In-situ patient weight sensor measurement system for hospital beds

Year Submitted: 2025
Published Date: 08 April 2025

Tags: Value Based Care, Risk Management, Safe Care, Care Process ＆ Redesign, Technology, Digital Health, Sensors, Digitalisation, Machine Learning, Automation

About this Content

Aims

Our project aimed to develop a novel, affordable under-mattress weighing device and compare its performance against those of three commercial devices (scale-integrated
bed, under-bed and sitting scales) in terms of accuracy, ease of use and cost.

Background

A major factor that influences the difficulty of weighing immobile patients is the type of weighing device. There are several commercial weighing devices and they can be
categorised as scale-integrated hospital beds, scale attachments to hospital beds or bedside scales.

Scale-integrated hospital beds have scales built into the bed frame. While the patient’s weight can be easily taken on the bed, such beds are expensive. Even if there are a few of such costly beds in a ward, there can be practical difficulties in moving immobile patients to such beds given the frequent need to cohort patients in specific sectors of the wards (for reasons such as better fall-risk and infection control management).

Scale attachments such as under-bed scales are usually designed to weigh the total weight of the bed and patient. The patient’s weight is obtained by subtracting the initial
weight of the bed from the total weight of the bed and patient. To weigh the patient, ramps are to be aligned such that each bed wheel can be rolled onto the weighing
platforms in unison. This procedure is generally tedious and physically strenuous, and it has to be repeated for every weight measurement.

Bedside scales include lifting scales and sitting scales. As their name implies, lifting scales are designed with a lifting platform, usually in the form of a sling, hammock,
stretcher or rigid board, in which the patient is weighed directly. The lifting mechanism is slipped under the patient and then attached to an overhead hoist, which lifts the patient
from the bed for weighing. However, these scales are cumbersome and the lifting itself may create discomfort for the patient. Sitting scales, on the other hand, are comparatively
cheap and can be conveniently brought to the patient’s bedside. However, significant effort is needed to bring immobile patients onto these weighing devices, either manually
(often requiring at least two nurses) or via unwieldy ancillary contraptions such as a hoist.

Methods

The novel device was designed to: (1) Improve nurses’ productivity by simplifying workload, (2) Minimise movement of immobile patient, (3) Be retrofittable to existing
infrastructure, sufficiently affordable and portable, (4) Accurately assess weight change (0.2 kg accuracy). With these design considerations, a novel under-mattress weighing device was developed. Patients can be weighed while in bed, without nurses having to move them to a scale to be weighed. It consists of modular wireless scales that are retrofittable and scalable to any existing hospital bed. Each module is fastened onto the bed frame with Velcro straps prior to the patient’s admission and no further installation is required after the first installation. It allows for easy installation, transportation and disinfection. The system also comes with a wall plug charger that recharges the four modules at once.

Results

The novel device prototype developed in this project fared well against the three other competitor devices in both technical and practical aspects. The study showed the novel device’s weight measurements to be accurate as well as comparable to the other devices (Intraclass Correlation Coefficient ICC = 0.99). All devices had an absolute accuracy that were within the error allowance of 0.2 kg and could accurately detect a graduation of 0.1 kg (incremental accuracy). The novel device was ranked second in terms of the ease-of-use rating, after the scale integrated bed. From the easiest to most difficult to use, devices were ranked in order of:
scale-integrated bed, under-mattress scale (novel device), under-bed scale and sitting scale. Having such a device in the wards to assist nurses in weighing immobile patients will not only improve the productivity of nurses but also increase the quality of patient care, especially in the geriatric wards and nursing homes. The novel weighing device is validated to be a cost-effective alternative to other commercial devices.

Lessons Learnt

Despite the availability of commercial devices, there is still a huge disparity between clinical requirements and the engineered product. There is much more that can go into an existing working product (e.g. ease of use, practicality, cost and design tradeoffs) so as to make it a truly useful medical device.

Keywords

Bed scale, In-bed monitoring, Nursing, Geriatric, Immobile

Innovators' Details

Connect with this contributor!

A/Prof Suresh Sahadevan - IGA@ttsh.com.sg

Project Attachment