A Hand-Held ETCO2 is an indispensable tool used in assessing the severity of obstructive respiratory disease in the emergency department. ETCO2 is higher in patients with COPD exacerbation who are admitted to the hospital compared to those who are discharged from the emergency department. There are 3 main types of End Tidal CO2 monitors sidestream, mainstream, and Microstream. Sidestream monitors rely on a separate monitor connected to the patient's airway by a tube. Gas samples are aspirated from exhaled gas flow via the ventilator circuit and are read at the monitor. ETCO2 is the amount of carbon dioxide (CO2) in exhaled air, which assesses ventilation. So a high ETCO2 is a good sign of good ventilation, while low ETCO2 is a bad sign that represents hypoventilation.