Technical report | Thoraco-abdominal Organ Locations: Variations due to Breathing and Posture and Implications for Body Armour Coverage Assessments

Abstract

Body armour provides protection to the vital organs and structures of the thorax and abdomen against ballistic, stab and fragmentation threats. The positions of the organs and structures determine the coverage requirements and hence the required dimensions of body armour. The aim of this study was to quantify thoraco-abdominal organ and structure boundaries for varied breathing and postural conditions and develop a preliminary database for use in body armour coverage analyses. This Technical Report documents the methodological details of the study and reports the descriptive statistics of the anatomical data. The data herein shows the necessity for consideration of breathing and postural conditions that can substantially affect the required dimensions of body armour coverage. The data may be used to establish a preliminary representative population database of thoraco-abdominal anatomical structure boundary positions with respect to the studied breathing and postural conditions. Such a database will facilitate more evidence-based design and assessment of the coverage afforded by body armour.

Executive Summary

Body armour is used by police and military personnel to provide passive protection of the vital organs of the thorax and abdomen against ballistic, fragmentation and stab threats. Optimising the amount of coverage provided by body armour requires consideration of the trade-off between the passive protection afforded by the armour and its potential to hinder wearers’ ability to actively protect themselves. Although body armour is available in a range of sizes and dimensions, there is a dearth of quantitative data in the literature regarding the absolute locations of the organs and anatomical structures for which coverage is required. Thus, the ability to evaluate the coverage provided by body armour is limited. Furthermore, changes to breathing and posture are hypothesised to result in changes in organ positioning and hence coverage requirements.

The aim of this study was to quantify the positions of internal thoraco-abdominal organs and structures relative to an external anthropometric landmark, for a cohort of young male adults and to quantify the effects of breathing and postural changes. MRI scanning was conducted in three scan conditions: supine expiration, supine inspiration and upright with shallow breathing near expiration.

The lateral boundaries of organs determine the width requirements of body armour. Inspiration resulted in the most lateral organ boundaries with the exception of the heart. The left cardiac boundary was more laterally positioned during expiration. The upright condition generally resulted in the most inferior organ boundaries, representing the most conservative locations for body armour length analysis. The upright condition also represents a common posture adopted by police and military personnel. Thus the upright data was used for an exemplar body armour coverage analysis. Furthermore, parametrised distributions of the upright organ boundary data have been presented for use in simple coverage analysis of existing or proposed body armour dimensions.

This report documents the methodological detail of the study and provides a preliminary database of organ boundary coverage data for use in body armour coverage analyses. The data herein shows the necessity for consideration of breathing and postural conditions which can substantially affect the required dimensions of body armour coverage. This initial study heralds a significant step in establishing a representative population database of thoraco-abdominal anatomical structure boundary positions that will facilitate more evidence-based design and assessment of the passive protection afforded by body armour.