Different End Points for Bronchial Hyperactivity (BHR) Tests.

Bronchial challenge tests (BCT) are being used to diagnose bronchial hyperactivity (BHR) and quantify its severity. In older children and adults, BCT is done using spirometry to measure the value of 20% fall in FEV1 as an indicator for positive reactivity. However, in young children and infants that cannot perform spirometry, other measurements are used as indicators for BHR. Traditionally, in these populations, appearance of wheezing on auscultation is used as the indicator for BHR. More recently, other measures like 50% increase in respiratory rate or 5% decreases in oxygen saturation are mentioned as possible options to determine positive BHR. Nevertheless, as these measurements probably measure different parameters they could vary in time of appearance. The investigators also noted that in older children who perform spirometry, the order of appearance of these different physiologic measures is not constant. Decrease in O2 saturation, appearance of wheezing and increase in respiratory rate (RR) do not all appear at the same time and not in the same order of events. Some children are noted to have a decrease in FEV1 without wheezing - those children can be difficult to diagnose as asthmatics in the primary care setting where asthma is being diagnosed on clinical grounds alone: wheezing and response to bronchodilators. Children who do not wheeze are difficult to diagnose and therefore, are not getting the appropriate treatment. Nevertheless, the data in current literature is very scant or not existing regarding these issues. Thus the investigators designed a study to prospectively try to answer the questions: do clinically significant differences exist in the time of appearances of these parameters and if so, how does it affect the diagnosis and the severity assessment of HRA in different age groups? in this study we measure the metacholine and / or adenosine concentration at the time when the following parameters appear (what comes first): 20% fall in FEV1, 5% fall in oxygen saturation, 50% rise in respiratory rate, wheezing heard by the investigators using stethoscope.