Pulmonary testing using peak flow meters of very low birth weight children born in the perisurfactant era and school controls at age 10 years

Impaired lung function and associated risk factors in children born prematurely: a systematic review and meta-analysis

BACKGROUND

Immature lung development and respiratory morbidity place preterm-born children at high risk of long-term pulmonary sequelae. This systematic review and meta-analysis aims to quantify lung function in preterm-born children and identify risk factors for a compromised lung function.

METHODS

We searched MEDLINE, Embase, Cochrane Library, Web of Science and Scopus for relevant studies published on preterm cohorts born since 1990. Studies comparing forced expiratory volume in 1 s (FEV1) in preterm-born children aged ≥5 years to term-born controls or normative data were included. Study quality was assessed using the Newcastle-Ottawa Scale for cohort studies. Standardised mean differences in FEV1 and secondary spirometry outcomes per study were pooled using meta-analysis. The impact of different demographic and neonatal variables on studies' FEV1 effect sizes was investigated by meta-regression analyses. Certainty of evidence was assessed using the Grading of Recommendations, Assessment, Development, and Evaluations framework.

RESULTS

We identified 42 studies with unique cohorts including 4743 preterm children and 9843 controls. Median gestational age in the studies was 28.0 weeks and age at assessment ranged from 6.7 to 16.7 years. Preterm children had lower FEV1 than controls (-0.58 sd, 95% CI -0.69- -0.47 sd, p<0.001) resulting in a relative risk of 2.9 (95% CI 2.4-3.4) for abnormal outcome, with high certainty of evidence. FEV1 was significantly associated with gestational age, birthweight, bronchopulmonary dysplasia and invasive mechanical ventilation in univariate meta-regression analyses (R2=36-96%).

CONCLUSION

This systematic review shows robust evidence of impaired lung function in preterm-born children with a high certainty of evidence.

Increasing airway obstruction through life following bronchopulmonary dysplasia: a meta-analysis

Background

Few studies exist investigating lung function trajectories of those born preterm; however growing evidence suggests some individuals experience increasing airway obstruction throughout life. Here we use the studies identified in a recent systematic review to provide the first meta-analysis investigating the impact of preterm birth on airway obstruction measured by the forced expiratory volume in 1 s (FEV1) to forced vital capacity (FVC) ratio.

Methods

Cohorts were included for analysis if they reported FEV1/FVC in survivors of preterm birth (<37 weeks' gestation) and control populations born at term. Meta-analysis was performed using a random effect model, expressed as standardised mean difference (SMD). Meta-regression was conducted using age and birth year as moderators.

Results

55 cohorts were eligible, 35 of which defined groups with bronchopulmonary dysplasia (BPD). Compared to control populations born at term, lower values of FEV1/FVC were seen in all individuals born preterm (SMD -0.56), with greater differences seen in those with BPD (SMD -0.87) than those without BPD (SMD -0.45). Meta-regression identified age as a significant predictor of FEV1/FVC in those with BPD with the FEV1/FVC ratio moving -0.04 sds away from the term control population for every year of increased age.

Conclusions

Survivors of preterm birth have significantly increased airway obstruction compared to those born at term with larger differences in those with BPD. Increased age is associated with a decline in FEV1/FVC values suggesting increased airway obstruction over the life course.

Geographical Differences and Temporal Improvements in Forced Expiratory Volume in 1 Second of Preterm-Born Children: A Systematic Review and Meta-analysis

Importance

Although preterm birth is associated with later deficits in lung function, there is a paucity of information on geographical differences and whether improvements occur over time, especially after surfactant was introduced.

Objective

To determine deficits in percentage predicted forced expiratory volume in 1 second (%FEV1) in preterm-born study participants, including those with bronchopulmonary dysplasia (BPD) in infancy, when compared with term-born control groups.

Data Sources

Eight databases searched up to December 2021.

Study Selection

Studies reporting spirometry for preterm-born participants with or without a term-born control group were identified.

Data Extraction and Synthesis

Data were extracted and quality assessed by 1 reviewer and checked by another. Data were pooled using random-effects models and analyzed using Review Manager and the R metafor package.

Main Outcomes and Measures

Deficits in %FEV1 between preterm-born and term groups. Associations between deficits in %FEV1 and year of birth, age, introduction of surfactant therapy, and geographical region of birth and residence were also assessed.

Results

From 16 856 titles, 685 full articles were screened: 86 with and without term-born control groups were included. Fifty studies with term controls were combined with the 36 studies from our previous systematic review, including 7094 preterm-born and 17 700 term-born participants. Of these studies, 45 included preterm-born children without BPD, 29 reported on BPD28 (supplemental oxygen dependency at 28 days), 26 reported on BPD36 (supplemental oxygen dependency at 36 weeks' postmenstrual age), and 86 included preterm-born participants. Compared with the term-born group, the group of all preterm-born participants (all preterm) had deficits of %FEV1 of -9.2%; those without BPD had deficits of -5.8%, and those with BPD had deficits of approximately -16% regardless of whether they had BPD28 or BPD36. As year of birth increased, there was a statistically significant narrowing of the difference in mean %FEV1 between the preterm- and term-born groups for the all preterm group and the 3 BPD groups but not for the preterm-born group without BPD. For the all BPD group, when compared with Scandinavia, North America and western Europe had deficits of -5.5% (95% CI, -10.7 to -0.3; P = .04) and -4.1% (95% CI, -8.8 to 0.5; P = .08), respectively.

Conclusions and Relevance

Values for the measure %FEV1 were reduced in preterm-born survivors. There were improvements in %FEV1 over recent years, but geographical region had an association with later %FEV1 for the BPD groups.

Intra-breath oscillometry for the evaluation of lung function in children and adolescents with a history of preterm birth

Objective:

To assess respiratory system impedance (Z_rs) and spirometric parameters in children and adolescents with and without a history of preterm birth.

Methods:

We evaluated a sample of 51 subjects between 11 and 14 years of age: 35 who had a history of preterm birth (preterm group) and 16 who had been born at term (full-term group). Lung function was measured by spirometry, spectral oscillometry, and intra-breath oscillometry.

Results:

Neither spirometry nor spectral oscillometry revealed any statistically significant differences between the preterm and full-term groups. However, intra-breath oscillometry demonstrated significant differences between the two groups in terms of the change in resistance, reactance at end-inspiration, and the change in reactance (p < 0.05 for all).

Conclusions:

Our findings suggest that abnormalities in Z_rs persist in children and adolescents with a history of preterm birth and that intra-breath oscillometry is more sensitive than is spectral oscillometry. Larger studies are needed in order to validate these findings and to explore the impact that birth weight and gestational age at birth have on Z_rs later in life.

Increased aortic stiffness and elevated blood pressure in response to exercise in adult survivors of prematurity

Objectives

Adults born prematurely have an increased risk of early heart failure. The impact of prematurity on left and right ventricular function has been well documented, but little is known about the impact on the systemic vasculature. The goals of this study were to measure aortic stiffness and the blood pressure response to physiological stressors; in particular, normoxic and hypoxic exercise.

Methods

Preterm participants (n = 10) were recruited from the Newborn Lung Project Cohort and matched with term‐born, age‐matched subjects (n = 12). Aortic pulse wave velocity was derived from the brachial arterial waveform and the heart rate and blood pressure responses to incremental exercise in normoxia (21% O₂) or hypoxia (12% O₂) were evaluated.

Results

Aortic pulse wave velocity was higher in the preterm groups. Additionally, heart rate, systolic blood pressure, and pulse pressure were higher throughout the normoxic exercise bout, consistent with higher conduit artery stiffness. Hypoxic exercise caused a decline in diastolic pressure in this group, but not in term‐born controls.

Conclusions

In this first report of the blood pressure response to exercise in adults born prematurely, we found exercise‐induced hypertension relative to a term‐born control group that is associated with increased large artery stiffness. These experiments performed in hypoxia reveal abnormalities in vascular function in adult survivors of prematurity that may further deteriorate as this population ages.

Cardio-respiratory, oxidative stress and acute mountain sickness responses to normobaric and hypobaric hypoxia in prematurely born adults

PURPOSE

We compared the effects of hypobaric and normobaric hypoxia on select cardio-respiratory responses, oxidative stress and acute mountain sickness (AMS) severity in prematurely born individuals, known to exhibit blunted hypoxic ventilatory response.

METHODS

Sixteen prematurely born but otherwise healthy males underwent two 8-h hypoxic exposures under: (1) hypobaric hypoxic [HH; terrestrial altitude 3840 m; P_iO₂:90.2 (0.5) mmHg; BP: 478 (2) mmHg] and (2) normobaric hypoxic [NH; P_iO₂:90.6 (0.9) mmHg; F_iO₂:0.142 (0.001)] condition. Resting values of capillary oxyhemoglobin saturation (SpO₂), heart rate (HR) and blood pressure were measured before and every 2 h during the exposures. Ventilatory responses and middle cerebral artery blood flow velocity (MCAv) were assessed at rest and during submaximal cycling before and at 4 and 8 h. Plasmatic levels of selected oxidative stress and antioxidant markers and AMS symptoms were also determined at these time points.

RESULTS

HH resulted in significantly lower resting (P = 0.010) and exercise (P = 0.004) SpO₂ as compared to NH with no significant differences in the ventilatory parameters, HR or blood pressure. No significant differences between conditions were found in resting or exercising MCAv and measured oxidative stress markers. Significantly lower values of ferric-reducing antioxidant power (P = 0.037) were observed during HH as opposed to NH. AMS severity was higher at 8 h compared to baseline (P = 0.002) with no significant differences between conditions.

CONCLUSION

These data suggest that, in prematurely born adults, 8-h exposure to hypobaric, as opposed to normobaric hypoxia, provokes greater reductions in systemic oxygenation and antioxidant capacity. Further studies investigating prolonged hypobaric exposures in this population are warranted.

REGISTRATION

NCT02780908 (ClinicalTrials.gov).

Carotid body size measured by computed tomographic angiography in individuals born prematurely

PURPOSE

We tested the hypothesis that the carotid bodies would be smaller in individuals born prematurely or exposed to perinatal oxygen therapy when compared individuals born full term that did not receive oxygen therapy.

METHODS

A retrospective chart review was conducted on patients who underwent head/neck computed tomography angiography (CTA) at the Mayo Clinic between 10 and 40 years of age (n = 2503). Patients were identified as premature ( < 38 weeks) or receiving perinatal oxygen therapy by physician completion or billing codes (n = 16 premature and n = 7 receiving oxygen). Widest axial measurements of the carotid body images captured during the CTA were performed.

RESULTS

Carotid body visualization was possible in 43% of patients and 52% of age, sex, and body mass index (BMI)-matched controls but only 17% of juvenile preterm subjects (p = .07). Of the carotid bodies that could be visualized, widest axial measurements of the carotid bodies in individuals born prematurely (n = 7, 34 ± 4 weeks gestation, birth weight: 2460 ± 454 g; average size: 2.5 ± 0.2 cm) or individuals exposed to perinatal oxygen therapy (n = 3, 38 ± 2 weeks gestation, Average size: 2.2 ± 0.1 cm) were not different when compared to controls (2.3 ± 0.2 cm and 2.3 ± 0.2 cm, respectively, p > 0.05).

CONCLUSIONS

Carotid body size, as measured using CTA, is not smaller in adults born prematurely or exposed to perinatal oxygen therapy when compared to sex, age, and BMI-matched controls. However, carotid body visualization was lower in juvenile premature patients. The decreased ability to visualize the carotid bodies in these individuals may be a result of their prematurity.

How best to capture the respiratory consequences of prematurity?

Chronic respiratory morbidity is a common complication of premature birth, generally defined by the presence of bronchopulmonary dysplasia, both clinically and in trials of respiratory therapies. However, recent data have highlighted that bronchopulmonary dysplasia does not correlate with chronic respiratory morbidity in older children born preterm. Longitudinally evaluating pulmonary morbidity from early life through to childhood provides a more rational method of defining the continuum of chronic respiratory morbidity of prematurity, and offers new insights into the efficacy of neonatal respiratory interventions. The changing nature of preterm lung disease suggests that a multimodal approach using dynamic lung function assessment will be needed to assess the efficacy of a neonatal respiratory therapy and predict the long-term respiratory consequences of premature birth. Our aim is to review the literature regarding the long-term respiratory outcomes of neonatal respiratory strategies, the difficulties of assessing dynamic lung function in infants, and potential new solutions.

Better measures are needed to predict chronic respiratory morbidity in survivors born prematurely http://ow.ly/1L3n30ihq9C

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.

Pulmonary Gas Exchange and Exercise Capacity in Adults Born Preterm

RATIONALE

Preterm birth, and its often-required medical interventions, can result in respiratory and gas exchange deficits into childhood. However, the long-term sequelae into adulthood are not well understood.

OBJECTIVES

To determine exercise capacity and pulmonary gas exchange efficiency during exercise in adult survivors of preterm birth.

METHODS

Preterm (n = 14), very low birth weight (<1,500 g) adults (20-23 yr) and term-born, age-matched control subjects (n = 16) performed incremental exercise on a cycle ergometer to volitional exhaustion while breathing one of two oxygen concentrations: normoxia (fraction of inspired oxygen, 0.21) or hypoxia (fraction of inspired oxygen, 0.12).

MEASUREMENTS AND MAIN RESULTS

Ventilation, mixed expired gases, arterial blood gases, power output, and oxygen consumption were measured during rest and exercise. We calculated the alveolar-to-arterial oxygen difference to determine pulmonary gas exchange efficiency. Preterm subjects had lower power output at volitional exhaustion than did control subjects in normoxia (150 ± 10 vs. 180 ± 10 W; P = 0.01), despite similar normoxic oxygen consumption. However, during hypoxic exercise, there was no difference in power output at volitional exhaustion between the two groups (116 ± 10 vs. 135 ± 10 W; P = 0.11). Preterm subjects also exhibited a more acidotic, acid-base balance throughout exercise compared with control subjects. In contrast to other studies, adults born preterm, as a group developed a wider alveolar-to-arterial oxygen difference and lower PaO2 than did control subjects during normoxic but not hypoxic exercise.

CONCLUSIONS

This study demonstrates that pulmonary gas exchange efficiency is lower in some adult survivors of preterm birth during exercise compared with control subjects. The gas exchange inefficiency, when present, is accompanied by low arterial blood oxygen tension. Preterm subjects also exhibit reduced power output. Overall, our findings suggest potential long-term consequences of extreme preterm birth and very low birth weight on cardiopulmonary function.

Household environment and behavioral determinants of respiratory tract infection in infants and young children in northern Bangladesh

OBJECTIVES

Respiratory tract infections (RTI) are one of the leading causes of under-five mortality in Bangladesh. Solid biomass fuels are the main source of domestic fuel used for cooking across Bangladesh, leading to smoke and pollution exposure in the home. This article aims to identify risk factors for RTI among children aged under five years in Bangladesh with a particular focus on the household environment, fuel use, and cooking practices.

METHODS

A cross-sectional household-health survey was carried out in 321 households in northern Bangladesh. The survey included care-giver interviews on cooking practices, child health, and household behaviors during cooking. Health status of the youngest child (under five years) from each household was recorded through maternal interviews, medical diagnosis, and assessment of biomarkers (C-reactive protein (CRP), hemoglobin) from finger-prick blood samples. Anthropometric status (weight, height) was recorded.

RESULTS

Children who spent ≥30 minutes/day within 5 feet of the stove during cooking had a significantly increased risk of moderate/severe RTI compared with children spending <30 minutes/day close to the stove (OR = 2.15, 95%CI: 1.20-3.86, P = 0.01), independent of socio-economic status (SES), biomass fuel type (wood, dung, plant-derived, compressed rice husks), child age, anthropometric status, CRP and hemoglobin.

CONCLUSIONS

In environments with a heavy reliance on solid biomass fuels, the amount of time a child spends near the stove during cooking may be an important risk for RTI. These novel findings from Bangladesh warrant further investigation of mother-infant behaviors during cooking in relation to child health, to ascertain whether the association is likely to be causal.

Respiratory outcomes of the surfactant positive pressure and oximetry randomized trial (SUPPORT)

OBJECTIVE

To explore the early childhood pulmonary outcomes of infants who participated in the National Institute of Child Health and Human Development's Surfactant Positive Airway Pressure and Pulse Oximetry Randomized Trial (SUPPORT), using a factorial design that randomized extremely preterm infants to lower vs higher oxygen saturation targets and delivery room continuous positive airway pressure (CPAP) vs intubation/surfactant.

STUDY DESIGN

The Breathing Outcomes Study, a prospective secondary study to the Surfactant Positive Airway Pressure and Pulse Oximetry Randomized Trial, assessed respiratory morbidity at 6-month intervals from hospital discharge to 18-22 months corrected age (CA). Two prespecified primary outcomes-wheezing more than twice per week during the worst 2-week period and cough longer than 3 days without a cold-were compared for each randomized intervention.

RESULTS

One or more interviews were completed for 918 of the 922 eligible infants. The incidences of wheezing and cough were 47.9% and 31.0%, respectively, and did not differ between the study arms of either randomized intervention. Infants randomized to lower vs higher oxygen saturation targets had a similar risk of death or respiratory morbidity (except for croup and treatment with oxygen or diuretics at home). Infants randomized to CPAP vs intubation/surfactant had fewer episodes of wheezing without a cold (28.9% vs 36.5%; P<.05), respiratory illnesses diagnosed by a doctor (47.7% vs 55.2%; P<.05), and physician or emergency room visits for breathing problems (68.0% vs 72.9%; P<.05) by 18-22 months CA.

CONCLUSION

Treatment with early CPAP rather than intubation/surfactant is associated with less respiratory morbidity by 18-22 months CA. Longitudinal assessment of pulmonary morbidity is necessary to fully evaluate the potential benefits of respiratory interventions for neonates.

Functional capacity during exercise in very-low-birth-weight premature children

OBJECTIVES

The functional capacity of children born prematurely with very-low-birth weight was compared with that of children born at full-term using the six-minute walk test (6MWT) and the ten-minutes shuttle walk test (10MSWT). The factors affecting walking distance were analyzed.

METHODS

A cross-sectional study was conducted with two groups of children aged 6-9 years, matched by sex and age. One group included children born before 37 weeks of gestation weighing <1,500 g and the second group included children born at term. Both groups were submitted to the 6MWT and 10MWST, performed on the same day with an interval of 20 min between tests and the sequence of the tests was randomized, by sealed-envelope technique. Physiological parameters were measured at the beginning and end of each test. The walking distance and factors affecting the walking distance were analyzed.

RESULTS

Thirty-seven children born prematurely and 37 born at term were studied. The premature children walked shorter distances in the 6MWT (480.9 ± 80.5 m vs. 518.3 ± 51.8 m, P = 0.010) than term children, and both groups walked similar distances in the 10MSWT (391.5 ± 99.0 m vs. 406.1 ± 79.2 m, P = 0.487). By multiple linear regression analysis, adjusted for confounders, walking distance was associated with height (OR: 3.6) and oxygen dependency at 28 days (OR: -67.7) in the 6MWT (P < 0.001) and with height (OR: 4.9) and oxygen dependency at 28 days (OR: -91.0) in the 10MSWT (P < 0.001).

CONCLUSION

In conclusion, this study suggests that children born prematurely with very low birth weight, especially those who had bronchopulmonary dysplasia present limited functional capacity during exercise.

Lung function outcome at school age in very low birth weight children

OBJECTIVE

The aim of this study was to assess pulmonary function and its predictors in very low birth weight (birth weight ≤1,500 g) children (VLBWc) with or without bronchopulmonary dysplasia (BPD), born at gestational age ≤32 weeks at a single tertiary center during 1996-1999, after the introduction of surfactant therapy.

METHODS

Of the 120 surviving VLBW children, 48 (40%) VLBWc (22 with prior-BPD) at age 8.5 ± 1.0 years and 46 age-matched controls (8.8 ± 1.4 years) born at term, underwent lung function study.

RESULTS

Adjusted values (z-score) of forced vital capacity (z-FVC), forced expiratory volume in 1 sec (z-FEV1), forced expiratory flow 25-75% (z-FEF25-75), carbon monoxide lung diffusion capacity (z-DLCO), and DLCO/alveolar volume (z-DLCO/VA) were significantly lower than controls (mean difference, 95% CI: -1.35, -1.81 to -0.90, P < 0.001; -1.31, -1.73 to -0.90, P < 0.001; -0.87, -1.29 to -0.46, P < 0.001; -0.98, -1.72 to -0.23, P < 0.001; -0.70, -1.22 to -0.18, P < 0.05; respectively). Residual volume (z-RV) and RV/total lung capacity (RV/TLC) ratio (%) were significantly higher in VLBWc than controls (mean difference, 95% CI: 1.06, 0.44 to 1.68, P < 0.001; 9.54%, 5.73 to 13.3%, P < 0.001; respectively). No differences were found in lung function between VLBWc (no-BPD vs. BPD) with the exception of a significant higher RV/TLC ratio in the BPD-subgroup (mean difference, 95% CI: 7.0%, 0.4 to 13%, P = 0.03). Lung function abnormalities were found in 30 (63%) VLBWc with evidence of airway obstruction and diffusing capacity impairment. A weak relationship was observed between gestational age with z-FVC (r = 0.30, P = 0.04), birth weight with z-FEV1 (r = 0.30, P = 0.04) and RV/TLC ratio (r = -0.49, P = 0.001). The duration of oxygen treatment correlated negatively with the z-DLCO/Va (r = -0.5, P = 0.02). No differences were found in FeNO levels between VLBWc and controls.

CONCLUSION

VLBWc at school age showed lung function abnormalities characterized by airway obstruction, hyperinflation, and diffusion impairment. Neonatal lung damage together with preterm birth may play a role in worsening the functional respiratory outcome.

Ventilatory control in infants, children, and adults with bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD), or chronic lung disease of prematurity, occurs in ~30% of preterm infants (15,000 per year) and is associated with a clinical history of mechanical ventilation and/or high inspired oxygen at birth. Here, we describe changes in ventilatory control that exist in patients with BPD, including alterations in chemoreceptor function, respiratory muscle function, and suprapontine control. Because dysfunction in ventilatory control frequently revealed when O2 supply and CO2 elimination are challenged, we provide this information in the context of four important metabolic stressors: stresses: exercise, sleep, hypoxia, and lung disease, with a primary focus on studies of human infants, children, and adults. As a secondary goal, we also identify three key areas of future research and describe the benefits and challenges of longitudinal human studies using well-defined patient cohorts.

Encouraging pulmonary outcome for surviving, neurologically intact, extremely premature infants in the postsurfactant era

OBJECTIVE

The aim of this study was to determine the long-term pulmonary outcome of extreme prematurity at a single tertiary-care center from 1997 to 2001 in the postsurfactant era.

METHODS

We assessed symptoms, exhaled nitric oxide, spirometry, methacholine challenge (provocative concentration of methacholine required to decrease FEV₁ by 20% [PC(20)]), lung volumes, diffusion, and cardiopulmonary exercise tolerance.

RESULTS

Of 279 infants born, 192 survived to discharge, and 79 of these developed bronchopulmonary dysplasia (BPD) (65 mild, 12 moderate, two severe). We studied a subgroup of 53 neurologically intact preterm subjects aged 10 ± 1.5 years (28 with BPD [born, 26.2 ± 1.4 weeks; birth weight, 821 ± 164 g] and 25 without BPD [born, 27.2 ± 1 weeks; birth weight, 1,050 ± 181 g]) and compared them with 23 term control subjects. Of the BPD cases, 21 were mild, seven were moderate, and none was severe; 77.4% of subjects received antenatal steroids, and 83% received postnatal surfactant. Sixty percent of the preterm subjects wheezed at age < 2 years compared with 13% of the control subjects (P < .001), but only 13% wheezed in the past year compared with 0% of control subjects (not significant). For preterm and control subjects, respectively (mean ± SD), FEV₁ % predicted was 85% ± 10% and 94% ± 10% (P < .001), with limited reversibility; residual volume/total lung capacity was 29.3% ± 5.5% and 25% ± 8% (P < .05); diffusing capacity/alveolar volume was 89.6% ± 9.2% and 97% ± 10% (P < .005); and PC(20) was 6.5 ± 5.8 mg/mL and 11.7 ± 5.5 mg/mL (P < .001). PC(20) was < 4 mg/mL in 49% of preterm subjects despite normal exhaled nitric oxide. Most measurements were similar in premature subjects with and without BPD. Peak oxygen consumption and breathing reserve were normal, but % predicted maximal load (measured in Watts) was 69% ± 15% for subjects with BPD compared with 88% ± 23% for subjects without and 86% ± 20% for control subjects (P < .01).

CONCLUSIONS

Pulmonary outcome was encouraging at mid-childhood for neurologically intact survivors in the postsurfactant era. Despite mechanical ventilation and oxygen therapy, most had no or mild BPD. Changes found probably reflect the hypoplastic lungs of prematurity.

Preterm birth and respiratory disease in later life

Chronic respiratory diseases are a common complication of preterm birth, particularly among very immature infants or those suffering from bronchopulmonary dysplasia. Major progress in the treatment of preterm newborns has changed the pattern of late respiratory complications. The major respiratory problem in infancy and early childhood is respiratory exacerbations caused by infections (particularly viral ones), which need hospitalization. The symptoms become mild in school-age children; however, a group of children still present with chronic airway obstruction defined by recurrent episodes of wheezing and decreased lung function tests (decreased forced expiratory volume). For some preterm infants, particularly those with bronchopulmonary dysplasia, obstructive lung disease persists into adulthood. They are very likely to develop chronic obstructive pulmonary disease or similar disease later in life. In these patients, a program of lung function monitoring and pulmonary prophylaxis by means of elimination of specific risk factors in adulthood is advisable.

[Bronchopulmonary dysplasia and prematurity. Short-and long-term respiratory changes]

Bronchopulmonary dysplasia (BPD) is the most frequent chronic lung disease in premature children. With the inclusion of antenatal steroid therapy, surfactant use and novel mechanical ventilation strategies, survival of premature newborns has increased, whereupon the incidence of BPD has not only decreased but has also risen in extremely premature newborns. This has led to a high respiratory morbidity in the first 2-3 years of life, with numerous admissions to hospital and respiratory exacerbations mostly due to viral infections. Although there is a trend towards improvement, during school age and adolescence, respiratory symptoms may persist, due to changes in pulmonary function often showing a lower exercise capacity. Although BPD symptoms are similar to those of asthma, as there is limitation in airflow and bronchial hyperresponsiveness (BHR), pathophysiological mechanisms could be different in both diseases. On the other hand, isolated prematurity plays an important role in the child's respiratory pathology, proving that pulmonary function alterations in preterm children are present since the first months of life. A higher respiratory morbidity has also been observed in these children when compared to full-term newborns, not only during the first years of life but also subsequently. In this study, different aspects of chronic respiratory disease associated with prematurity will be analysed, drawing special attention to clinical symptoms, respiratory function changes, BHR and exercise capacity. All these aspects will be reviewed from early childhood until adolescence and young adult age. Similarities and differences between BPD and asthma will also be discussed.

Daycare attendance and risk for respiratory morbidity among young very low birth weight children

Daycare attendance and very low birth weight (VLBW, < or =1,500 g) are associated with respiratory morbidity during childhood. The objective of this study was to evaluate whether daycare attendance is associated with even higher risk for respiratory problems among VLBW children. We hypothesized that VLBW children attending daycare, in a private home or daycare center, are at higher risk for respiratory problems than VLBW children not attending daycare. We also investigated whether the effect of daycare is independent or synergistic with respiratory risk resulting from being VLBW, as indicated by having bronchopulmonary dysplasia (BPD) as a neonate. We conducted a prospective study of VLBW children followed from birth to age 2-3 (N = 715). Logistic regression was used to evaluate the relationship between daycare attendance and respiratory problems, adjusting for known neonatal risk factors for poor respiratory outcomes. Attending daycare in either a private home or in a daycare center was significantly associated with higher risk of lower respiratory infections than never attending. Attending a daycare center was also associated with higher risk for wheezy chest, cough without a cold, and respiratory medication use. While having BPD was associated with increased risk for respiratory problems, daycare attendance and BPD were not found to be synergistic risk factors for respiratory problems among VLBW children, but acted independently to increase risk. This implies that the increase in risk for respiratory problems associated with daycare attendance may be similar among VLBW children and those of normal birth weight.