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Relationship between an index of tidal flow and lower respiratory illness in the first year of life
Author(s) -
Adler Alan,
Tager Ira B.,
Brown Randall W.,
Ngo Long,
Hanrahan John P.
Publication year - 1995
Publication title -
pediatric pulmonology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.866
H-Index - 106
eISSN - 1099-0496
pISSN - 8755-6863
DOI - 10.1002/ppul.1950200303
Subject(s) - medicine , respiratory illness , index (typography) , respiratory system , respiratory disease , intensive care medicine , lung , world wide web , computer science
The ratio of time to tidal peak flow (T me ) to total tidal expiratory time (T e ) has been reported to be decreased in infants who later develop wheezing lower respiratory tract illness (LRI) in the first year of life. The relationship between T me / T e to the subsequent occurrence of LRI was studied in 98 infants in whom the first measurement of pulmonary function (PFT) was made before the age of 6 months and before the occurrence of any LRI. Occurrence of LRI was evaluated by standardized questionnaires at well‐baby visits, through biweekly telephone calls to mothers, and review of all visits to physicians. T me / T e was derived from 10 tidal breathing loops during stable respiration. Partial expiratory flow‐volume curves were obtained with the rapid compression technique, and passive respiratory mechanics were evaluated by the single breath occlusion technique. Analysis of T me / T e was stratified by age (⩽ 10 weeks, > 10 weeks to 6 months) to take into account the age‐related decline in T me / T e . Among 80 infants first tested at ⩽10 weeks, T me / T e was 12.4% shorter in those who developed a LRI vs. those who did not ( P = 0.46); for 18 infants tested after 10 weeks, the difference was 1.9% ( P = 0.39). Among male infants, the decrease in T me / T e was observed only for those studied at 40 weeks (16%, P = 0.16). For females, decreases were observed for those tested at 10 weeks (11%, P = 0.83) and those tested after 10 weeks (17.5%, P = 0.09). Poisson regression analysis which included data for multiple measurements of T me / T e , over the first year of life and adjusted for age‐at‐test and maternal smoking during pregnancy also demonstrated a greater decrease in T me / T e in female infants who subsequently develop an LRI ( P = 0.08). Level of T me / T e was not consistently related to level of respiratory system resistance (RRS) or flow at functional residual capacity (V̇FRc). Level of V̇FRC has been shown previously to be related to the occurrence of LRI and in this study to R R S( P = 0.007). The results indicate (1) a shortened T me / T e is only weakly associated with the development of LRI in the first year of life; (2) this ratio is a less precise and an epidemiologically less useful measure than is V FRC to investigate groups of infants with and without LRI and without clinically significant underlying lung disease. Pediatr Pulmonol. 1995; 20:137–144 . © 1995 Wiley‐Liss, Inc.