Oxygen mask: All about oxygen therapy and its types

Oxygen mask is an oxygen delivery system with the help of different oxygen devices used to regulate the supplement oxygen to the subject to increase the oxygenation. As oxygen can be delivered via many different routes. 

A gas exchange can be affected in the setting of respiratory or cardiac problems that results in hypoxemia. 

Hypoxemia: “it refers to low oxygen content in the blood”. 

Hypoxia: “which means low oxygen supply in bodily tissues in order to maintain adequate homeostasis”. Hypoxia is caused by hypoxemia. So, if there is not enough oxygen in the blood, the blood cannot deliver enough oxygen to the body tissues as it circulates, and this leads to hypoxemia. Which decreases oxygen in the blood, it can occur from an infection such as sepsis, fever or anemia. 

FiO2: “It is defined as the percentage or concentration of oxygen that a person inhales”. If FiO2 of normal room air is 0.21 that is 21%. We inhale on a day-to-day basis, 21% oxygen,78% nitrogen and 1% trace elements such as carbon dioxide, neon, helium and methane. 

Oxygen therapy is used for helping people with lungs disease or breathing problems, they get the oxygen they need for their body to function. Supplemental oxygen is indicated for people who have hypoxemia. Because of impaired oxygen diffusion across the respiratory membrane, hyperventilation or significant lung tissue loss as a result of tumors or surgery. 

People who have severe anemia blood loss or other illness, where if there are not enough red blood cells or hemoglobin to deliver oxygen may also require oxygen mask therapy. 

Oxygen therapy is the supplementation of oxygen concentration greater than 21%. Oxygen therapy that is the delivery of oxygen at higher concentration than room air at a higher FiO2, is used to treat hypoxia. There is a wide range of oxygen masks or oxygen delivery devices which are divided into two types: 

• Low-flow oxygen therapy (variable performance)
• High-flow oxygen therapy (fixed performance)  

Nasal cannula is a plastic tubing with 2 protruding for insertion into the nostrils for the delivery of oxygen. After wearing the prongs inside the nostrils, the nasal cannula is taken behind the ear and then tightened. It is safe and simple to use and easily tolerated by patients and patients can eat and speak by wearing a nasal cannula and this is not much expensive. 

The use of nasal cannula oxygen mask is for those people who have asthma, underdeveloped lungs in newborn, COPD disease, pneumonia and cystic fibrosis.

Using nasal cannula at oxygen flow rate of about 1 to 6 liters per minute and FiO2 of about 24% to 44% can be achieved. 

A Nasal catheter is a thin single lumen flexible tube which is passed through the nose and ends with its tip in the posterior part of the nasal cavity above the uvula. Nasal catheter usually comes 40cm long with open distal end and lateral eyes. The size varies between 8 French to 18 French.  Nasal catheters are usually well tolerated, and they are unlikely to be dislodged. Humidification of oxygen is not necessary because the tip of the catheter lies in the nasal cavity. 

With the help of nasal catheter, oxygen flow rate of 2 to 3 liters per minute can be given. Which FiO2 of about 35% to 40% can be achieved.

Transtracheal oxygen mask (TTO) is a thin catheter inserted with a guide wire between the second and third tracheal ring. Transtracheal oxygen catheter (TTOC) is used for long-term oxygen therapy or for oxygen dependent patients.

The Oxygen flow rate of trans tracheal oxygen devices is about 0.25 to 4 liters of oxygen can be administered and FiO2 of about 22% to 35% can be achieved. 

It improves oxygen compliance by reducing total oxygen usage if 50% to 70%.

Simple face mask also called (Hudson mask). It is a low-flow oxygen device. Simple face mask sits on face over mouth and nose and has an elastic strap. It has a metal strip in order to get adjusted on the nasal bone. It has exhalation ports and an elastic strap that is too tight at the back, and it has an oxygen feeding line. Simple face oxygen mask is very simple and safe to use. It is easily tolerated by patients and the best choice for those patients who are mouth breathers and easy to apply.

The Oxygen flow rate of simple face mask is about 5 to 8 liters per minute is administered. FiO2 of about 40% to 60% can be achieved. 

Non re-breathing masks are also called NRBM. It is a simple face mask with an oxygen reserve wire and there are two one-way valves called expiration and inspiration valves. It has an oxygen feeding line and an oxygen reservoir bag. NRBM is a low flow oxygen device with high FiO2. Non re-breathing mask sits on the face and over mouth and nose and has an elastic strap. The reservoir bag delivers a high concentration of oxygen.  

Inspiration valve:

“It is between the face mask and a plastic reservoir bag that is attached to a supply of oxygen”. Inspiration valve does not allow the exhalation of the air or outside air from entering the bag. So, only oxygen flows from the back to the mask. 

Expiration valve:

“Expiration valve allows exhalation of the air to flow into the atmosphere but doesn’t allow the outside air to enter”. 

The main function of non-rebreathing mask is during exhalation, the inspiration valve closes, and expiration valve is opens. Hence, CO2 is not available during inhalation.

Using a non-rebreather mask the oxygen flow rate is about 10 to 15 liters per minute can be administered and FiO2 is about 95% to 100% can be achieved. A Minimum of at least 10 liters oxygen should be administered through a non-rebreather mask in order to prevent rebreathing. It provides high FiO2. The reservoir bag provides extra oxygen when the patient breathes faster or deeper. It doesn’t dry the mucous membrane in short term. The two one-way valves allow only to breath pure oxygen and hence carbon dioxide retention is prevented.

Partial re-breathing mask is similar to non-rebreathing mask. The only difference is it doesn’t have one-way valves. The partial rebreathing mask can be defined as simple masks with additional reservoir that allows the accumulation of the oxygen enriched gas for rebreathing. 

This mask includes exhalation ports, oxygen feeding line and a reservoir bag. The main function of partial rebreather mask is CO2 is exhaled into the reservoir bag and the side ports close during exhalation a then CO2 is inhaled.

Partial rebreather mask requires a minimum oxygen flow rate is 6 to 10 liters per minute can be administered and FiO2 of about 60% to 80%. 

The inspired gas doesn’t mix with the room air by using partial rebreathing mask. Patients can breathe room air through exhalation ports if oxygen supply gets interpreted. 

The Venturi or entrainment mask is a high flow device that delivers a fixed oxygen concentration. Venturi mask consists of a face mask which sits on the face covering mouth and nose. It has a metal piece or nasal clip which gets adjusted on the nasal bone. Venturi oxygen mask has exhalation ports and elastic straps. It has interchangeable Venturi valves or jet adapters.

Different colored Venturi valves are available in order to supply specific concentration of oxygen. Venturi masks use the Bernoulli principle to entrain room air where pure oxygen is delivered through a small orifice of Venturi valves. The exhaling gases are rapidly flushed from its holes. Therefore, there is no rebreathing and no increase in dead space. 

There is accurate and constant FiO2 despite varied respiratory rates and tidal volumes in Venturi mask. The Venturi oxygen mask doesn’t dry the mucous membrane and humidification is not needed because Venturi mask mixes oxygen with room air creating high flow of oxygen of a desired concentration. 

The Oxygen rate of Venturi mask depends on colored Venturi valves. Each color valve supplies specific oxygen concentration and flow rate. The colors include: 

Blue: 24% FiO2, 2 liters per minute of oxygen. 

White color: 28% FiO2, 4 liters of oxygen per minute. 

Orange color: 31% FiO2, 6 liters of oxygen per minute. 

Yellow color: 35% of FiO2, 8 liters of oxygen per minute. 

Red color: 40% FiO2 that is 10 liters of oxygen per minute. 

Green color: 60% FiO2 that is 15 liters of oxygen per minute. 

So, the oxygen flow rate of Venturi mask is 2 to 15 liters per minute with FiO2 from 40% to 60% 

• Check the Venturi mask jet port holes are not block with patient blanket or gown which will affect the FiO2 being delivered. 
• When using Venturi mask, check the flow rate FiO2 as ordered. 
• You must check the elastic strap; the strap should not be too loose or too tight and access the skin condition. 

• Be careful with positioning. Regarding positioning, Oxygenation is optimal in upright position and for patients who are awake and requiring oxygenation support should be upright unless the contraindication in such position is present. 

Tracheostomy mask is a procedure in which an artificial is created in the throat to assist with patients breathing or to create an alternative airway. This is used for opening from outside which may be permanent or semi-permanent into the pipeline. This mask is common in patients with prolonged stay in ICU or ventilator support. 

Tracheostomy oxygen mask covers the tracheostomy and gently lies over and secured with an elastic band that is adjustable for the patient fitting loosely over to allow adequate oxygen delivered to support the patient’s need. This mask is used for those patients who are suffering from tracheostomy. 

Both terms refer to a small opening in the neck to create a new path for air to get into the windpipe. In tracheostomy, doctors make an opening through the front neck into the trachea (windpipe) and a tracheostomy tube is placed into the hole to make it open for breathing. While on the other hand, the Tracheotomy is actually an incision of the trachea or windpipe. Because of this, both terms are often used interchangeably by man people. 

There are various types of tracheostomy procedures depending on the circumstances of the patient and the treatment. Similarly, there are different types of tracheostomy tubes, and each has specific functions. These are the following types of tracheostomy: 

1. Emergency tracheostomy  
2. Elective tracheostomy  
3. Permanent tracheostomy 
4. Percutaneous tracheostomy 
5. Mini tracheostomy (Cricothyroidotomy) 

Tracheostomy can also be classified as high, mild or low, depending on the level at which it is inserted into the trachea. 

1. Cuffed (allow airway clearance but no protection from aspiration) 
2. Non-cuffed (allow airway clearance and also some protection from aspiration) 
3. Double lumen tubes 
4. Tubes with speaking valves 
5. Metallic tubes and others. 

The oxygen flow rate of tracheostomy mask is 10 to 15 liters per minute and FiO2 is between 60% to 80%. 

The procedure of tracheostomy is preferably done under general anesthesia. But in Emergency, it may necessitate local anesthesia only.  

T piece kits provide spontaneously breathing intubated Patients with supplementary oxygen during the transport and in the recovery room. Fixed Venturi valves can also be incorporated into oxygen recovery T piece kits, specially 40% valve. T piece has a good control over both positive inspiratory pressure or peek inspiratory pressure of PIP and positive expiratory pressure of PEEP.

It has the ability to administer effective PEEP in contrast to the self-inflating bag. it delivers CPAP by the same mechanism if you are not occluding the T piece, but you are just holding a good seal of the mask over the face. It controls the inspiratory time when you are uploading the T piece longer you occlude the longer inspiratory time. There is more consistent delivery with multiple users as long as you train them in getting a good seal with T piece oxygen mask. 

Oxygen flow rate of T piece is 8 to 10 liters per minute with FiO2 30% for babies and 21% for those who are 32 weeks above. 

It is considering high-flow oxygen which delivers moderate flow of oxygen to the patient, helps correct or prevent hypoxemia. It also decreases myocardial or cardio work. Face tent din device delivers humidified oxygen in the form of the mist at an accurate concentration. A Humidifier in the face tent is used for the patient to make more moisture go into its flow. 

In Face tent mask aerosol mask, you have a metal piece at the top of this mask that is placed over the bridge of the nose. This metal piece confirms the shape of nose so that it can be secured to the patient’s face.

There are two exhalation ports on the mask and blue tube is attached to the front of the aerosol mask, and tube is then connected to the bottle of sterile water. The bottle is connected with a dial regulator that controls the concentration or amount of oxygen. The aerosol mask is ideal for administrating nebulizer treatments. This device helps prevent drawing oral mucous by providing high humidity oxygenation.

Oxygen flow rate of face tent aerosol mask is 10 to 15 liters per minute with FiO2 from 28% to 100% should be used.