Glossary of Children's Hospital Terms

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O2 or Oxygen: A colorless, odorless gas found in air and required to sustain life. The percentage of oxygen found in room air is 21%.  Oxygen can be given in concentrations up to 100% using special delivery devices such as a mask, or endotracheal tube.

O2 sat or Oxygen saturation: A measurement of the percentage of hemoglobin that is carrying oxygen.  A normal oxygen saturation is above about 93%.
O.R or Operating Room: A facility equipped for performing surgery.
Obesity: The state of being over a normal weight. A person has traditionally been considered to be obese if they are more than 20 % over their ideal weight. That ideal weight must take into account the person’s height, age, sex, and build.
Obstructive sleep apnea: Sleep apnea is a breathing disorder characterized by interruptions of breathing during sleep. There are two types of sleep apnea: central and obstructive.
  • Central sleep apnea occurs when the brain fails to send the right signals to the breathing muscles to start breathing.
  • Obstructive sleep apnea occurs when air cannot flow into or out of the person's nose or mouth although efforts to breathe continue.Obstructive sleep apnea is much more common than central sleep apnea. In obstructive sleep apnea, the throat collapses or is obstructed during sleep causing the individual to snort and gasp for breath. Hundreds of these episodes can occur every night causing daytime sleepiness and, it is thought, increasing the risk of hypertension (high blood pressure) and heart problems.
Obtunded: Mentally dulled. Head trauma may obtund a person.
Occlude:  To close, obstruct, or prevent the passage. To occlude an artery is to obstruct the flow of blood. Occlude can also mean to bring together. To occlude the teeth is to align the upper and lower teeth, as for chewing or closing the mouth.
Occupational therapy: Therapy to help learn or relearn daily living and developmental skills. An occupational therapist is a professional trained in this area of treatment.
Oliguria: Less urination than normal.
Oncology: The study and treatment of cancer.
Open fracture: A fracture in which the bone is sticking through the skin which is also called a compound fracture.
Osteomyelitis: Inflammation of the bone due to infection.  Osteomyelitis is sometimes a complication of surgery or injury, although infection can also reach bone tissue through the bloodstream.
Ostomy: An operation to create an opening from an area inside the body to the outside.
OTC (over-the-counter): Available without a prescription so these drugs can be bought over the counter like aspirin for instance.  OTC drugs are in contrast to prescription drugs that require a doctor's order.
Oxygenation: State describing the amount of oxygen in the blood.