Friday, January 01, 2021

We Can Cut the Number of Hospital Acquired Covid Infections


The virus that causes Covid-19 is spread mainly by inhaling droplets from infected people who are within two metres or less, and by aerosols of virus particles, which may persist in air for 30 minutes or more.

10-20% of hospitalised  Covid-19 cases caught the virus in hospital.

This situation can be improved with some pretty basic technology.  

The transmission risk from Covid-19 cases

People in hospitals who are known to be infected with Covid-19 are putting out droplets containing the Sars-CoV-2 in large amounts when they cough, speak and breathe , especially in the first week since symptoms began.

People with Covid who are receiving oxygen delivered via mask or cannula will be continually exhaling droplets into the hospital environment. The air in their vicinity and in their room will contain a considerable quantity of virus, both as droplets and as aerosols.

Bed coverings and the floor within a couple of metres will be hosting significant amounts of virus. This virus will feed back onto the patient, continually re-infecting them every time they breathe in, or when they touch their face after letting their hands rest on their sheets. The floors can be cleansed at frequent intervals, but the bed linen presents an infection risk to anyone who handles it.


The health and safety of health care workers needs to be protected

The air in the vicinity of the patient poses a health and safety risk to anyone who enters the room or indeed breathes air in the vicinity of the room. PPE is used to reduce this risk, but PPE does not present an impenetrable shield, and 649 healthcare workers (including 36 doctors) have died from Covid-19 contracted while giving care.

The simplest way to capture expired air is by means of a hood positioned over the head. Air will be withdrawn from the hood through a tube positioned above the head at a rate greater than 6 litres/minute, which is the volume of air that is exhaled by a human at rest. The material of the hood will be of transparent plastic that can be sterilised. This hood will produce an upward flow of air across the face, and all expired air will be safely collected.

I produced Figure 1 below with the help of a professional artist friend, (thanks Stephan Marjoram). It shows one configuration of an air management hood. In this embodiment, the hood is open, and the body of exhaled breath is managed by the flow of air. This was my concept, and is very similar to the NIOSH hood (below) but I have abandoned development in favour of the market-ready Medihood.

Figure 1

(c) R Lawson

After getting to  this stage, I picked up on similar technologies that have been developed and marketed, so it makes sense for me (and anyone who wants to help this effort) to try to get them taken up by the NHS in order to save stress and lives of the doctors, nurses, doctors, paramedics, physiotherapists and all the other heroic but exhausted health care workers.

The number 1 option in my opinion is the Medihood, developed in the University of Melbourne, which uses a flexible plastic film tent. 

It is available commercially here. 


The NIOSH Ventilated Headboard 

This has been developed in the USA, and is very similar to my sketch, being open at the chest.


There is an Italian design which has a sealed dome over the patient’s head and neck. This is designed to deliver pressurised oxygen, so it is in a different category. https://www.uchicagomedicine.org/forefront/patient-care-articles/helmet-based-ventilation-is-superior-to-face-mask-for-patients-with-respiratory-distress

I want to stress that  do not have any financial interest in the success of this project. 

I am pressing to get this life-saving technology rolled out, under careful audit, in all places that treat Covid (and other transmissible respiratory infections). 

[Update: I am delighted to report that on 15 January 2021 a Medihood generously provided free of charge by the manufacturers, Evan Evans of Melbourne, was delivered to a Hospital in the South West for use with Covid patients who need dialysis]

More information about this development is on the right sidebar.

There is a Zoom meeting on this technology here : http://greenerblog.blogspot.com/2021/01/zoom-meeting-on-melbourne-isolation.html















[i] https://www.sciencedirect.com/science/article/pii/S0160412020317876#b0305 The highest viral loads were found in personal samplers worn by the sampling team when in the presence of a patient receiving oxygen via nasal cannula (mean: 19 and 48 copies/L), indicating that this treatment may promote the spread of airborne virus.”


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