexamethasone develop a left ventricular myocardial hypertrophy that can be symptomatic and clinically significant. Preterm infants included in future studies with the goal to find the minimum dose and duration of dexamethasone treatment should be strictly monitored echocardiographically for this side effect.

Effect of inhaled budesonide therapy on lung function in schoolchildren born preterm

We investigated the effect of inhaled glucocorticoid (GC) on bronchial obstruction and on bronchial lability in schoolchildren born preterm. Twenty-one children with bronchial obstruction, increased responsiveness to a beta2-agonist, and/or increased diurnal variation in peak expiratory flow (PEF) were selected for an open longitudinal study of the value of inhaled GC. None of these children had an earlier diagnosis of asthma or current GC treatment. Eighteen children with median (range) birth weight 1025 (640-1600) g and gestational age 28 (24-35) weeks, age at study 10.1 (7.7-13) years, were treated with inhaled budesonide in initially high (0.8 mg m(-2) day(-1) for 1 month) and subsequently lower dose (0.4 mg m(-2) day(-1) for 3 months). Daily symptom scores were recorded. Spirometric values were measured in the clinic at the beginning and end of each treatment period. At home, children used a data storage spirometer. After treatment with budesonide for 4 months, spirometric values in the clinic did not significantly change. The median forced expiratory volume in 1 sec (FEV1) was 74% of predicted both at entry and after budesonide treatment. However, the median number of > or = 20% diurnal change in PEF values at home decreased during treatment. According to the present study, inhaled budesonide for 4 months had no significant effect on basic lung function but may decrease bronchial lability in schoolchildren born preterm.

Awake daytime oximetry measurements in the management of infants with chronic lung disease

OBJECTIVE

To assess the value of 1-h daytime awake oximetry as a means of weaning oxygen flows in infants with oxygen dependent chronic lung disease.

METHODS

A cohort study of oxygen dependent infants enrolled in a 3-month period. One hour of awake oximetry data were compared with equal time periods defined within a polysomnographic study and at the same oxygen flow rate. Sensitivity results were derived from the decision to wean oxygen to a lower flow or air.

RESULTS

Twenty-two infants were enrolled and 27 studies were performed. The infants that could be weaned had an awake median of mean oxygen saturations of 97% and spent 14% of the time < or = 95% but only 2% < or = 92%, while for those not weaned, the awake median of mean oxygen saturations was 94% with 43% of their time < or = 95% and 26.8% < or = 92% saturation.

CONCLUSIONS

Daytime oximetry can predict the outcome of polysomnography with a sensitivity of 100% and a specificity of 65%, and could be used to wean oxygen or as a screening tool for polysomnographic studies in infants with chronic lung disease provided there are reasonably long periods of monitoring and mean oxygen saturations above 95%.

Evaluation of criteria for chronic lung disease in surviving very low birth weight infants. Newborn Lung Project

Criteria in common use for the diagnosis of chronic lung disease of prematurity or bronchopulmonary dysplasia in the neonatal period have not been sufficiently compared and validated against indicators of later respiratory complications. In this study of all 680 infants < or = 1500 gm birth weight admitted to six perinatal centers August 1, 1988, to July 31, 1990, 524 were alive and had no major congenital anomalies at 5 years old. Of 419 who had given permission to release their names and addresses, 272 were located and participated in a follow-up study. The following diagnostic criteria for bronchopulmonary dysplasia and chronic lung disease of prematurity were used during the initial hospitalization: (1) use of supplemental oxygen on day 30 of life, (2) a comprehensive bronchopulmonary dysplasia severity score applied at 25 to 35 days of life developed by a clinician panel to adjust for practice variation in ventilatory support and blood gases, (3) use of supplemental oxygen on day 30 of life with radiographic evidence consistent with bronchopulmonary dysplasia between days 25 and 35 of life, (4) radiographic evidence consistent with bronchopulmonary dysplasia alone, and (5) use of supplemental oxygen at 36 weeks' postconceptional age. These criteria were assessed against use of bronchodilators or steroids during the first 2 years of life, diagnosis of asthma, and hospitalizations for respiratory causes up to age 5. Although all criteria were significantly associated with all the outcomes, radiographic evidence was most predictive. These results indicate that, during a period when 21% of neonates were exposed to antenatal steroids, 24% received surfactant and 9% received postnatal corticosteroids, radiographic evidence was more predictive of long-term respiratory outcome than other commonly used criteria.

Bronchopulmonary dysplasia in infants with respiratory distress syndrome in a developing country: a prospective single centre-based study

The aim of this prospective study was to determine the incidence of bronchopulmonary dysplasia (BPD) in and the outcome of neonates ventilated for respiratory distress syndrome (RDS). The study was conducted in a developing country prior to the use of surfactant replacement therapy and the results are compared to published reports from the developed world. BPD was defined as oxygen dependency beyond day 28 of life. The incidence of BPD over a 9-month-period was 8.2% of all neonates requiring ventilation (n = 169) and 41% (n = 38) of neonates ventilated for RDS (n = 92). Of those neonates who developed BPD, 26% were still being ventilated on day 28. Of the infants, 21 (55%) developed type 1 BPD and 17 (45%) type 2 BPD. There was no statistical difference in the severity of lung disease on any of the study days between type 1 and type 2 BPD although neonates with type 2 BPD required assisted ventilation and supplemental oxygen for a longer period: 30 versus 12 days and 95 versus 49 days, respectively. Of those neonates who developed BPD, 8 (21%) died prior to discharge from hospital and a further 5 infants (17%) died subsequent to discharge. Of the latter five, three died from treatable causes (gastroenteritis n = 2, pneumonia n = 1). Of the 25 (83%) children seen at follow up, 68% were developing normally, 20% were classified as having suspect development and 12% had developed cerebral palsy at corrected postnatal ages of 12-24 months. None of the results differed significantly from those of neonates being ventilated in the developed world, except for the causes of post-discharge deaths.

CONCLUSION

Health services providing ventilation for neonates in the developing world will have to take the needs of children with BPD into account when planning a neonatal service which should include among others a widely available and easily accessible primary health care system.

Sonographic prediction of chronic lung disease in the premature undergoing mechanical ventilation

The aims of the study are to investigate the possible role of ultrasound (US) of the chest in predicting the development of chronic lung disease (CLD) in patients with hyaline membrane disease (HMD) and to determine the optimal age for the sonographic examination. One hundred and five consecutive prematures undergoing mechanical ventilation were prospectively studied by US of the chest. The US examinations were performed at birth and at least once a week until discharge from the neonatal unit. The sonographic patterns observed behind the diaphragm and their evolutions were recorded and correlated with the clinical and radiological data at day 28, which corresponds to the currently accepted limit for determining the presence of CLD. CLD is currently defined as oxygen dependency on day 28 with radiographic abnormalities. A diffuse retrodiaphragmatic hyperechogenicity was observed in all the patients with HMD. The hyperechogenicity resolved completely in patients with an uncomplicated clinical evolution. In contrast, in patients with CLD the hyperechogenicity resolved only partially, resulting in less diffuse and less extensive hyperechogenicity. Day 18 was the earliest day where the persistence of the abnormal retrodiaphragmatic hyperechogenicity was observed in 100% of the patients presenting CLD at day 28. At that time, 95.2% of the patients without abnormal hyperechogenicity showed uncomplicated evolution and no CLD. US can be a useful diagnostic tool to determine the occurrence of CLD and to predict as early as day 18 the prematures at risk for the disease.

Antiviral therapy in neonatal chronic lung disease

Infants born prematurely who develop chronic lung disease frequently suffer acute respiratory deteriorations. In a randomized trial, we assessed if treatment of such relapses with the antiviral agent Ribavirin increased the speed of recovery and improved lung function at follow-up. During the acute deterioration and its treatment, respiratory rate and requirement for respiratory support were recorded. Once discharged from hospital, respiratory symptoms and admissions for chest-related illnesses were documented. Infants were recalled at 6 months of age for lung function measurements. Forty-four infants (23 given Ribavirin), median gestational age of 26 weeks, completed the trial and had lung function measurements at 6 months. Although viral infections were identified in relatively few patients, the interim analysis demonstrated Ribavirin administration for 3 days was associated with a greater reduction in respiratory rate and inspired oxygen concentration (P < 0.02). At follow-up, there was no significant difference between groups in the proportion of infants who were symptomatic or required re-admission to hospital for chest-related illnesses; the Ribavirin group, however, had lower airways resistance (P < 0.01) and higher specific conductance (P < 0.02). We conclude that antiviral therapy seems to speed the rate of recovery from acute respiratory deteriorations seen in preterm infants with chronic lung disease; this is associated with improved lung function, but not lower respiratory morbidity, at follow-up.

Perinatal death as a consequence of fetal stabbing: was it murder?

At 22 weeks gestation, a fetus received a stab wound to the abdomen when the mother was subjected to a knife attack. Premature labour followed 2.5 weeks later. The baby received full intensive care, but died at 4.5 months of age from complications directly related to the premature birth. The person who committed the assault was indicted with murder of the infant according to the precept of transferred malice. In the absence of any clear legal precedent, the judge ruled that the indictment was not consistent with the principles of criminal law, since the malice directed towards the mother could not be regarded as being transferred to the fetus. This was because the wounding of a non-viable fetus with death following 4 months later did not amount to a deliberate killing, and in addition, it was not the intention of the Defendant at the time of the stabbing to kill the infant.

Chest radiograph appearance at 24 h of age--prediction of chronic oxygen dependency

Chronic oxygen dependence is associated with immaturity, male sex and low birthweight, but amongst that high risk group further criteria are necessary to predict those most at risk. We previously developed a chest radiograph scoring system which, when used at 1 month of age, proved useful in predicting chronic oxygen dependency at 36 weeks post-conceptional age (PCA). We have now assessed whether the scoring system, if applied at 24 h of age, added predictive value to readily available demographic and ventilatory data. 50 infants, birthweight less than 1200 g and ventilated from birth, were examined. They had a median gestational age of 27 weeks (range 23-34), birthweight of 886 g (range 470-1172) and chest radiograph score of 7 (range 2-13). Univariate analysis revealed that oxygen dependency at 28 days and 36 weeks PCA was significantly associated with low gestational age, male sex and high ventilatory requirements, in addition to a high chest radiograph score. Stepwise regression analysis, however, demonstrated that a high chest radiograph score predicted oxygen dependence at 28 days, independent of immaturity, low birthweight, male sex and high ventilatory requirements. A chest radiograph score of more than 5 rendered an infant four times more likely to be oxygen dependent at 28 days than those with lower scores. We conclude the chest radiograph appearance at 24 h of age could be used as a criterion to institute interventional strategies aimed at reducing chronic oxygen dependence.

Relationship between lung function results in the first year of life and respiratory morbidity in early childhood in patients born prematurely

The relationship between lung function results at 6 months and 1 year of age to respiratory symptoms in the first 3 years of life in prematurely born population has been determined. In 88 infants (median gestational age, 29 weeks) thoracic gas volume (TGV) and airway resistance (R(aw)) was measured and specific conductance (SGaw) calculated at 6 months and 1 year of age. During 3 years of prospective follow-up neither TGV measured at either 6 months or 1 year, nor R(aw) and SGaw at 6 months, differed significantly between infants who were asymptomatic or symptomatic. At 1 year, however, R(aw) and SGaw were significantly higher and lower respectively in patients who were symptomatic than in those who were asymptomatic in any of the 3 years. An elevated R(aw) (> or = 50 cmH2O/L/s) measured at 1 year, but not at 6 months, was associated with a significant relative risk of symptoms in the first, second, and third year of life. We conclude that in prematurely born patients an abnormal airway resistance at 1 year predicts symptoms in early childhood.

Influence of lung function and reflex activity on the success of patient-triggered ventilation

The influence of lung function and reflex activity on the success of patient-triggered ventilation (PTV) has been determined. Lung function was assessed by measurement of compliance using a single breath technique. Reflex activity was assessed by measurement of the strength of Hering Breuer reflex indicated by the degree of prolongation of expiration following end inspiratory occlusion. PTV was considered to have failed if the infant became apnoeic or required an increased level of respiratory support. Twenty premature infants (median gestational age 29 weeks) in the recovery stage of respiratory distress, were studied at a median postnatal age of 2.5 days. PTV failed ultimately in six infants, although compliance of the respiratory system of that group did not differ significantly from the rest of the cohort, their Hering Breuer reflex was significantly weaker (P < 0.01). In addition, the infants in whom PTV failed were significantly more immature and of lower birthweight (P < 0.01) compared with those in whom it succeeded. We conclude that failure of PTV is more likely in immature infants who have a weak Hering Breuer reflex.

Pathophysiology and treatment of bronchopulmonary dysplasia. Current issues

Although much has been learned about BPD in the 25 years since its initial description, BPD remains a significant complication of prematurity. Substantial advances into the understanding of its pathophysiology and pathogenesis have been made and are reflected in new therapeutic interventions. Much current research is directed towards the role of prevention, exploring new approaches for accelerating lung maturation with combined maternal steroid and thyrotropin releasing hormone (TRH) therapy, surfactant replacement therapy, high frequency oscillatory ventilation, antioxidant administration, manipulation of endogenous antioxidants, and other pharmacologic strategies to minimize lung injury. The impact of other technologies, such as synchronized intermittent mandatory ventilation, perfluorocarbon (liquid) ventilation, and perhaps inhaled nitric oxide therapy may become additional parts of the clinical regimen for some cases of severe neonatal respiratory failure. Less information is available on mechanisms which can hasten lung healing. Ongoing studies of inflammatory products, growth factors, and cytokines may lead to new therapies which will favorably influence the fibroproliferative phase of disease. In the meantime, the medical and social impact of BPD continues to remain a significant problem not only during infancy but also throughout life. Mildred Stahlman, MD, recently wrote that (a)s sanguine as the future looks for surfactant therapy, it may leave us with more very low-birth weight infants who survive, whose potential for normal pulmonary growth and development is unknown, and whose very immature organ systems, besides the lung, are still susceptible to metabolic, neurologic, and other problems. As more survivors are reaching young adulthood, respiratory and neurodevelopmental complications persist. Thus, as advances in the care of the premature newborn with respiratory distress have dramatically improved survival, the management of chronic lung disease and related problems remains a continuing challenge.

Comparison of helium dilution and nitrogen washout measurements of functional residual capacity in premature infants

Comparison has been made of measurements of functional residue capacity (FRC) by a helium gas dilution (He) and a nitrogen washout (N2) technique. Twenty infants (median gestational age, 29.5 weeks) were studied at a median postnatal age of 25 days. No infant was oxygen dependent. The coefficient of repeatability of FRC (He) was 6.4 mL/kg and of FRC (N2), 6.3 mL/kg. The coefficient of repeatability of the two methods combined was 13.8 mL/kg. In 10 infants the results of two techniques differed by more than 20% of the mean FRC; those infants were born at a significantly earlier gestation than the rest of the cohort (P < 0.01). We conclude that, except in very immature infants, techniques for measuring FRC (He) and FRC (N2) yield reproducible and comparable results in convalescent premature infants.

Reduction in the risk of bronchopulmonary dysplasia from 1980-1990: results of a multivariate logistic regression analysis

A retrospective analysis (1980-1990) of normally formed low birthweight (< 2500 g) infants surviving to at least 28 days following intermittent positive pressure ventilation (IPPV) for longer than 12 h was performed. Bronchopulmonary dysplasia (BPD) was defined as oxygen dependency at 28 days with characteristic radiographic findings. Logistic regression analysis of risk factors, before and after the initiation of IPPV was performed on 412 infants. Decreasing birth weight (BW) and gestational age (GA) were associated with an increased risk of BPD. When controlled for these variables, predictive factors prior to IPPV were gender, age at IPPV, respiratory diagnosis, and year of birth. Following IPPV, duration of peak inspiratory pressure > 25 cm H2O, duration of fraction of inspired oxygen (FiO2) > 0.60 (DO2), maximum peak inspiratory pressure (MPIP), maximum FiO2, patent ductus arteriosus, bacteraemia and either pneumothorax or pulmonary interstitial emphysema were associated with an increased risk of BPD. Adjusting for BW and GA, there was a significant reduction in BPD risk from 1980-1990 (relative odds of 0.88 for each year compared to the previous year). This trend could be largely accounted for by decreases in MPIP and DO2 during the study period. Surfactant treatment was not independently associated with a significant change in the risk of BPD. Based on this analysis, we developed a scoring system for predicting the risk of BPD in the neonatal period which we evaluated in a random sample of infants. This predicted infants at risk of BPD with a sensitivity of 65% and a specificity of 88%.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of chronic lung disease on blood pressure levels at follow up

Thirteen preterm infants (median gestational age 28 weeks) who had developed neonatal chronic lung disease (CLD) and 13 gender- and gestational age-matched controls (without CLD) were prospectively followed. The infants were seen at monthly intervals for 6 months. At each attendance the infants were examined and their blood pressure (BP) measured using a noninvasive Doppler technique. No infant developed symptoms related to hypertension and there were no significant differences in their BP levels at follow up. Our results suggests significant BP elevation is uncommon following neonatal CLD.

Vitamin A levels at birth of high risk preterm infants

Vitamin A levels were measured shortly after birth in preterm infants at high risk of developing chronic lung disease (CLD). Eleven infants, median gestational age 24 weeks, developed CLD. Their results were compared to 11 infants who, although they required mechanical ventilation for at least 48 hours, did not develop CLD. The median gestational age of this latter group was 30 weeks (range 27-35). The median vitamin A level of the infants who developed CLD was 0.62 umol/l (range 0.41-0.95), which was significantly higher than the median level of the infants who did not develop CLD, which was 0.36 umol/l (range 0.13-0.89). We conclude preterm infants who develop CLD are not predisposed to develop that complication by low vitamin A levels at birth.

Blood pressure levels at follow-up of infants with and without chronic lung disease

Hypertension at follow-up is a recognized association of chronic lung disease (CLD) in premature infants. The aim of this study was to assess the timing of maximum effect of the presence of CLD on blood pressure levels and the duration of its effect. Eighteen infants with CLD and 36 without CLD were recruited into the study. Measurements of systolic blood pressure were made using a Doppler technique, when the infants attended for routine premature baby follow-up. Comparison of the two groups' blood pressure revealed the infants with CLD had significantly higher blood pressure levels at 2-3 months (p < 0.001) and 4-5 months (p < 0.05) but not at 6-7 or 8-9 months. We conclude that differences in blood pressure levels between infants with and without CLD are maximum at 2-3 months and that the association of CLD and elevated blood pressure levels is a temporary one.

Vitamin A status in preterm and term infants at birth

Vitamin A status was determined in infants born at term or prematurely to assess if vitamin A levels at birth were related to gestational age. Vitamin A levels were measured in cord blood samples from 13 infants born at term and in blood samples obtained within two hours of birth in 26 preterm infants (median gestational age 31 weeks, range 27-35). None of the preterm infants developed chronic lung disease. The vitamin A levels of the term infants (median 0.71 mumol/l, range 0.34 to 1.27) were significantly higher than those of infants born preterm (median 0.35 mumol/l, range 0.12 to 1.22), p < 0.01. Vitamin A levels correlated significantly with gestational age (vitamin A level = 0.024 gestational age (weeks) -0.23, r = 0.39, p < 0.02. We thus conclude that gestational age must be taken into account when interpreting vitamin A levels.

Longitudinal assessment of infant lung function following pregnancies complicated by prolonged and preterm rupture of the membranes

Serial measurements of functional residual capacity (FRC) were made in 22 infants (median gestational age at delivery 32 weeks, range 25-40) during the first 2 years of life. All infants had been delivered from pregnancies complicated by prolonged and preterm rupture of the membranes (PPROM) of at least 1 week in duration. The onset of membrane rupture was at a median of 26 weeks (range 15-32) with a median duration of 5.5 weeks (range 1-21). The mean FRC at all postnatal ages studied: 25 ml/kg at 6 and 12 months and 24 ml/kg at 18 and 24 months did not differ significantly from the control population (mean 24 ml/kg). There was, however, a wider scatter of results in the study population: four infants born very preterm consistently had FRC results above the 95% confidence limits of the controls but only two infants had FRCs consistently below this range. These results suggest PPROM may not be an invariable association of abnormal antenatal lung growth.

Effect of dexamethasone on blood pressure--relationship to postnatal age

The relationship of the change in blood pressure levels of very preterm infants treated with dexamethasone to postnatal age was investigated. Sixteen infants, median gestational age 26 weeks (range 23-33) (early treatment group), and 15 infants, median gestational age 26 weeks (range 24-32) (late treatment group) were recruited. Dexamethasone was administered at a median postnatal age of 17 days (range 3-26) and 50 days (range 29-112), respectively. The systolic blood pressure at the start of treatment and the maximum systolic blood pressure achieved during therapy were both significantly lower (P less than 0.01) in the early rather than the late treatment group. The change in blood pressure, however, that is, from the pre-treatment level to the maximum systolic blood pressure achieved during therapy, was similar in the two groups (median 38 mmHg, range 23-59 early treatment group and median 34 mmHg, range 16-66 late treatment group). We conclude that, even in the first 4 weeks of life, dexamethasone can cause a marked elevation of systolic blood pressure. As a consequence, regardless of the postnatal age at which dexamethasone is administered, blood pressure levels must be measured regularly.

Positive end expiratory pressure in acute and chronic respiratory distress

The optimum level of positive end expiratory pressure (PEEP) was determined in 16 infants with respiratory distress syndrome (median gestational age 29 weeks, median postnatal age 1 day) and in 16 infants with chronic respiratory distress (median gestational age 25 weeks, median postnatal age 15 days). All infants were studied at a PEEP sequence of 3, 0, 3, 6, and 3 cm H2O, all other ventilator parameters being kept constant. Each PEEP level was maintained for 20 minutes and at the end of each period arterial blood gas was checked. During acute respiratory distress syndrome there were no significant changes in oxygenation but arterial carbon dioxide tension (PaCO2) significantly decreased from a mean of 4.93 kPa at 3 cm H2O to 4.40 kPa at 0 cm H2O and increased to a mean of 5.87 kPa at 6 cm H2O. In the infants with chronic respiratory distress, oxygenation fell from a mean of 8.66 kPa at 3 cm H2O to 6.40 kPa at 0 cm H2O and improved at 6 cm H2O to a mean of 10.50 kPa. There were no significant changes in PaCO2. We conclude that addition of PEEP, up to 6 cm H2O, may be useful even after the first week of life. High levels of PEEP, however, have previously been reported, in certain infants, to result in circulatory disturbance. It is therefore important to assess the use of 6 cm H2O PEEP in a controlled study of longer term clinical outcome.

Tumour necrosis factor in the bronchoalveolar secretions of infants with the respiratory distress syndrome and the effect of dexamethasone treatment

BACKGROUND

Tumour necrosis factor alpha may contribute to the lung damage that occurs in the adult respiratory distress syndrome. Whether it occurs in the lungs of preterm infants with respiratory distress syndrome is unknown.

METHODS

Tumour necrosis factor alpha concentrations in the bronchopulmonary secretions of 28 ventilated preterm infants were determined by the enzyme linked immunosorbent assay.

RESULTS

Concentrations were low in the first three days of life, being undetectable in nine of the 20 infants whose bronchopulmonary secretions were sampled. From day 4 concentrations were increased and detectable in all but two of 14 infants. Similar concentrations were found in samples taken on days 8-20 and 21-40. Greater mean concentrations occurred in those infants requiring oxygen for a long time. In six infants who received dexamethasone treatment for prolonged ventilator dependency treatment was associated with a reduction in tumour necrosis factor alpha concentrations.

CONCLUSIONS

Tumour necrosis factor may contribute to the neonatal respiratory distress syndrome, as suggested for the adult respiratory distress syndrome. The therapeutic effects of dexamethasone treatment in neonatal respiratory distress syndrome may be mediated, at least in part, by reduced production of pulmonary tumour necrosis factor.

Ipratropium bromide for symptomatic preterm infants

Twelve preterm infants, median gestational age 31.5 weeks, were entered into a randomised, placebo-controlled trial of bronchodilator therapy. Their postnatal age was a median of 17.5 months and all suffered from recurrent respiratory symptoms. The infants received either inhaled placebo or 40 micrograms of ipratropium bromide (active therapy) three times a day utilising a coffee cup as a spacer device. Each therapy was administered for 2 weeks. The symptom score during the active period was reduced by 59% compared to the placebo period (P less than 0.01) and this was associated with 38% improvement in lung function in the active period compared to a 20% change in functional residual capacity over the placebo period (P less than 0.01). We conclude inhaled ipratropium bromide appears to be an effective treatment for symptomatic infants at follow up.

Relationship of symptoms to lung function abnormalities in preterm infants at follow-up

Recurrent respiratory symptoms are common in preterm infants in the first 2 years of life. The aim of this study was to determine the lung function abnormalities associated with such symptoms. Forty preterm infants, with a median gestational age of 29 weeks were studied at a median postnatal age of 12 months. Twenty-two suffered from recurrent symptoms, defined as wheezing and/or coughing on at least 4 days per week over the previous month. Lung function was assessed by measurement of functional residual capacity (FRC), using a helium gas dilution technique, and airway resistance (Raw) and thoracic gas volume (TGV) plethysmographically. No significant difference was found in TGV between symptomatic and asymptomatic infants, but the median FRC was lower (P less than 0.01), Raw higher (P less than 0.01), and FRC:TGV ratio lower (P less than 0.001) in the symptomatic infants. These lung function abnormalities in the symptomatic infants are suggestive of gas trapping.