Introduction: The respiratory system exists for exchange of gases between blood and the environment. Most drugs used in anesthetics including inhalation and intravenous anesthetics, muscle relaxants, opioids and benzodiazepine have a functional impact on the respiratory system in addition volatile anesthetics are administered to the lung by inhalation. Therefore it is important for the anesthetist to understand the function of respiratory system, effects of anesthetic on the respiratory system as well as focused assessment of respiratory system. The organs of respiration can be divided into air passages (upper and lower airways); which has been discussed in module one of unit three, the alveoli in the lungs where the exchange of gases between air and blood takes place will be discussed her. In this session you will learn to adopt relevant knowledge of respiratory physiology and effects of anesthetics on respiratory system, appropriate skill and right attitude of making focused assessment.