Ethnic origin and lung function of infants born prematurely

Pulmonary Morbidity in Infancy after Exposure to Chorioamnionitis in Late Preterm Infants

RATIONALE

Chorioamnionitis is an important cause of preterm birth, but its impact on postnatal outcomes is understudied.

OBJECTIVES

To evaluate whether fetal exposure to inflammation is associated with adverse pulmonary outcomes at 6 to 12 months' chronological age in infants born moderate to late preterm.

METHODS

Infants born between 32 and 36 weeks' gestational age were prospectively recruited (N = 184). Chorioamnionitis was diagnosed by placenta and umbilical cord histology. Select cytokines were measured in samples of cord blood. Validated pulmonary questionnaires were administered (n = 184), and infant pulmonary function testing was performed (n = 69) between 6 and 12 months' chronological age by the raised volume rapid thoracoabdominal compression technique.

MEASUREMENTS AND MAIN RESULTS

A total of 25% of participants had chorioamnionitis. Although infant pulmonary function testing variables were lower in infants born preterm compared with historical normative data for term infants, there were no differences between infants with chorioamnionitis (n = 20) and those without (n = 49). Boys and black infants had lower infant pulmonary function testing measurements than girls and white infants, respectively. Chorioamnionitis exposure was associated independently with wheeze (odds ratio [OR], 2.08) and respiratory-related physician visits (OR, 3.18) in the first year of life. Infants exposed to severe chorioamnionitis had increased levels of cord blood IL-6 and greater pulmonary morbidity at age 6 to 12 months than those exposed to mild chorioamnionitis. Elevated IL-6 was associated with significantly more respiratory problems (OR, 3.23).

CONCLUSIONS

In infants born moderate or late preterm, elevated cord blood IL-6 and exposure to histologically identified chorioamnionitis was associated with respiratory morbidity during infancy without significant changes in infant pulmonary function testing measurements. Black compared with white and boy compared with girl infants had lower infant pulmonary function testing measurements and worse pulmonary outcomes.

Growth, lung function, and physical activity in schoolchildren who were very-low-birth-weight preterm infants

Objective:

To compare somatic growth, lung function, and level of physical activity in schoolchildren who had been very-low-birth-weight preterm infants (VLBWPIs) or normal-birth-weight full-term infants.

Methods:

We recruited two groups of schoolchildren between 8 and 11 years of age residing in the study catchment area: those who had been VLBWPIs (birth weight < 1,500 g); and those who had been normal-birth-weight full-term infants (controls, birth weight ≥ 2,500 g). Anthropometric and spirometric data were collected from the schoolchildren, who also completed a questionnaire regarding their physical activity. In addition, data regarding the perinatal and neonatal period were collected from the medical records of the VLBWPIs.

Results:

Of the 93 schoolchildren screened, 48 and 45 were in the VLBWPI and control groups, respectively. No significant differences were found between the groups regarding anthropometric characteristics, nutritional status, or pulmonary function. No associations were found between perinatal/neonatal variables and lung function parameters in the VLBWPI group. Although the difference was not significant, the level of physical activity was slightly higher in the VLBWPI group than in the control group.

Conclusions:

Among the schoolchildren evaluated here, neither growth nor lung function appear to have been affected by prematurity birth weight, or level of physical activity.

Impact of ethnicity and extreme prematurity on infant pulmonary function

The impact of birth before 27 completed weeks of gestation on infant pulmonary function (PF) was explored in a multi-ethnic population in comparison to more mature preterm controls (PTC) and healthy fullterm infants. Plethysmographic lung volume (FRCpleth ) and forced expired volume (FEV0.5 ) were obtained at ∼12 months post-term age in 52 extremely preterm (EP) infants (median [range] gestational age [GA]: 26 [23-27] weeks; 40% White mothers; 79% with BPD), 41 PTC (GA:35 [30-36] weeks; 37% White mothers) and 95 fullterm infants (GA:40 [37-42] weeks; 86% White mothers). Using reference equations based on identical equipment and techniques, results were expressed as z-scores to adjust for age, sex and body size. FEV0.5 was significantly lower in EP infants when compared with PTC (mean difference [95% CI]: -1.02[-1.60; -0.44] z-scores, P < 0.001), as was forced vital capacity (FVC) but there were no significant differences in FRCpleth or FEV0.5 /FVC ratio. FEV0.5 , FVC, and FEV0.5 /FVC were significantly lower in both preterm groups when compared with fullterm controls. On multivariable analyses of the combined preterm dataset: FEV0.5 at ∼1 year was 0.11 [0.05; 0.17] z-scores higher/week GA, and 1.28 (0.49; 2.08) z-scores lower in EP infants with prior BPD. Among non-white preterm infants, FEV0.5 was 0.70 (0.17; 1.24) z-scores lower, with similar reductions in FVC, such that there were no ethnic differences in FEV0.5 /FVC. Similar ethnic differences were observed among fullterm infants. These results confirm the negative impact of preterm birth on subsequent lung development, especially following a diagnosis of BPD, and emphasize the importance of taking ethnic background into account when interpreting results during infancy as in older subjects.

Lung function tests in neonates and infants with chronic lung disease: lung and chest-wall mechanics

This is the fifth paper in a review series that summarizes available data and critically discusses the potential role of lung function testing in infants and young children with acute neonatal respiratory disorders and chronic lung disease of infancy (CLDI). This review focuses on respiratory mechanics, including chest-wall and tissue mechanics, obtained in the intensive care setting and in infants during unassisted breathing. Following orientation of the reader to the subject area, we focused comments on areas of enquiry proposed in the introductory paper to this series. The quality of the published literature is reviewed critically with respect to relevant methods, equipment and study design, limitations and strengths of different techniques, and availability and appropriateness of reference data. Recommendations to guide future investigations in this field are provided. Numerous different methods have been used to assess respiratory mechanics with the aims of describing pulmonary status in preterm infants and assessing the effect of therapeutic interventions such as surfactant treatment, antenatal or postnatal steroids, or bronchodilator treatment. Interpretation of many of these studies is limited because lung volume was not measured simultaneously. In addition, populations are not comparable, and the number of infants studied has generally been small. Nevertheless, results appear to support the pathophysiological concept that immaturity of the lung leads to impaired lung function, which may improve with growth and development, irrespective of the diagnosis of chronic lung disease. To fully understand the impact of immaturity on the developing lung, it is unlikely that a single parameter such as respiratory compliance or resistance will accurately describe underlying changes. Assessment of respiratory mechanics will have to be supplemented by assessment of lung volume and airway function. New methods such as the low-frequency forced oscillation technique, which differentiate the tissue and airway components of respiratory mechanics, are likely to require further development before they can be of clinical significance.

Progressive decline in plethysmographic lung volumes in infants: physiology or technology?

During the last 30 years, there has been an unexplained trend toward declining values for plethysmographic assessments of lung volume at functional residual capacity (FRC) in infants. The aim of this study was to compare data collected from healthy infants using contemporary equipment with published reference data and to explore reasons for discrepancies. Lung volumes were measured in 32 healthy infants (age, 4-93 weeks; weight, 3.9-12.4 kg) using a new, commercially available infant plethysmograph. Mean (SD) FRC was 19.6 (3.4) ml/kg (within subject coefficient of variation 3.4 [2.3%]), which was on average 7.0 [3.5] ml/kg and 2.3 [1.2] SD (Z) scores lower than the recently collated reference data from an American Thoracic Society task force. A total of 66% of these healthy infants had a FRC that was below the predicted normal range. Comparison of equipment, software, and protocols with those from previous reports revealed the importance of minimization of dead space and of adequate subtraction of all compressible occluded volume when calculating FRC in infants. These findings emphasize the need to establish reference data for lung function tests in infants that are appropriate for the equipment and protocols in current use.

Forced expiratory flow in uninfected infants and children born to HIV-infected mothers

The Pediatric Pulmonary and Cardiovascular Complications of Vertically Transmitted HIV (P(2)C(2) HIV) Study is a multicenter study examining pulmonary and cardiac outcomes in offspring of HIV-infected mothers. This portion of the P(2)C(2) study tests the hypothesis that infants exposed to, but uninfected by, maternal HIV have normal maximal expiratory flow at functional residual capacity (V'max,(FRC)). We obtained 500 measurements of V'max,(FRC) by rapid thoracic compression in 285 children ages 6-30 mo in five U.S. centers. The data were compared with those from a healthy cohort of children described elsewhere. V'max,(FRC) rose with height in a linear relationship. The slope of the regression line in the exposed infants did not differ statistically from the slope in the comparison group, but the intercept was about 20% lower (p < 0.001). Height and weight were comparable in the two cohorts, and the differences between intercepts persisted after adjusting for birth weight and gestational age. However, maternal HIV infection cannot be assumed to be the cause as the cohorts may have differed in other variables, such as socioeconomic status and frequency of maternal smoking and drug use. Also, measurements varied substantially within and between our five centers, probably in part because of different racial and ethnic distributions. In summary, maternal HIV infection probably has only a modest effect, if any, on maximal expiratory flow at functional residual capacity in uninfected infants.

Prediction of survival for preterm births by weight and gestational age: retrospective population based study

OBJECTIVE

To produce current data on survival of preterm infants.

DESIGN

Retrospective population based study.

SETTING

Trent health region.

SUBJECTS

All European and Asian live births, stillbirths, and late fetal losses from 22 to 32 weeks' gestation, excluding those with major congenital malformations, in women resident in the Trent health region between 1 January 1994 and 31 December 1997.

MAIN OUTCOME MEASURES

Birth weight and gestational age specific survival for both European and Asian infants (a) known to be alive at the onset of labour, and (b) admitted for neonatal care.

RESULTS

738 deaths occurred in 3760 infants born between 22 and 32 weeks' gestation during the study period, giving an overall survival rate of 80.4%. The survival rate for the 3489 (92.8%) infants admitted for neonatal care was 86.6%. For European infants known to be alive at the onset of labour, significant variations in gestation specific survival by birth weight emerged from 24 weeks' gestation: survival ranged from 9% (95% confidence interval 7% to 13%) for infants of birth weight 250-499 g to 21% (16% to 28%) for those of 1000-1249 g. At 27 weeks' gestation, survival ranged from 55% (49% to 61%) for infants of birth weight 500-749 g (below the 10th centile) to 80% (76% to 85%) for those of 1250-1499 g. Infants who were large for dates (>/=27 weeks' gestation) had a slightly reduced, but not significant, predicted survival. Similar survival rates were observed for Asian infants. The odds ratio for the survival of infants from a multiple birth compared with singleton infants was 1.4 (1.1 to 1.8). Survival graphs for infants admitted for neonatal care are presented by sex.

CONCLUSION

Easy to use birth weight and gestational age specific predicted survival graphs for preterm infants facilitate decision making for clinicians and parents. It is important that these graphs are representative, are produced for a geographically defined population, and are not biased towards the outcomes of particular centres. Such graphs, produced in two stages, allow for the changing pattern of survival of infants from the start of the intrapartum period to immediately after admission for neonatal care.

Asthma prevalence and risk factors in selected Head Start sites in Chicago

Prevalence of and risk factors for asthma were examined in 1085 Head Start families at 18 Head Start sites in four high-risk community areas in 1994. A total of 13.9% of the families reported diagnosed asthma in their Head Start child and 18.8% reported that their child wheezed in the last 12 months. A total of 26.9% of respondents reported asthma in the immediate family of the child. Low birth weight (1500-2499 g), very low birth weight (<1500 g), and self-reported exposure to dampness or mold in the last 12 months were significantly associated with self-reported diagnosed asthma (OR = 1.93; 95% CI 1.17-8.73), (OR = 4.5; 95% CI 1.25-16.3), and (OR = 1.94; 95% CI 1.23-3.04), respectively. The young age of the children in Head Start, as well as the high prevalence of asthma in their families, suggest that the Head Start programs offer an unusual opportunity for asthma prevention programs.

Airway resistance and spirometry in children with perinatally acquired human immunodeficiency virus-type 1 infection

Airway resistance was measured by the interrupter technique in 54 children [aged 63.8 months (range: 9.1-131.6 months)], with perinatal human immunodeficiency virus-type 1 (HIV-1) infection and in a control group of 315 gender, height, and race-matched healthy children. In addition, 14 HIV-infected children, aged 75-131 months, had spirometry performed. Resistance was significantly higher in infected children than in controls (0.84 +/- 0.3 vs 0.64 +/- 0.08 kPa x l(-1) x s; t = 9.991; P < 0.0001). Resistance decreased with age in controls (r = -0.95; P < 0.001), but not in infected children (r= -0.22; P = 0.105). Resistance did not correlate with mothers' intravenous drug addiction, perinatal data, T-cell subset numbers, treatment, clinical course, or presence of respiratory complications. Resistance was higher (t = 3.103; P < 0.003) in p24 antigen-positive than in negative children. Thirty-nine children underwent a second evaluation 12.3 months (range 11.1-14 months) after the first. Resistance was higher (t = 3.960; P < 0.0001) at the second evaluation compared to the first. Eight of 14 children had abnormal spirometric measurements. We conclude that perinatal HIV-1 infection is associated with increased airway resistance and often abnormal spirometry. The degree of abnormalities in resistance depends on the duration of the infection rather than on HIV-1-related respiratory complications.