DISCUSSION
Our study supports our assumption that wearing facial PPE reduces staff understanding and conventional communication in simulated ITU and theatre settings. Despite the small sample size, results suggest that the louder background environments such as theatre produced the most pronounced (statistically significant) effect on speech comprehension. The excess noise generated in such environments can be attributed to many factors (aptly summarised in the paper by Kam et al, 199419) that range from equipment and type of surgical/anaesthetic activity to numbers of personnel and consequent raised voice levels. We have demonstrated that wearing PPE will complicate communication further. In this study, speech comprehension wearing PPE within the theatre simulated environment (70dB) was significantly worse than wearing no PPE. Raising of voice in a theatre simulated environment when wearing PPE caused a significant improvement of BKB scores to a level that was not significantly different from scores when not wearing PPE.
Despite the observed variance in SNR, BKB scores were still generally poorer with PPE which may indicate a difficulty in understanding un-related to volume or SNR.
Background levels of noise in our simulation were derived from environmental recordings that correlated with prior studies where noise levels in the operating theatre exceed World Health Organisation recommendations20. It has been suggested that noise masking speech often results in surgeons having to repeat themselves and consequently, it takes longer for other members of the team to respond or assist20. Research exists on background noise and its impact on adherence of staff to the WHO surgical safety checklist, but outside of calls for quiet during the ‘Time Out’, perceptions of barriers to communication during the rest of the procedure is less well investigated21.
We have confirmed anecdotal reports that communication difficulties due to PPE will impact on healthcare workers. Safety of healthcare staff is paramount and the ongoing use of PPE as the initial coivd-19 pandemic wanes is likely to continue. Therefore we anticipate that these communication issues will be exacerbated, particularly in operating theatres, where anaesthetists, operating department practionners, nurses and surgeons will wear AGP PPE for prolonged durations once some longer procedures and elective operating recommences. Interpretation of our findings should be in light of the fact that we simulated background noise and the study candidates were healthcare staff without hearing impairment who regularly work together, which may mean our results would not be reproduced “in the field”. Clinical situations regularly involve a variety of shift-working healthcare providers and the additional cognitive load of actually treating patients. Nonetheless, our simulation used validated speech testing and we are unaware of any other studies which have assessed communication difficulties with Covid-19 PPE to this standard.
The importance of speech understanding for achieving success on shared objectives has been extensively researched in military and industrial occupational settings, with need to communicate with co-workers in noisy backgrounds regularly resulting in the removal of protective equipment22. There are obvious and immediate implications in theatre e.g. safety compromised, wrong instrument being selected or inadequate delivery of the WHO checklist.
Studies have suggested that as much as 12 dB SNR is required for speech understanding in the presence of background noise levels up to 110 dB SPL23 but thresholds for adults have also been recorded with ratios close to 0 dB or <0 dB24.
One impact of PPE we have not discussed is the removal of visual cues to communication. Various studies have demonstrated that visual features strongly affect the perception of speech17. This contribution is most pronounced in noisy environments where the intelligibility of audio-only speech is quickly degraded25.
We recommend that regular reminders to speak up and acknowledge communication difficulties at key times during ITU ward rounds and theatre pre-operative briefs may help staff to improve communication whilst wearing PPE. Some specialty guidelines have recommended wearing photographs of staff members over their PPE or writing their name and roles on the apron26. Some centres have advocated communicating with hand signals, transparent masks or hoods17, white-boards or even two way radio/walkie-talkies in cellophane bags where possible27. Others have suggested possible wireless microphone and speaker systems incorporated into PPE28(micrashell) or even already provided PPE designs with voice amplification solutions29 that utilise mobile phone technology. For modern multidisciplinary teams, this may not be a suitable solution when there needs to be multidirectional conversation and information exchange. Solutions like CARDMEDIC (a free to use collection of communication flashcards) have been designed to help healthcare workers speak to patients despite PPE, but we are unaware of any similar device specific to communication between healthcare workers i.e. in theatre (https://www.cardmedic.com/)30.
The drawbacks in this study were principally the small sample size that did not allow us to measure an effect size. In addition the study was performed in one hospital site only and representative environmental noise levels could differ across different hospital sites. We welcome the opportunity to work with other teams across the UK and further afield in testing, trialling and simulation, as well as supporting qualitative work for any PPE communication solutions for future working practices.