An Evaluation of a Vibro-Tactile Display Prototype for Physiological Monitoring Jessie Y. C. Ng, MASc*, Jo C. F. Man, MASc*, Sidney Fels, PhD, PEng*, Guy Dumont, PhD*, and J. Mark Ansermino, MBBCh, MSc (Inf), FFA† *Department of Electrical and Computer Engineering, University of British Columbia, Vancouver, Canada; †Department of Anesthesia, University of British Columbia, Vancouver, Canada Visual displays and auditory alarms are used to convey information on physiological variables in an operating room. However, the exponential growth in the number of physiological variables and the high probability of false alarms has amplified demands on the clinician’s attention. We have extended existing tactile technology to improve situational awareness and produce a practi- cal clinical advisory device. A vibro-tactile display, us- ing two vibrating motors applied to the volar surface of the forearm, was compared to an auditory alarm in a simulated clinical environment. Compared with audi- tory alarms, the vibro-tactile alarm was as easy to learn and had a better identification rate when used alone or combined with the auditory alarm. Most users pre- ferred the vibro-tactile alarm although the prototype caused some discomfort. Furthermore, a combined vibro-tactile and auditory alarm had reduced accu- racy when compared with the vibro-tactile alarm alone. The vibro-tactile modality shows considerable promise for clinical practice but will require further clinical testing and refinement, especially with re- gard to user comfort. (Anesth Analg 2005;101:1719 –24) T he exponential growth in the number of moni- toring devices within the operating room and intensive care unit has amplified the clinician’s cognitive load. Routine inclusion of monitoring vari- ables such as electrocardiogram, invasive arterial blood pressure monitoring, pulse oximetry, gas anal- ysis, cardiac output monitoring, and electroencepha- logram recordings make it difficult for the clinician to simultaneously appreciate each variable over an ex- tended period of time. The presence of an abnormal clinical condition is signaled in one of two ways: by a primitive alarm system automatically triggered when a single variable fluctuates beyond its preset threshold or by the anes- thesiologist visually tracking changes to a signal pat- tern over time. Known clinical interventions and arti- facts resulting from diathermy interference or movement exacerbate the complexity of this situation to the extent that more than 90% of alarms currently generated in the clinical environment can be dis- missed as insignificant, with one third triggered by artifacts (1). Responsiveness to auditory alarms dimin- ishes with increased exposure to false alarms and with escalating noise pollution of the operating room and intensive care unit. However, if clinicians switch to an increased reliance on visual cues, through an en- hanced inspection of the monitor, they risk compro- mising their careful clinical observation of the patient. Tactile displays stimulate the skin’s sensory recep- tors to give the illusion of direct contact with an object (2), and are ideally suited to enhance situational awareness, such as in a haptic navigation guidance system (3). Suitable applications for these devices arise whenever environmental or social factors make the use of visual or auditory communication impractical, or when continuous observation of, or the repeated switching of attention to, a visual display might be unsafe. This is precisely the situation found in the clinical environment of the operating room. Such a modality of communication does not detract from other forms of social or patient interaction nor does it disturb other individuals in the environment. As the largest sensory organ in the body, the skin forms an approximate surface area of 1.8 m 2 of mechanorecep- tors (4), and responds to a number of physical prop- erties including vibration, pressure, and temperature with a high degree of precision and discrimination. Accepted for publication June 16, 2005. Address correspondence and reprint requests to Mark Anser- mino, MBBCh, MSc (Inf), Director of Research Department of Pedi- atric Anesthesia British Columbia Children’s Hospital Room 1L7, 4480 Oak Street, Vancouver, V6H 3V4 Canada. Address e-mail to anserminos@yahoo.ca. Mark Ansermino is the recipient of the Canadian Anesthesiolo- gist’s Society Career Scientist Award. DOI: 10.1213/01.ANE.0000184121.03150.62 ©2005 by the International Anesthesia Research Society 0003-2999/05 Anesth Analg 2005;101:1719–24 1719