THE OXYGEN IMBROGLIO

Shortages of Oxygen has been a hot topic in India during the last several weeks. It started with a few Opposition-run State Governments blaming that India had exported the largest quantity of Oxygen from the country when the requirement was mounting in the country due to the Covid-10 pandemic. The Government and Industry clarified that it was Industrial oxygen that was exported and not medical oxygen. The Union Government pointed out that earlier this year, the PM-CARES Fund had allocated Rs 201.58 crores for the installation of an additional 162 PSA Medical Oxygen Generation Plants inside public health facilities and many states had not done the job. This is the context of this blog.

The mainstay of treatment for patients with COVID-19 is ‘supportive care’. Rather than treating the underlying viral infection, supportive care aims to maintain the function of the body’s vital organs to keep the individual alive while the disease progresses and eventually resolves. Severe bilateral pneumonia is the main feature of severe COVID-19. Supplemental oxygen is a first essential step for the treatment of severe COVID-19 patients with hypoxemia and should be a primary focus. Infected and damaged lungs are less effective at allowing oxygen to pass from the environment to the bloodstream.

The main reason for being admitted to a hospital with COVID-19 is to receive supplemental oxygen, to increase the amount of oxygen in the lungs and blood, which will be sufficient treatment before recovery in most cases. This can be administered in a number of ways, including into the nose using plastic tubing, or via a loose-fitting face mask: 1) Nasal cannula-based oxygen therapy for those with 2-5 litre requirement of oxygen per minute. 2) Mask-based for those with 6-15 litre requirement. 3) High-frequency nasal cannula oxygen therapy for those with 15-50 litres and ventilator support above that. AIIMS director Randeep Guleria said that ’20 percent of the patients need oxygen therapy and five percent need ventilation.

Medical experts were increasingly preferring non-invasive oxygen therapy over ventilation as doubts over the effectiveness of ventilator increased after an overwhelming majority of Covid-19 patients on the ventilator were dying in India and abroad. It was thought that ventilators were worsening the lung damage caused by Covid-19. Doctors have stopped using ventilators for management of COVID-19 (except very late) as early ventilation was said to increase the chances of death. Many people stay at home till late and approach hospitals for admission at a stage when oxygen demand is pretty high (five-six fold) as compared to the low flow stage. Late presentation (low presentation baseline oxygen saturation) can exponentially increase the risk of death. Hence medical community suggests early care and therapy (oxygen/steroid/heparin) in the pulmonary phase (90-95 percent saturation).

Cryogenic separation is most effective when any of the three criteria need to be met: high purity oxygen is required (>99.5%), high volumes of oxygen are required (≥10to the power of 2  tons of oxygen/day), or high-pressure oxygen is required. Cryogenic air separators take more than an hour to start up. Additionally, since cryogenics can produce such a high purity of oxygen, the waste nitrogen stream is of usable quality.

Pressure swing adsorbers (PSA) are a much newer technology as compared to cryogenic ASU. PSA devices are best suited for processes that do not require extremely high purities of oxygen (<95%). While PSAs can achieve as high as 99.9%, the cost associated with going above 99.5% in a PSA device rises tremendously. Furthermore, PSA devices are best suited for small volumes of oxygen production, typically on the order of 10 to the power of 1 ton/day. Since the output of oxygen is largely controlled by the bed size in the PSA systems, costs rise linearly when higher volumes of oxygen are required. PSA devices take only a few minutes for start-up.

Membrane Technology: Conventional membrane technology involves passing air over a membrane filter. The filter will allow fast gasses to pass and slow gasses will stay. Oxygen is considered a fast gas and nitrogen and argon are considered slow gasses. Varying levels of purity can be achieved by varying the time that the gas spends undergoing filtration. Previous membrane technology could only produce purity levels of less than 50%. But the recent The ion transport membrane (ITM) was developed by Air Products and Chemicals, in conjunction with the United States Department of Energy and Ceramatec can produce greater than 99% purity and high volume (equivalent to volumetric flow of cryogenic separation systems) Oxygen at much lower costs than cryogenic separation!

MEDICAL OXYGEN: The air we breathe is a mix of several gases, such as oxygen, nitrogen, carbon dioxide, and hydrogen. The term ‘medical oxygen’ means high-purity oxygen, which is used for medical treatments and developed for use in the human body. Oxygen is also used in industries for combustion, oxidation, cutting, and chemical reactions. The difference is that purity levels of industrial oxygen are not appropriate for human use. There can be impurities, which can make people ill. Medical oxygen cylinders should also be free of contaminants.

Years ago, gas supply vendors typically maintained two separate storage facilities for oxygen: "welding or industrial or technical" (a non-USP, or illegal to sell for human consumption label) variety and gas intended for human use in respirators or medical procedures (a USP label). Since most gas supply vendors have decided that it is simply not cost-effective to store separate grades of medical gases, almost all oxygen sold in the US is a USP grade- the United States Pharmacopoeia- (meets USP requirements for human consumption). However, there are distinct differences in how the cylinders are filled. Most vendors in the US are now filling all cylinders with USP gas. If the vendor fill station operator sees that a cylinder is labeled as a medical or emergency oxygen cylinder, or intended for human respiration, then the cylinder is evacuated and filled with USP/Medical oxygen. But most welding or Industrial grade oxygen cylinders are filled with USP oxygen without an evacuation-between-fills step. Grade 4.5 oxygen is USP oxygen that has a purity greater than 99.995 % oxygen Grade 5 (or "five nines") oxygen is USP oxygen that is certified 99.999 % pure. It is sometimes called research grade.  This is the highest purity of oxygen manufactured in the US and is typically found only in top-end chemical research facilities. Its non-research use is associated with specialty welding of titanium and titanium alloys for the nuclear or aerospace industry.

It is heartening to note that the Government of India has taken up the responsibility of supplying Oxygen to the states, and have requested/instructed industries to chip in producing medical oxygen stopping the production of industrial oxygen to the minimum. The Prime Minister's Office has approved funds for the installation of 551 dedicated Pressure Swing Adsorption (PSA) Medical Oxygen Generation Plants in public health facilities in the country.  The Indian Railways have done a great job of running Oxygen Expresses delivering as on today 9^th May 4500 MT oxygen across the country.

Countries like the United States, Russia, Ireland, Thailand, France, Italy, Germany, have been contributing to India’s medical requirement by building oxygen plants, sending ventilators, oxygen concentrators, rapid testing kits, and medicines. The Oxygen imbroglio has almost come to an end!