Categories of Oxygen Therapy: Low-Flow vs High-Flow Systems

Oxygen therapy is a treatment in which the patient is provided with extra oxygen to breathe. Also called supplemental oxygen, it is provided to people whose bodies are incapable of taking in the required amount of oxygen. Oxygen therapy is an important topic in anesthesia. Read this blog post to the end and ace your NEET PG preparation.   

Categories of Oxygen Therapy: Low-Flow vs High-Flow Systems

• Depending on this, there are two categories of oxygen therapy.
  • Low-flow oxygen therapy
  • High-flow oxygen therapy
• These therapies are given because the patient is not able to maintain their saturation in the natural atmosphere. Oxygen therapy is, therefore, given to the patient if their O2 saturation is low due to any kind of illness or injury, be it at a cellular or a higher level. It is administered at a concentration of pressure greater than that found in the atmosphere. 

Low Flow System Vs. High Flow System

Low Flow System

1. Nasal Cannula

• Used in low to medium concentrations of O₂ (22-44%)
• Amount delivered-
  • 1 l/min – 24% 
  • 2 l/min -28%
  • 3 l/min – 32%
  • 4 l/min – 36%
  • 5 l/min – 40%
  • 6 l/min – 44%

• This device provides preliminary oxygen to the patient. It can deliver oxygen at a concentration of 22 to 44%. 
• When attached to the flow metre connected to the central pipeline supply of an ICU or cylinders and turned on at 1L per minute, they deliver oxygen of about 24%. Atmospheric oxygen is 20 to 21%. When the concentration of oxygen is increased, it leads to an increase in the concentration of FiO2. This device can only deliver up to 6L per minute. Every litre corresponds to its subsequent FiO2. This device is not beneficial for a capacity of > 6 litres.

Advantages of Nasal Cannula

A nasal cannula can be used in home settings, and patients are able to talk and eat with O2 support.

Disadvantage of Nasal Cannula

It may cause irritation of nasal and pharyngeal mucosa. If the flow is given for more than 6L, the FiO2 may vary. 

2. Face Mask

It is a simple O2 mask. There are partial rebreather masks and non-rebreather masks. These face masks are used when the patient's oxygen requirement increases. They have a flow rate of 6 to 10 litres per minute and supply 35 to 60% O2.

Advantages of Face Mask

An increased delivery of oxygen can be made but for a shorter duration due to damage to the skin surface from the mask.

 Disadvantages of Face Mask

Tight seals are required, which can make many patients feel claustrophobic. There is a potential for skin breaching, which can be uncomfortable for the patient while eating or talking.

3. Partial Rebreathing Mask

This consists of a mask and a reservoir bag. The bag should be inflated continuously during inspiration and expiration to avoid rebreathing. The flow rate is 6 to 8 L per minute, with the FiO2 at 80%. 

Advantages of Partial Rebreathing Mask

The patient can inhale room air through the opening of the oxygen supply is cut.

Disadvantage of Partial Rebreathing Mask

This device has a tight seal which can be uncomfortable for patients.

4. Non-Breathing Mask

These instruments deliver oxygen at a concentration of 95 to 100% (0.9 -1% FiO2), the highest among all instruments. In this case, the flow rate is 10 to 15 L/m. 

Advantages of Non-Breathing Mask

These instruments deliver the highest possible oxygen concentration for patients suffering from severe hypoxemia.

Disadvantage of Non-Breathing Mask

This instrument is not good for long-term oxygen use. It can cause suffocation. It is expensive.

All these devices have variable performance since they are dependent on the person's tidal volume and respiratory rate.

Fixed-Performance Devices

If the patient’s tidal volume or respiratory rate is not normal, fixed-performance devices provide an accurate volume of oxygen.

1. Venturi Mask

Oxygen is delivered at a concentration of 24 to 60% with the help of a Venturi Mask. The flow rate is 4 to 15 liters per minute.  A constant amount is delivered through this mask, which is not dependent on the respiratory rate or the patient's tidal volume.  Color coding is done on these masks, according to which they deliver a specific percentage of oxygen to the patient.

Advantages of Venturi Mask

A very precise concentration of oxygen is provided. It does not dry out the mucosa or cause irritation.

Disadvantage of Venturi Mask

It might be uncomfortable. It might cause skin irritation.

2. High-Flow Nasal Cannula (HFNC)

These have humidifiers, heated tubes, a nasal cannula, and an oxygen blender. 

Advantages of High-Flow Nasal Cannula (HFNC)

There is Peak End Expiratory Pressure (PEEP). At the end of respiration, the alveoli collapse. In order to avoid a complete collapse, Peak End Expiratory pressure has to be present. Constant FiO2 at 100% is delivered. These decrease the anatomical dead space and provide the patient with the maximum amount of oxygen possible.

PEEP (peak end-expiratory pressure)

PEEP is needed in these devices to avoid the collapse of the alveoli. Until the oxygen supply is replenished, the patient can inhale the air in the room. 

Frequently Asked Questions

Q: What are PEEP devices used for?

Answer: PEEP is peak end-expiratory pressure and is needed in devices to avoid the collapse of the alveoli.

Q: What are the advantages of Venturi Mask?

Answer: It does not dry out the mucosa or cause irritation.

Q: What is the Advantage of Nasal Canula?

Answer: A nasal cannula can be used in home settings, and patients are able to talk and eat with O2 support.

And that is everything you need to know about Oxygen Therapy for your NEET PG preparation. For more informative and interesting posts like this, download the PrepLadder App and keep following our blog!