Dr. Prakash Budhathoky

During the second wave of the coronavirus pandemic, we faced an acute shortage of life-saving oxygen just like India had experienced. In big cities and hospitals, several COVID-related deaths occurred due to a lack of oxygen. The same kind of crisis has continued till now. In paediatric and neonatology, it’s an established fact that too much oxygen inhalation is considered bad.
Oxygen is given only when it’s necessary. Researchers have looked at the optimum level of oxygen to be delivered. There is a very thin line differentiating what will be useful and what will be probably harmful. Oxygen saturation was the indicator relied upon to decide on oxygen therapy.

Increased Oxygen: Hyperoxia
Hyperoxia maintains a PaO2 of more than 100 mmHg for a prolonged time; though the duration is unknown, it is probably within hours and not minutes. When one is having a FiO2 of 100%, there are good and bad effects. Good effects – vascular PO2, peri capillary diffusion and oxygen delivery improve and inflammation starts to settle down. But vascular perfusion may also start decreasing, reactive oxygen species increasing, leading to lipo-oxidative stress at the tissue level.

FiO2 Greater than 60% causes lung atelectasis. The Lorraine-Smith effect, where pulmonary oxygen toxicity may present as severe pulmonary inflammation, leads to pulmonary edema and is referred to as the formation of excess ROS and RNS. Vascular effects include a decrease in cardiac output and heart rate. The Paul-Bert effect can give rise to profound vasoconstriction and generalised tonic-clonic seizures. But these are very rare side effects. Several trials have been published on the effects of hyperoxia in intensive care and emergency medicine on conditions like ACS, MI, stroke, cardiac arrest, including in the last two years of the pandemic.

A 50% increase in mortality has been observed in patients who spent 40% time in optimal oxygen saturation range vs patients who spent 80% time in optimal time. Trials over the past 24-36 months have also looked at restrictive oxygen strategies. The American Heart Association does not recommend oxygen therapy in patients with MI until their oxygen saturation is low. Too much oxygen may worsen the outcomes. The Stroke oxygen trial showed no benefit of oxygen in stroke patients. No difference in mortality was observed. It was found that unnecessary oxygen to patients was not good and giving oxygen to patients to achieve oxygen saturation of 97-100% was not helping the patients.

Modality
The problem was a dynamic change in the need was not available. There was very little information about dynamic change in terms of oxygen requirement. This was dependent on the devices used ventilator, high-flow nasal oxygen (HFNO), non-invasive ventilation (NIV), etc.
Supply was limited to four ways: Liquid medical oxygen, oxygen cylinders, portable oxygen concentrators or PSA (pressure swing adsorption) plants. There were not many PSA plants in the country at that time. The country had to turn to the industrial-grade oxygen available. A lot of oxygen was sourced from steel plants. Industrial grade oxygen seemed to be as good as LMO, though the purity was around 92-93%. However, the problems were that these plants were in different parts of the country as well as the shifting pandemic, which moved from one part of the country to the other. The cryogenic tankers took longer to reach their destination (speed limit for safety) and so the crisis very quickly turned into an acute shortage.

Hygiene
There are limited refilling plants for oxygen cylinders; they are associated with ease of hoarding, questionable hygiene practices. Oxygen concentrators helped, but there was a problem of limitation of flow; many of them only gave 5-10 L of oxygen. Hoarding is also possible and oxygen purity declines after using it for some time at the maximal capacity. PSA plants are sustainable solutions, but the zeolite used has to be imported. They cannot be operationalized overnight. They are not the primary source of oxygen; they are best used as a backup. Oxygen produced has 94-95% purity. Solutions needed at that point in time were dynamic need calculation, allocation formula, distribution techniques, substores for ease of transport.

Mumbai Model
The Mumbai model of oxygen management has won much praise. It was a decentralised process. The city is divided into 24 wards. Real-time data was available as every bed in the city was mapped. Six substores were created across the city. And smaller tankers, which could move easily in the city, were used to transport oxygen from hospital to hospital. The oxygen stewardship programme was introduced. One litre of oxygen saved is one litre produced. Keep oxygen restrictive strategy – keep oxygen saturation between 90 to 94% in patients who were monitored. Leaks, old pipes were repaired. Oxygen stewards were appointed to each hospital. Each hospital had an oxygen committee. Mumbai has long-term sustainable solutions: increased capacity building and keeping emergency oxygen stores for 2 weeks requirements.

At Last, Saving oxygen may be a strategy now. In a pandemic situation, in ICUs, oxygen saturation can be maintained at as low as 88% or up to 92% in a monitored environment and =93% in an unmonitored environment. We should be targeting less oxygen saturation than what was being done before. As soon as the target is reached, oxygen can be reduced by a litre every time and see how the patient maintains at this level. Wastage needs to be taken care of hence oxygen stewardship programmes are going to be necessary for the future.

(Dr. Budhathoky is the Central Treasurer of Nepal Medical Association)