Human Factors and Anaesthetic Practice: Why the Equipment Makes a Difference | PDD

Human Factors and Anaesthetic Practice: Why the Equipment Makes a Difference


on March 12 2020

Ergonomics (or human factors) is the scientific discipline concerned with the understanding of interactions among humans and other elements of a system, and the profession that applies theory, principles, data and methods to design in order to optimize human well-being and overall system performance.”

In healthcare, such studies can be traced back to the early 1900’s – for example, the introduction of the scrub nurse to reduce time spent locating tools during surgery. Ergonomics and Human Factors practice are inherently broad and multi-disciplinary, but one thing that unites us all is a focus on design. This can relate to the design of organisational structures, systems, environments, tools, informational resources, as well as equipment. 

When it comes to the design of hospital equipment – we currently go through a recognised process of Usability Engineering. This process optimises the design of equipment in relation to Human Factors. For example, providing equipment that is easy to handle and control, safe to use and prevents incorrect use. Some of the best examples in this area relate to anaesthetic practice. In this case, the Usability Engineering process makes a big difference because the consequence of failure is high. Take an anaesthetic trolley for example (image below). Although the principle of providing anaesthesia to the patient is well understood and practiced, the interaction with the machine is not always as predictable.

anaesthetic trolley image

Image credit: Chris Frerk

History of Anaesthesia

To understand the modern context, it can help to go back in time. One of the first anaesthetic procedures in the UK occurred in 1846 at Gower Street in London. The procedure was performed by Dr. Francis Boott alongside James Robinson and Robert Liston. The procedure involved an improvised apparatus built around a sponge soaked in ether. The ether dripped downwards, with vapour being concentrated at the bottom of the device. The vapour was then inhaled through a flexible tube.

Image credit:  Wellcome Image

Early observations indicated that the room temperature impacted on the quality of the anaesthesia. This insight was used to improve the design of the equipment by regulating the effect through a variable temperature water bath. This shows how medical practice, design and engineering go hand in hand to support new ways of doing things. Fast forward to the current day and exactly the same process occurs – observations are made regarding existing practice, this is reflected in the design of equipment and a process of test and evaluation occurs.

Back in the mid-1800s, the vapour was being inhaled through a mouthpiece. Over time, the practice has evolved to involve a tube being inserted into the trachea. Intubation is the procedure by which the tube is inserted into the trachea. The tube may have a cuff (that needs to be inflated when the tube is in the correct position). The tube may have varying forms of curvature and flexibility. It is important that the tube does not become damaged. It is important that the tube is located correctly. This process provides a good case study because the insertion procedure has to be performed within a certain time period and with expert judgement and skill.

Anaesthesia procedure shown

Anaesthesia and Equipment Design

As ergonomists, we seek to understand this type of practice and support the design of equipment that supports safe and effective work. Observing clinicians performing a procedure can show us the myriad of factors that impact and allow the system to be optimised accordingly. For intubation and airway management, factors may include the positioning of the patient, the size and type of tube that is used, the way that the tube is guided/inserted, the potential to provide visualisation etc. There may be difficult scenarios, such as airway obstruction, poor visualisation/difficulty finding the right location. Different patients may provide different challenges in terms of the size and shape of the airway and way in which the tube is advanced. There will also be the need to consider the choice of equipment and interactions with other systems in the hospital.

For these reasons, we work closely with medical professionals and include observational studies – a type of study where ergonomists move out of the controlled, lab-based environments and move into context to benefit from the ecological validity that can be provided. By conducting this type of study we can then analyse, prioritise and ideate accordingly. Observational research is critical. This is especially the case for this type of equipment, as it sometimes the subtle or non-obvious factors that provide the greatest opportunity for improvement.

Endotracheal intubation on a medical practice puppet
Endotracheal intubation on a medical practice puppet


It follows that Ergonomists consider the design of the supporting system, as well as the design of the equipment itself. For the case in question, research has shown that events leading to harm can result from planning errors, task fixation, a loss of situational awareness and/or a failure to anticipate difficulty.  Since the 1970s, anaesthetists have been performing practice routines and drills (much like their contemporaries in aviation). This goes hand in hand with the process of equipment design.

Although a typical Usability Engineering process will consider basic aspects of use (e.g. users know that the device has not been damaged, is sterile, can be assembled correctly, etc.), we are seeing an increasing trend to look past this and consider the broader aspects relating to the organisational setting, for example, task factors (how the equipment fits into an overall plan), organisational factors (how does the equipment interact with hospital process) and patient factors (how to select equipment that fits).

Simulation and training can include normal and abnormal scenarios and take into account the skills, rules and knowledge that surround the practice. Some of this will be equipment related (for example, the handling of the tube) and some will go beyond the equipment (selecting the right tube). It follows that such exercises can include normal and abnormal scenarios. There are various approaches to doing this. We can work with clinical professionals to make sure we have a good idea about what may help and hinder a procedure. We can look at a video of current practice and what has/has not worked well in the past.

It is also the case that anaesthetists have access to an incredible array of technology. For example, there are ways to teach and train anaesthetist that make use of simulated environments, VR and augmented reality. This type of exercise can be leveraged to encompass varying forms of feedback and test process. We can use simulation to apply challenging scenarios for a given design – an analogous example form the aviation industry would be attempting a difficult landing using a new design of instrumentation. It is increasingly the case that with modern technology for a given design we can test equipment with every form of challenging scenario.  


Ergonomists seek to optimise the design of systems given that errors in device use are rarely attributed to the user; rather they are a consequence of a failure of several parts of the system. To some extent, this has always been reflected in the process of developing medical equipment – i.e. the design will reflect collaboration between medics and a range of technologists. For anaesthetic practice, the equipment makes a difference as it can prevent a procedure from going wrong. At the same time, although we would like to make an unsinkable ship, things aren’t that simple. We need to look beyond the immediate device interaction to consider broader factors such as policy, process and training. Equipment makers are increasingly becoming a part of medical practice because the success of the procedure depends on the success of the technology.