Paediatrics (RCH) - Theses

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    Respiratory function, exercise and ventilation distribution in late adolescence in survivors born extremely preterm or extremely low birth weight
    GIBSON, ANNE-MARIE ( 2013)
    Rationale: Ongoing respiratory morbidity is a common outcome of extremely preterm birth (EP <28 weeks’ gestation) or extremely low birth weight (ELBW; birth weight <1000 g). Respiratory outcomes and exercise capacity in late adolescence for EP/ELBW survivors in the era after surfactant was introduced into clinical practice in the early 1990s have not been reported. Since EP/ELBW survivors have high rates of long-term pulmonary sequelae, including bronchopulmonary dysplasia (BPD), reductions in pulmonary function, exercise capacity and activity levels would be expected compared with normal birth weight (NBW; birth weight >2499 g) controls. Objective: To compare results from comprehensive lung function and cardiopulmonary exercise testing, including airflow, lung volumes, diffusing capacity and ventilation efficiency at 18 years of age in the largest geographical cohort of EP/ELBW survivors in the post-surfactant era with NBW controls. Within the EP/ELBW group to compare pulmonary outcomes between those who had BPD and those who did not. In the EP only group to determine the relationships between lung function and exercise capacity with growth restriction in utero. Methods: 208 EP/ELBW survivors (35% had BPD) born in 1991 or 1992, and 153 NBW controls performed spirometry, lung volumes, diffusing capacity, and gas-washout. 114 EP/ELBW subjects (31% had BPD) and 98 NBW controls performed cardiopulmonary exercise tests to a satisfactory level according to standardised guidelines. Main Results: The EP/ELBW group had significant impairments in spirometry, bronchodilator response, airways resistance, ventilation efficiency in the conducting lung zone, residual volume, and diffusing capacity compared with NBW controls. Those who had bronchopulmonary dysplasia in the newborn period had the greatest impairments. Within the EP only group growth restriction was associated with impairments in airflow and diffusing capacity. Being growth restricted and having BPD did not worsen the airflow impairment. On exercise testing EP/ELBW birth was associated with a significant increase in breathing frequency, and significant reductions in peak ventilation, peak expiratory tidal volume and peak inspiratory tidal volume. EP/ELBW participants with BPD had no further impairments in cardiopulmonary variables related to exercise testing compared with EP/ELBW subjects who did not have BPD. Within the EP only group growth restriction was associated with altered ventilatory patterns and greater use of the ventilatory reserve to achieve maximal exercise. Conclusions: EP/ELBW survivors have significant impairments in airflow, air-trapping, diffusion and ventilation efficiency within the lungs. These lung function impairments are more severe in those who had BPD as a neonate. EP/ELBW subjects alter their respiration to achieve maximal oxygen consumption levels comparable to NBW controls. BPD is not associated with further cardiopulmonary exercise impairment. Growth restriction was associated with impairment in airflow and gas exchange and diffusion capacity, this was not associated with BPD.
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    Respiratory function tracking in survivors of prematurity and low birth weight
    GIBSON, ANNE-MARIE ( 2009)
    INTRODUCTION: To investigate longitudinal ‘tracking’ in lung growth, decline or stability of adult preterm/very low birth weight survivors over the study period. To investigate whether those who have clinically abnormal lung function fall further behind their contemporaries or demonstrate evidence of ‘catch-up’ growth. METHODS: 210 babies born ≤34 weeks’ gestation and with birth weights ≤ 1500g in 1977-1982 were followed up at 8, 11, 14, 18 and 25 years of age. Respiratory outcome was evaluated using Spirometry. Spirometry was performed at each of the follow-up periods. Mixed model regression was used to assess longitudinal lung function trajectories and the influence of Bronchopulmonary dysplasia, being small for gestational age and abnormal lung function. Restricted maximum likelihood modelling was used for longitudinal FEV1 z-score as it allows for analysis of data from different time points that are not necessarily evenly spaced, without being affected by missing data. RESULTS: 137 VLBW children completed lung function testing at 8 years of age. Twenty VLBW children (14.6%) had abnormal FEV1 z-scores and 26 (21.0%) [Defined as >2 standard deviation’s below the mean]. VLBW survivors showed minimal ‘catch-up’ in FEV1 z-score over the 13 years of the study; those without BPD (Bronchopulmonary dysplasia) FEV1 improved 0.034 (p=0.014) z-scores, those with BPD FEV1 improved 0.033 (p=0.039) z-scores. VLBW with BPD survivors did not return to within normal limits; those with abnormal FEF25-75 z-scores did not show significant ‘catch-up’ growth (p=0.41) and remained abnormal. CONCLUSIONS: Mixed models do not reveal any significant effects from being born with VLBW and its interaction with age; it does lead to a reduction in FEV1/FVC mean z-score. Although those VLBW individuals who were small for gestational age had significantly reduced FEV1, FVC and FEV1/FVC mean z-scores and these small for gestational age individuals show evidence of ‘catch-up’ growth in terms of lung function, with the exception of FEV1/FVC z-score which falls further from their contemporaries. This effect on FEV1 and FVC z-scores may suggest some protective element or compensatory mechanism of being born small for gestational age. Reassuringly, Bronchopulmonary dysplasia as a neonate did not significantly affect lung function variables as these individuals as they age. Those with clinically abnormal lung function show a progressive failure to achieve optimal lung function whether or not they had Bronchopulmonary dysplasia.