While just one component of a system for delivering oxygen to patients at risk of hypoxia, or a shortage of oxygen reaching cells, nasal cannulas are the part that actually sits at the base of the nostrils to enable oxygen from a tank to which it is connected by a clear, plastic tube or hose, to enter the breathing passages. Nasal cannulas are used for people, usually elderly, with chronic breathing problems, such as occurs from diseases like emphysema. The amount of oxygen delivered from the tank through the nasal cannula is calibrated according to the specific needs of each individual patient. Nasal cannulas are generally used for patients with breathing difficulties, but for whom a sudden intake of large quantities of oxygen are not required. The latter category is generally only administered in a hospital or other medical facility for patients experiencing trauma. Nasal cannulas, in contrast, are more a function of enabling people with diminished lung capacity to continue to lead relatively normal lives. When attached to a mobile oxygen tank, use of nasal cannulas enables users to remain mobile, albeit with the caveat of having to transport the oxygen tank wherever they go.
Let’s begin with a definition. A “nasal cannula” is a thin, flexible plastic tube which delivers oxygen to the patient through the tubes and into the nostrils. These tubes are attached to a tank or compressor. At the top of the loop on the opposite end are slightly curved, dual-pronged openings which go into the patient’s nose. The additional loops of tubing are fitted over the ears and under the chin, secured with a sliding connector to keep it from slipping out of place.
A simple oxygen face mask is a plastic device that is contoured to fit over a patient's nose and mouth. It is used to deliver oxygen as the patient breathes through either the nose or the mouth. A simple oxygen mask has open side ports that allow room air to enter the mask and dilute the oxygen, as well as allowing exhaled carbon dioxide to leave the containment space. It also has narrow plastic tubing fixed to the bottom of the mask that is used to connect the mask to an oxygen source. An adjustable elastic band is connected to each side of the mask and slides over the head and above the ears to hold the mask securely in place.
Then, an oxygen face mask, called a “re-breather” is fitted over the nose and mouth; this delivers oxygen to the patient as he or she breathes from either the mouth or the nose. The re-breather is a small bag made of a soft plastic; it holds back the first third of a patients exhalations and the remaining two-thirds escapes through the holed on the sides. The purpose of the re-breather is to use carbon dioxide as a stimulant for respiration.
In addition to re-breather masks, there are also non-re-breather masks. These masks are like simple face masks but they have several one-way valves in the sides, which prevent air from entering but allow exhaled air to escape the mask. This way, larger amounts of oxygen are collected in the reservoir bag and are available for the inhalation .
A third type of oxygen mask is called a “Venturi.” Venturi masks have larger tubes which connect to the oxygen sources. Venturi masks also have choices of wide or narrow tubes which allow specific amounts of oxygen into the mask.
No matter which mask is used, the purpose is the same: to deliver concentrated oxygen for patients who are hypoxic (not enough oxygen entering the body tissues). There are numerous reasons patients present with hypoxemia including respiratory disease, cardiac disease and cardiac episodes, shock, trauma, severe blood loss, seizures, hypokalemia (severe electrolyte imbalance) or low hemoglobin. If a patient is treated quickly enough, non-invasive delivery of oxygen often prevents more severe, invasive measures, such as intubation and mechanical ventilation.
Source: Encyclopedia of Nursing & Allied Health, ©2002 Gale Cengage. All Rights Reserved