A 15-year survey of chronic lung disease of prematurity

Smoking in the family is most predictive of the development of childhood asthma in preterm babies <30 weeks gestation: Results of the Respiratory Outcomes Study 2 (RESPOS2)

OBJECTIVES

The Respiratory Outcomes Study 2 (RESPOS2) investigated the relationship between neonatal outcomes (specifically, chronic lung disease [CLD]) and environmental factors on the development of asthma and atopic outcomes at primary school age for preterm babies (PBs) <30 weeks gestational age (GA).

METHODS

The study included all surviving PBs <30 weeks GA admitted to the Neonatal Intensive Care Unit at Canberra Hospital, Australian Capital Territory between 2007 and 2009. Parents were sent a questionnaire regarding asthma and atopy symptoms when the PBs were aged 5-7 years old. Data were compared based on CLD status.

RESULTS

There were 103 PBs included in the study with a 68.9% response rate to the respiratory questionnaire (71/103). Of these PBs, 15/71 (21.1%) received a diagnosis of CLD. There were no significant differences with regards to asthma, hay fever or eczema in PBs either with or without CLD. The most significant predictor for the development of asthma was smoking in the family (Odds Ratio [OR]: 11.66, 95% Confidence Interval [CI]: 2.01-67.56) with a trend toward significance for family history of asthma (OR: 3.83, 95% CI: 0.85-17.25).

CONCLUSION

The RESPOS2 has confirmed previous reports that CLD in PBs <30 weeks GA is not associated with the development of childhood asthma, hay fever or eczema. In our group of PBs, the strongest predictor of the development of asthma was smoking in the family.

Respiratory outcomes study (RESPOS) for preterm infants at primary school age

OBJECTIVE

Pulmonary function abnormalities and hospital re-admissions in survivors of neonatal lung disease remain highly prevalent. The respiratory outcomes study (RESPOS) aimed to investigate the respiratory and associated atopy outcomes in preterm infants <30 weeks gestational age (GA) and/or birth-weight (BWt) <1000 g at primary school age, and to compare these outcomes between infants with and without chronic lung disease (CLD).

METHODS

In the RESPOS 92 parents of preterm infants admitted to the Neonatal unit in Canberra Hospital between 1/1/2001 and 31/12/2003 were sent a questionnaire regarding their respiratory, atopy management and follow-up.

RESULTS

Fifty-three parents responded, including 28 preterm infants who had CLD and 25 who had no CLD. The gestational age was significantly lower in the CLD group compared to the non-CLD group [26.9 (26.3-27.5) CLD and 28.6 (28.3-29.0) non-CLD] [weeks [95% confidence interval (CI)]], as was the birth weight [973 (877.4-1068.8) CLD versus 1221 (1135.0-1307.0) non-CLD] [g (CI)]. CLD infants compared to non-CLD infants were significantly more likely to have been: given surfactant, ventilated and on oxygen at 28 days and 36 weeks. These neonates were also more likely to have: been discharged from the neonatal unit on oxygen, exhibit a history of PDA or sepsis and to have a current paediatrician. However, despite these differences, there was no significant difference in the proportion of asthma or atopic disease between the two groups.

CONCLUSIONS

The RESPOS could not demonstrate respiratory and/or atopy differences between the CLD and the non-CLD groups at primary school age.

Early changes in respiratory compliance and resistance during the development of bronchopulmonary dysplasia in the era of surfactant therapy

Despite the availability of surfactant treatment, extremely low birth weight (ELBW) infants continue to be at high risk of developing bronchopulmonray dysplasia (BPD). Evidence suggests that pathologic changes occur within the first few days of life. We hypothesized that the changes in early respiratory system compliance and resistance in ELBW infants with or without hyaline membrane disease (HMD) would correlate with BPD severity and aid in its prediction. Respiratory system compliance (Crs) and resistance (Rrs) were measured at the end of weeks 1, 2, 3, and 4 in 46 infants weighing 1,000 g or less at birth, using the single breath airway occlusion method. Twenty-four infants had HMD and 22 did not. Fifteen infants with and 10 infants without HMD developed BPD with radiological changes and oxygen needs at 28 days. Twelve BPD infants required supplemental oxygen beyond 36 weeks, defined as chronic lung disease (CLD). Irrespective of whether the infant initially had HMD, the week 1 results showed that infants who subsequently developed BPD had a significantly higher respiratory system resistance than those who did not (P = 0.0014). Though week 1 compliance was lower, it was not statistical significant. Multiple logistic models consisting of simple neonatal variables and week 1 respiratory mechanics showed that Rrs was independently associated with subsequent BPD (P = 0.026) and CLD (P = 0.016), while compliance was not. Prediction of CLD improved with the inclusion of Rrs results as compared to prediction using clinical variables alone. Throughout the 4-week study period, Rrs was significantly higher in BPD infants than in those without BPD, and resistance was particularly abnormal in those who had CLD or subsequently required corticosteroid treatment. These observations provide rationale for interventions to prevent BPD within the first week of life. Respiratory mechanics measurements could be useful in the assessment of therapeutics in the current surfactant era.

Role of ureaplasma urealyticum in lung disease of prematurity

AIM

To examine the role of Ureaplasma urealyticum colonisation or infection in neonatal lung disease.

METHODS

Endotracheal aspirates from ventilated infants less than 28 weeks of gestation were cultured for U urealyticum and outcomes compared in infants with positive and negative cultures.

RESULTS

U urealyticum was isolated from aspirates of 39 of 143 (27%) infants. Respiratory distress syndrome (RDS) occurred significantly less often in colonised, than in non-colonised infants (p=0.002). Multivariate logistic regression analysis showed that in singleton infants, ureaplasma colonisation was the only independent (negative) predictor of RDS (OR 0.36; p=0. 02). Both gestational age (OR 0.46; p=0.006) and isolation of U urealyticum (OR 3.0; p=0.05) were independent predictors of chronic lung disease (CLD), as defined by requirement for supplemental oxygen at 36 weeks of gestational age. Multiple gestation was also a major independent predictor of RDS and CLD.

CONCLUSIONS

Colonisation or infection with ureaplasma apparently protects premature infants against the development of RDS (suggesting intrauterine infection). However, in singleton infants, it predisposes to development of CLD, independently of gestational age. Treatment of affected infants after birth is unlikely to significantly improve the outcome and methods are required to identify and treat the women with intrauterine ureaplasmal infection, before preterm delivery occurs.

Cytological changes in endotracheal aspirates associated with chronic lung disease

Endotracheal aspirates taken serially from mechanically ventilated premature infants born at < 28 weeks gestation between March 1992 and August 1993 were studied to determine whether early cytological changes would be a good predictor of lung damage in infants who develop chronic lung disease (CLD). CLD was diagnosed if the infant required supplemental oxygen at 36 weeks corrected gestational age. Fifty-five infants were enrolled in the study, five died and of the 50 infants remaining, 17 (34%) developed CLD. The infants with CLD had a significantly lower gestation (25.5 +/- 1.8 (mean +/- 1 SD) versus 26.2 +/- 0.9 weeks, p < 0.05), significantly more required surfactant (14/17 vs. 16/33, p < 0.05) and were ventilated for a significantly longer period (43.3 +/- 26.6 vs. 19.3 +/- 12.8 days, p < 0.0001). Endotracheal aspirate cytology showed that infants with CLD had significantly more degenerated columnar epithelial cells on day 3 (p = 0.001), and more neutrophils on day 10 (p = 0.007). Though not predictive of CLD, cytological changes consistent with bronchial epithelial and pulmonary damage followed by an inflammatory response were found in the tracheal aspirates of a group of infants clinically diagnosed with CLD.

Chronic oxygen dependency in infants born at 24-32 weeks' gestation: the role of antenatal and neonatal factors

OBJECTIVES

To study the incidence of chronic oxygen dependency (COD) among ventilated survivors born at 24-32 weeks gestation from 1986 to 1994 and to identify antenatal and neonatal factors that may have changed with time; and to identify antenatal and neonatal factors that could contribute to the development of COD in infants born at 24-32 weeks gestation using a case control model.

METHODOLOGY

Infants born at 24-32 weeks gestation in one tertiary referral centre between 1986 and 1994 and admitted to the neonatal intensive care unit for respiratory support were studied. Data accumulated prospectively since 1986 in survivors of ventilation were analyzed to identify antenatal and neonatal factors that could have changed with time. The cohort of infants who developed COD were matched for gestation and time of birth with a control group of infants who did not have COD. Significant factors that could have contributed to the development of COD were identified using forward logistic regression analysis.

RESULTS

The number of mothers admitted for threatened premature labour (TPL), and pregnancy induced hypertension decreased with time while the use of antenatal steroids and maternal antibiotics increased. More infants were delivered by Caesarean section during the later years. There was an increase in neonatal septicaemia with time while there were decreases in hyaline membrane disease, pneumothorax, pulmonary interstitial emphysema, use of high peak inspiratory pressure (PIP) and high inspired oxygen. The incidence of COD decreased. The case controlled study revealed a significant positive association between COD and male gender, birthweight less than the 10th percentile for gestation, PIP over 30 cm H2O, septicaemia and significant patent ductus arteriosus (PDA) requiring indomethacin. There was a negative association with TPL.

CONCLUSIONS

Further decrease in COD can be achieved only if septicaemia, PDA and the use of high PIP can be avoided. The most effective way of reducing the incidence of COD is by reducing the incidence of prematurity.