Protecting anaesthesia breathing system hoses from crushing and occlusion

Background

The breathing system hoses and associated capnograph tubing on anaesthesia workstations are at risk of being crushed or run over by mobile theatre equipment and occluded which, in the severest cases, can lead to significant patient harm or death.

Index events

In a recently reported case [1,2] the coroner determined that a young woman had died at the end of routine anaesthesia when the breathing system was run over by the wheels of the bed or some other theatre equipment. No Report to Prevent Future Deaths was issued.

Additionally, the Association of Anaesthetists received personal communication from an anaesthetist following a separate clinical incident where the wheels of the anaesthesia workstation had occluded their patient’s breathing system. This led to amendments to the bronchospasm page in the Association’s Quick Reference Handbook for anaesthesia emergencies [3].

Following these events, a structured search was made of incidents reported to the National Reporting and Learning System (NRLS) and Learning From Patient Safety Events (LFPSE) and this identified eight incidents where a breathing system was obstructed by compression; three of these were by the anaesthesia workstation wheels, three by bed or trolley wheels, one where a system became trapped in the anaesthesia workstation drawer and one with unknown mechanism, but with evidence of crushing.

There is therefore an ongoing risk of breathing systems and/or capnograph tubing being crushed or run over and obstructed by the wheels of the anaesthesia workstation, but also by the wheels of operating tables, trolleys, beds and any other sufficiently heavy wheeled equipment that comes into the operating theatre. There is a risk of systems becoming compressed between two pieces of equipment, but this appears to be a lesser risk.

What protections exist?

Mobile X-ray machines provide an interesting comparison. The wheels of these machines invariably have cable deflectors built into the front and back of their casters [Fig.1]. The purpose of these is to deflect and prevent damage to the expensive cables that run to the C-arm. This does not appear to be a requirement of an ISO standard, but is presumably a response to product feedback and lessons learned in the field.

Of the main anaesthesia workstation manufacturers, Mindray, GE and Drager now offer a similar feature [Fig.2]. Ideally the protection would be on the leading and trailing sides of the caster, as occlusion can occur at either, and this is not universal. Nonetheless, including this protection is a very welcome development.Some items, for instance the Hill-Rom PST500 operating table [Fig.3], have shrouding of the wheels, but not sufficient to prevent rolling over a breathing system because the shroud does not reach fully to the floor when the wheel is in contact with the floor.

The CASTrGARD [4] [Fig.4] is an aftermarket device that can be fitted to existing anaesthesia workstations to act as a hose and cable pusher. We are not aware of any other such device.

The ISO governing anaesthesia workstations does not require cable or hose deflectors to be fitted to casters [5].

SALG makes a number of recommendations:

1. Anaesthetists and those working with them should take precautions to protect the breathing circuit from occlusion:
   1. Use the shortest circuit practicable
   2. Ensure the breathing system is routed safely along its entire length, including the use of tube holders as a routine
   3. Take measures to ensure breathing circuit/capnograph lines are never on the floor. This may require suspending them in between machine and patient [Fig.5]
   4. Take extra care at times of particular risk, particularly when moving the anaesthesia workstation and moving patient trolleys and operating tables.
2. Organisations should take steps to reduce the risk:
   1. They should audit the risk in their theatres and consider at a minimum adopting CASTrGARD or similar devices
   2. They should procure and use the shortest possible breathing system for each operating theatre. Long circuits should not be provided unless clinically necessary.
   3. They should ensure staff working in the theatre environment are educated about this risk
   4. In the future, they should consider procuring equipment that includes protection against this risk in preference to equipment that does not.
3. Those responsible for critical care areas should be aware of this communication. It is likely to be relevant in critical care areas as well, where ventilator breathing circuits may be exposed to similar risks. We will share the report with national critical care organisations.
4. ISO should examine this risk and consider mandating engineered solutions in future standards covering anaesthesia workstations and other relevant wheeled equipment likely to enter theatre. They should also consider the same in relation to critical care areas. We will share this report with ISO and its representatives.
5. Manufacturers should consider, even in the absence of any ISO mandate, voluntarily making changes to the design of casters of relevant equipment so that they cannot run over hoses. We will share this report with manufacturers and their trade bodies.
6. NHS Patient Safety should consider the need for an alert on this topic. We will share this report with them.

References

[1] Hospital Trolley Probably Caused Teenager’s Death, Coroner Says. BBC News, 9/11/2022

[2] Teenager Died After Breathing Tube Became Blocked, Coroner Finds. Guardian, 9/11/2022

[3] Quick Reference Handbook. Association of Anaesthetists, 2023

[4] Castrgard [Accessed 4/1/2024]

[5] Medical electrical equipment — Part 2-13: Particular requirements for basic safety and essential performance of an anaesthetic workstation. International Standards Organisation [Accessed 4/1/2024]

Fig.1 Wheels of mobile X-ray machines, showing cable deflectors, at front and back of all castors, and reaching fully to the ground.

Fig.2 Wheel of Mindray A9 anaesthesia workstation, showing cable deflector on leading edge.

Fig.3 Wheel shroud on an operating table, showing incomplete deflection protection (metal post is deployed table brake, which retracts when table is to be moved)

Fig.4 CASTrGARD in use

Fig.5 Example of a long breathing system being suspended to prevent trailing on floor.