KANBrief 1/25
Ambulance service personnel are subjected to heavy stresses when transporting patients. Situations repeatedly arise in which, for example, a wheeled stretcher carrying a person must be lifted. A study involving measurements, conducted at the Institute for Occupational Safety and Health of the DGUV (IFA), revealed that musculoskeletal stresses, particularly on the lumbar spine, can be reduced substantially by the use of more highly automated wheeled stretchers.
An analysis conducted by the German Federal Employment Agency of the shortage of skilled workers showed that the ambulance services are already suffering from such a shortage. In addition, not all ambulance service workers are able to work through to the statutory retirement age, owing to the physical stresses involved. The increase in the average body weight of patients and the rising proportion of women working in the ambulance services are also a factor. As a result, musculoskeletal stresses occurring during patient transport are attracting greater attention.
The present study of wheeled stretchers is a follow-on project to an earlier study of the transport of patients on stairways. An online survey in which over 4,000 persons took part revealed that stairways continue to be the most significant factor in the stress; loading and unloading wheeled stretchers into and from ambulances was also frequently mentioned, however. The employees are particularly conscious of the stress upon the shoulders and back. Although more highly automated equipment is available, it is rarely used in practice at present, a situation criticized by some employees.
Persons are routinely transported on wheeled stretchers in the ambulance services. (A similar situation exists in the funeral services.) Transfer of a patient to the ambulance usually requires the ambulance service personnel to lift a large part of the total weight, comprising the patient, the wheeled stretcher, and in some cases also medical equipment. The wheeled stretcher is lowered to the ground, the patient is placed upon it, and wheeled stretcher and patient are then lifted to the loading height of the vehicle. Entirely mechanical wheeled stretchers are lifted by muscle force; by contrast, electrohydraulic wheeled stretchers require only the touch of a button.
Processes for loading the wheeled stretcher into the vehicle differ widely. Entirely mechanical wheeled stretchers are pushed onto a stretcher platform in the usual way, the undercarriage retracts and platform and stretcher are then pushed forwards and upwards into a horizontal position. In a semi-automatic system, a mechanical wheeled stretcher is pushed partly onto a loading system, then drawn into the vehicle automatically at the touch of a button. Electrohydraulic wheeled stretchers are engaged with a sliding loading carriage, and the undercarriage of the wheeled stretcher is retracted and the wheeled stretcher drawn horizontally into the vehicle automatically.
In order to compare the physical stresses arising in use, the IFA performed measurements on these three different wheeled stretcher and pull-in/lock-in systems under laboratory conditions on behalf of several accident insurance institutions. To simulate the lifting and loading/unloading processes as realistically as possible during the laboratory measurements, a dummy was placed on the wheeled stretcher, and employees in the ambulance services were recruited as test subjects.
Measurements were performed by means of the CUELA measurement method during use of the wheeled stretchers by a total of 20 test subjects. Body posture and movement and hand action forces were recorded. The subjectively perceived stress and the affected body regions were recorded by means of a questionnaire.
The results reveal differences between the three systems with respect to the objective biomechanical parameters (hand action force, posture and intervertebral disc compression force in the lumbar spine (L5/S1)) and the subjectively perceived stress. Body posture was acceptable during use of all wheeled stretchers. Handling of the entirely mechanical wheeled stretcher with stretcher platform necessitates high hand action forces; these forces give rise to high intervertebral disc compression forces for the individuals handling the stretcher, including for both individuals when the stretcher is handled by a team of two as per the recommendations.
Electrohydraulic assistance and automated pull-in considerably reduce the required force and in turn the compression forces on L5/S1. The measurements showed that the physical stress arising during handling was reduced the most by the electrohydraulic wheeled stretcher with pull-in system: this system eliminates the need for the wheeled stretcher to be lifted manually to the loading height, and the associated stress does not therefore arise. During loading and unloading by a single person/by two people, both peak and median values for the compression force are halved, the peak values P95 from 6.8/5.6 kN for one/two persons respectively to 2.7 kN, the median P50 from 3.2/2.9 kN for one/two persons respectively to 1.6 kN. The stress perceived subjectively by the test subjects is also consistent with the results of the measurements.
As a result, all employees, and in particular women and older employees, benefit significantly from stretchers with power assistance. A need exists for technical equipment that safeguards employees’ health. This need is exacerbated by the shortage of skilled workers. The EN 1865-2 standard, Patient handling equipment used in ambulances – Power-assisted stretcher, which was recently revised, specifies that such loading systems must support the ambulance crews by eliminating the need for manual lifting operations during normal use. The national foreword to DIN EN 1789, Medical vehicles and their equipment – Road ambulances, now views power-assisted stretcher loading systems as the state of the art and recommends their use. The switch to electrohydraulic wheeled stretchers would be a further step towards reducing musculoskeletal stress during patient transport.
Dr Stephanie Griemsmann
stephanie.griemsmann@dguv.de
Dr Christoph Schiefer
christoph.schiefer@dguv.de