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Functional residual capacity (FRC) measurements by plethysmography and helium dilution in normal infants
Author(s) -
McCoy Karen S.,
Castile Robert G.,
Allen Elizabeth D.,
Filbrun David A.,
Flucke Robert L.,
BarYishay Ephraim
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.1950190507
Subject(s) - functional residual capacity , medicine , plethysmograph , expiration , supine position , anesthesia , chloral hydrate , mean difference , lung volumes , respiratory system , lung , confidence interval
Comparative measurements of functional residual capacity (FRC) made by plethysmography (FRC pleth ) and by helium dilution (FRC He ) were obtained on 27 infants and young children without known pulmonary disease (14 males, 13 females; 4 weeks–26 months; mean age 32.2 weeks) while under chloral hydrate sedation. Clinical histories, clinical examinations, and pulmonary functions were normal for all members of the group. FRC pleth , whether measured near end expiration (EE) or near end inspiration (EI), and corrected to mean expiratory levels of at least 3 breathing cycles, was consistently and significantly greater than FRC He . Comparative values for mean (± standard deviation) were FRC pleth EE, 182.0 (±79.7) mL and FRC pleth El, 171.8 (±77.4) mL vs. FRC He 154 (±72.2) mL, P < 0.0001 and P < 0.005, respectively. Normalizing values by weight, FRC pleth EE was 23.8 mL/kg (±5.3) vs. FRC he 20.2 (±4.7) mL/kg, mean (+ standard deviation). The difference between FRC pleth and FRC he , expressed as FRC pleth – FRC He /FRC pleth × 100, was 9% for occlusions at end inspiration and 16% for occlusions at end expiration. The following equations describe our FRC results in relation to length: InThe difference between FRC pleth and FRC He was more marked when occlusions were performed at end expiration than at end inspiration. We conclude that normal infants and young children, at least when studied supine and sedated, have a small but significant amount of airway closure. © 1995 Wiley‐Liss, Inc.