Bronchopulmonary dysplasia. Chronic pulmonary disease following neonatal respiratory failure

Risk prediction of bronchopulmonary dysplasia in preterm infants by the nomogram model

Backgrounds and Aims

Bronchopulmonary dysplasia (BPD) has serious immediate and long-term sequelae as well as morbidity and mortality. The objective of this study is to develop a predictive model of BPD for premature infants using clinical maternal and neonatal parameters.

Methods

This single-center retrospective study enrolled 237 cases of premature infants with gestational age less than 32 weeks. The research collected demographic, clinical and laboratory parameters. Univariate logistic regression analysis was carried out to screen the potential risk factors of BPD. Multivariate and LASSO logistic regression analysis was performed to further select variables for the establishment of nomogram models. The discrimination of the model was assessed by C-index. The Hosmer-Lemeshow test was used to assess the calibration of the model.

Results

Multivariate analysis identified maternal age, delivery option, neonatal weight and age, invasive ventilation, and hemoglobin as risk predictors. LASSO analysis selected delivery option, neonatal weight and age, invasive ventilation, hemoglobin and albumin as the risk predictors. Both multivariate (AUC = 0.9051; HL P = 0.6920; C-index = 0.910) and LASSO (AUC = 0.8935; HL P = 0.7796; C-index = 0.899) - based nomograms exhibited ideal discrimination and calibration as confirmed by validation dataset.

Conclusions

The probability of BPD in a premature infant could be effectively predicted by the nomogram model based on the clinical maternal and neonatal parameters. However, the model required external validation using larger samples from multiple medical centers.

Inflammatory Mediators in Tracheal Aspirates of Preterm Infants Participating in a Randomized Trial of Inhaled Nitric Oxide

BACKGROUND

Ventilated preterm infants frequently develop bronchopulmonary dysplasia (BPD) which is associated with elevated inflammatory mediators in their tracheal aspirates (TA). In animal models of BPD, inhaled nitric oxide (iNO) has been shown to reduce lung inflammation, but data for human preterm infants is missing.

METHODS

Within a European multicenter trial of NO inhalation for preterm infants to prevent BPD (EUNO), TA was collected to determine the effects of iNO on pulmonary inflammation. TA was collected from 43 premature infants randomly assigned to receive either iNO or placebo gas (birth weight 530-1230 g, median 800 g, gestational age 24 to 28 2/7 weeks, median 26 weeks). Interleukin (IL)-1β, IL-6, IL-8, transforming growth factor (TGF)-β1, interferon γ-induced protein 10 (IP-10), macrophage inflammatory protein (MIP)-1α, acid sphingomyelinase (ASM), neuropeptide Y and leukotriene B4 were measured in serial TA samples from postnatal day 2 to 14. Furthermore, TA levels of nitrotyrosine and nitrite were determined under iNO therapy.

RESULTS

The TA levels of IP-10, IL-6, IL-8, MIP-1α, IL-1β, ASM and albumin increased with advancing postnatal age in critically ill preterm infants, whereas nitrotyrosine TA levels declined in both, iNO-treated and placebo-treated infants. The iNO treatment generally increased nitrite TA levels, whereas nitrotyrosine TA levels were not affected by iNO treatment. Furthermore, iNO treatment transiently reduced early inflammatory and fibrotic markers associated with BPD development including TGF-β1, IP-10 and IL-8, but induced a delayed increase of ASM TA levels.

CONCLUSION

Treatment with iNO may have played a role in reducing several inflammatory and fibrotic mediators in TA of preterm infants compared to placebo-treated infants. However, survival without BPD was not affected in the main EUNO trial.

TRIAL REGISTRATION

NCT00551642.

Inflammatory Mediators in Tracheal Aspirates of Preterm Infants Participating in a Randomized Trial of Permissive Hypercapnia

BACKGROUND

Ventilator-induced lung injury is considered to be a main factor in the pathogenesis of bronchopulmonary dysplasia (BPD). Optimizing ventilator strategies may reduce respiratory morbidities in preterm infants. Permissive hypercapnia has been suggested to attenuate lung injury. We aimed to determine if a higher PCO₂ target range results in less lung injury compared to the control target range and possibly reduces pro-inflammatory cytokines and acid sphingomyelinase (ASM) in tracheal aspirates (TA), which has not been addressed before.

METHODS

During a multicenter trial of permissive hypercapnia in extremely low birthweight infants (PHELBI), preterm infants (birthweight 400-1,000 g, gestational age 23 0/7-28 6/7 weeks) requiring mechanical ventilation within 24 h of birth were randomly assigned to a high PCO₂ target or a control group. The high target group aimed at PCO₂ values of 55-65, 60-70, and 65-75 mmHg and the control group at PCO₂ values of 40-50, 45-55 and 50-60 mmHg on postnatal days 1-3, 4-6, and 7-14, respectively. TA was analyzed for pro-inflammatory cytokines from postnatal day 2-21. BPD was determined at a postmenstrual age of 36 weeks ± 2 days.

MAIN FINDINGS

Levels of inflammatory cytokines and ASM were similar in both groups: interleukin (IL)-6 (p = 0.14), IL-8 (p = 0.43), IL-10 (p = 0.24), IL-1β (p = 0.11), macrophage inflammatory protein 1α (p = 0.44), albumin (p = 0.41), neuropeptide Y (p = 0.52), leukotriene B₄ (p = 0.11), transforming growth factor-β₁ (p = 0.68), nitrite (p = 0.15), and ASM (p = 0.94). Furthermore, most inflammatory mediators were strongly affected by the age of the infants and increased from postnatal day 2 to 21. BPD or death was observed in 14 out of 62 infants, who were distributed evenly between both groups.

CONCLUSION

The results suggest that high PCO₂ target levels did not result in lower pulmonary inflammatory activity and thus reflect clinical results. This indicates that high PCO₂ target ranges are not effective in reducing ventilator-induced lung injury in preterm infants, as compared to control targets.

TRIAL REGISTRATION

ISRCTN56143743.

Aerobic and lung performance in premature children with and without chronic lung disease of prematurity

OBJECTIVE

This study intended to identify pulmonary and exercise-related effects of chronic lung disease of infancy (CLD) versus prematurity (PRE) without CLD in children 5 to 7 years old who were born prematurely (24-30 weeks of gestation) with very low and extremely low birthweight of 500 to 1500 g (VLBW, ELBW).

SUBJECTS

Seventeen CLD and 14 PRE were compared with 24 term controls (CON). The premature children had no overt manifestations of a neuromuscular disease.

METHODS

Pulmonary function at rest and following exercise, and aerobic exercise performance were measured.

RESULTS

Peak [latin capital V with dot above]O2 and maximal aerobic power were not different among the groups, but O2 uptake at a given mechanical power was higher in the CLD than in PRE and in CON (P < 0.05). At rest, forced vital capacity was significantly lower in CLD than in PRE (P < 0.05) and CON (P < 0.0005), and FEV1 and FEF25-75 were lower in CLD than CON (P < 0.0005 and P < 0.005, respectively). Exercise-induced bronchoconstriction (EIB) was more prevalent among the 2 premature groups (P < 0.05).

CONCLUSIONS

Our children 5 to 7 years old born at VLBW or ELBW, with or without CLD, have some degree of pulmonary dysfunction at rest and following exercise and a higher prevalence of EIB with no reduction in maximal aerobic exercise performance. The findings suggest that the pulmonary limitations are associated with low birthweight even in the absence of CLD. The higher O2 uptake at a given mechanical power in the CLD group may cause early fatigability during prolonged exercise, even when aerobic performance is normal.

Permissive hypercapnia

Although lifesaving, mechanical ventilation can result in lung injury and contribute to the development of bronchopulmonary dysplasia. The most critical determinants of lung injury are tidal volume and end-inspiratory lung volume. Permissive hypercapnia offers to maintain gas exchange with lower tidal volumes and thus decrease lung injury. Further physiologic benefits include improved oxygen delivery and neuroprotection, the latter through both avoidance of accidental hypocapnia, which is associated with a poor neurologic outcome, and direct cellular effects. Clinical trials in adults with acute respiratory failure indicated improved survival and reduced incidence of organ failure in subjects managed with low tidal volumes and permissive hypercapnia. Retrospective studies in low birth weight infants found an association of bronchopulmonary dysplasia with low PaCO(2). Randomized clinical trials of low birth weight infants did not achieve sufficient statistical power to demonstrate a reduction of BPD by permissive hypercapnia, but strong trends indicated the possibility of important benefits without increased adverse events. Herein, we review the mechanisms leading to lung injury, the physiologic effects of hypercapnia, the dangers of hypocapnia, and the available clinical data.

Pulmonary function in children with initial low birth weight

The objective of this analysis was to examine the effect of low birth weight and prematurity on bronchial air-flow, bronchial reactivity, airway symptoms and asthma diagnosis at school age. A cross-sectional epidemiological study was performed in three small towns in the eastern part of Germany on 2470 school children aged 5-14 (89.1% of eligible children). A 78 item questionnaire to determine risk factors at birth and in early childhood was employed. 7.8% of the children were born before completing 38 gestational weeks; 6.6% had a birth weight less than 2500 g. Pulmonary function analysis were done by a mobile plethysmography at the school. There were only weak restrictions in lung volume in term low birth weight (LBW) children (100 ml lower TLC, p = 0.107), and flow (257 ml lower PEFR, p = 0.108), were low. However, bronchial hyper-responsiveness indicated by 292 ml lower FEV1.0 after cold air bronchial provocation, was significantly increased compared to term normal birth weight children (p < 0.001). The effect of LBW was less in older children, only slightly stronger in girls and increased in children mechanically ventilated during the postnatal period. Correspondingly, there was a higher prevalence of diagnosed asthma in term LBW children (OR 1.6, 95%-confidence interval 1.0-2.6), however these were without an increased risk for any allergic sensitization. LBW, therefore, seems to be a risk factor for smaller lungs and hyperreactive airways primarily in term born children, whereas in preterm children the immature bronchial system seems to be recover by school age.

Hyperoxia-induced airway remodeling and pulmonary neuroendocrine cell hyperplasia in the weanling rat

Infants dying with bronchopulmonary dysplasia (BPD) demonstrate increased numbers of pulmonary neuroendocrine cells (PNEC). These infants also possess altered airway epithelial and smooth muscle dimensions reminiscent of oxygen-exposed animals. Because the pathogenesis of BPD involves oxygen toxicity, we hypothesized that chronic hyperoxia would induce both airway remodeling and PNEC hyperplasia. To test this theory, we compared the small airway morphology of 21-d-old rats subsequently exposed to 2 wk of > 95% O2 (Ox; n = 12) with that of normoxic controls (Con; n = 12). In paraffin-embedded sections, airways < 1500 microns cut in cross-section were analyzed using light microscopy and image analysis software. The degree of epithelial and smooth muscle hyperplasia was assessed with proliferating cell nuclear antigen (PCNA). PNEC content was assessed via immunohistochemical staining for calcitonin gene-related peptide (CGRP) and the number of solitary PNEC (PNECsol) and PNEC clusters (neuroepithelial bodies, NEB) counted per section. We found that oxygen exposure increased epithelial and smooth muscle wall thickness (epithelium: Con, 12.3 +/- 1.4 versus Ox, 14.8 +/- 1.4 microns, p < 0.05; smooth muscle: Con, 7.0 +/- 1.0 versus Ox, 10.0 +/- 1.0 microns, p < 0.05). The changes in wall dimensions were accompanied by a 20% increase in fractional PCNA labeling of the epithelium but not the smooth muscle. Both PNECsol and NEB number increased in the Ox group (PNECsol Con, 3.6 +/- 2.6 versus Ox, 6.3 +/- 3.1/100 mm epithelium, p < 0.05; NEB Con, 7.1 +/- 4.0 versus 11.9 +/- 3.6/100 mm epithelium, p < 0.05). These findings document an association between hyperoxia, airway remodeling, and PNEC hyperplasia and imply that PNEC products may contribute to the pathogenesis of oxygen-related pulmonary diseases such as BPD.

A wheezy infant unresponsive to bronchodilators

When infants with recurrent wheezing have a clinical course inconsistent with asthma, an extensive list of alternative diagnoses needs to be considered. Anatomic malformations, such as congenital heart disease, laryngotracheomalacia, and diaphragmatic hernia, should be considered for immediate medical stabilization and early surgical correction. Life-threatening infections such as bacterial epiglottitis, retropharyngeal cellulitis, and viral myocarditis require prompt intervention. A careful history and physical examination reveal important diagnostic clues that, in this case, prompted a directed evaluation to rule out common masqueraders of asthma such as foreign body aspiration, cystic fibrosis, gastroesophageal reflux, viral pneumonitis, or pulmonary tuberculosis. On occasion, such a search is unrevealing and a diagnostic challenge remains. In those situations, judicious use of modern technology to scrutinize anatomic (high-resolution computed tomography) and functional (infant pulmonary function tests) pathology, and justifiable invasive procedures such as bronchoscopy and lung biopsy, uncover the true diagnosis, allowing for optimal management.

[Anesthesia for laparoscopic surgery in pediatrics]

The increasing use of laparoscopic surgery in children is associated with the enlargement of the spectrum of indications to appendicectomy, extramucosal pylorotomy and cure of oesophageal reflux. It is also linked with new problems, mainly due to physiologic modifications elicited by pneumoperitoneum and patient's posture. Although sufficient data are not yet available, the respiratory and cardiovascular modifications are probably similar to those occurring in adults, at least in children more than 4-month-old, as long as the intra-abdominal pressure remains under 15 mmHg. The use of higher intra-abdominal pressures has not been reported in children. In this case, the cardiovascular changes consist mainly in an increase in arterial pressure. In some children, non specific decreases in heart rate and in blood pressure can be observed. The latter can be elicited by a surgical complication, hypovolaemia, head-elevated position or deep anaesthesia. In the newborn and infant under 6 months, intra-abdominal pressures of 15 mmHg or more carry a risk of low cardiac output due to a decrease in contractility and compliance of the left ventricle. In this group of age it is therefore recommended to establish a pressure not higher than 6 mmHg. Moreover, in these very young children, the risk for reopening of the right-left shunts can result in heart insufficiency and systemic gas embolism. Peroperative respiratory changes include an increase in PetCO2 and more rarely a decrease in SaO2. The interpretation of the former depends on the site of gas sampling in the anaesthetic system. It is easily controlled by an increased minute ventilation. Various causes, such as bronchial intubation, inhalation of gastric contents or gas embolism, can decrease SaO2. Contra-indications for laparoscopic surgery include hypovolaemia, heart diseases, increased intracranial pressure and alveolar distension. Therefore newborns are patients at high risk in so far as their foramen ovale or their ductus arteriosus is patent, the pulmonary arterial resistances remain increased and a bronchodysplasia is existing. In some cases a special disease is often associated. As an example recurrent bronchitis or asthma is associated with an oesophageal reflux and a sickle-cell disease in patients with cholelithiasis. These patients require special pre-, per- and postoperative care for prevention of complications. Anaesthesia for laparoscopic surgery does not require a major extension of the usual security regulations. Special attention must be paid to arterial pressure. Therefore end-expiratory concentration of the halogenated anaesthetic agent should not be kept higher than 1.5 times the MAC related to the age during maintenance of anaesthesia.(ABSTRACT TRUNCATED AT 400 WORDS)

Selective dorsal rhizotomy: outcome and complications in treating spastic cerebral palsy

Selective dorsal rhizotomy has shown great promise as a treatment for the functional disabilities and deforming hypertonia of spastic cerebral palsy. At New York University Medical Center, 200 children underwent this procedure between 1986 and 1990. All groups, whether walkers, crawlers, or nonlocomotors, showed improvement in the tone and range of most muscles tested. Half of these patients experienced complications. Thirty-five of these were serious and included bronchospasm (5.5%), aspiration pneumonia (3.5%), urinary retention (7%), and sensory loss (2%). There are, however, clear indications that warn of these complications; monitoring and prophylactic treatment can minimize their effects, and the possibility of such problems is more than offset by the proven benefits of this operative procedure.

Ureaplasma urealyticum in a neonatal intensive care population

The incidence of Ureaplasma colonization at birth and its effect on the development of chronic lung disease (CLD) and on mortality was studied in a neonatal intensive care population. Ureaplasma colonization was associated with a birthweight < 1000 g (odds ratio [OR] 3.45 confidence intervals [CI] 2.13-5.60) and a gestational age < 30 weeks (OR 2.54 CI 1.71-3.79). In a case-controlled study of 112 infants, significant associations with Ureaplasma colonization were maternal pyrexia in labour (n = 38 vs 21; P = 0.015), the requirement for antibiotics in labour (n = 39 vs 16; P = 0.0005) and vaginal delivery (n = 78 vs 58; P = 0.009). Risk factors associated with the development of CLD were birthweight < 1000 g (OR 3.77 CI 2.53-5.62) and delivery by Caesarean section (OR 1.65 CI 1.11-2.43). Within the group delivered by Caesarean section. Ureaplasma colonization was also associated with an increased risk of CLD (OR 1.97 CI 1.08-3.62). Ureaplasma colonization of infants at birth is associated with factors suggestive of maternal chorioamnionitis as well as preterm birth and low birthweight. In infants delivered by Caesarean section, Ureaplasma colonization is associated with an increased risk of chronic lung disease.

The effect of extracorporeal membrane oxygenation on the survival of neonates with high-risk congenital diaphragmatic hernia: 45 cases from a single institution

At The Children's Hospital, Boston (TCH), in the 3 years before extracorporeal membrane oxygenation (ECMO) was available, infants with high-risk congenital diaphragmatic hernia (CDH) had a 47% survival rate. In February 1984, ECMO was introduced and offered to all high-risk CDH infants with a 100% predicted mortality. Since February 1984, 45 infants with high-risk CDH presented to TCH. Twenty-six (58%) were supported with ECMO; 19 (42%) never met the criteria for 100% predicted mortality and were supported with conventional mechanical ventilation (CMV). Overall survival was 49%. Nine (35%) of the 26 ECMO patients survived. Thirteen (68%) of the 19 CMV patients survived. Although there was no change in survival, there was a change in the cause of death. Deaths in the ECMO group were either early (n = 8, secondary to a complication of ECMO or lack of pulmonary improvement) or late (n = 9). The late deaths were infants who were successfully weaned from ECMO, never weaned from CMV, and who died secondary to complications of chronic lung disease.

Longitudinal changes in lung function during the first three years of premature infants with moderate to severe bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a chronic obstructive pulmonary disease of prematurely born infants following prolonged mechanical ventilation and oxygen therapy. Developmental changes in pulmonary function of children with BPD during their early years have been difficult to study. We longitudinally studied maximal expiratory flow-volume curves by the forced deflation technique in 11 infants who had previous tracheostomy with moderate to severe BPD. Patients were classified into: those who were mechanically ventilated for less than 5 months (Group A), and those who were ventilated for 10 or more months (Group B). At 6 months of age, forced vital capacity (FVC) was 28.1 and 25.5 mL/kg in Group A and B, respectively, significantly less than normal (41.8 mL/kg). The maximum expiratory flow at 25% FVC (MEF25) at 6 months of age was 6.9 and 8.1 mL.kg-1.s-1 in Group A and B, respectively, (predicted value, 39.2 mL.kg-1.s-1). FVC reached the normal range by 12 months of age in Group A, but remained lower until 36 months of age in Group B. MEF25 gradually increased in Group A, reaching 18.0 mL.kg-1.s-1 at 36 months of age, whereas in Group B it was severely decreased at the same age (3.5 mL.kg-1.s-1). More than 75% of the patients had airway hyperreactivity at all ages. We have demonstrated that in patients with moderate to severe BPD, vital capacity is moderately decreased, but catches up to normal levels by 36 months of age. In contrast, severe lower airway obstruction persists in all infants, although in those with moderate BPD gradual improvement is seen. These findings suggest that in BPD neither obstruction of the smaller intrathoracic airways nor bronchial hyperreactivity resolves during the first 3 years of life.

Pulmonary neuroendocrine cells. Their secretory products and their potential roles in health and chronic lung disease in infancy

Pulmonary neuroendocrine cells (PNEC) are granulated epithelial cells distributed throughout conducting airways. Among the bioactive products identified within the secretory granules of these cells are potent mitogens and bronchoactive and vasoactive agents. The secretory status of these cells, which are in greatest number in the fetus and newborn, is modulated by neural reflexes and by changes in airway gas composition. The aggregate data suggest roles for PNEC in airway "chemoception" and/or regulation of airway epithelial differentiation. Marked increases in PNEC are observed in bronchopulmonary dysplasia, where airway and alveolar fibrosis, epithelial metaplasia, and airway and vascular smooth muscle hypertrophy contribute to marked pathophysiologic changes in lung function. Considering the biologic effects of PNEC secretory products, particularly gastrin-releasing peptide on airway epithelial cell and fibroblast proliferation, we propose that an increase in PNEC secretory products in the regenerating airway epithelium may contribute to the development of the pathologic alterations in lung structure seen in bronchopulmonary dysplasia. In this proposed scheme, secretion of abnormally large amounts of bronchoactive and vasoactive agents from PNEC (e.g., serotonin, gastrin-releasing peptide) in response to airway hypoxia and hypercapnia may be partially responsible in the genesis of reactive airway disease and pulmonary hypertension seen in this disease.

Tracheobronchial abnormalities in infants with bronchopulmonary dysplasia

Twelve preterm infants with bronchopulmonary dysplasia underwent bronchoscopy to determine if airway abnormalities were contributing to persistent pulmonary problems. Indications for bronchoscopy were persistent atelectasis, lobar hyperinflation, or both on chest radiograph (11 patients), unexplained respiratory distress (three patients), and aspiration of tissuelike material from a tracheostomy (one patient). Bronchoscopy revealed abnormalities of the trachea, bronchi, or both in all infants, including partial or near total airway occlusion by abnormal growth of tissue (10 patients); tracheomalacia, bronchomalacia, or both (three patients); and inspissated secretions (two patients). Seven infants died during initial hospitalization. Tracheobronchial abnormalities should be considered as a cause of persistent pulmonary problems in infants with bronchopulmonary dysplasia.

Oxygen toxicity in the premature baboon with hyaline membrane disease

Immaturity, pulmonary barotrauma, and oxygen toxicity have been implicated in the pathogenesis of bronchopulmonary dysplasia (BPD). Although the physiologic and biochemical consequences of oxygen toxicity have been described in newborn and adult animals, there have been no controlled observations in prematures. We compared the physiologic and morphologic effects of prolonged hyperoxia with those of clinically appropriate oxygen in premature baboons with hyaline membrane disease (HMD) supported with conventional positive pressure ventilation and continuous distending airway pressure (PPV/PEEP). Twenty-one premature baboons were delivered at 140 days gestation, intubated and resuscitated, and supported with PPV/PEEP and standard NICU techniques for 11 days. The FIO2, PaO2, PaCO2, pHa, ventilator and airway pressures, and blood pressure were intermittently measured and recorded. The physiologic observations could be divided into 3 distinct phases. During Phase 1 (0 to 42 h) there were no significant intergroup differences, and (a/A)PO2 and IO2 (oxygenation index; (a/A)PO2/Paw) remained stable. In Phase 2 (43 to 96 h) there was a rapid improvement in (a/A)PO2 and IO2 in both groups, but the response in the hyperoxic animals was significantly dampened. During Phase 3 (97 to 264 h) there was continued improvement in the "prn" animals, which contrasted with progressive deterioration in those exposed to FIO2 1.0. Five of 11 "prn" and 3 of 10 FIO2 1.0 baboons developed air leaks during Phase 1 or early Phase 2. Four of 10 of the hyperoxic animals died after the late onset of air leak. Pathologic changes of BPD were found in all FIO2 1.0 animals surviving more than 6 days but in none of the "prn" long-term survivors.(ABSTRACT TRUNCATED AT 250 WORDS)

Early onset of airway reactivity in premature infants with bronchopulmonary dysplasia

Pulmonary function during the early development of bronchopulmonary dysplasia (BPD) in premature infants is not well understood. Furthermore, it is not known how early airway reactivity appears in BPD. During a 14-month period we studied 32 infants (mean gestational age, 27.3 wk; mean birth weight, 1.02 kg) with respiratory distress syndrome in whom BPD eventually developed. We obtained maximal expiratory flow-volume (MEFV) curves by manual inflation of the lung followed by forced deflation with a negative pressure on 64 occasions (mean postnatal age, 43.1 days). At each test MEFV curves were obtained in 3 conditions: baseline; after normal saline aerosolization with manual ventilation as a control; and after bronchodilator. Maximal expiratory flow at 25% of FVC (Vmax25) was markedly decreased at baseline and remained decreased after saline control. The FVC also was decreased in both baseline and saline control studies. After bronchodilator there was a marked (p less than 0.001) increase in Vmax25 (+214% above saline control) together with a significant (p less than 0.001) increase in FVC (+21%). Of 23 infants studied after 3 wk of postnatal age, 21 exhibited a more than 30% increase in Vmax25 above control (defined as airway reactivity). The remaining 2 infants were already receiving bronchodilator therapy. The most premature infant with demonstrable airway reactivity was 26 wk postconception, and the youngest was 12 days old. In 13 infants who were studied initially before 3 wk of age, there was a highly significant correlation (r = 0.91 p less than 0.001) between the degree of airway reactivity and the severity of respiratory disease as determined by the duration of ventilator dependence. Airway reactivity may play an important role in the development and severity of BPD.

Perinatal factors and the development of chronic lung disease in preterm infants: a case control study

A case control study of neonates was performed to determine those factors contributing to the development of chronic lung disease (CLD). During the 5 years 1981-84 there were 487 neonatal survivors at gestations of 25-32 weeks; 391 of these developed respiratory failure (oxygen therapy required for more than 6 h). Fifty-six of the latter developed CLD (oxygen therapy required for more than 28 days and a coarse reticular pattern on chest X-ray). These neonates were predominantly of the shortest gestational ages, regardless of the initial chest X-ray diagnosis. Forty-three of these infants with CLD were matched for gestation and initial chest X-ray appearance (respiratory distress syndrome, n = 20; normal, n = 15; non-specific, n = 8) with 42 control infants. The mean duration of oxygen therapy (P less than 0.001), maximum FiO2 (P less than 0.001), incidence (P less than 0.01) and duration of intermittent positive pressure respiration (IPPR; P less than 0.05) and peak IPPR (P less than 0.05) were significantly greater in the CLD group. Mean birthweight (P less than 0.001), arterial cord pH (P less than 0.05) and base excess (P less than 0.05) were significantly lower in the CLD group. Factors that were not statistically significant in the development of CLD included antenatal fetal heart rate abnormality, hypertensive disease of pregnancy, acute intrauterine infection (chorioamnionitis or umbilical vasculitis), administration of antenatal steroids, sex, patent ductus arteriosus and pneumothorax. The association between CLD and ventilator/oxygen therapy is confirmed. Contrary to other reports, male sex, clinical patent ductus arteriosus and pneumothorax were not associated with CLD.