India is currently facing a medical oxygen shortage due to an unprecedented surge in COVID-19 cases. The supply of medical oxygen is extremely important for severe COVID-19 patients as one of the most common symptoms of the virus is shortness of breath and difficulty in breathing. One of the ways through which medical oxygen can be supplied is Liquid Medical Oxygen (LMO).
What is Liquid Medical Oxygen?
Liquid Medical Oxygen is high purity oxygen used for medical treatment. It has been developed for use in the human body. Due to its low melting and boiling points, oxygen is in a gaseous state at room temperature. Liquification enables storage in larger volume and easier transportation, noted a health ministry explainer on Thursday.
How is liquid medical oxygen produced?
There are various methods through which LMO can be produced. The most common production method is the separation of oxygen in Air Separation Units (ASUs).
ASUs are production plants that separate large volumes of gases. ASUs use a method known as the 'Fractional Distillation Method' to produce pure oxygen from atmospheric air.
What is the Fractional Distillation Method?
In the Fractional Distillation Method, the various gases constituting atmospheric air are separated into different components after cooling them into a liquid state. Liquid oxygen is then extracted from it.
"Atmospheric air is first cooled to -181 degree celsius . Oxygen liquifies at this point. Since, the boiling point of Nitrogen is -196 degree celsius, it remains in a gaseous state. But Argon has a boiling point similar to that of oxygen (-186 degree celsius) and hence a significant amount of Argon liquifies along with Oxygen," noted the health ministry document.
The mixture of oxygen and argon thus produced is drained, decompressed and passed through a second low-pressure distillation vessel in order to separate the two gases.
Ultimately, purified liquid oxygen is obtained using cryogenic containers.
What is the Pressure Swing Adsorption Technique?
Pressure Swing Adsorption Technique is another method through which LMO can be produced. In this method, liquid oxygen is produced non-cryogenically through selective absorption. This method leverages the property that under high pressure, gases tend to be attracted to solid surfaces. The higher the pressure, the more the adsorption of gas.
"If a gas mixture such as air is passed under pressure through a vessel containing an adsorbent bed of 'zeolite' that attracts nitrogen more strongly than oxygen, a part or all of the nitrogen will stay in the bed, and the gas exiting the vessel will be richer in oxygen, relative to the mixture entering the vessel," explained the Union Health Ministry.
Hospitals can also opt for on-site generation of oxygen by this method, where oxygen is produced from ambient air by concentrating it.
In addition to the above sources of medical oxygen, there are also portable oxygen generators known as 'Oxygen Concentrators' that can be used at home.
Judicious use of medical oxygen
The union health ministry had urged citizens to ensure judicious use of medical oxygen as it is a vital resource during a health emergency such as the COVID-19 pandemic. Director, AIIMS, Prof. Randeep Guleria said in a COVID-19 media briefing, "Judicious use of oxygen is the need of the hour. Misuse of oxygen cylinders is a serious matter of concern these days. A few people stock Oxygen Cylinders at home fearing that they may need it later. This is not advisable."
He added that if a patient's oxygen saturation level is 94% or above, it still means there is sufficient oxygen in their body. Use of medical oxygen by these individuals can deprive someone whose saturation level is well below 90% or 80%, he added. Guleria stated that even oxygen saturation levels of 92 or 93 should not be considered critical; instead, this level is only a buffer that enables the patient to reach the hospital on time.(Edited by Mohammad Haaris Beg)