A new JHI study highlights the dangers associated with reusable PPE, and related to PPE doffing in general. The study used a clinical simulation suite to monitor the spread of fluorescent material added to the outside of an N95 respirator during routine care for mannequin adult patients (with COVID-19!). Whilst some modes of PPE reuse were better than others, all of the clinicians involved in the study ended up contaminating the clinical environment with fluorescent material originating from the mask.

During the COVID-19 pandemic, in most parts of the world, we got to the point of reusing PPE that was designed to be disposable on a couple of occasions. This included masks, gowns, and eye protection. The risks associated with contamination of the clinical environment and self-contamination when doffing PPE have been highlighted by other studies (see here). This study focussed in on the risk of contamination originating from reusable N95 respirators.

28 clinicians (including doctors and nurses) participated in the study, and each undertook the same clinical assessment of the mannequin patients on five sequential occasions. They were bedecked in an N95 respirator, visor, gloves, and gown for each of the assessments. The respirator was reused for each of the assessments. Three different modes to manage this reuse were tested: putting the respirator on a table, hanging it on a hook, or putting it in a paper bag (the CDC-recommended method). Unbeknown to the participants, the respirators had been ‘painted’ on the outside with a standardised dose of fluorescent material, which had been formulated and tested to be spread by touch. The extent to which the fluorescent material had spread to the participants’ body and surround areas was then measured systematically.

The key findings are that:

• All of the participants experienced contamination to their head, neck, and truck, and in the clinical workstation.
• The level of contamination increased throughout the five sequential clinical assessments that were undertaken.
• The tabletop method seemed to result in less contamination than the hook or bag method.
• Contamination of the workstation outside of the immediate clinical area occurred for 25/28 (85%) of participants.
• Most participants had contamination of the inside of their respirators by the end of the five assessments (50% for hook, 88% for bag, and 75% for tabletop).

One the one hand this study doesn’t take us very far forward. You don’t need this study to convince most people that reuse of respiratory (or any other PPE for that matter) is a bad idea and risks contamination of clinical areas and healthcare worker self-contamination. Also, this study was in a simulated environment, so may not reflect real-world clinical activity. Perhaps most importantly, the fluorescent contaminant may not be a great model for the spread of infectious micro-organisms. Related to this, whilst initial studies showed that hand gelling did “remove” the fluorescent marker, the mechanism for this is unclear to me and this was not specifically evaluated. Since hand gelling during the use of PPE is the key mitigation against the spread of contamination from PPE, this is a potentially important limitation.

On the other hand, this study goes some way in quantifying the risk of the spread of contamination originating from PPE, especially when PPE is reused. Whilst contact transmission isn’t the most important route for the spread of respiratory viruses, it can be involved in transmission dynamics, and there are other organisms for which we use PPE where contact transmission is predominant.

As we consider our next steps in the use of PPE for the next phase of the pandemic and as we consider to focus in on the risks attached to all infectious diseases, now is a good time for a reminder about the risk of contamination during PPE doffing.