UBC Theses and Dissertations
Development and initial evaluation of tactile displays and tactile alert schemes for physiological monitoring Ng, Yee Lam Ginna
Current standard monitoring systems typically comprise multiple visual and auditory displays to convey the physiological status of an anesthetized patient to the attending anesthesiologists during a surgery. The overwhelming amount of information conveyed by these systems appears to overload the anesthesiologists, which degrades their responsiveness to the adverse situations in the patient and may ex pose the patient to higher risk. In this thesis, we propose exploring other sensory modalities, such as the sense of touch, to reduce the visual and auditory burden imposed by the current monitoring systems. Tactile technology was first explored in navigation and orientation applications for improving the awareness of pilots and drivers to their surrounding environment. Recent medical research also began to investigate this technology for clinical applications such as assisting minimal invasive surgery and needle-based im age guided therapy. No study, however, has examined the use of tactile technology to convey physiological information to the anesthesiologists. We therefore propose the use of a wearable tactile display as a complementary advisory device for the current monitoring systems. The tactile display can convey physiological information to the anesthesiologists in a silent and subtle manner without worsening the noise pollution problem in the already noisy operating room. The use of tactile display can help enhance the communication to the anesthesiologists of adverse physiological changes occurred in the patients, thus improving patient’s safety. Four user studies were described in this thesis to evaluate different aspects of a wearable tactile display. The first study compared the performance of three tactile display prototypes, namely, an electrotactile display on the forearm, a vibrotactile display on the forearm, and a vibrotactile display on the wrist, We found vibrotactile stimulation to be superior to electrotactile stimulation in terms of training time, alert identification accuracy, and user comfort. Response time and accuracy of vibrotactile alert identification appeared negligibly affected by the choice of stimulation location on the wrist or the forearm. The second study investigated the potential use of Tactons (structured, abstract tactile messages) in designing a tactile alert scheme with 36 distinct tactile alerts. We examined the use of rhythm, roughness, and spatial locations of the Tactons to provide users with easily interpretable pretable alerts and demonstrated an accuracy of 81% in tactile alert identification on the abdomen. A higher accuracy could be achieved by using only rhythm and spatial location. In the third study, we evaluated the tactile perception on the ab domen for four tactile alert schemes distinguished by the two encoding parameters, the mean () and the standard deviation (0’) in the number of pulses in the tactile alerts, Among the four alert schemes tested, results demonstrated an optimal per ception when the scheme with [i 3, a> 0] was used. A mean accuracy of 94% in tactile alert identification was achieved for an information transmission rate of 3.73 bits. The final study evaluated the usability of a tactile display on the abdomen under simulated low and high clinical workload conditions. Participants did not en counter difficulties in learning the tactile alerts and using the vibrotactile interface. No statistical differences were detected in the response time and in the accuracy of tactile alert identification between these two workload conditions. This important finding suggests the efficacy of the tactile display in improving the communication to the anesthesiologists on adverse physiological changes occurred in the patients even at high workload condition. Our collective findings demonstrate the possible use of tactile display to enhance physiological monitoring of patients and provide insights for future development of tactile displays in the clinical environment.
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