A pulmonologist is a physician who specializes in the diagnosis and treatment of conditions related to the lungs and respiratory tract. These specialists are similar to critical care specialists in that their patients often require mechanical ventilation to assist their breathing. Pulmonologists diagnose and treat patients with conditions such as asthma, cystic fibrosis, asbestosis, pulmonary fibrosis, lung cancer, COPD, and emphysema. Exposure and inhalation of certain toxic substances may also warrant the services of a pulmonologist. Some of the tools and tests pulmonologists use to diagnose a patient are a stethoscope in order to listen for abnormal breathing sounds, chest X-rays, CT scans, blood tests, bronchoscopy.