This chapter discusses the diagnosis, evaluation and management of asthma. Airflow restriction may be severe, leading to asthma patients presenting in an upright or tripod position, with cyanosis, altered mental status, and respiratory arrest. Asthma exacerbations initially produce tachypnea and a resultant low carbon dioxide level; a normal or elevated carbon dioxide level may indicate fatigue and impending respiratory failure. Laboratory testing and ECG should be used to differentiate asthma exacerbations from alternative etiologies or comorbid conditions. Patients should be placed on supplemental oxygen therapy as needed to maintain adequate oxygen saturations. Patients must be monitored for signs of impending respiratory failure. Constant positive airway pressure (CPAP) and bi-level positive airway pressure (Bi-PAP) may be considered for patients with severe asthma. The goal of ventilator management in asthmatic is to oxygenate and ventilate without worsening hyperinflation, which causes barotrauma and hemodynamic instability.