Wilhelm Scheele (1773) and Joseph Priestly (1774) discovered what they termed ‘dephlogisticated air’, later named oxygen by Antoine Lavoisier in 1777. Its address on periodic table is p block, period 2, at number 13 in the 2nd row. It is a highly reactive nonmetal, oxidizing agent with an atomic number of 8 and is 3rd most abundant element in universe. Fresh water contains about 6ml dissolved O2 per liter versus 5 ml in sea water. It supports combustion but in pure form it does not burn. It is recycled in nature as it is used by living beings and produced by photosynthesis in green plants and algae.
We all know life sustains on earth due to oxygen, admixed in its atmosphere or in combination with hydrogen as water. 1/5th of earth’s atmosphere and 2/3rd of human body is composed of oxygen. The air one breathes, the water one drinks, and food one eats contains oxygen. In normal concentrations in all these things we rarely notice its importance, but once it is lesser than normal in the atmosphere or in one’s body, we feel its deficiency in various ways and started gasping for it. One feels its need once we go up the mountain, down the depths of the ocean, or if we have a lung or a heart disorder. With Covid-19 affecting mostly the lungs that primarily deals with oxygen we have realized its importance and the demand has whopped up. Everywhere one sees, it is the oxygen that is in news.
In its gaseous form it is something that is normally not seen, not felt, not smelt, not colored, tasteless, and perhaps not valued till this pandemic stuck. Its liquid and solid form is pale blue. Just a little change from O2 to O3 it becomes ozone, a protective biosphere layer that absorbs UV radiation. It is considered at par with a drug or a pharmaceutical product and as per WHO is listed as an essential medicine.
Necessary in a particular amount, if we exceed or recede that quantity, it is dangerous. Its concentration in human body normally is 95% and above, but its need is felt once the level goes down than 90%. People living at high altitude and patients with long standing lung or heart disease tolerate and are accustomed to lesser levels. It has a medicinal value as it is important for cellular respiration in humans (used as oxygen therapy in many diseases) and finds use in industrial production of steel, plastics and textiles, welding and cutting, as rocket propellant, life support systems in aircraft, submarines, space flights and diving.
How do we measure it in human body? We can do it invasively by directly checking on withdrawn blood by the blood gas analyzer. Also non-invasively by the probe attached to a monitor or by a small portable device pulse oximeter (invented by Takuo Aoyagi), that has become the most famous device of 2020.
How do we get oxygen? On a large scale its production is done in oxygen plant with fractional distillation, pressure swing adsorption, electrolysis of water. India has 12 big manufacturers and 500 small gas plant owners. In a plant it is separated from atmosphere and collected in different grades, industrial (welding, research, aviation breathing) and medical oxygen. Oxygen is extracted from air and compressed at very high pressure of 2200 PSI and is available as 7q big hospital cylinders or 1.43 q smaller portable cylinders, and even in backpacks. World-wide a hundred million tons is extracted from air annually for industrial use. Another form that takes far lesser space is the liquid oxygen (1L of liquid is equivalent to 880 L of gaseous) is prepared when gaseous form is cooled at – 297°F. For economic reasons O2 is often transported in bulk as a liquid in specially insulated tankers. Once exposed to room temp it quickly converts to gaseous form. These have 99.9% purity.
For a common man once it is oxygen, the visual of a huge, heavy, seamless, rusty iron cylinders with white colored neck containing compressed oxygen comes to one’s mind. These cylinders are attached to the central piped oxygen system of a hospital, delivered to patient in a ward as per the need. Filled up cylinders can be used bedside anywhere, and got refilled again and again. But today we can have individual machines for a patient at home which over time have been upgraded to small, colorful, light weight concentrators. Concentrator does not store oxygen, it uses ambient air, filters out nitrogen, to supply oxygen through a nozzle, and delivers 90-95% pure oxygen. They may deliver oxygen continuously or intermittently as per patient inhalation. They can be small portable battery operated or can be bigger and electricity done. Oxygen can get it delivered to the body through the nasal prongs, various types of masks, high flow nasal devices or directly to the lungs through a ventilator.
This pandemic has its mortality related to the hypoxemia that it sets in by affecting the lungs. And just giving oxygen is a primary mode of treatment in some cases. Around 5% need oxygen in wards or home, and about 2% need ICU oxygen. Very few and very sick may need ventilator support which is again oxygen delivered sophisticatedly.
Oxygen did find its use for recreational use after the concept of ‘air stations’ in polluted areas of Tokyo and Beijing, with first “Oxygen bar” opened in Toronto in 1996, thereafter in north America and later in many parts of the world, where one sells oxygen for recreational use. It is even flavored with scents to enhance the experience. But even after the hype of commercialization it never has been so popular as after the Covid-19 pandemic.
From being taken for granted, to the need for even rationing it for patient use, oxygen is finding its due. Hospitals are desperate to have it in abundance. But are falling short on the demand. It has been rationed to prevent misuse, a human rights violation. Prices have gone up, it is being used judiciously, production has been increased from 750 tons’ to more than 5000 tons daily. At its highest demand in a Covid pandemic this vital life saver is used in thousands of liters per day (100 % varying from 2 to 60 liters per minute which is around 3600 liters per hour).
With the world changed by a zillion, we need to have oxygen in our future budgets both at the governmental as well at the individual level. We need to check our level (smart phones/watches will do it), we need to have it available at lesser scale in our homes (small concentrators or piped home supply) and at bigger level in hospitals and hospices (individual plants).
Dr Muzafar Maqsood Wani is Consultant Nephrologist, SKIMS, Sringar