Yes methacholine Challenge is used to determine if you have asthma. They use increasing concentrations of irritants. If you drop below 80% of your baseline established at the beginning of the test then that confirms asthma.....when you do the baseline expiratory breaths try as hard as you can since this then establishes a reliable base to measure the decrease caused by the irritants...i hope you see this.....good luck....i have had 3 of them