EFFECT OF PATTERN OF PRECEDING INSPIRATION ON FEV1 IN ASTHMATIC-CHILDREN

In adults, both peak expiratory flow (PEF) and forced expiratory volum e in one second (FEV1) are significantly influenced by the time course of the inspiration preceding the forced expiration, The aim of this s tudy was to evaluate the effects of three different inspiratory manoeu vres on PEF, FEV1, and forced vital capacity (FVC) in asthmatic childr en. Twenty five symptomless asthmatic children performed forced expira tion preceded by three different inspiratory manoeuvres, which consist ed of: a rapid inspiration with a 2 s end-inspiratory breathhold (Mano euvre No. 1); a rapid inspiration without an end-inspiratory breathhol d (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 mano euvres were performed in a randomly assigned sequence. each morning fo r three consecutive days, In each session, the manoeuvres were repeate d three times and the highest value was chosen. Both FVC and FEV1 obta ined with Manoeuvre No. 3 were significantly lower than the correspond ing values obtained with Manoeuvre Nos, 1 and 2. The mean (SD) FVC val ues were 2.76 (0.66) L with Manoeuvre No. 1, 2.67 (0.58) L with Manoeu vre No. 2 and 2.52 (0.52) L with Manoeuvre No. 3. The corresponding va lues of FEV1 were 2.25 (0.53), 2.22 (0.53) and 2.07 (0.44) L, respecti vely. By contrast, the values of PEF, obtained with a portable peak fl ow meter, were similar with the three different inspiratory manoeuvres . The results of this study show that in symptomless asthmatic childre n the preceding inspiratory manoeuvre may influence forced vital capac ity and forced expiratory volume in one second, Hence, in order to red uce variability due to interference by physiological factors and so im prove reproducibility of pulmonary function tests, the inspiratory man oeuvres must be accurately standardized.