Detecting Patient Position Using Bed-Reaction Forces and Monitoring Skin-Bed Interface Forces for Pressure Injury Prevention and Management

Pressure injuries are largely preventable, yet they affect one in four Canadians across all healthcare settings. A key best practice to prevent and treat pressure injuries is to minimize prolonged tissue deformation by ensuring at-risk individuals are repositioned regularly (typically every 2 hours). However, adherence to repositioning is poor in clinical settings and expected to be even worse in homecare settings. Our team has designed a position detection system for home use that uses machine learning approaches to predict a patients position in bed using data from load cells under the bed legs. The system predicts the patients position as one of three position categories: left-side lying, right-side lying, or supine. The objectives of this project were to: i) determine if measuring ground truth patient position with an inertial measurement unit can improve our system accuracy (predicting left-side lying, right-side lying, or supine) ii) to determine the range of transverse pelvis angles (TPA) that fully offloaded each of the great trochanters and sacrum and iii) evaluate the potential benefit of being able to predict the individuals position with higher precision (classifying position into more than three categories) by taking into account a potential drop in prediction accuracy as well as the range of TPA for which the greater trochanters and sacrum were fully offloaded. Data from 18 participants was combined with previous data sets to train and evaluate classifiers to predict the participants TPA using four different position bin sizes ([~]70{degrees}, 45{degrees}, [~]30{degrees}, and 15{degrees}) and the effects of increasing precision on performance, where patients are left side-lying at -90{degrees}, right side-lying at 90{degrees} and supine at 0{degrees}). A leave-one-participant-out cross validation approach was used to select the best performing classifier, which was found to have an accuracy of 84.03% with an F1 score of 0.8399. Skin-bed interface forces were measured using force sensitive resistors placed on the greater trochanters and sacrum. Complete offloading for the sacrum was only achieved for the positions with TPA angles <-90{degrees} or >90{degrees}, indicating there was no benefit to predicting with greater precision than with three categories: left, right, and supine.