The basics of caring for acutely unwell patients are simple: air needs to go in and out and blood needs to go round and round. Across the world, the pandemic has consistently shown how poorly equipped healthcare systems are for addressing these needs. Much attention has been paid to vaccines, drug therapies and ventilators in recent months, while relatively little has been said about the most basic human requirement of all – oxygen.

Oxygen is all around us, and yet there are acute shortages of it in many healthcare settings. This is because the infrastructure needed to supply oxygen to patients, such as large vacuum-insulated evaporators (which are like giant, very cold vacuum flasks), is relatively expensive and needs regular maintenance and top-ups of liquid oxygen. Where this isn’t available, hospitals might use concentrators that extract oxygen from the surrounding environment. These require electricity and compressed air – which, again, are scarce in many places. Or they might use cylinders, which can store and deliver short-term oxygen therapy. But they need regularly refilling, which depends on secure supply lines.

I am a doctor who specialises in respiratory and intensive care medicine. Thankfully, I have never been in a situation where I needed to provide a patient with oxygen therapy when none was available. But this is exactly the situation facing healthcare workers in many other countries. During the pandemic, systems for delivering oxygen came under pressure almost everywhere. In the UK, hospitals that were decades old struggled to cope with surges of patients needing the type of high oxygen flows used in modern therapy. In some low- and middle-income countries, the infrastructure to deliver oxygen to patients was nonexistent.

Human lungs are enormous gas exchange surfaces made up tiny little air sacs called alveoli (when flattened out, these are the size of roughly half a tennis court). The purpose of lungs is to transfer oxygen from the air to the blood to maintain the function of our body’s cells, and to transfer carbon dioxide from our blood back out into the air. The virus that causes Covid-19, influenza and other causes of pneumonia make the lungs less efficient at transferring oxygen into the blood, a situation known as acute hypoxaemic respiratory failure.

The immediate treatment for patients with acute hypoxaemic respiratory failure is oxygen. Though the World Health Organization has included oxygen for the treatment of respiratory failure in its List of Essential Medicines since 2017, people continue to die through a lack of it. In 2017, pneumonia – a treatable condition – killed more than 2.5 million people worldwide, of whom a third were children under five years old. Before the pandemic, I worked together with colleagues in Uganda to research the effects of acute hypoxaemic respiratory failure in African countries. We found that 4.5% of patients arriving at emergency departments in Uganda had this condition, most commonly caused by pneumonia. The average age of these patients was 38 years; 77% of them died before ever leaving hospital.

Studies have shown that oxygen therapy can reduce the risk of death from pneumonia by 35%, and that improved access to oxygen would save the lives of more than 120,000 children every year. Oxygen can be administered to patients who need it via simple face masks that use up to 15 litres of oxygen a minute, high-flow systems that use up to 60 litres of oxygen a minute, or high-pressure systems that can use more than 70 litres of oxygen a minute. The key element is a secure, plentiful and uninterrupted supply.

Complex treatments such as expensive drug therapies or mechanical ventilators can provide marginal improvements in survival, though often it is the simple things that save the most lives. Governments and health policymakers have long failed to address the scarcity of oxygen in hospitals across the world. Ensuring every patient who needs it has access to oxygen, both during the pandemic and in the future, isn’t an insurmountable challenge; indeed, if scientists can work out how to provide oxygen for astronauts to live in the International Space Station for months at a time, we can surely ensure it’s delivered to those who need it here on Earth, wherever they live.

The pandemic has thrown a spotlight on the inequalities of access to essential treatments such as drugs and vaccines. Oxygen must be included in this list. Improving the world’s supply would mean investing in robust supply chains able to meet surges in demand as well as the infrastructure – vaporisers, electricity, pipework, engineers and cylinders – used to supply it. Medical oxygen accounts for only about 1% of the world’s liquid oxygen supply; the rest is used mainly for industrial purposes such as mining and steel production. Providing medical oxygen to patients could prevent thousands of deaths every year.

• Dr Charlotte Summers is a lecturer in intensive care medicine at the University of Cambridge