Like many other people, you might take oxygen therapy for granted. At the end of the day, oxygen therapy is just putting a mask on the patient’s face and turn on the oxygen supply, right?
WRONG! While it might look like that, there’s a lot of thinking that goes on behind it. Such as what mask to use, and what flow rate to give. In critical situations, oxygen therapy can be both lifesaving and life-threatening. So you must know how and when to administer oxygen properly.
Why is Oxygen Therapy Administered?
Oxygen is delivered to patients who have Hypoxemia (low oxygen level in the blood). As you should know, oxygen travels through the lungs and eventually makes its way into the blood. From there, it then goes around the body supplying all the tissues and cells with oxygen.
Patients with Hypoxemia will not have enough oxygen to deliver around their body, and in turn, this will cause damage to various organs.
You can check for Hypoxemia by:
Looking at the patient (Blue lips, blue fingertips/toes)
Check if the patient is oriented or confused
Pulse Oximeter/ SpO2 ( in healthy adults, we aim for >96%)
Arterial Blood Gas
If you notice Hypoxemia symptoms, you should contact the medical team, and discuss starting oxygen therapy. Similar to any other medication, oxygen has to be prescribed by a doctor, but you should be able to identify the need for oxygen without waiting for the medical team.
How is Oxygen Therapy Delivered?
Oxygen is delivered through different masks, that are attached to an oxygen tank.
Nasal Prongs
Normal Face Mask
Venturi Mask
Nebulizer Mask
Non-Rebreather Mask
Let’s look into them one by one
1. Nasal Prongs
Nasal prongs are ideal for stable patients who need a low flow of oxygen with a low or medium concentration. You can set the flow rate between 1-4 litres/ minute, which gives around 24-40% oxygen. Giving a flow rate higher than 6L/min will damage your patient’s nasal passage.
One of the benefits of using nasal prongs is that it allows the patients to eat, drink and talk normally.
Ps. You will not be able to accurately measure the amount of oxygen delivered, as it depends a lot on how often the patient breathes. For this reason, nasal prongs are not suitable for patients in a critical stage or others who need controlled oxygen therapy such as COPD patients.
2. Normal Face Mask
A regular face mask gives a more significant volume of oxygen than a nasal cannula, with the most common flow rates being 5-10L/min. In specific cases, you can increase the flow rate up to 15L/min, and this will deliver around 70% oxygen concentration.
Similarly to the nasal prongs, you can not control the amount of oxygen accurately as the patient will be inhaling room air as well. However, this also presents an advantage, as mixing room air with oxygen will keep your patient’s nasal passages moist.
Ps. Do not use a Normal Face Mask with less than 5L/min flow rate, as your patient may ‘rebreathe’ carbon dioxide, which can lead to hypercapnia (high carbon dioxide levels in the body) and even acid-base imbalance.
3. Venturi Mask
Venturi masks are ideal if you want to measure the oxygen delivery accurately. These masks are very similar to the normal face mask, with the addition of a ‘venturi valve’. As oxygen moves through the valve, it increases its speed, and it allows a specific percentage of air to enter through the holes in the valve.
When opening a venturi mask, you will notice different valves with different colours. Each valve will give you a different concentration of oxygen ranging between 24-60% at a flow rate of 10L/min. Since you can choose the concentration, you can accurately measure the amount of oxygen delivered to your patient. This makes it ideal for COPD patients who require a specific percentage of oxygen in their body to breathe.
4. Non- Rebreather Mask
A Non-Rebreather mask is basically a regular face mask, with a one-way valve and a reservoir bag. When attaching the mask, you need to wait for the reservoir bag to fill up with oxygen before attaching it to your patient’s face.
With this method, you can administer 90-95% oxygen concentration with a flow rate of 15L/min. This approach is typically used in acutely ill patients who are still breathing naturally and who do not have COPD.
5. Nebuliser mask
A nebuliser mask is similar to a normal face mask, but it has a small container at the bottom where you can add medication. When you turn on the oxygen flow to approximately 10L/min the liquid medication in the nebuliser container turns into mist. This mist is then inhaled by the patient. In most cases, you’ll be administering Bronchodilators diluted in Saline through nebuliser masks.
6. Continuous Positive Airway Pressure (CPAP)
Up until now, all the masks mentioned supplied oxygen, and it was up to the patient to inhale it, but the CPAP works by continuously having a low level of positive pressure. This pressure will not allow the patient to exhale completely, and so it prevents the lungs from collapsing.
The CPAP machine is often used for patients with Type 1 Respiratory Failure who can still breathe naturally, and to prevent the collapse of upper airways in sleep apnea.
You patient, however, is likely to complain that the mask is too tight and that it is drying up his airways.
Conclusion
These are the most commonly used masks in a ward setting when patients are awake and alert. However, there are other methods to deliver oxygen, especially if the patient is under anaesthesia (example: during surgery) or if the patient is unresponsive (example: during a CPR). We will get into those later on until then focus on these masks!
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