Hospital Bed Mattress Pressure Cycling to Relieve Shear Stress
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Solution Overview
Problem
Hospital beds with orientation adjustable components cause shear stress on occupants' skin due to friction at the mattress interface, leading to skin breakdown and tissue stretch, especially when the head section is elevated from a horizontal to a non-horizontal position.
Innovation Solution
A hospital bed with a mattress comprising inflatable and deflatable bladders of two classes (A and B) that are coordinated by a controller to adjust occupant/support interface pressure (OSIP) in phase with changes in the bed's orientation, providing a relatively lower OSIP at one location and a relatively higher OSIP at another to relieve shear and tissue stretch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the head section is elevated from horizontal to non-horizontal orientation, then the bed provides proper positioning and support for the occupant, but shear stress and tissue stretch occur at the occupant/mattress interface due to friction
Solution Approach 1:
The mattress uses periodically alternating inflation and deflation of air cells to create cyclic pressure changes at the occupant/mattress interface. This periodic action reduces friction during orientation changes, allowing the occupant's body to translate without excessive shear stress on the skin while still providing support when needed.
Solution Approach 2:
The system changes the pressure parameter of the air cells dynamically. During orientation changes, the air cells are deflated to reduce interface pressure and friction. When support is needed, the cells are re-inflated to restore pressure. This parameter change allows the mattress to adapt to different operational states.
2Reliability
If friction at the occupant/mattress interface is increased to prevent sliding, then support is improved, but shear stress on the skin increases leading to potential skin breakdown
Solution Approach 1:
The mattress transitions from a static structure to a dynamic one by continuously adjusting the inflation state of air cells. This dynamic adaptation allows the mattress to provide high friction and support when the occupant is stable, while reducing friction during orientation changes to prevent skin damage. The system responds to occupancy detection and orientation change commands to modulate its mechanical properties.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces shear stress and tissue stretch by alternating pressure between bladder classes, allowing the tissue to return to a relaxed state and maintaining support, thereby mitigating skin breakdown and improving comfort during orientation changes.
Implementation Method 1
a mattress supported by the frame, the mattress including at least one A bladder and at least one B bladder, the bladders being inflatable and deflatable out of phase with each other
Data Source
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AI summary
A bed comprises a frame 34 with at least one orientation adjustable section (44, 46, 48), a mattress 58 supported by the frame and having at least one A bladder and at least one B bladder. The bladders are inflatable and deflatable cut of phase with each other in coordination with at least one of a) issuance of a command for the frame section to change orientation and b) an actual change in orientation of the frame Also described is an associated method for operating an occupant support at least part of which its orientation relative to other parts of the occupant support. The method comprises providing, in response to a change of orientation of the orientation adjustable part, a relatively lower occupant/support interface pressure (OSIP) at a location A and a higher OSIP at a location B followed by providing a relatively higher OSIP at the location A and a relatively lower OSIP at the location B.