Oxygen therapy is administered in a variety of ways depending upon the circumstance, the patient’s requirements and the devices used. It is required in order to provide additional oxygen to the patient and to increase the level of oxygen in the body needed by your body to function.
In most cases the oxygen first passes through a pressure regulator which controls the oxygen pressure as it passes from an oxygen cylinder to the device which is at a lower pressure. Once the oxygen is at this lower pressure, the flow of the oxygen can be controlled by a flow-meter and is measured in litres of oxygen per minute (lpm). The usual flow rate for most devices is between 0 and 15 lpm but can be as high as 25 lpm in some units. Many flow-meters are based on a ‘Thorpe tube’ design which can be set to ‘flush’ which is useful in an emergency situation.
In room air the content of oxygen is only 21%, which although is adequate for healthy individuals, needs to be increased to help those with certain diseases or medical conditions in order to increase the oxygen that manages to get through to their blood stream. Usually increasing the oxygen to 30-35% is enough to make a significant difference and this can be achieved using a nasal cannula, a thin tube with an individual tube for each nostril. This can provide the oxygen at a low flow rate (0.25 to 6 lpm) to achieve an oxygen level of 24-40%.
To achieve higher oxygen concentrations various face masks can be used including a simple face mask, which can deliver oxygen at 5-15 lpm to achieve 28-50% oxygen levels. The Venturi mask can provide oxygen up to 40% and a partial re-breathing mask, which includes a reservoir bag attached to it can provide oxygen at between 40% and 70% concentration.
For patients requiring 100% oxygen the most common device is the non-breather or reservoir mask. This is similar to the re-breathing mask but has a number of valves to stop air that has been exhaled from the lungs from returning to the bag. At a flow rate of 10 lpm up to 80% oxygen levels can be achieved.
For patients requiring the therapy on a constant long-term basis, the oxygen can be warmed and humidified before administration through the nasal cannula to prevent irritation and dryness.
If a patient cannot breathe independently then positive pressure may be needed to force air into the lungs, which is provided by complex artificial respirator machines such as ventilators or a continuous positive airway pressure machine.