Airway hyper-responsiveness (AHR) to different stimuli is the hallmark of asthma but is also seen in COPD patients. It means that different stimuli at a low dose which is not affect airway diameter in normal individual can cause airway constriction in asthmatic patients. Measurement of airway hyper-responsiveness is one of the best diagnostic tool in diagnostic of asthma disease in early stage. Airway responsiveness could measured using different Pharmacological agonists such as methacholine and histamine, cold air, hypo and hyper osmotic solutions as well as other stimuli. To measure airway responsiveness, increment dose or concentrations of the stimuli should be administered usually by inhalation root, ,measuring a Pulmonary function test (PFT) indicating airway diameter such as forced expiratory volume in one second (FEV1) or specific airway conductance (sGaw), constructing of dose (or concentration) response curve to stimuli and determination of dose (or concentration) causing specific reduction of measured PFT such as PD20 or PD35 (PC20 or PC35).
AHR to different stimuli including Pharmacological agonists and other stimuli is the hallmark of asthma but is also seen in COPD patients. It means that different stimuli at a low dose which is not affect airway diameter in normal individual can cause airway constriction in asthmatic patients. This is the reason when asthmatic patients exposed to low cold air, the environmental or food stimuli thy will get airway constriction and difficult breathing. Measurement of airway hyper-responsiveness is one of the best diagnostic tool in diagnostic of asthma disease in early stage. However, it is seen in COPD patients as well as other respiratory diseases and even in heart diseases. Airway responsiveness could measured using different Pharmacological agonists such as methacholine and histamine, cold air, hypo and hyper osmotic solutions as well as other stimuli. To measure airway responsiveness, increment dose or concentrations of the stimuli should be administered usually by inhalation root in a specific time intervals. After a defined period of administration of each dose or concentration of stimuli, a pulmonary function test (PFT) indicating airway diameter such as forced expiratory volume in one second (FEV1) or specific airway conductance (sGaw) should be measured. When the final dose or concentration of stimuli was administered and PFT was measured, a dose (or concentration) response curve to stimuli should be constructed. From dose (or concentration) response curve, a dose (or concentration) causing specific reduction of measured PFT such as PD20 or PD35 (PC20 or PC35) should be determined as the criteria of AHR. If This criteria was lower tha a defined unite, it will indicate AHR.