FEF25-75 as a marker of airway obstruction in asthmatic children during reduced mite exposure at high altitude.

Sensitivity of forced expiratory flow between 25% and 75% of the vital capacity (FEF25-75) in detecting airway obstruction was investigated in 14 children with mild-moderate asthma, allergic to house dust mites, while at high altitude (1756 m). Forced vital capacity (FVC), forced expiratory volume in 1 sec (FEV1), FEF25-75, and peak expiratory flow (PEF) were measured every 2 weeks for 12 weeks (total, 84 measurements). The presence or absence of wheezing at the chest auscultation was ascertained before each test. During the study period, a significant improvement of both mean (SD) FEF25-75 [61 (12)% vs. 68 (11)% of the predicted value, p = 0.005] and PEF [95 (16)% vs. 103 (13)%, p = 0.002] was observed. FEV1 changed only marginally [82 (7)% vs. 86 (6)%, p = 0.05]. Wheezing was present on 12/84 occasions. Wheezing was associated with abnormal FEF25-75 values on most occasions but not with abnormal FEV1 or PEF. FEF25-75 was decreased on 51% of days in which wheezing was absent. FEV1 and PEF were, respectively, normal in 69% (p < 0.0001) and 92% (p < 0.0001) of measurements in which FEF25-75 was abnormal. These results suggest that FEF25-75 may be considered a good indicator of airflow obstruction and a sensitive marker of respiratory improvement in asthmatic children during reduced antigen exposure.

Effect of pattern of preceding inspiration on FEV1 in asthmatic children.

In adults, both peak expiratory flow (PEF) and forced expiratory volume in one second (FEV1) are significantly influenced by the time course of the inspiration preceding the forced expiration. The aim of this study was to evaluate the effects of three different inspiratory manoeuvres on PEF, FEV1, and forced vital capacity (FVC) in asthmatic children. Twenty five symptomless asthmatic children performed forced expiration preceded by three different inspiratory manoeuvres, which consisted of: a rapid inspiration with a 2 s end-inspiratory breathhold (Manoeuvre No. 1); a rapid inspiration without an end-inspiratory breathhold (Manoeuvre No. 2); and a slow inspiration lasting about 5 s with an end-inspiratory breathhold of at least 4 s (Manoeuvre No. 3). All manoeuvres were performed in a randomly assigned sequence each morning for three consecutive days. In each session, the manoeuvres were repeated three times and the highest value was chosen. Both FVC and FEV1 obtained with Manoeuvre No. 3 were significantly lower than the corresponding values obtained with Manoeuvre Nos. 1 and 2. The mean (SD) FVC values were 2.76 (0.66) L with Manoeuvre No. 1, 2.67 (0.58) L with Manoeuvre No. 2 and 2.52 (0.52) L with Manoeuvre No. 3. The corresponding values of FEV1 were 2.25 (0.53), 2.22 (0.53) and 2.07 (0.44) L, respectively. By contrast, the values of PEF, obtained with a portable peak flow meter, were similar with the three different inspiratory manoeuvres. The results of this study show that in symptomless asthmatic children the preceding inspiratory manoeuvre may influence forced vital capacity and forced expiratory volume in one second. Hence, in order to reduce variability due to interference by physiological factors and so improve reproducibility of pulmonary function tests, the inspiratory manoeuvres must be accurately standardized.

Peak expiratory flow variation and bronchial hyperresponsiveness in asthmatic children during periods of antigen avoidance and reexposure.

Changes of diurnal variation of peak expiratory flow rate (%PEF variation) and their relationship with bronchial hyperresponsiveness (BHR) to methacholine (PC20) were evaluated in 12 children with mild-to-moderate asthma and house-dust mite allergy, during successive periods of stay in a mite-free environment at high altitude (1756 m) and at their home at sea level. The children remained at the high altitude from October until the end of December; then they spent a 3-week period at home and returned to high altitude residence in January. PEF was measured daily, in the morning and in the evening, during the 3 months' stay at high altitude and them for 10 days after the return in January. PC20 was assessed in 8/12 children, once a month from October to December, and at the return in January. Mean absolute PEF values did not change significantly throughout the study. From October to December, patients showed a significant decrease of mean %PEF variation (P = 0.04), while PC20 showed an increase (P = 0.05). After the 3 weeks at home, both %PEF variation (P = 0.03) and PC20 (P = 0.05) significantly worsened. The correlation between PC20 values and mean %PEF variation in the 2 days before and after each methacholine test was r = -0.63 (P = 0.001). Our data suggest that there is a beneficial effect of a prolonged stay in a mite-free environment, on both PEF variability and BHR, also in asthmatic children with good pulmonary function. PEF variability and bronchial responsiveness to methacholine were significantly correlated also for small changes of the two variables.

Nedocromil sodium vs. sodium cromoglycate pressurized aerosol in the prevention of bronchoconstriction induced by ultrasonic nebulized distilled water in asthmatic children.

To compare the effectiveness of nedocromil sodium (NS) and sodium cromoglycate (SCG), administered by metered dose inhaler (MDI) with a 700 mL holding chamber (Fisonair Fisons UK) in preventing bronchoconstriction induced by inhalation of ultrasonically nebulized distilled water (UNDW), 12 asthmatic children were studied in a randomized, double-blind, placebo-controlled, intrapatient study. Following a baseline challenge with UNDW, the protective effect of NS, SCG, or placebo was evaluated in each subject. Cumulative doses of delivered nebulized water producing a 20% fall in forced expiratory volume in 1 sec (PD20 UNDW) was measured. Mean (+/- SD) PD20 UNDW was 4.83 (+/- 4.84), 10.16 (+/- 7.05), 1.58 (+/- 0.5), and 15.93 (+/- 0.23) respectively, for baseline, and placebo, SCG, and NS-treated groups. A significant (P < 0.05) protection from UNDW induced bronchoconstriction by NS was observed in comparison with placebo, while no such effect was evident when the children were treated with SCG.

Plasma fibronectin concentrations in healthy newborns and in children.

Plasma fibronectin (FN) concentrations were measured by an immunonephelometric method in cord blood from 76 healthy newborns (45 full term and 31 preterm), in 181 healthy children, from 1 month-15 years old, divided by age into seven groups and in 81 control adults. FN levels in newborns were 35% of those of adults. There was no difference between plasma FN in term and preterm (gestational age greater than 30 weeks) infants. Preterm newborns below the gestational age of 30 weeks showed particularly low FN levels. No clear correlation was seen with birth weight. In the child population, a strong increase in FN values was noted in the first 6 months of life, rising to 65% of the normal adult values. No further increase occurred until puberty.