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The impact of respiratory protective equipment on difficult airway management: a randomised, crossover, simulation study

Summary The current international COVID‐19 health crisis underlines the importance of adequate and suitable personal protective equipment for clinical staff during acute airway management. This study compares the impacts of standard air‐purifying respirators and powered air‐purifying respirators during simulated difficult airway scenarios. Twenty‐five anaesthetists carried out four different standardised difficult intubation drills, either unprotected (control), or wearing a standard or a powered respirator. Treatment times and wearer comfort were determined and compared. In the wearer comfort evaluation form, operators rated mobility, noise, heat, vision and speech intelligibility. All anaesthetists accomplished the treatment objectives of all study arms without adverse events. Total mean (SD) intubation times for the four interventions did not show significant differences between the powered and the standard respirator groups, being 16.4 (8.6) vs. 19.2 (5.2) seconds with the Airtraq™; 11.4 (3.4) vs. 10.0 (2.1) seconds with the videolaryngoscope; 39.2 (4.5) vs. 40.1 (4.8) seconds with the fibreoptic bronchoscope scope; and 15.4 (5.7) vs. 15.1 (5.0) seconds for standard tracheal intubation by direct laryngoscopy, respectively. Videolaryngoscopy allowed the shortest intubation times regardless of the respiratory protective device used. Anaesthetists rated heat and vision significantly higher in the powered respirator group; however, noise levels were perceived to be significantly lower than in the standard respirator group. We conclude that standard and powered respirators do not significantly prolong simulated advanced intubation procedures.


Introduction
Airway management in critically ill patients contaminated with chemical, biological radiological or nuclear substances requires personal protective equipment (PPE) [1,2]. The past two decades have focused on the hazards for frontline medical staff posed by the deliberate release of weaponised chemical, biological, radiological or nuclear substances. The occupational hazards of healthcare workers during naturally occurring pandemics, however, have a much longer history. Bio-aerosol infection risks to healthcare professionals may arise from direct patient contact, but are especially high during aerosol-generating procedures such as: intubation; bronchoscopy; noninvasive ventilation; high-frequency oscillating ventilation; induction of sputum; and surgical procedures involving high speed devices. Notably, during the 2003 severe acute respiratory distress syndrome pandemic, 21% of those who had the disease were healthcare workers [3]. In Canada, this was reported as 43%, with anaesthetists being amongst the highest risk group [3,4]. Public Health England [5]  is drawn into the mask through a filter either when the wearer breathes in, or from a power-assisted filtering device [12]. The visor provides protection against particulates, splashes and gases, yet should allow good visibility for the wearer. A half mask respirator is a facepiece which only covers the nose, mouth and the chin of the wearer, held in place with adjustable straps [12]. Half masks do not have a visor for eye protection and provide lower assigned protection factor levels than full facemasks [13].
In recent years, powered air-purifying respirators have been introduced; a complete powered filtering device consisting of a battery-operated turbo unit, a filter and a loose-fitting headtop, for example, a hood or visor [12].
Although they are bulkier and more expensive, powered respirators eliminate the need for fit testing and problems of heat build-up, dead-space ventilation and airflow resistance [12][13][14]. This is the first study comparing the impact of modern powered respirators and standard respirators on simulated difficult airway procedures. The primary outcome measure of this study was as the difference in intubation times for various airway management procedures, with wearer comfort a secondary outcome.

The study received Guy's and St Thomas' NHS Foundation
Trust Research and Development approval. The study did not require review by a research ethics committee, as the research only involved staff as participants.
The objective was to recruit 25 anaesthetists within our hospital Trust whose duties involved responding to trauma calls. Exclusion criteria for the participants included those suffering from asthma, claustrophobia or a history of panic disorder.
Twenty-five subjects gave written and informed

Results
Within the study period, we were able to recruit 25 volunteers. All anaesthetists participating in the study successfully accomplished the treatment objectives of all the study arms. All interventions ended with successful tracheal tube placement. The treatment times are displayed in Table 1.
Intubation times were significantly shorter when using videolaryngoscopy, regardless of the respiratory protective device used. Airway management times of the Airtraq group, the videolaryngoscopy and the fibreoptic intubation Anaesthetists rated their personal sensation of heat buildup and perceived vision significantly higher in the powered respirator group; however, noise levels scored significantly lower compared to the standard respirator group (Table 2).

Discussion
Employers in the UK have a legal responsibility to control substances hazardous to health in the workplace, and to prevent and adequately control their employees' exposure to those substances [13]. In the event of a chemical or radiological incident, casualties are a potential source of dangerous contamination to healthcare workers and should therefore be decontaminated before hospital admission.  [8-11, 17, 18] but this is the first study to compare the use of modern respirators and powered respirators during advanced airway management procedures. Our main finding was that the use of videolaryngoscopy for difficult airway management proved to have certain advantages whilst wearing respiratory protection. Videolaryngoscopy is already widely advocated under normal circumstances [19] but also allows the anaesthetist to keep their head further away from the patient during airway management in COVID-19 patients [7,20].    [10,21], their weight, bulk and connection to the corrugated breathing tube may impede the mobility of the wearer to a certain extent. It must also be noted that if the air supply to the powered respirator fails, then these devices will not provide any protection to the wearer. The user will then be exposed to contaminants in the ambient air, and increased levels of carbon dioxide due to rebreathing [12].
Therefore it is prudent to have charged, spare batteries readily available. Finally, we should note that our study took place in a controlled, simulated environment, and the participants were not required to physically exert themselves, and therefore we are unable to comment on