A respiratory disease is a term that is used to describe a pathological condition that affects organs that are involved in the human system of respiration. The conditions that are usually described involve the trachea, the upper tract for respiration, bronchioles, the bronchi, pleural cavity, pleura and alveoli. The muscles and the nerves involved in respiration are also involved in the study of respiratory diseases commonly known as pulmonology. Respiratory diseases might be life threatening such as lung cancer or mild such as the common cold. Respiratory disease scan be classified into a variety of categories and they include: restrictive lung diseases, pleural cavity disease, respiratory tract infections, pulmonary vascular disease, inflammatory lung disease and obstructive lung diseases. Diagnosis of the respiratory disease is usually done through a series of tests which are conducted by a pulmonologist.