Also sometimes referred to as intensivists, critical care specialists are physicians with specialized training in the diagnosis and management of life-threatening conditions. Some of these conditions affect vital organs like the heart and lungs, those that make breathing difficult or impossible, and those that affect entire organ systems, like the renal system.
Critical care specialists are typically found in a hospital's intensive care unit where they monitor patients with life-threatening conditions and make determinations as to the best course of treatment.

An internist is a physician who focuses on the diagnosis and treatment of conditions that affect the adult population—both acute and chronic.
These doctors are often who adults see as their primary physicians because they treat a broad range of illnesses that do not require surgical or specialist interventions. They also work to help a patient maintain optimal health in order to prevent the onset of disease.
In addition to treating the common cold and flu, internists also treat chronic diseases like diabetes and heart disease.

Trauma surgeons treat patients who come to emergency rooms and require surgery after any kind of accident. They know how to act quickly, assess the patient’s condition, and decide on a course of action. They work fast to coordinate with other physicians and specialists in the hospital if needed, such as neurosurgeons and radiologists, so they can properly diagnose the injury and stabilize patients.
Common trauma injuries include bleeding, burns, brain or other internal injuries, shock and loss of limbs. Because they treat patients in traumatic situations, they’re also typically skilled in offering some level of emotional support to help the patient cope with confusion and grief that may result from their accident.