Ability of new lung function tests to assess methacholine-induced airway obstruction in infants.

We assessed the ability of innovative lung function tests to detect bronchial obstruction induced by methacholine bronchial challenge. Fifty-five recurrently wheezy infants (mean age 16 +/- 5.2 months) free of respiratory symptoms underwent baseline lung function tests. Forty-two completed the methacholine challenge. Maximal flow at functional residual capacity (VmaxFRC) was obtained using the squeeze technique; compliance and resistance of the respiratory system (Crs, Rrs) was measured with the passive expiatory flow volume technique; tidal volume breathing patterns were analyzed from recordings of respiratory rate (RR), tidal volume (VT), and inspiratory time divided by total cycle of duration (Ti/Ttot). Expiratory tidal flow volume (V/VT) curves were described with multiple indices such as the ratio of expiratory time necessary to reach peak tidal expiratory flow (Fpet) to expiratory time (Tme/Te). Transcutaneous oxygen tension (PtCO2) was measured as an indicator of response to methacholine challenge. Of 42 infants 41 responded to methacholine by a change > or = 2 standard deviations from baseline values. The mean SD unit changes were 9.8 in PtCO2, 3.7 for VmaxFRC, 2.8 for Crs, 2.09 for Rrs, 3.1 for RR, 1.6 for Ti/Ttot, 2.2 for Tme/Te 3.9 for PFVt. We conclude that these noninvasive lung function tests, especially VmaxFRC and Fpet, can be used to detect minor or moderate airway obstruction. Further studies are needed to determine the value of the tests in assessing bronchial disease and effects of its treatment.

Dissociation of symptom scores and bronchial hyperreactivity: study in asthmatic children on long-term treatment with inhaled beclomethasone dipropionate.

The aim of the study was to evaluate the effects of inhaled steroids (IS) on the improvement of clinical asthma symptoms and on the decrease in bronchial hyperreactivity (BHR). Twenty-four children with severe asthma were given 1,000 micrograms beclomethasone dipropionate (BDP) daily and compared with ten asthmatic control children. The study included the evaluation of daily clinical score, of exercise induced asthma, of bronchial obstruction (forced expiratory volume in 1 sec, FEV1), and of BHR at months 0, 1, 2-3, and 4-5 (M0, M1, M2-3, and M4-5). BHR was assessed by standardized inhaled carbachol provocation measuring plethysmographic specific airway resistance (SRaw). The carbachol dose causing a 40% decrease in specific conductance (SGaw) was determined (PD40 SGaw). Clinical scores decreased at M1 (P less than 0.01) and throughout the study. FEV1 increased at M1 (P less than 0.05), M2-3 (P less than 0.01), and M4-5 (P less than 0.05) compared to M0. PD40 SGaw only increased significantly at M1 and M2-3. No individual correlation was found between clinical scores and PD40 SGaw at any testing, or between the decrease of clinical scores and the decrease of BHR. We conclude that bronchoconstrictive challenge tests do not adequately assess the clinical efficacy of IS. In clinical practice non-specific BHR should be preferentially measured for diagnosing atypical forms of asthma.

[Efficacy of a powder inhaler (Turbuhaler) in moderate asthmatic crises in children]. / Efficacité d'un inhalateur de poudre (Turbuhaler) dans la crise d'asthme modérée de l'enfant.

The use of a metered dose inhaler can be difficult in children, and requires the juxtaposition of an inhalation chamber. Powder inhalers offer different means of administration and are simpler to use and can be easily carried in the pocket or in a school satchel. The aim of this study is to assess the use of a beta-2-mimetic powder inhaler (Bricanyl Turbuhaler) in children presenting with an exacerbation of asthma. Thirty children aged from 4 to 14 years were included in an open random study in parallel groups. After a baseline measure of pulmonary function, the children inhaled 500 microgram of powdered terbutaline, or with metered dose aerosol attached to a spacer device (Nebuhaler). A significant bronchodilatation was apparent in the two groups of children which was measured at 15 and 30 minutes after the inhalation of the drug (measures of peak flow and forced expiratory volume in one second and of specific airways resistance were made). The bronchodilator response was similar whatever the method of inhalation. Although the inspiratory flow is decreased in an exacerbation this work shows that it is possible to advise the use of a powder inhaler in children presenting with a moderate exacerbation of asthma.

Repeatability of lung function tests during methacholine challenge in wheezy infants.

BACKGROUND: The repeatability of lung function tests and methacholine inhalation tests was evaluated in recurrently wheezy infants over a one month period using the rapid thoracic compression technique. METHODS: Eighty-one wheezy, symptom free infants had pairs of methacholine challenge tests performed one month apart. Maximal flow at functional residual capacity (VmaxFRC) and transcutaneous oxygen tension (Ptco2) were measured at baseline and after methacholine inhalation. Provocative doses of methacholine causing a 15% fall in Ptco2 (PD15 Ptco2) or a 30% fall in VmaxFRC (PD30 VmaxFRC) were determined. RESULTS: Large changes in VmaxFRC were measured from T1 to T2 with a mean difference between measurements (T2-T1) of 7 (113) ml/s and a 95% range for a single determination for VmaxFRC of 160 ml/s. The mean (SD) difference between pairs of PD30 VmaxFRC measurements was 0.33 (1.89) doubling doses with a 95% range for a single determination of 2.7 doubling doses. Repeatability of PD15Ptco2 was similar. A change of 3.7 doubling doses of methacholine measured on successive occasions represents a significant change. CONCLUSIONS: Baseline VmaxFRC values are highly variable in wheezy, symptom free infants. Using either VmaxFRC or Ptco2 as the outcome measure for methacholine challenges provided similar repeatability. A change of more than 3.7 doubling doses of methacholine is required for clinical significance.

Relationship between bronchial responsiveness and clinical evolution in infants who wheeze: a four-year prospective study.

Recurrent illness involving wheezing during the first years of life is transient in most children. The role of bronchial hyperresponsiveness as a factor influencing the persistence of wheezing from infancy to school age remains unknown. In a prospective study we investigated whether infants who wheezed and subsequently developed persistent asthma differed from infants who wheezed and later became asymptomatic either in the initial degree of bronchial hyperresponsiveness or in the persistence of bronchial hyperresponsiveness with age. One hundred and twenty-nine infants with three or more wheezing episodes before 2 yr of age were followed during 4 yr with a clinical evaluation and a methacholine challenge performed every 6 mo until the child was 4 yr old and once per year thereafter. The clinical score significantly improved with time in most children. The proportion of children with persistent wheezing after 2 and 4 yr of follow-up was only 31% and 20%, respectively. Persistent wheezers had significantly lower VmaxFRC values at initial evaluation and higher SRaw values at the end of follow-up than infants who became asymptomatic. We used transcutaneous oxygen tension (PtcO(2)) to measure the response to methacholine. No significant difference in PD(15) PtcO(2) between groups with subsequently different clinical progression was observed at initial evaluation. Bronchial hyperresponsiveness persisted 4 yr later in all children but children with persistent wheezing showed significantly lower PD(15) PtcO(2) values than children who became asymptomatic, as early as 30 mo of age. However, an acceptable early PD(15) PtcO(2) cut-off point predictive for subsequent clinical progression could not be identified. The level of bronchial hyperresponsiveness in infants who wheezed was not predictive of the persistence of asthma 4 yr later.