The second wave of the COVID-19 pandemic is affecting lakhs of people across India every day. According to experts, shortness of breath (medically called dyspnea) is the most common clinical feature in hospitalized patients during this wave.

Patients with severe illness in COVID-19 exhibit shortness of breath, usually accompanied by low blood oxygen saturation levels (medically called hypoxaemia). Oxygen saturation (SpO2) is the amount of oxygen present in the blood and should be more than 94% at room air. A SpO2 level below 90% is known as hypoxaemia. Such patients require ‘oxygen therapy’. 

Oxygen Therapy and COVID-19

According to WHO (World Health Organization), oxygen therapy or supplemental oxygen is the provision of medical oxygen as a healthcare intervention. Medical oxygen contains about 82% pure oxygen and is free from any contamination. It is advisable to give only high-quality, medical-grade oxygen to concerned patients.

Oxygen therapy is only recommended for all severe and critical patients of COVID-19 with low doses ranging from:

  • 1-2 liter(s)/min in children

  • 5 liters/min in adults

The output capacity of oxygen concentrators is generally measured in LPM or liter per minute. 

Need For Supplemental Oxygen in India

Over the past few weeks, a sudden supply of additional oxygen to treat hypoxaemia has resulted in a rise in demand for supplemental oxygen support systems. 

An alternative to oxygen cylinders is oxygen concentrators that are used to treat mild to moderate cases of respiratory problems in COVID-19. This makes oxygen cylinders available to treat the more severe cases. 

With the surging COVID-19 infections, there is a shortage of oxygen cylinders and concentrators in the market. Nonetheless, it will be helpful to know about oxygen concentrators and their role in COVID-19.

Introduction to Oxygen Concentrators

An oxygen concentrator is an electrically powered medical device that takes in air from the environment and removes nitrogen (atmospheric air has about 78% nitrogen and 21% oxygen) from it to concentrate oxygen and deliver it to a patient suffering from hypoxaemia. An oxygen concentrator may also operate on batteries. 

The continuous supply of concentrated oxygen to the patient improves and stabilizes their blood oxygen saturation levels. 

An oxygen concentrator can produce about 95% concentrated oxygen. A pulse oximeter (a device to measure the blood oxygen level in your blood) should be used to identify hypoxaemic patients before using an oxygen concentrator to supply oxygen to them. 

An oxygen concentrator includes the following components with distinct functions:

  • A gross particle and intake filter- takes in atmospheric air. 

  • A compressor- compresses (reduces the volume of) the air.

  • A heat exchanger- reduces the temperature of the pressurized air. 

  • Sieve beds with zeolite [a mineral that preferentially adsorbs nitrogen gas (N2) at high pressures]- depressurize (lose air pressure) and release nitrogen back into the air. 

  • Valves- open to release concentrated oxygen into a reservoir.

  • A reservoir- stores the concentrated oxygen.

  • A flowmeter- releases oxygen continuously at a specified flow rate. 

  • Devices connecting the oxygen supply to the patient (e.g. oxygen tubing, nasal cannulas, and face masks)

Types of Oxygen Concentrators

There are two types of oxygen concentrators: stationary and portable. 

  • Stationery ones are large, cannot be moved around, and are made to supply large quantities of concentrated (~95%) oxygen. 

  • Portable oxygen concentrators are small, suitable for traveling and outdoor use, and have a lower output capacity (2 to 10 liters). 

Noteworthy limitations of portable oxygen concentrators:

1. Downtime: Oxygen concentrators need to be paused for a predetermined time (~20-30 minutes) for every few hours of continuous running. The exact requirement is generally mentioned on the equipment or in the user manual, specific to the machine. 

2. Power back-ups: Oxygen concentrators can be useful if you have a continuous electrical power supply. If there are frequent power cuts in your area, the oxygen concentrator may be of no use without an additional battery backup or a generator.

Oxygen concentrators are reliable and economic when compared to oxygen cylinders and centralized piped oxygen supply systems. However, they need an uninterrupted power supply and regular maintenance. Further, technicians need to be trained for the proper implementation and maintenance of oxygen concentrators.

Other Sources of Medical Oxygen

Besides oxygen concentrators, other sources of medical oxygen supply are oxygen cylinders and oxygen pipeline systems. Oxygen cylinders are metal vessels in which oxygen is stored as a gas under pressure. The oxygen pipeline system supplies high-pressure oxygen from a liquid oxygen source through pipes.  

A comparative study of oxygen concentrators, oxygen cylinders, and piped oxygen supply is made in this table. 

The bottom line is that oxygen concentrators should only be used after consultation with your doctor and under medical supervision. Let your doctor know if your blood oxygen levels fall below 94%.


1. World Health Organization. 2021. WHO technical specifications for oxygen concentrators. [online] Available at: <> [Accessed 30 April 2021].

2. 2021. [online] Available at: <> [Accessed 30 April 2021].

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