Aerosols, Airways, Attitudes and the Anaesthetist

: Quantitating the Aerosol Generating Procedure

Abstract

The term aerosol generating procedure (AGP) was introduced in the 1990s to describe medical interventions that both induce coughing and were associated with an increased risk of tuberculosis transmission. Over the subsequent 30 years, the focus of risk has shifted from the induced cough to the notion that AGPs introduce energy into a patient's respiratory tract. This additional energy is considered to generate infectious aerosols, facilitating airborne transmission of pathogens not normally transmitted via the airborne route. Throughout the COVID-19 pandemic, performance of these ‘high-risk’ AGPs required airborne precautions; precautions not universally implemented across healthcare settings. However, there were no studies demonstrating any of these medical procedures generate respiratory aerosol and the current list of ‘high-risk’ AGPs is based on a small number of low-quality epidemiological studies.

The clinical studies in this thesis have measured respiratory aerosol generation during facemask ventilation, airway suctioning, tracheal intubation and tracheal extubation in anaesthetised patients. The results demonstrate these procedures generate less aerosol than the patient’s own breathing and coughing and so should not be defined as high-risk AGPs. In contrast, awake tracheal intubation, cardiac defibrillation, chest compressions and manual ventilation during cardiac arrest generate very high concentrations of respiratory aerosol.
A complementary survey of UK anaesthetists identified concerns that COVID-19 AGP guidelines were negatively impacting healthcare delivery, patient safety and anaesthetic training. Anaesthetists reported that the risk assessment for airborne transmission of SARS-CoV-2 was based primarily on whether an AGP was being undertaken rather than individual patient interactions.

The findings from these studies can help inform infection prevention and control guidelines. However, they also demonstrate the need to reassess the term AGP – the risk of nosocomial disease transmission should not be placed wholly on a procedure but should form part of a multifactorial individualised risk assessment.

Date of Award	15 Jul 2024
Original language	English
Awarding Institution	University of Bristol
Supervisor	Anthony Edward Pickering (Supervisor) & Jonathan P Reid (Supervisor)