When hospital consultant Ron Daniels began treating coronavirus victims he was struck by how many of his patients could hold conversations despite low blood oxygen levels, which would normally be extremely hard for someone with a serious lung or respiratory illness.
“If they have bacterial pneumonia they would normally be pretty breathless and tired,” said Dr Daniels, a specialist at UK intensive care units. “Patients with Covid-19 do not seem to get that.”
This unusual feature of the disease is among the reasons why clinicians are reassessing when and how to deploy the ventilators seen as critical for treating those with the most acute symptoms — and which have become the most sought-after medical tool for fighting the pandemic.
As governments around the world rush to procure the life-saving machines as the number of confirmed cases nears 3m, some physicians have flagged up a tendency to use them too quickly in those struck down by the virus, potentially causing harm.
“We as a medical community are still learning new things about diseases that have been here since the dawn of humanity,” said Craig Jabaley, a professor at the Emory University School of Medicine in the US, who believes a patient’s situation should be properly assessed before “intubating” with a ventilator. “Coronavirus is a few months old — so we are learning new things about it all the time.”
When a patient is placed on a ventilator, they are sedated and a tube is inserted into their windpipe through which pressured oxygen is piped to mimic breathing. This invasive process is generally reserved for the most severely ill patients as it carries the risk of complications such as lung damage, kidney dysfunction and infections.
During the early stages of the outbreak, doctors in many countries placed patients on to ventilators based on low levels of blood oxygen. This typically manifests as shortness of breath, dizziness or confusion and if not treated can lead to organ damage.
But some doctors say it is becoming clear that, in Covid-19 patients, there are benefits from intubating slightly later, at a lower pressure initially to avoid injury to the lungs and often only if other therapies have failed.
“At the beginning we were treating the numbers — peoples’ low blood-oxygen levels — whereas now we have migrated . . . towards ventilating based on symptoms. We are looking instead at how breathless a person is and how tired they are,” said Dr Daniels.
In contrast to some other forms of respiratory failure, many Covid-19 patients do not have “stiff” lungs, said Dr Jabaley. He pointed out that questions around timing of ventilation were not unique to this virus. “The medical community has been having this debate about when to transition patients from non-invasive respiratory support for many years,” he said.
Ventilators are no panacea. Of the 12 per cent of Covid-19 patients who were put on ventilators in New York’s largest hospital system, there was an 88 per cent mortality rate, according to a recent paper.
Yet some experts believe that fear of missing a window of opportunity for potentially life-saving treatment may have led some medics to pursue early intubation.
“At the beginning of the pandemic the idea was that these patients are sick — we need to get them ventilated quickly,” said Alison Pittard, dean of the UK’s Faculty of Intensive Care Medicine.
But she said experience had since shown success with non-invasive ventilation methods, which include oxygen piped through nasal tubes or continuous positive airway pressure (CPAP) devices with tight-fitting masks that keep the airways open.
Giacomo Grasselli, who coordinates intensive care units in the hard-hit Italian region of Lombardy, highlighted the benefits of patients undergoing CPAP being placed face down to improve oxygenation — known as proning. “You need some patient co-operation, but it is feasible and on a gut feeling I think it is useful,” he said.
One drawback is that CPAP devices generate aerosols and droplets that some warn could pose an infectious risk to healthcare workers. Nasal tubes also consume large quantities of oxygen, putting a strain on supplies.
Because a Covid-19 patient can worsen suddenly, there is also the danger that life-saving intubation could be delivered too late, when they are too exhausted to recover.
Yet the many unknowns about the pathology mean there is no easy consensus in the debate. Leo Heunks, head of the European Respiratory Society’s intensive care medicine group, disagreed that there was an emerging trend to intubate later and said doctors were actually intervening with the treatment earlier. He argued that patients who spent more time on non-invasive support risked suffering lung damage as they strained to breathe on their own.
“We started to realise that when we delay intubation too much, the patients start to damage their own lungs,” he said. “Once you get to a critical phase of Covid you are going to need intubation anyway. Why don’t you just rest the lungs?”
For now, practitioners will keep refining their clinical methods as greater knowledge of the virus is gleaned.
Luciano Gattinoni, professor at the Medical University of Göttingen in Germany, said the key test for invasive ventilation should be continuous vigorous inspiratory efforts — in other words, very heavy breathing — which left untreated could lead to lung injury.
“Remember, with this technique we do not cure the patient,” he said. “We buy time to keep the patient alive while the body fights against the virus.”