A temporal search engine for a massive multi-parameter clinical information database

We describe a novel search engine that is capable of rapid execution of queries concerning changes in the gradients and absolute (and relative) values of multiple irregularly sampled and asynchronous physiological parameters over many time scales. The search engine enables search criteria for multiple physiological parameters using gradient bounds, rates of change, and threshold breeches over various time scales. Multiple signals can be searched and combined in a Boolean manner to form complex queries. Pre-computed ranges and multi-scale gradients are used to significantly reduce the search time for locating temporal events. We have implemented the search engine in MATLAB and tested the algorithm on a massive multi-parameter intensive care unit database (MIMIC II). To illustrate the use of our search approach, a set of numerical search criteria were developed by clinicians to locate evidence for important pathophysiological conditions.