The change of airway responsiveness and alveolar macrophage (AM) immunity occurs during the pathogenesis of asthma. Macrophage-associated airway protection in patients with asthma is affected positively or negatively by propofol general anesthesia. The investigators hypothesized that the effects of propofol on asthmatic AMs and corresponding airway reactivity in vivo is different from the in vitro research. Through in vivo airway hyperresponsiveness (AHR) observation and clinical investigation of AM immune functions from asthma patients undergoing propofol general anesthesia to clarify the precise effects of propofol on AM immunity, and to provide theoretical basis for the clinical administration of propofol in asthmatic patients. This would optimize the practice of clinical anesthesia, especially for those with the tendency of AHR.