Science

Gentler ventilation techniques helping boost Covid survival, doctors say

The invasive nature of mechanical ventilation can leave a patient dependent on the machine, potentially having a negative effect on outcomes.

Doctors’ haste to mechanically ventilate Covid-19 patients at the start of the pandemic could have contributed to the higher rate of death in spring compared to now, a senior medic has said.

Dr Alison Pittard, dean of the Faculty of Intensive Care Medicine in London, said doctors’ evolving understanding of the virus had dramatically upped the survival rate.

She said that in August 84% of people hospitalised with coronavirus survived, compared to just 66% at the start of the pandemic.

Coronavirus
Ventilators are stored and ready to be used by Coronavirus patients at the ExCel centre in London (Stefan Rousseau/PA)

There is now some evidence to suggest the use of mechanical ventilation may have a negative impact on patient outcomes.

She told Sky News on Sunday: “Initially we used to put patients straight onto mechanical ventilation – so we would bring them to intensive care, sedate them and put them on ventilators.

“But we have slowly started to realise that perhaps we could manage some patients without doing that.”

Dr Pittard said intensive care teams now use a variety of interventions to help patients breathe, and full mechanical ventilation is a last resort.

Full mechanical ventilation requires a patient to be intubated and air is then pushed into the lungs, rather than being sucked in by the action of the diaphragm.

The process of sedating the patient, and in some cases even inducing short-term paralysis, to override their breathing reflex weakens the respiratory muscles.

This can make it hard for doctors to take the patient off the machine even if they manage to get the virus under control, limiting the availability of respirators and putting pressure on other resources.

Professor Derek Hill, professor of medical imaging at University College London, said: “After 48 to 72 hours of heavy sedation or paralysis, the respiratory muscles weaken.

“This makes it more difficult to wean the patients from mechanical ventilation so that they can support breathing without assistance.

“This prolongs the period of respiratory assistance required and reduces the availability of ventilators from successful discharge of patients from intensive care, in addition to other associated resources such as staff and drugs.”

Medical imaging is the study and development of different technologies to allows medics to get an accurate picture of what is happening inside the body.

Prof Hill, who is not a medical doctor, has also worked extensively on mechanical ventilation techniques.

He told the PA news agency: “It has been found during treatment of Covid-19 patients that non-invasive ventilation, which provides oxygen through a mask, but with the ventilator providing a bit of ‘positive pressure’ can be an effective alternative to invasive ventilation.”

The positive pressure helps the flow of oxygen to the lungs without taking over the actual physical process of breathing from the individual.

Continuous positive airway pressure (CPAP) ventilators, that provide a flow of oxygen through a face mask, were widely used for less serious conditions such as sleep apnoea before the pandemic hit.

“CPAP ventilators don’t require the same level of skilled staff as invasive intensive care unit (mechanical) ventilators,” Dr Hill said.

“It is thought that Boris Johnson was treated with CPAP while at St Thomas’ Hospital in April.”

A report by the National Audit Office (NAO) published last month revealed the Government had spent £569 million on ventilators since the start of the pandemic in a bid to meet its target of 30,000 extra machines.

But the NAO – which monitors public spending – found thousands of the machines are now sitting idle in warehouses due to lack of demand.

The NAO did not criticise the spending, saying Government had done what it thought was best to safeguard public health.

Gareth Davies, the head of the NAO, said: “As with all aspects of its pandemic response, the Government should ensure that the learning from this experience is used to enhance its contingency planning for future public health emergencies.”

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