585 - Spirometry phenotypes at 8 years in children born extremely preterm or extremely low birthweight

Poster Number: 585
Publication Number: 585.2985

Background: Despite the well-known association between preterm birth and poor respiratory function, spirometry phenotypes of abnormal respiratory function are not well-described in school-aged children born extremely preterm (EP; < 28 weeks’ gestation) or extremely low birth weight (ELBW; < 1000 g birthweight).

Objective: To describe abnormal spirometry phenotypes in children born EP/ELBW and to identify the perinatal and early life variables associated with each spirometry phenotype.

Design/Methods: All survivors born EP/ELBW in Victoria, Australia, in three eras (1991-1992, 1997, 2005) who had expiratory airflow data at 8 years were eligible. Using the definitions proposed by a recent study, we categorized abnormal spirometry phenotypes into three groups including prematurity-associated obstructive lung disease (POLD, forced expiratory volume in 1s (FEV1) < lower limit of normal (LLN; < 5th centile), FEV1/forced vital capacity (FVC) < LLN); prematurity-associated preserved ratio of impaired spirometry (pPRISm, FEV1 < LLN, FEV1/FVC ≥LLN), prematurity-associated dysanapsis (pDysanapsis, FEV1≥LLN, FEV1/FVC< LLN). The independent predictors of these abnormal spirometry phenotypes were determined by multivariable linear regression analysis.

Results: Of the 544 eligible children, 72% (n=389) had normal spirometry, 8% (n=44) had POLD, 11% (n=61) had pPRISm, and 9% (n=50) had pDysanapsis. Bronchopulmonary dysplasia was associated with both POLD (OR 2.73, 95% CI 1.27 to 5.84; p=0.01) and pPRISm (OR 2.04, 95% CI 1.11 to 3.72; p=0.02) (Table 1). While lower gestational age (OR per week 0.79, 95% CI 0.63 to 0.97; p=0.03) and poorer weight gain between birth and 2 years (OR per z-score 0.71, 95% CI 0.55 to 0.93; p=0.01) were associated with pPRISm, higher birthweight (OR per z-score 1.74, 95% CI 1.19 to 2.56; p=0.004) and weight gain between birth and 2 years (OR per z-score 1.47, 95% CI 1.08 to 2; p=0.015) were associated with pDysanapsis (Table 1).

Conclusion(s): Over ¼ of children born EP/ELBW have three distinct abnormal spirometry phenotypes at 8 years of age. Each phenotype is associated with different perinatal or early life variables. The limitations of this study include the absence of lung volumes, which would have allowed for better distinction between obstructive and restrictive lung problems, and the lack of an ideal definition of dysanapsis in the literature. As abnormal lung function is common, our data highlight the need for further research, particularly into the physiological interpretation of abnormal spirometry patterns in children born extremely preterm.