Saturday, 28 March 2020

COVID Questions No 4 - What PPE should I wear at the moment and when should I wear it? (Updated 2 April 2020)

This post was originally written on 28th March 2020 and then significantly updated on 2 April 2020 in line with new PHE UK guidance published on that day.

Understandably, there is a lot of confusion and anxiety about the Personal Protective Equipment (PPE) that is needed to minimise the risk of COVID-19 infection being acquired by healthcare professionals.  Guidance is continually changing and the need to to protect ourselves as healthcare professionals in very real.

Different PPE is available for different circumstances and this post will explain what we are advised we should use and when according to the latest Public Health England (PHE) guidance.  Please note that this advice is continually being reviewed and updated.  I will also explore some of the pragmatic ways that we can reduce our infection risk and explain some of the complexities of the PHE guidance.  I will do my best to keep this post up to date but it is essential to look at the most recent guidance from your relevant organisation since decisions about PPE use are also made locally depending on the known prevalence of COVID-19 in specific areas.

There are two main things to understand when using PPE.  The first is what level of risk there is and the other is what level of precaution is advised for that level of risk.

What is the level of risk?

Working in a health care organisation already confers a certain level of risk.  In a time when we are asking people to undertake "social distancing," healthcare workers are going into environments which are probably the most densely populated public buildings at the moment.  These buildings contain the patients and staff in our area most likely to transmit COVID-19 infection.  As such, just turning up to work means that we come into an area where it is difficult to avoid people who put us at some risk.  Every door handle, computer keyboard and telephone is a potential way of catching the infection.

For this reason, most public health organisations have advised staff who are high risk should remove themselves from the workplace altogether.

Those who are physically at work can do a lot to protect themselves and their co-workers.  We should be minimising the number of meetings and restricting the number of people at these meetings as much as possible.  We should be vigilant about hand hygiene at all times, especially when we have used a phone, touched a door handle or other surface such as a computer keyboard.  Any way that we can find to avoid hand contact with surfaces should be adopted.  I now have continuous right shoulder pain and a bruise over my greater trochanter from barging doors open that I would previously have pushed with my hand.

Contact with asymptomatic patients (no fever or cough) is relaitively low-risk but still has the potential for infection.  Not enough is known about COVID-19 to be able to say how possible it is that a completely asymptomatic person might infect another person.  What is known is that in the absence of symptoms, the risk of infection comes primarily from direct contact or high risk procedures.  Someone who is not spreading droplets can transfer infection via surfaces or by having physical contact.

Healthcare workers who are seeing asymptomatic patients can reduce their risk in several ways.  Increasingly patient contacts are being avoided, for the benefit of staff and the public.  Clinic visits are becoming telephone or video consultations.  We are finding that there are opportunities to reduce follow-up and we are getting better at safety-netting rather than arranging a "routine" appointment for a review.

The risk of face-to-face clinical examination is being reduced, for example by avoiding throat examination unless it is necessary, rather than including oropharyngeal examination as a routine part of the assessment.

For face-to-face clinical contact that cannot be avoided, the risk of direct transmission of infection should be removed by good hand hygiene and avoidance of high risk procedures.
Now for the most significant change in the new guidance.  When it is determined that you are dealing with a high level of COVID-19, PHE recommend using mask, gown and gloves for all patient contact or close proximity, whether symptomatic or not.  That decision is made by individual health care providers based on the prevalence of COVID-19 in their patient population.
If a person is working in an area with symptomatic patients but has no direct patient contact and is not within 2 metres (about 6 feet) of patients, PHE recommends that a fluid resistant surgical mask is worn.
Contact and close proximity with symptomatic patients carries the further risk of infection transmission by droplets.  These patients are referred to as hot, but the "hot" patient includes children with a cough as well as febrile patients for this reason.  When having face-to-face contact with a symptomatic child, additional PPE is recommended in the form of:
  • Disposable gloves
  • Disposable moisture resistant apron
  • Moisture resistant mask (surgical mask)
  • Eye protection if there is a risk of splashing of secretions (e.g. from oropharyngeal examination)
The gloves and apron should be put on before approaching the patient and removed after leaving the patient.  PHE now recommends that the surgical mask can continue to be used afterwards.  It is imprtant to avoid contaminating the mask be touching it.

Droplets are small but large enough so that they will not bypass a surgical mask.  Essentially they are a projectile, not a vapour and so the risk of infection comes from the droplet travelling in a line from the patient to the clinician, not from the air breathed around the mask.  The size of a droplet causes it to be deposited in the upper airway rather than entering the bronchial tree, which is thought to further reduce its infective risk.  For this reason, filtered masks (FFP) as not required when the level of risk is droplet spread.
Contact with contaminated aerosol carries the additional risk that the infection could be breathed in.  The definition of an aerosol is a small droplet (smaller than 10┬Ám) that is capable of being suspended in the room air and breathed in as far as the lower airways.

The current evidence for what creates a risk of aerosol transmitted infection is the basis for the current PHE guidance on when to use the appropriate PPE for this risk.  The current list is as follows:

Procedures included in the current PHE guidance list of areosol generating procedures (AGP)
  • Intubation, extubation and related procedures e.g. manual ventilation and open suctioning of the respiratory tract (including the upper respiratory tract)*
  • Tracheotomy/tracheostomy procedures (insertion/open suctioning/removal)
  • Bronchoscopy and upper ENT airway procedures that involve suctioning
  • Upper Gastro-intestinal Endoscopy where there is open suctioning of the upper respiratory tract
  • Surgery and post mortem procedures involving high-speed devices
  • Some dental procedures (e.g. high-speed drilling)
  • Non-invasive ventilation (NIV) e.g. Bi-level Positive Airway Pressure Ventilation (BiPAP) and Continuous Positive Airway Pressure Ventilation (CPAP)
  • High Frequency Oscillatory Ventilation (HFOV)
  • Induction of sputum
  • High flow nasal oxygen (HFNO)
Note that the wording of some of the list has changed, presumably in an attempt to be more correct.  I think that it is important to point out that one of the most commonly persormed AGPs could be lost in here.  "Non-invasive ventilation (NIV) e.g. Bi-level Positive Airway Pressure Ventilation (BiPAP) and Continuous Positive Airway Pressure Ventilation (CPAP)" includes use of bag-valve-mask ventilation.  In the current pandemic, if a child has a respiratory arrest you should put on aerosol PPE before providing CPR.

Rather than get caught up in the science of why things are on or off this list, I would say that the list is possibly better named "very high risk procedures."  The list is compiled by experts who have looked at both the available evidence and the hypothetical risk of each.  My personal opinion is that the list is a valid way of determining when best to use each level of PPE.

Any contact with patients who are undergoing such procedures requires aerosol PPE.
  • Filtering face piece (FFP) mask, which should have been fit tested to the clinician previously
  • Eye protection
  • Disposable gown (with full length arms)
  • Disposable gloves
Avoidance of aerosol generating procedures is also recommended where possible.  For example, it has been recommended that HFOT is not used in COVID-19 babies.

Stay safe.  Avoid unnecessary risk.  Clean everything.  Touch nothing you don't have to. Use the appropriate PPE and don't overuse PPE that is in limited supply and will be much needed for the high risk scenarios over the next few weeks.

Edward Snelson
@sailordoctor

Disclaimer: In the interests of the infographics not being awful, I did none of the drawings myself.  Full credit for the drawings goes to my vey talented daughter Naomi Snelson.  Thanks for the great pictures.