In asthma, the significant role of pathogenesis is chronic airway inflammation, bronchial hyperresponsiveness, and variable airflow obstruction. Asthma with irreversible or fixed airflow obstruction (FAO) is a clinical phenotype resulting from chronic airway inflammation with having longer disease duration, suggesting that airway remodeling contributes to the decline in lung function seen in individuals with asthma. Although this condition frequently occurs in patients with severe asthma, there are pieces of evidence occurring in those with mild to moderate asthma. According to previous research, low lung function, FEV1 less than 60% predicted, is a robust independent predictor of subsequent asthma attacks and other asthma outcomes, including asthma control and SABA use. In a recent study, the patients with mild to moderate asthma who received mild to medium dosed inhaled corticosteroid plus long-acting beta-2 agonist with or without asthma control showed evidence of FAO with or without bronchodilator reversibility. Therefore parasympathetic activity may be affected by FAO in those patients. The autonomic nervous system plays an essential role in asthma, especially from the parasympathetic, promoting bronchoconstriction and regulating airway inflammation and remodeling. This study hypothesizes that a cholinergic mechanism may play a significant role in FAO across patients with mild, moderate, and severe asthma. This might increase the fundamental evidence leading to early-step treatment with anti-cholinergic medication in early asthma severity driven by FAO.