Development of an Anti-Bedsore Bed with Alternating Pressure Points and a Sub-Bed PID-Controlled Cooling System

Abstract

Background and Objectives: Bedsores are injuries caused by the death of skin cells and underlying tissues due to prolonged pressure on specific parts of the body, which reduces blood circulation to those areas and results in insufficient oxygen supply to the tissues. Additionally, moisture combined with long-term pressure can cause skin maceration, making it more susceptible to developing bedsores. If the condition becomes severe and bacteria enter the wound, causing an infection, it becomes difficult to treat and poses a risk of death from septicemia. Therefore, the present research aimed to design and develop an anti-bedsore bed, as well as to evaluate its efficiency.

Methodology: This research was divided into two phases. The first involved designing an Anti-Bedsore Bed based on the principle of alternating weight-bearing points to distribute pressure, which is the primary cause of bedsores, while the second phase focused on performance testing. The evaluation included a load-bearing test where test objects were placed on the mattress base with weight increments of 50 kg up to 150 kg, maintaining each load for 8 hours to study the deflection of the mattress base. Additionally, an under-bed cooling system was tested at a simulated ambient temperature of 33 °C to identify the optimal parameters ( and )  for achieving a rapid temperature response toward a target temperature of 28 °C. Finally, user perception was assessed by having 40 healthy volunteers, categorized by gender and BMI, lying on the Anti-Bedsore Bed for 30 minutes during the operation; data were collected through structured interviews covering their awareness of the bed’s alternating movement, vibrations during operation, physical discomfort, and heat sensation at the skin-mattress contact area.

Main Results: The Anti-Bedsore Bed is divided into three primary sections, namely, a stationary outer frame composing of pillars and beams that support the inner structure and utilize limit switches to regulate movement of the inner bed; a mobile inner bed featuring two sets of interleaved mattress bases that move vertically in alternating loops to distribute the patient’s body weight at set intervals; a cooling unit installed beneath the bed that employs a PID (closed-loop) controller system to adjust fan speed for optimal patient comfort and sweat reduction. Performance testing demonstrated that the mattress base maintained a deflection of 0.236 mm under a maximum load test of 150 kg, while the PID-controlled cooling system achieved its best performance with parameters  and  set to 90, 15, and 0.1, respectively, resulting in a response slope of -0.101 ºC/s and a steady-state error of only 0.25 ºC. Furthermore, subjective evaluations from healthy volunteers indicate that the physical sensation or discomfort experienced while lying on the shifting mattress bases remained at a low level.

Conclusions: The Anti-Bedsore Bed is composed of three primary elements, i.e., a fixed outer frame, a movable inner frame, and a specialized cooling system, all of which function by alternating pressure points through two sets of mattress bases that interchangeably shift upward and downward. This equipment can support a maximum load of 150 kg and is engineered to rapidly lower and stabilize the ambient air temperature beneath the bed without significant fluctuations. Clinical trials involving volunteers indicate that while both male and female users perceived the mechanical movements at a similarly low level, individuals with Body Mass Index (BMI) over 30 reported more extensive heat and discomfort compared to other groups, a result attributed to their physiological tendency to accumulate more body heat.

Practical Application: An Anti-Bedsore Bed prototype has been developed to benefit bedridden patients by effectively reducing the occurrence of bedsores.