Hospital Covid outbreaks soared in part because the wrong staff were given full personal protective equipment (PPE), a new study suggests.
An international team of researchers has established that less severely ill patients are far more likely to infect people around them than those critical enough to require oxygen.
The findings appear to contradict official guidelines, which ration the best PPE to doctors and nurses treating patients who require medical oxygen, on the basis that doing so requires the performance of “aerosol-generating procedures”.
Often working in intensive care units, these staff are given eye protection, a tight fitting particle respirator mask, long-sleeved fluid-repellent gowns and gloves.
Those working with less ill Covid patients had to go without eye protection, were given only a standard surgical mask, as well as a disposable apron and gloves.
However, the new findings show that the typical activities of less severely ill Covid patients – breathing, talking, shouting, coughing and exercising – actually generated 100 times more aerosol particles than those receiving oxygen.
The study found that oxygen therapies – officially considered the most high-risk for infection – actually reduced the amount of aerosols.
It was carried out after figures emerged showing that staff working on wards who wear only standard surgical masks have around two to three times higher rates of infection than those working in ICU.
The study, conducted in two UK hospitals and in Australia, comes a year after NHS staff reported significant shortages of PPE as the first wave built to its peak.
Nurses at one trust had to resort to using bin liners when aprons ran out.
Professor Euan Tovey, who co-authored the study at the University of Sydney, said: “The coughing and laboured breathing common in patients with Covid-19 produces a lot more droplets and aerosols than is produced by patients being treated with oxygen therapies.
“Surgical facemasks provide inadequate protection against aerosols and staff safety can only be increased by more widespread use of specialised tight-fitting respirators – N95 or FFP3 masks – and increased indoor ventilation.
“Also, as the respiratory therapies did not significantly increase aerosols, these treatments should be made widely available to patients with Covid-19 who need them."
Larger respiratory particles, or “droplets”, measuring 1/200th of a millimeter, are generally agreed to fall to the ground within two metres.
However, lighter particles, known as aerosols, smaller than 1/200th of a millimeter, can stay airborne for longer, spread further, can be inhaled deep into the lungs and bypass looser fitting facemasks.
To test which type of patient is more potentially infectious, the researchers asked 10 healthy volunteers to sit, one by one, in a chamber with extremely clean air.
They firstly performed respiratory activities such as normal breathing, talking, coughing and exercising.
The volunteers then repeated the experiments while receiving oxygen therapies commonly used in hospitalised patients with severe Covid, sigh-flow oxygen to the nose, and non-invasive ventilation.
Aerosol particles – measured by an optical particle counter – decreased 100-fold compared to the first set of experiments.
Published in the journal Anaesthesia, the study points out that as the volunteers were all healthy, it can only be extrapolated that the results would apply to infectious Covid particles.
Professor Tim Cook, who took part in the research from the Royal United Hospitals Bath NHS Foundation Trust, said: “Our findings strongly support the re-evaluation of guidelines to better protect hospital staff, patients and all those on the front line who are dealing with people who have, or are suspected of having, Covid-19."