What type of therapy uses methods to eliminate undissolved gases from body fluids?

Extracorporeal therapy is the correct answer as it refers to medical treatments that occur outside of the patient's body, specifically designed to manipulate blood or other body fluids. This type of therapy can involve methods like dialysis or procedures that help eliminate undissolved gases from body fluids. Such techniques are critical for managing conditions that involve the removal of unwanted substances, ensuring effective function of bodily systems.

In contrast, intravenous therapy primarily focuses on delivering fluids, medications, or nutrients directly into a patient's vein. While it may support a patient's overall treatment, it does not involve the specific removal of gases from body fluids.

Pharmacotherapy involves the use of medications to treat or manage diseases but does not inherently include the process of eliminating gases from body fluids.

Oxygen therapy is specifically related to the administration of oxygen to improve oxygen saturation in patients but does not pertain to the removal of gases from body fluids. Therefore, while each of the other options addresses different therapeutic areas, extracorporeal therapy is uniquely designed for the elimination of undissolved gases, making it the correct choice.