Bronchodilator responsiveness in normal infants and young children.

UNLABELLED: Several studies have demonstrated that normal infants exhibit bronchoconstriction after inhalation of nonspecific agonists and that the induced airway narrowing can be reversed by the inhalation of a beta-agonist. However, there are very limited data on baseline airway tone and the airway response to a beta-agonist in this subject population. The purpose of our study was to evaluate in normal infants baseline airway responsiveness to the inhaled beta-agonist, albuterol, using changes in maximal expiratory flows. Forty-one healthy infant volunteers with no history of respiratory disease or recurrent wheezing (ages 5.4 to 141.4 wk) were studied. Maximal expiratory flow- volume curves were obtained at baseline and 10 min after inhalation of albuterol (n = 28) or placebo (n = 13) using a metered-dose inhaler with a spacer. The mean percent change was significantly greater (p < 0.05) in the albuterol versus placebo group for FEV(0.5) (2.2% versus -1.5%), FEF(75%) (10.6% versus -3.1%), and FEF(85%) (12.9% versus 0.5%). Six of 28 albuterol-treated infants demonstrated increases in FEF(75%) greater than two standard deviations from the mean change in FEF(75%) seen in the placebo group. These infants were younger and more frequently exposed to maternal smoking during pregnancy. We conclude that normal healthy infants have overall levels of baseline airway tone that are similar to that reported in adults and older children; however, among the infants we evaluated the response to an inhaled bronchodilator was greatest in the youngest infants and in those exposed to tobacco smoking. KEYWORDS: airway responsiveness; asthma; tobacco smoke; infant pulmonary function; bronchodilator

Lungs in infants and young children: improved thin-section CT with a noninvasive controlled-ventilation technique--initial experience.

Three sedated young children underwent thin-section computed tomography (CT) of the chest while breathing and during controlled respiratory pauses induced by means of a step increase in positive-pressure ventilation applied via a face mask. Motion-free inspiratory and expiratory thin-section CT images were successfully acquired during 8-12-second respiratory pauses. This simple, reproducible technique produced thin-section CT images that were clearer and more clinically useful than those obtained during quiet tidal breathing.

Functional residual capacity (FRC) measurements by plethysmography and helium dilution in normal infants.

Comparative measurements of functional residual capacity (FRC) made by plethysmography (FRCpleth) and by helium dilution (FRCHe) 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. FRCpleth, 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 FRCHe. Comparative values for mean (+/- standard deviation) were FRCpleth EE, 182.0 (+/- 79.7) mL and FRCpleth El, 171.8 (+/- 77.4) mL vs. FRCHe, 154 (+/- 72.2) mL, P < 0.0001 and P < 0.005, respectively. Normalizing values by weight, FRCpleth EE was 23.8 mL/kg (+/- 5.3) vs. FRCHe, 20.2 (+/- 4.7) mL/kg, mean (+/- standard deviation). The difference between FRCpleth and FRCHe, expressed as FRCpleth - FRCHe/FRCpleth x 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: In (FRCHe) = 2.74 x ln (length) - 6.53 r2 = 0.781 slope = 2.74 +/- 0.29 SE Y intercept = 6.53 +/- 1.12 SE ln (FRCPleth EI) = 2.69 x ln (length) - 6.21 r2 = 0.752 slope = 2.69 +/- 0.31 SE Y intercept = 6.21 +/- 1.29 SE The difference between FRCpleth and FRCHe was more marked when occlusions were performed at end expiration than at end inspiration.(ABSTRACT TRUNCATED AT 250 WORDS)