New reference equations to improve interpretation of infant lung function

Abstract

Summary. Rationale: With increasing use of infant pulmonary function tests (IPFTs) in both clinical and research studies, appropriate interpretation of results is essential. Objectives: To investigate the potential bias associated with ''normalising'' IPF by expressing results as a ratio of body size and to develop reference ranges for tidal breathing parameters, passive respiratory mechanics (compliance [C rs ] and resistance [R rs ]) and plethysmographic functional residual capacity (FRC p ) for white infants during the first 2 years of life. Methods: IPFTs were measured using the Jaeger BabyBody system and standardized protocols. Reference equations, adjusted for body size, age, and sex where appropriate, were created using multilevel modeling. Results: The ratio of lung function to body length changes markedly with growth, thereby precluding its use for any outcome. While the ratio of tidal volume and C rs to body weight remained relatively constant with growth, this was not the case for FRC p . Even in healthy infants, a strong inverse relationship was observed between lung function/body weight and weight z-score which could distort interpretation of results in growth-restricted infants with lung disease, such as cystic fibrosis. Reference equations were derived from 153 healthy white infants on 232 test occasions (median age 35.5 weeks [range: 2.6-104.7]). Crown-heel length was the strongest predictor of IPF. Conclusions: When reporting IPF, use of size-corrected ratios should be discouraged, with interpretation instead based on appropriate reference equations. The current equations are applicable to white infants and young children up to 2 years of age, studied using the same commercially available equipment. The extent to which these equations are applicable to infants and young children of other ethnic backgrounds or who are tested with different equipment needs to be established.

Impaired Growth at Birth and Bronchopulmonary Dysplasia Classification: Beyond Small for Gestational Age

“…17 We observed further differences in growth patterns in the < 26 weeks GA at birth group in both length and length-for-weight measurements, suggesting that impaired linear growth or disproportionate weight-to-length may be closely linked to the development of BPD in infants born < 26 weeks GA. A recent study evaluating new references in infant pulmonary function implicated length measures as the strongest determinant of lung function throughout infancy. 18 Thus, routine weight-to-length measurements may identify these at-risk infants earlier. In addition to length impairment, head circumferences were significantly smaller in infants who developed moderate/ severe BPD when compared with infants with no/mild BPD.…”

Computerized Dead-Space Volume Measurement of Face Masks Applied to Simulated Faces

“…The mean V T in infants 9 months old was recently documented as 81.5 Ϯ 28.2 mL, with a mean V T of 9.7 Ϯ 1.3 mL/kg. 7 Additionally, the V T may be variably reduced in a variety of diseases (eg, pneumonia, cystic fibrosis, bronchopulmonary dysplasia) characterized by rapid breathing frequency and stiff, low-compliance lungs.…”

Monitoring early lung disease in cystic fibrosis: where are we now?

“…These equations have been shown to grossly overestimate abnormality when applied to data measured on a different commercially made device [17]. Equations for FRCpleth have recently been published from 153 infants [18], but again should be considered equipment specific. Use of contemporaneous healthy controls or equipment specific equations in studies is essential for meaningful interpretation of data [19] and important to appraise in research reports.…”