Not a Fogging Clue: Is HOCL the answer to reducing fallow times?

Not a Fogging Clue: Is HOCL the answer to reducing fallow times?

Private Dentists are leading the way in conducting Aerosol Generating Procedures (AGPs) during the COVID-19 pandemic. While NHS dentists are restricted currently to non-AGPs, private practices in England are conducting AGPs in line with Public Health England and the FGDP advice. Those in Scotland and Wales are following the advice of Public Health Scotland and Public Health Wales respectively. While everyone recognises that practicing safely is a top priority there is also a financial imperative to optimise income generating surgery time. AGPs have fallow time associated with them and private practices are keen to examine ways to reduce this safely. One suggested practice that has come to the fore is fogging with hypochlorous acid (HOCL). So we ask, will this work and what do we need to know to use this as an effective fallow time reduction technique?

Last Tuesday, Richard Howarth, inventor of the Provizage visor, conducted his first AGP. Once finished he and his principle nurse Stephanie, de-gloved, de-gowned took off their visors and left the room in compliance with the Public Health England guidelines. An hour later they returned to the surgery to decontaminate the room confident in the knowledge that it was aerosol free. They could then disinfect surfaces, tools and visors in readiness for the next patient. Richard’s practice has organised AGPs to fall before lunch and towards the end of the working day, reducing the economic effect of fallow time and maximising patient flow through. “Like most dental practices we are working at full tilt to catch up on the back log of patients who had treatment programmes in place that were curtailed by the COVID lockdown. Working efficiently to maximise patient flow is important, so minimising the impact of AGP fallow time is a prime consideration. For us at present our AGPs are low, but for practices with lots of cons the impact of fallow time will be significant,” reflects Richard.

So why is fallow time so long? Public Health England have based the time on a room’s natural air flow. Air changes in a room dilute aerosol naturally. Six air changes dilute an aerosol to around 1%. Under normal circumstances a room undergoes six air changes in an hour. Therefore, Public Health England’s recommendation is a fallow time of one hour for an AGP. A private dental practice can generate more than £300 an hour, so a practice with 4 to 5 cons per day is looking at £1,500 of potential income generating surgery time disappearing into thin air literally. No wonder DCPs are looking at ways to get this time down.

Some dentists hope that the Public Health England advice will change and that a 30 minute fallow time will be introduced after 4^th July. However, private practices are looking hard at how to reduce fallow time further, even if the recommendations change. Many practices have considered speeding up the rate of air exchange in the room. Extraction systems can deliver 12 air changes in a room in an hour, cutting fallow time to 20 minutes. There is installation cost and time to consider to calculate the ROI.  In hot summer weather this method may seem appealing. However, to quote Game of Thrones fans, “Winter is coming”. The economic and environmental impact of heating a room 12 times an hour is likely to be significant. Some heating systems may simply not cope.

Step into the limelight HOCL. Hypochlorous acid is a remarkable oxidant. It kills viruses in seconds, is part of your natural immune system and can be made from salt and water. Electrolysis of salt solution to create HOCL was discovered in the 1970s. Also, unlike Hypochlorite it does not rust metal. This looks ideal, so why is every dentist not fogging around their surgery with it?

While we are clear about HOCL’s ability to kill virus quickly on contact, there is no definitive study that tells us what a fallow time would drop to after you have fogged a room with HOCL. Perhaps a leading University should take up the challenge? There are different types of fog too. You can dry fog or wet fog depending on the size of droplets. Wet fogging does not leave a surface wet though. Again there is no evidence that can form a protocol for wet and dry fogging. How long do we fog for and how much HOCL is required? In short we don’t yet have a fogging clue how to be effective. Instinctively and logically we would expect HOCL fogging to reduce fallow time significantly, but without the facts it’s difficult to implement. Would you write the risk assessment on instinct?

There are other questions to be asked about fogging including the price and availability of the equipment and the HOCL. While there are fogging machines and machines to electrolyse salt water to create HOCL on the market, their price and availability needs to be assessed.

In the meantime during the summer, take advantage of the weather, engage extraction mode on your air conditioning and as they said in Good Morning Vietnam, “You got a window? Open it.” Set your stop watches for an hour and go to lunch.

Other suggestions to reduce fallow time could include using high-volume aspiration (HVA) and rubber dam. HVA has been shown to reduce aerosol generation by more than 90%. Reducing the aerosol generated and the length of generation may provide a useful solution. Given that you can demonstrate that aerosol generation has ceased, the fallow time could start immediately. This could be during treatment, reducing the fallow time needed when the patient is out of the chair and hence the surgery down time. However, this has risks attached to it and associated liability. Public Health England will point out the potential for wafting air due to movement in the room and have adopted the one hour rule once the room is vacated. FGDP have taken a more pragmatic view looking at Aerosol Generated Exposure (AGE) conceding adoption of a shorter fallow time. You pay your money and take your choice.

It’s important to share best practice as a profession to help us all practice safely and profitably. Let us know about your fallow time experiences and your thoughts on maximising surgery time to improve patient flow and experience.