Oxygenation - Oxygen therapy: Nursing skills

Oxygen therapy is the delivery of extra oxygen to those with conditions that cause hypoxemia, when oxygen levels in the blood are low; and hypoxia, which is when there is not enough oxygen at the tissue level to meet the needs of the body.

This includes patients with diseases that interfere with the lungs’ ability to absorb oxygen, like pneumonia, chronic bronchitis, emphysema, and pulmonary fibrosis; blood problems, like anemia, where the blood doesn't carry enough oxygen; and heart problems, like heart failure, where the heart has trouble pumping blood around the body.

Now, oxygen is considered a medication, so an order is needed.

An oxygen setup consists of an oxygen source and a delivery device. There are several sources for oxygen therapy. With a wall outlet, oxygen is delivered into each patient room from a central supply.

In contrast, an oxygen tank contains oxygen gas under pressure and is typically portable, so it can be carried along as the patient moves. However, this should be moved very carefully; if the tank tips over and the valve breaks open, pressurized oxygen can burst out forcefully and result in severe trauma. Oxygen tanks have a gauge that shows how much oxygen is left. There are also liquid oxygen systems which store oxygen as a liquid at very cold temperatures and then convert it to a gas for use. They are used either for bulk storage of oxygen for a hospital system or can be portable for home use for patients with high oxygen needs, where having a compact way to storge large amounts of oxygen is helpful.

Finally, oxygen concentrators pull in air from the atmosphere and selectively remove nitrogen to deliver air that is about 90 to 95% oxygen to the patient. These devices are easy to use and can deliver an unlimited amount of concentrated oxygen as long as they have a power supply. One caveat is that some units are designed to only deliver up to 5 liters of oxygen per minute, and so those aren’t a good fit for patients who have high-flow oxygen needs.

All oxygen sources are attached to a flow meter that indicates the flow rate, or the liters of oxygen leaving the device per minute. This usually falls somewhere between 1 and 15 liters per minute.

Now, the flow rate coming from the oxygen tank must be matched to an appropriate delivery device.

The delivery device is the part of the equipment that attaches to the patient.

The various delivery devices available can administer different flow rates of oxygen, so it is important to choose one that fits the oxygen needs of the patient.

Generally, increasing the flow rate of oxygen through an appropriate device will increase something called the fraction of inspired oxygen, or FiO2 for short, which represents the percentage of oxygen in the air that the patient is breathing in.

For example, a common choice of oxygen delivery device is the nasal cannula, which can deliver oxygen up to 6 liters per minute at a FiO2 of up to 44%.

A nasal cannula consists of two prongs that are placed into the nostrils and a band of tubing, which wraps around the cheeks and sits behind the ears to keep it in place. A nasal cannula is simple to apply and is less intrusive, so it lets the patient eat, drink, and talk freely. However, a nasal cannula should not be used with high flow rates, as this can cause the nasal passages to dry out and sometimes bleed.

Also, the concentration of oxygen delivered is lower because room air is mixing in with each breath, making this option not suitable for patients with high oxygen needs, such as those in respiratory distress. Bear in mind that if the bands are too tight, they might irritate the skin around the nose, cheekbones, and ears.

This might potentially lead to open sores, so remember to make sure the skin is intact and free from signs of irritation before continuing with the device. A nasal cannula is also not the preferred device for patients who breathe through their mouth.

Another commonly used device is a simple face mask, which covers the patient’s nose and mouth and is secured by an elastic band placed around the back of the patient’s head. It has holes on each side of the mask where carbon dioxide exhaled by the patient can exit. It should be used with a flow rate of 6 to 10 liters of oxygen per minute and can deliver an FiO2 of up to around 50%. It’s usually used for short periods of time, like when a patient needs to be transported. Compared to nasal cannula, face masks are not as comfortable for the patient; and they make it harder to eat, drink, and talk.

Now, when a patient’s need for oxygen is higher, other types of masks can be used, like a nonrebreather mask. This type of mask is attached to a reservoir bag that’s filled with oxygen. The mask also has a series of one-way valves that help direct the air to the right location.

One-way valves on the sides of the mask allow exhaled air containing carbon dioxide to leave the mask; during inhalation they prevent room air from entering the mask.

A one-way valve located between the mask and the bag allows the patient to pull the oxygenated air from the bag during inhalation, but then it clamps shut in exhalation so that the patient’s exhaled carbon dioxide doesn’t dilute the concentration of oxygen in the bag.

The oxygen flow rate must be at least 10 to 15 liters per minute to keep the reservoir bag inflated, and it can deliver a FiO2 of up to 80%. When using a nonrebreather mask, it’s essential to always make sure the reservoir bag remains at least partially inflated.

Another method of oxygen delivery for patients with significant oxygen needs is a high-flow nasal cannula. This device is larger in diameter than the standard nasal cannula and can deliver a flow rate of 60 liters of humidified oxygen per minute and a FiO2 of up to 100%.