Oxygen Therapy

Oxygen therapy is known as the administration of oxygen as a medical intervention. It is indicated in patients whose oxygen supply is compromised due to both acute and chronic health conditions and can be administered in many different ways.

Oxygen therapy can be administered virtually wherever the patient is. Most commonly, oxygen is delivered to patients in an ambulance, hospital, or doctor’s office. These medical facilities carry oxygen in the form of a compressed gas. It is stored under pressure in large, metal cylinders and delivered to patients via a regulator that controls the flow rate. Oxygen therapy can also be administered at a patient’s home. In this case, oxygen is first stored as a liquid until it is transferred to another smaller, portable unit where it then turns into a gas.

Oxygen is a natural compound that is essential to cell metabolism, and thus tissue development and function. Therefore, without an adequate oxygen supply, the body could not function and would shut down. The respiratory tract includes the nasopharynx, oropharynx, laryngopharynx, trachea, bronchi, bronchioles, and alveoli—with the major respiratory organs being the nose, mouth, trachea, and lungs. The respiratory tract is lined with cilia, which are fine hair-like structures designed to filter any foreign particles out of air as it passes through. Once the oxygen reaches the alveoli, it is diffused into the walls of the pulmonary capillaries, where it binds to hemoglobin and is transported throughout the body. If any part of the respiratory tract is damaged, obstructed, or temporarily impaired then the patient will need oxygen therapy in order to sustain adequate levels of oxygen in the blood.

Pulse oximetry is a way of measuring the levels of oxygen in the blood. Obtaining a patient’s pulse ox reading will help the provider determine and assess the need for oxygen therapy.

Acute conditions that indicate the need for oxygen therapy include symptoms of respiratory distress or failure, hypoxia or hypoxemia, asthma attacks, and severe bronchitis or pneumonia. An emergency healthcare provider can assess a patient’s need for oxygen therapy based on the rate, rhythm, and quality of respirations. If any prove to be inadequate, a form of oxygen therapy will be initiated immediately. Thus, oxygen therapy is widely used in pre-hospital medicine.

Chronic conditions that indicate the need for oxygen therapy include Chronic Obstructive Pulmonary Disorder (COPD), Cystic Fibrosis (CF), and Chronic Heart Failure (CHF).

Oxygen therapy can be delivered to patients by means of a nasal cannula, a mask, or a ventilator. The most common delivery device is a nasal cannula. A nasal cannula is a long tube placed on the patient’s face between the nose and upper lip. It has two small plastic prongs projecting up from the tube that deliver oxygen directly into the patient’s nose, while still allowing the patient to breathe room air. Nasal cannulas can be used in both emergency interventions as well as in maintenance oxygen therapy. Face masks are oxygen delivery devices that are placed over the patient’s nose and mouth, and are only used in emergency interventions. A non-rebreather mask (NRB) is a mask designed to deliver oxygen to the patient at a much higher concentration than a low-flow oxygen mask. It has a reservoir bag attached to it to provide supplemental oxygen, and its unique design allows a one-way valve to let exhaled air out while preventing room air from being inhaled. A bag-valve mask (BVM) is used in emergency situations only, when a healthcare provider performs manual, artificial ventilations by means of a mask creating a seal over the patient’s nose and mouth or by an endotracheal tube. Continuous positive airway pressure (CPAP) and ventilators are machines used to support breathing when a patient becomes apneic, either in cases of respiratory arrest or sleep apnea.

Oxygen therapy can also be used as a means of drug administration. For example, nebulizers administrating vasodilators such as albuterol can come in a liquid form and be mixed with oxygen for the patient to inhale.

Typical flow rates for nasal cannulas range from two to six liters per minute, whereas masks generally require a flow of ten to fifteen liters per minute.

Oxygen therapy is generally very safe. However, in some cases when too much oxygen reaches the blood stream, the production of nitric oxide will increase, which stimulates free radicals to bind with it, creating peroxynitrite. Elevated levels of peroxynitrite can cause hypoxia, resulting in eventual cell death.

Image Caption: Medical oxygen regulator. Credit: Heggyhomolit/Wikipedia (CC BY-SA 3.0)