Structural and Functional Lung Impairment in Adult Survivors of Bronchopulmonary Dysplasia

RATIONALE: As more preterm infants recover from severe bronchopulmonary dysplasia (BPD), it is critical to understand the clinical consequences of this condition on the lung health of adult survivors.

OBJECTIVES: To assess structural and functional lung parameters in young adult BPD survivors and preterm and term controls Methods: Young adult survivors of BPD (mean age 24) underwent spirometry, lung volumes, transfer factor, lung clearance index and fractional exhaled nitric oxide measurements together with high-resolution chest tomographic (CT) imaging and cardiopulmonary exercise testing.

MEASUREMENTS AND MAIN RESULTS: 25 adult BPD survivors, (mean ± SD gestational age 26.8 ± 2.3 weeks; birth weight 866 ± 255 g), 24 adult prematurely born non-BPD controls (gestational age 30.6 ± 1.9 weeks; birth weight 1234 ± 207 g) and 25 adult term birth control subjects (gestational age 38.5 ± 0.9 weeks; and birth weight 3569 ± 2979 g) were studied. BPD subjects were more likely to be wakened by cough (OR 9.7, 95% CI: 1.8 to 52.6), p<0.01), wheeze and breathlessness (OR 12.2, 95%CI: 1.3 to 112), p<0.05) than term controls after adjusting for sex and current smoking. Preterm subjects had greater airways obstruction than term subjects. BPD subjects had significantly lower values for FEV1 and FEF25-75 (% predicted and z scores) than term controls (both p<0.001). Although non-BPD subjects also had lower spirometric values than term controls, none of the differences reached statistical significance. More BPD subjects (25%) had fixed airflow obstruction than non-BPD (12.5%) and term (0%) subjects (p=0.004). Both BPD and non-BPD subjects had significantly greater impairment in gas transfer (KCO % predicted) than term subjects (both p<0.05). Eighteen (37%) preterm participants were classified as small for gestational age (birth weight < 10th percentile for gestational age). These subjects had significantly greater impairment in FEV1 (% predicted and z scores) than those born appropriate for gestational age. BPD survivors had significantly more severe radiographic structural lung impairment than non-BPD subjects. Both preterm groups had impaired exercise capacity compared to term controls. There was a trend for greater limitation and leg discomfort in BPD survivors.

CONCLUSIONS: Adult preterm birth survivors, especially those who developed BPD, continue to experience respiratory symptoms and exhibit clinically important levels of pulmonary impairment.

Lung clearance index in adults and children with cystic fibrosis

Background: Lung clearance index (LCI) has good clinimetric properties and an acceptable feasibility profile as a surrogate endpoint in Cystic Fibrosis (CF). Although most studies to date have been in children, increasing numbers of adults with CF also have normal spirometry. Further study of LCI as an endpoint in CF adults is required. Therefore, the purpose of this study was to determine the clinimetric properties of LCI over the complete age range of people with CF. Methods: Clinically stable adults and children with CF and age matched healthy controls were recruited. Results: LCI and spirometry data for 110 CF subjects and 61 controls were collected at a stable visit. CF Questionnaire-Revised (CFQ-R) was completed by 80/110 CF subjects. Fifty-six CF subjects completed a second stable visit. The LCI CV% was 4.1% in adults and 6.3% in children with CF. The coefficient of repeatability of LCI was 1.2 in adults and 1.3 in children. In both adults and children, LCI (AUCROC=0.93 and 0.84) had greater combined sensitivity and specificity to discriminate between people with CF and controls compared to FEV1 (AUCROC=0.88 and 0.60) and FEF25-75 (AUCROC=0.87 and 0.68). LCI correlated significantly with the CFQ-R treatment burden in adults (r=-0.37; p<0.01) and children (r=-0.50; p<0.01). Washout tests were successful in 90% of CF subjects and were perceived as comfortable and easy to perform in both adults and children. Conclusions: These data support the use of LCI as a surrogate outcome measure in CF clinical trials in adults as well as children.