Ergonomics in the anaesthetic workplace



# Introduction
For the purposes of this guideline, we define ergonomics as the scientific study of the interaction between anaesthetists and their workspace environment to promote safety, performance and well-being. Musculoskeletal problems, such as back pain, account for 40% of sickness absence among NHS staff and cost approximately 400 million per
year. Legally, employers are obliged to provide a safe working environment for their staff. Under the Manual Handling Operations Regulations 1992 (as amended), employers are required to avoid the need for hazardous manual handling, so far as is reasonably practicable; assess the risk of injury from any hazardous manual handling that cannot be avoided; and reduce the risk of injury from hazardous manual handling, so far as is reasonably practicable. It requires employees to follow appropriate systems of work laid down for their safety; make proper use of equipment provided for their safety; co-operate with their employer on health and safety matters; inform the employer if they identify hazardous handling activities; and take care to ensure their activities do not put others at risk.
The foundation for avoiding pain or discomfort at work is to adopt and maintain a good posture. What isand monitoring as recommended by the Association [bib_ref] Recommendations for standards of monitoring during anaesthesia and recovery 2021, Klein [/bib_ref].
Temperature, humidity, noise, lighting and electrical safety Temperature and humidity are controlled by the ventilation system, while noise, lighting and electrical safety are separate aspects. Ergonomists can provide specialist help with the effects of the physical environment on anaesthetists. Guidelines on the provision of anaesthetic services have been published by the Royal College of Anaesthetists; this includes guidelines for the environment. Building regulations require that all enclosed workspaces be ventilated by either natural or mechanical means.

## Temperature
Employers are required to make a suitable assessment of the risks to the health and safety of their employees and take action where necessary and where reasonably practicable. While there is no absolute legal requirement for a specific temperature in the workplace, the minimum temperature in the operating theatre should be at least 21C. A meaningful figure cannot be given for a maximum temperature due to the high temperatures found in some workplaces. Vertical air temperature difference between head and ankle levels should be < 3C.

## Thermal comfort
The temperature of the ambient air alone is not a valid or accurate indicator of an individual person's thermal comfort. It should always be considered in relation to other factors. These comprise environmental factors (air temperature, radiant temperature, air velocity and humidity) and personal factors (clothing insulation, including personal protective equipment, work rate and metabolic heat). In particular, thermal radiation is the heat that radiates from warm objects. Radiant heat may be present if there are sources of heat in the operating theatre such as some types of equipment. For air velocity, as the design of operating theatres should incorporate appropriate ventilation systems for the control of infection, this will affect the flow of air within the room and hence the thermal comfort of personnel.
Clothing can be used to control thermal comfort but can also be a cause of thermal discomfort. A person's physical characteristics should always be taken into account when considering their thermal comfort, as factors such as their size and weight, age, fitness level and sex can all have an impact on how they feel, even if all other factors such as air temperature, humidity and air velocity are constant.
There are differences between men and women in terms of thermal comfort and temperature preference [bib_ref] Thermal comfort and gender: a literature review, Karjalainen [/bib_ref].
The stability of the temperature (and humidity) in the operating theatre can be disrupted by opening doors and movement of people and equipment [bib_ref] Real-time measurements of relative humidity and temperature in hospital operating room, Wong [/bib_ref].

## Humidity
There are two aspects to humidity: absolute humiditythe amount of water vapour present in a particular volume of air, usually expressed in units of g.m -3 ; and relative humiditythe amount of water vapour in the air relative to the maximum amount that can be contained in the air at a particular temperature, expressed as a proportion.
Generally, relative humidity rather than absolute humidity is important when discussing thermal comfort. In the UK, levels of relative humidity in the range of 40-70% are recommended for the workplace environment.

## Clothing, including personal protective equipment
Three properties of clothing material to consider are thermal resistance, water-vapour resistance and air permeability. Results from tests carried out according to standards can help a purchaser make an informed choice of appropriate clothing (including personal protective equipment) for use in the operating theatre.

## Noise
Any unwanted sound is a noise and this may disturb patients and staff. Noise in the operating room arises from various sources, including staff activities; conversations and communications; ventilation; surgical equipment; and alarms and music [bib_ref] Noise in the operating room, Katz [/bib_ref]. Surgical procedures may need to be undertaken in a noise-free environment. It is, therefore, important that there is no transfer of noise between adjacent theatres.
Three parameters are important in assessing the level of noise in operating theatres. Two are in relation to external noise; that is, noise emanating from outside the operating theatre. The third is related to the noise level from mechanical and electrical services within the operating theatre itself. There are noise rating curves, a set of curves based on the sensitivity of the human ear and used to give a single figure for noise levels at a range of frequencies.
Typically, noise rating curves are determined between 63 Hz and 4 kHz. In operating theatres, noise rating should be 40 dB, or 50 dB for ultra-clean laminar-flow operating theatres.

## Music
Music is commonly played in operating theatres [bib_ref] Music and communication in the operating theatre, Weldon [/bib_ref]. The appropriate use of music in the operating theatre can reduce stress and improve the performance of some staff [bib_ref] Patient safety in the cardiac operating room: human factors and teamwork, Wahr [/bib_ref]. However, music can impair communication [bib_ref] Music and communication in the operating theatre, Weldon [/bib_ref]. Music that is pleasing and helpful to one practitioner might be distracting to other operating theatre personnel.

## Conversation and communication
Non-essential conversation and communication can be distracting, leading to errors. The sterile cockpit concept was introduced into aviation to reduce the effect of distractions during the critical phases of flight, normally below 10,000 feet, effectively take-off and landing. This requires pilots to refrain from all non-essential conversation and activity during these critical phases. In anaesthesia, induction and emergence can be considered analogous to take-off and landing. During these phases, it has been suggested that the concept of a 'sterile cockpit' should apply [bib_ref] Critical phase distractions in anaesthesia and the sterile cockpit concept, Broom [/bib_ref]. However, each team in the operating theatre has a different cognitive work-load at different times during a case [bib_ref] Is the "sterile cockpit" concept applicable to cardiovascular surgery critical intervals or..., Wadhera [/bib_ref]. This potentially leads to a casual conversation just when another team member needs absolute quiet.
Anaesthetists should politely and firmly make clear that they are not going to discuss any non-emergency matters during drug preparation, with the aim of reducing medication errors [bib_ref] Who is distracting whom?, Moppett [/bib_ref].

## Audible alarms
Alarms generated by anaesthetic equipment can be grouped into three types: high, medium and low priority. Priority levels are determined by the combination of the potential results of failure to respond to the cause of the alarm condition (death or irreversible injury, reversible injury or minor injury or discomfort) and the onset of potential harm (immediate, prompt or delayed). Alarm systems can be an issue for patient safety if they fail to warn of hazards effectively or adversely affect the performance of the operator [bib_ref] Alarms are still a problem!, Edworthy [/bib_ref]. A high false alarm rate may lead to desensitisation and neglect [bib_ref] The effect of audible alarms on anaesthesiologists' response times to adverse events..., De Man [/bib_ref]. This can lead to inappropriate muting of audible alarms and cause anaesthetists to ignore those alarms that are indicating an urgent response. Appropriate setting of alarm trigger levels is therefore important.

## Lighting
Lighting should be sufficient to enable people to work and use facilities without experiencing eyestrain. Minimum values for illumination are 200 lx for work requiring perception of detail. Greater levels of illumination are required in particular healthcare settings. In the anaesthetic room this is 1000 lx at the head of the trolley 1 m from the light source. However, in the operating theatre itself, the luminaire should provide between 15,000 and 30,000 lx at the operating table 1 m from the light source.

## Lighting related to anaesthetic equipment
Brightness and contrast controls on the screen of the anaesthetic workstation should be adjusted to suit lighting conditions in the operating theatre.
When selecting laryngoscopes, the brightness, direction and quality of light are important factors to consider. Illumination provided by laryngoscopes should be at least 500 lx. This level of illumination should be Information (Appendix S1).

## Anaesthetic workstations
The anaesthetist, or a trained nominated person, is responsible for ensuring that the anaesthetic machine is plugged in, switched on and that the battery back-up is charged as part of the Association checklist for anaesthetic equipment. Most medical equipment is designed for right-handed people. In a study that looked at 2437 Korean men and women, 6% were left-handed, 8% were ambidextrous and the rest, right-handed. The right-handed and ambidextrous used their right hands for tasks that required accuracy rather than force. The left-handed used the left hand for tasks that required a certain amount of force rather than accuracy. This implies that, in all participants, the right hand was used for tasks that required accuracy [bib_ref] Hand dominance and hand use behaviour reported in a survey of 2437..., Jung [/bib_ref].
It has been shown that the performance of the nondominant hand is detrimental and may affect outcome in critical task performance [bib_ref] Hand dominance and implications for left-handed operation of controls, Garonzik [/bib_ref]. Anaesthetists must make workplace adjustments to optimise their performance with their dominant hands. Ideally equipment should be designed that is essentially neutral and may serve both groups effectively, for example, by placing the reservoir bag and common gas outlets at the centre of the machine.

## Patient monitors
Monitoring, as recommended by the Association, is

## Lateral transfer
This occurs when the patient needs to be moved from a trolley or bed to the operating table (and back again) and
can finish with the patient in the supine or prone position.

## Supine to supine lateral transfer
If the patient is conscious and able to mobilise themselves then this should be encouraged, with staff available to ensure safety throughout the transfer. If the patient is anaesthetised, the number of staff required to safely position the patient will depend on the patient's size. For a patient who weighs 70 kg, this is the anaesthetist and three staff members, using a lateral transfer device. There is a range of each of the different types of lateral transfer devices on the market and staff should be familiar with the equipment used in their place of work . It is important to ensure the bed is at a suitable height for the transferring staff with a pull point (i.e.
the starting position of the staff member's hands) between their waist and nipple line.

## Supine to prone lateral transfer
The patient is likely to be anaesthetised when positioning the patient in the prone position, therefore the anaesthetist controls the head, neck and airway. An additional four members of staff are required to facilitate the transfer. If a mechanical assist device is available, this should be utilised.

## Positioning the patient on the operating table
Once the patient has been transferred on to the operating table, they may need to be moved into another position to facilitate the planned procedure.

## Lateral position
In order to safely position the patient in this position, a minimum of three members of staff plus the anaesthetist is required for patients weighing > 50 kg.

## Lithotomy position
Putting the patient safely into this position depends on the patient's weight. If the patient is not excessively overweight this can usually be done with one person per leg. It is important to move both legs simultaneously to prevent damage to the patient's pelvis [bib_ref] Positioning the surgical patient, Macdonald [/bib_ref].

## Positions achievable using mechanical theatre tables
There are a number of other positions that can be achieved using modern mechanical theatre tables (e.g. the beach chair and Trendelenburg positions). This protects operating theatre staff from musculoskeletal injury, but puts patients at risk, therefore knowledge and training in how to operate the theatre table is essential.

## Special circumstances
Certain patients, such as those with proven or suspected unstable vertebral fractures, require extra precautions in order to position them safely. This will often involve specialist pieces of equipment and staff members trained in their use.

## Intra-operative phase
The operating theatre should be 55 m 2and have a recommended 20 air changes per hour.
Anaesthetists often remain seated during maintenance of anaesthesia and should follow the same advice that is advocated for staff that spend time at a desk working at a

## Box 1 rules of manual handling
- Do not lift or handle unnecessarily. If there is a means to execute the movement without manually handling the patient, or another load, then it should be used. - If a load is being moved across a distance, avoid carrying it and use a trolley.
- Co-ordinate a lift with team members who will be involved in the movement of a patient. If the patient's weight is a concern, take further action such as having additional handlers or hoists on stand-by.

## Postoperative phase
Once the patient is stable and ready for transfer to the postanaesthesia care unit, the same principles of safe patient transfer should be employed.

## Regional anaesthesia
The practice of regional anaesthesia has increased in recent years, mainly due to the widespread availability of ultrasound equipment. The provision of regional anaesthesia is not limited to anaesthetists alone, and colleagues in pre-hospital medicine, emergency medicine and intensive care are also providing some of these techniques [bib_ref] Regional anesthesia by nonanesthesiologists, Pawa [/bib_ref]. The successful practice of regional anaesthesia relies heavily on optimisation of ergonomics, and lack of attention to detail in this area is associated with block failure or suboptimal performance [bib_ref] Characterizing novice behavior associated with learning ultrasound-guided peripheral regional anesthesia, Sites [/bib_ref]. Additionally, lack of attention to ergonomics can result in the development of musculoskeletal disorders in the practitioner [bib_ref] Upper limb disorders in anaesthetists -a survey of Association of Anaesthetists members, Leifer [/bib_ref]. The interaction between the anaesthetist, the patient, the equipment used and the environment where the procedure is performed are all important factors in the successful deployment of regional anaesthesia , see also Supporting Information, [fig_ref] Figure S2: Equipment trolley placed on the dominant side for left-and right-handed operators, respectively [/fig_ref]. The anaesthetist should be able to perform the procedure while maintaining asepsis without leaning on, or over, the patient and without exerting excessive thoracolumbar flexion [bib_ref] An ergonomic task analysis of spinal anaesthesia, Ajmal [/bib_ref]. Examples of lateral transfer devices.

## Friction-reducing sheet
Inserted under the patient to reduce the frictional force required to be overcome when transferring the patient. Often used in combination with a slider board. Various designs available such as boards with vinyl coverings and rollers, or simple boards that are used in combination with a friction reducing sheet. It is important that the patient's weight does not exceed the manufacturer's safe working load.

## Slider board

## Air-assisted transfer device
These devices float patients on a layer of air from one surface to another, reducing the frictional forces required for transfer. Use of this type of device should be considered for heavier patients. study assessing spinal anaesthesia, performed while the anaesthetist was in the standing position, the optimal needle entry angle and anaesthetist comfort level was when the spinal table was raised to the level of the nipple or xiphoid process of the anaesthetist (see also Supporting Information, [fig_ref] Figure S3: Operating table at two different heights during insertion of spinal anaesthesia [/fig_ref] [bib_ref] Higher operating table for optimal needle-entry angle and less discomfort during spinal..., Sohn [/bib_ref].
Ultrasound-guided regional anaesthesia for peripheral nerve blocks
Modern regional anaesthesia utilises ultrasound imaging technology. This introduces further ergonomic considerations in addition to general principles. There are well-described industry standards for prevention of musculoskeletal disorders for sonographers. While these do not specifically relate to ultrasound for regional anaesthesia, many principles are relevant.

## Ultrasound machine
The machine should be fully adjustable and suitable for use The act of performing an ultrasound-guided regional nerve block consists of a number of phases, each with potential ergonomic challenges [bib_ref] Characterizing novice behavior associated with learning ultrasound-guided peripheral regional anesthesia, Sites [/bib_ref] (Box 3). If any of these steps are not successfully adopted, the likelihood of achieving a successful nerve block is reduced. Turning the trunk, turning the head 45or more and non-dominant hand Box 3 Phases for performing regional blocks [bib_ref] An ergonomic task analysis of spinal anaesthesia, Ajmal [/bib_ref] - Ergonomic principles for performing procedures.

## Environment
There should be sufficient space to perform the procedure The area should be quiet and free from distraction
The ambient temperature should be at least 21C Lighting should be adjustable, preferably with a dimmer switch

## Patient
The patient should be comfortable on a trolley, bed or operating table
The patient should be positioned in a stable and secure manner, with attention to pressure areas.
Access to the patient should be unobstructed and there should be no objects impeding access to the patient (e.g. table attachments)
The level of the patient relative to the anaesthetist should be adjusted in order that the neck of the anaesthetist is not flexed > 60E If in the standing position, optimal heights recommended are within 5 cm above to 10 cm below the elbow needling are associated with fatigue and suboptimal block performance [bib_ref] Monitor position and the accuracy and speed of ultrasound-guided nerve blocks, Langford [/bib_ref].

## Needle insertion
The needle can be advanced towards the target structure either perpendicular to the ultrasound beamout-of-plane, In-plane needling can be achieved by placing the hands and long axis of the ultrasound probe in two orientations (see also Supporting Information, [fig_ref] Figure S4: In-plane needling variations [/fig_ref] :
ACROSS the visual axiswith the needle insertion perpendicular to the visual axis or ALONG the visual axiswith the needle insertion parallel to the visual axis.
Speed and accuracy of in-plane needling is improved when the in-plane needling ALONG the visual axis is employed [bib_ref] In-plane ultrasound-guided needle insertion ALONG or ACROSS the visual axis hand positions, Wilson [/bib_ref]. Although these studies were performed in phantoms, the principles hold true for ultrasound-guided regional anaesthesia in actual patients and are recommended for novice practitioners.

## Hand dominance
There is a range of opinions regarding dominant-hand needling vs learning to be ambidextrous to achieve ergonomic advantage. Although bench top studies have shown that visual-spatial aptitude is more relevant than hand dominance in learning ultrasound skills [bib_ref] Looking into learning: visuospatial and psychomotor predictors of ultrasound-guided procedural performance, Smith [/bib_ref] , there are significant differences in the way that novices will perform a nerve block compared with an expert [bib_ref] Ergonomic task analysis of ultrasound-guided femoral nerve block: a pilot study, Ajmal [/bib_ref].
Therefore dominant-hand needling is recommended for novices.

## Procedures
When performing procedures, such as arterial cannulation or central venous access, similar principles to performing regional nerve blocks apply .

## Intensive care unit

## Supporting information
Additional supporting information may be found online via the journal website. Appendix S1. Ergonomics during the COVID-19
pandemic.
[fig] Recommendations 1: Musculoskeletal injuries are common in anaesthetists and they should aim to make their posture as natural and neutral as possible at all times 2 Wherever possible, patients should position themselves on the operating trolley or table and remain there for their procedure and first-stage recovery 3 All purchased equipment should be assessed using ergonomic principles to ensure it is acceptable for its intended use and that it is adjustable to maintain comfort for the anaesthetist, including those who are pregnant or have disabilities 4 All staff should receive regular teaching in manual handling as part of their mandatory training 5 Room temperature should be at least 21C, the relative humidity should be in the range of 40-70%, there should be adequate and adjustable lighting and noise should be no louder than 80 dB and for short periods only 6 Good ergonomic practice is one where the patient is at a height that approximates to the level of the umbilicus, T10 dermatome or waist of the anaesthetist 7 If the anaesthetised patient is lying on an operating table or trolley for tracheal intubation, the table height should be adjusted until the patient's forehead is at the level of the anaesthetist's xiphoid process or nipple 8 Tasks such as regional anaesthetic nerve blocks, central venous cannulation and siting of arterial lines should be performed with the preparation trolley on the side of the dominant hand, the ultrasound machine directly opposite the operator's view and the monitor at eye level. [/fig]
[fig] : If the load, such as a patient, is on a heightadjustable surface, raise it upwards before the movement in order that all handlers remain upright during the move. Stand as close to the object being moved as possible as this will limit any reaching. Handling the load at arm's length results in five times the amount of stress than is the case if the load remains very close to the trunk when it is handled. Stand with feet apart and with one foot in front of the other when moving a load. This stance will offer stability to the handler. The floor area around or under the object being moved should be kept clear of cables, hoses or other pieces of equipment. Lower the upper body by flexing the knees. This is less stressful for the lower back than simply bending forward at the waist, which results in the weight of the upper body being added to the overall lift. Raise the head before lifting commences. This will assist in reducing any forward bending. Use the feet to move with the load, where possible, rather than reaching forward when putting the load down. Avoid placing anything at low levels that might encourage bending. computer screen. The anaesthetist must monitor the patient, administer medications and perform other interventions that require frequent changes in posture. The anaesthetist should remain outside the immediate surgical area for purposes of infection prevention and control. There should be ergonomic seating and a desk for documentation (Box 2). Tracheal extubation During tracheal extubation, the anaesthetist should be positioned correctly in order to manage the airway, administer drugs and monitor the patient. This presents more ergonomic challenges than during anaesthetic induction, which is usually performed in a calmer, more predictable scenario than tracheal extubation. The machine, patient and anaesthetist should be in the triangle, with each of them within 45from the sagittal plane within the arc of movement. The assistant plays an important role by providing equipment, such as suction, and should be positioned appropriately in order to aid the anaesthetist. [/fig]
[fig] Figure S1: Tracheal intubation performed with the operator positioned facing the patient and behind the supine or semi-recumbent patient. [/fig]
[fig] Figure S2: Equipment trolley placed on the dominant side for left-and right-handed operators, respectively. [/fig]
[fig] Figure S3: Operating table at two different heights during insertion of spinal anaesthesia. [/fig]
[fig] Figure S4: In-plane needling variations. [/fig]