Design and Evaluation of a Multi-sensor Unit for Measuring Physiological Stressors of Medical Transport

Patients who undergo inter-hospital transfer experience increased relative mortality, ranging from 10 to 100% higher than non-transferred patients. The high-cost, increased risk of complications and poor outcomes of transferred patients warrant the critical examination of potential causes. One of the major causes may be the external stressors that patients are exposed to during medical transport. To realize simultaneous measurements of external stressors, we developed a multisensor unit for measuring vibration, noise, ambient temperature, and barometric pressure. For preliminary evaluation, the sensor unit was tested on 29 medical transports, 11 air transports by a helicopter and 18 ground missions by an ambulance. The average whole-body vibration for each air and ground transport was calculated at 0.3510m/s and 0.5871m/s respectively. Air transports produced much higher level of noise than the ground transports. We found no significant difference between two modes in terms of average temperature and the temperature changes. Barometric pressure drops significantly during air transport, indicating potential use of this data for automatic mode classification. INTRODUCTION According to the American College of Surgeons National Trauma Data Bank, a total of 61,909 patients were transported by a helicopter and 161,556 patients were transported by ground between 2007 and 2009 (1). Despite the higher cost and limited availability of a helicopter transport, recent studies have supported the use of helicopters for the rapid transfer of patients that are experiencing a time-sensitive emergency such as trauma or myocardial infarction (2, 3, 4). Therefore, it was considered as a predictor of higher survival compared with ground transport (5). Among many time-sensitive emergencies, fast and safe medical transport of and traumatic patients is in particular important as they are more sensitive to time and vibration exposed during the transport (7, 8). Despite the effort made for quick and safe transport, patients that undergo inter-hospital transfer for non-urgent conditions such as transfer between intensive care units, experience increased relative mortality ranging from 10-100% higher than non-transferred patients (7, 8). Identifying causes of the increased mortality has remained elusive. The high-cost, increased risk of complications and poor outcomes of transferred patients warrant the critical examination of potential causes. Several studies have been conducted on measuring external stressors, such as vibration, noise, and temperature, using commercially available sensors. As an example, a set of sensors, a microphone, triaxial accelerometers, and electrocardiogram (ECG) device was used to measure the whole body vibration (WBV) and acoustic noise in relation to the rate and regularity of an infant’s heartbeat (9). The study found that both sound and WBV levels exceeded the recommended limits where higher WBV was associated with a lower heart rate, and a higher sound level was correlated with a higher heart rate (9). Another study used gyroscopes and a global positioning system (GPS) to measure gyration at each location/time (10). In this study, we hypothesized that one of the major causes of increased mortality is the external stressors that patients are exposed to during medical transport. Several studies have investigated environmental stressors with commercially available sensors while only focusing on one specific stressor or a couple of external stressors using commercially available sensors (11, 12, 13, 14). Our study focuses on the development of a multi-sensor unit to realize simultaneous measurements of Proceedings of the ASME 2013 International Mechanical Engineering Congress and Exposition IMECE2013 November 15-21, 2013, San Diego, California, USA