The Entropy of Morbidity Trauma and Mortality

In this paper it is shown that statistical mechanics in the form of thermodynamic entropy can be used as a measure of the severity of individual injuries (AIS), and that the correct way to account for multiple injuries is to sum the entropies. It is further shown that summing entropies according to the Planck-Boltzmann (P-B) definition of entropy is formally the same as ISS, which is why ISS works. Approximate values of the probabilities of fatality are used to calculate the Gibb’s entropy, which is more accurate than the P-B entropy far from equilibrium, and are shown to be again proportional to ISS. For the categorisation of injury using entropies it is necessary to consider the underlying entropy of the individuals morbidity to which is added the entropy of trauma, which then may result in death. Adding in the underlying entropy and summing entropies of all AIS3+ values gives a more extended scale than ISS, and so entropy is considered the preferred measure. A small scale trial is conducted of these concepts using the APROSYS In-Depth Pedestrian database, and the differences between the measures are illustrated. It is shown that adopting an entropy approach to categorising injury severity highlights the position of the elderly, who have a reduced physiological reserve to resist further traumatic onslaught. There are other informational entropy-like measures, here called i-entropy, which can also be used to classify injury severity, which are outlined. A large scale trial of these various entropy or i-entropy measures needs to be conducted to assess the usefulness of the measures. In the meantime, an age compensated ISS measure such as ASCOT or TRISS is recommended. Injury Severity Scaling Injury scaling, as a means of classifying the severity of impact trauma has a long history. Some of the earliest research into impact trauma was conducted at Cornell University Medical School in 1952 by De Haven and colleagues [1], and was related to aircraft crashes. The sixties saw many developments when a number of first generation methodologies were also proposed by: