A simple guide to Transmission Based Precautions

"From what we know, COVID-19 is mainly spread via contact and droplet transmission."

In the wake of the Covid-19 Pandemic, Clinical Consultant, Josie Winter, outlines the Transmission Based Precautions.

Topics covered in this article

Re-cap: Standard Infection Control Precautions

Re-cap: The 6 Links in the Chain of Infection

The 3 types of transmission

What are the implications for healthcare workers in terms of infection transmission?

Using current guidance and clinical judgement to guard against transmission

What is the best PPE to wear to prevent the modes of transmission?

Aerosol generating procedures list

Thank you Josie!

Re-cap: Standard Infection Control Precautions

Recently, I re-visited the 10 Standard Infection Control Precautions (SICPs) to help remind you all that SICPS should be used by all staff, in all healthcare settings, at all times, for all patients.

This is regardless of whether COVID-19 is in your setting or not.

There may be occasions where the 10 SICPs may not be sufficient to prevent transmission of a pathogen (a bacterium, virus, or other microorganism that can cause disease).

Re-cap: The 6 Links in the Chain of Infection

In another article here on Nurses.co.uk we refreshed ourselves about The 6 Links in the Chain of Infection when I spoke with Liam Palmer about Covid 19.

Link number 4 in that chain of infection is 'A mode of transmission'.

I've added our handy infographic below to remind you of this:

How a virus spreads: The 6 Links In The Chain Of Infection

As our infographic above hopefully makes clear, Link 4 relates to the transmission or the passing on of the microbe from one person to the next.

This article is all about these different modes of transmission - we are, here, essentially going into detail about Link 4 in the '6 Links In The Chain Of Infection'.

Let's dive in!

The 3 types of transmission

The mode of transmission can essentially happen in 3 ways:

1. Contact Transmission

2. Droplet Transmission

3. Airborne Transmission

1. Contact Transmission

Contact transmission can happen either directly, when an infected person touches or exchanges body fluids with someone else.

Or Indirectly, Covid-19 may live on objects for a short period of time.

If you touch an object, like a handle or light switch, just after an infected person, you might be exposed to infection.

The indirect transmission may then happen when you then touch your mouth, nose, or eyes before washing your hands.

2. Droplet Transmission

When a person coughs, sneezes or talks, large droplets fly through the air and can infect people nearby ,these are called respiratory droplets.

Droplets are a relatively large size (≥ 5μm / 5 microns or larger).

Droplet sizes are measured in microns. A micron is 1/1000 millimetre, or about 1/25,000 of an inch and are written like using this symbol μm.

Droplets containing the virus from the infected person usually do not travel very far and do not stay in the air for long either.

This is why we are being asked to keep at least a 2-meter distance.

3. Airborne Transmission

Much smaller droplets can also be produced when we sneeze and cough, as well as when we talk and breathe.

These are called aerosols, and they can travel a lot further, and can stay airborne for a longer period of time.

Airborne transmission is different from droplet transmission as it refers to the pathogen being present in a droplet nuclei (Airborne droplet nuclei develop when the fluid of smaller droplets (≤ 5 µm) evaporate).

These much smaller particles (<5μm or smaller) can remain in the air for a longer period of time than the larger droplets .

What are the implications for healthcare workers in terms of infection transmission?

The impact of these modes of transmission has important implications for healthcare workers, and others working in close proximity to those who are infected, particularly in relation to what PPE to use.

An additional layer of precautions (also called Transmission Based Precautions) has been recommended for use.

To further confuse things Transmission Based Precautions are normally categorised by the mode of transmission (some infectious agents can be transmitted by more than one route).

From what we know, COVID-19 is mainly spread via contact and droplet transmission.

However, there are numerous medical procedures (see figure 3) carried out in a healthcare setting that will generate aerosols (Aerosol generating procedure- AGP).

This is where you will need to adopt Airborne precautions.

For all healthcare workers any doubt about what equipment to wear and when causes unnecessary worry.

Guidance for transmission Based Precautions and Personal Protective Equipment can be found here.

Using current guidance and clinical judgement to guard against transmission

You should use the current guidance from Public Health England and your clinical judgement to make the decision on the necessary precautions and correct personal protective equipment you will need.

Ask yourself the following questions

- What is the suspected or known infectious agent?

- Could it be COVID-19?

- How severe is the illness caused by the infectious agent?

- What is the mode of transmission of the infectious agent?

- Which healthcare setting you are in?

- What clinical procedures you are undertaking?

What is the best PPE to wear to prevent the modes of transmission?

There has been a lot of confusion in recent weeks regarding what PPE and more specifically what face masks to wear, and what level of protection they actually provide.

There are essentially 2 types of face mask being utilised in healthcare settings at the moment:

1) Standard fluid resistant surgical face mask (FRSM (IIR)

Used as a droplet transmission precautions and is effective protection from larger droplets (larger than 5 microns).

2) FFP3 Respirator Mask

Used as an airborne transmission precaution, and they effectively filter out 95% of the smaller airborne particles (smaller than 5 microns).

Visual Adaptation of PHE - PPE (Guidance Updated 02-04-2020)

It is important that all healthcare professionals feel safe to perform their job and a single set of recommendations has recently been updated, which cover all health and social settings.

Aerosol generating procedures list

- 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)

- Continuous Positive Airway Pressure Ventilation (CPAP)

- High Frequency Oscillatory Ventilation (HFOV)

- Induction of sputum

- High flow nasal oxygen (HFNO)

Thank you Josie!

Josie Winter of Advanced Clinical Solutions helped put this article together.

You can find Josie and her team - if you need help dealing with compliance audits, clinical training, safety investigations, supervision/coaching of staff - here - get in touch with Josie!