Respiratory disease is a medical term that encompasses pathological conditions affecting the organs and tissues that make gas exchange possible in higher organisms, and includes conditions of the upper respiratory tract, trachea, bronchi, bronchioles, alveoli, pleura and pleural cavity, and the nerves and muscles of breathing.
Respiratory diseases range from mild and self-limiting, such as the common cold, to life-threatening entities like bacterial pneumonia, pulmonary embolism, and lung cancer.The study of respiratory disease is known as pulmonology. A doctor who specializes in respiratory disease is known as a pulmonologist, a chest medicine specialist, a respiratory medicine specialist, a respirologist or a thoracic medicine specialist. Respiratory diseases can be classified in many different ways, including by the organ or tissue involved, by the type and pattern of associated signs and symptoms, or by the cause (etiology) of the disease. Inflammatory lung disease Characterised by a high neutrophil count, e. . asthma, cystic fibrosis, emphysema, chronic obstructive pulmonary disorder or acute respiratory distress syndrome.
 Allergic reactions due to exposure to certain agents (i. e. foods) are a relatively common cause of acute respiratory disease. Obstructive lung diseases Obstructive lung diseases are diseases of the lung where the airways (i. e. bronchi, bronchioles, alveoli) become reduced in volume or have free flow of gas impeded, making it more difficult to move air in and out of the lung.Chronic Obstructive Pulmonary Disease (COPD), which includes asthma an example of an obstructive lung disease, is where the airways become damaged, causing them to narrow.
Restrictive lung diseases Restrictive lung diseases (also known as interstitial lung diseases) are a category of respiratory disease characterized by a loss of lung compliance, causing incomplete lung expansion and increased lung stiffness. E. g. in infant respiratory distress syndrome (IRDS). Respiratory tract infections Infections can affect any part of the respiratory system.They are traditionally divided into upper respiratory tract infections and lower respiratory tract infections. Upper respiratory tract infection common cold however, sinusitis, tonsillitis,pharyngitis and laryngitis are Lower respiratory tract infection pneumonia, tuberculosis Diagnosis Respiratory diseases may be investigated by performing one or more of the following tests Chest x-ray Pulmonary function test Computed tomography scan Culture of microorganisms from secretions such as sputum Bronchoscopy Biopsy of the lung or pleuraVentilation – perfusion scan Ultrasound scanning Epidemiology Respiratory disease is a common and important cause of illness and death around the world.
In the US, approximately 1 billion “common colds” occur each year.  In the UK, approximately 1 in 7 individuals are affected by some form of chronic lung disease, most commonly chronic obstructive pulmonary disease, which includes asthma, chronic bronchitis, and emphysema.  Respiratory diseases (including lung cancer) are responsible for over 10% of hospitalizations and over 16% of deaths in Canada