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Length and Circumference Assessment of Body Parts – the Creation of Easy-To-Use Predictions Formulas

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Length and Circumference Assessment of Body Parts – the Creation of Easy-To-Use Predictions Formulas 49th International Conference on Environmental Systems ICES-2019-170 7-11 July 2019, Boston, Massachusetts Length and Circumference Assessment of Body Parts – The Creation of Easy-To-Use Predictions Formulas Jan P. Weber1 Technische Universität München, 85748 Garching b. München, Germany The Virtual Habitat project (V-HAB) at the Technical University of Munich (TUM) aims to develop a dynamic simulation environment for life support systems (LSS). Within V-HAB a dynamic human model interacts with the LSS by providing relevant metabolic inputs and outputs based on internal, environmental and operational factors. The human model is separated into five sub-models (called layers) representing metabolism, respiration, thermoregulation, water balance and digestion. The Wissler Thermal Model was converted in 2015/16 from Fortran to C#, introducing a more modularized structure and standalone graphical user interface (GUI). While previous effort was conducted in order to make the model in its current accepted version available in V-HAB, present work is focusing on the rework of the passive system. As part of this rework an extensive assessment of human body measurements and their dependency on a low number of influencing parameters was performed using the body measurements of 3982 humans (1774 men and 2208 women) in order to create a set of easy- to-use predictive formulas for the calculation of length and circumference measurements of various body parts. Nomenclature AAC = Axillary Arm Circumference KHM = Knee Height, Midpatella Age = Age of the subject LSS = Life Support System ARL = Acromion-Radiale Length LTC = Lower Thigh Circumference BCF = Biceps Circumference, Flexed M = Male BMI = Body Mass Index NC = Neck Circumference BUC = Buttock Circumference NC = New Convection Calculation CAC = Calf Circumference NG = New Geometry CAH = Calf Height NP = New Properties CEH = Cervicale Height RSL = Radiale-Stylion Length CHC = Chest Circumference SH = Sitting Height CHCBB = Chest Circumference Below Breast SSH = Suprasternale Height CRH = Crotch Height Stature = Height of the subject dkg = deci-kilogram TC = Thigh Circumference EC = Elbow Circumference TRH = Tenth Rib height EHS = Eye Height, Sitting TUM = Technical University of Munich F = Female V-HAB = Virtual Habitat FAC = Forearm Circumference VO2MAX = maximal oxygen consumption FHL = Forearm-Hand Length WCN = Waist Circumference (Natural GUI = Graphic User Interface Indentation) HC = Head Circumference WCO = Waist Circumference (Omphalion) ICRP = International Commission on Weight = Weight of the subject Radiological Protection WH = Wrist Height KC = Knee Circumference WRC = Wrist Circumference 1 External Researcher, M.Sc., Institute of Astronautics, Boltzmannstraße 15, Building 6 /2nd Floor. Copyright © 2019 Jan P. Weber, Institute of Astronautics, Boltzmannstraße 15, 85748 Garching b. München I. Introduction ITHIN the past five decades the Wissler Thermal Model became one of the most sophisticated and well W accepted human thermal models today, especially gaining strong acceptance in the field of aerospace engineering. Within this time frame it underwent several iterations1–5 with changes both in structure of the human build-up (especially fidelity) and the underlying simulation algorithms. Today the Wissler Thermal Model consists of 21 right-circular cylinders representing the human body. While the Wissler Thermal Model is accepted by many entities, the author found that the model is lacking in documentation (e.g. code commenting), shows physical properties which are not in alignment with data reported in literature and most obviously lacks in the prediction of the human build-up (both externally and internally)6,7. While previous research by the author7 was intended as a topical review of the general findings, this year paper is intended to describe the findings in more detail and show the approach taken by the author to improve the Wissler Thermal Model. A. The 2009 Wissler Human Thermal Model The newest iteration of the Wissler Human Thermal Model was published by E.H. Wissler in 20095. The model consists of 21 right-circular cylinders representing the human. Two elements represent the head and neck, three the torso, while each arm and leg are separated into four cylinders as shown in Figure 1. Each cylinder is sub-divided into 15 nodal layers of tissue and up-to a further six layers for clothing representation. Each nodal layer is itself sub-divided into 12 angular nodes to account for angular changes within each layer / element. Each of the up-to 5061 nodes contains (depending whether it is a tissue or clothing node) data about the local physical and physiological properties such as density, thermal conductivity, specific heat, temperature, blood perfusion rate and metabolic rate. As described in an earlier publication8 the Wissler Thermal Model incorporates many features such as distributed energy production (depending on the local metabolic rate assigned to each node and the activity performed during the simulation), axial heat transfer between the elements via blood, and radial heat transfer using an alternating direction implicit numerical method to calculate the heat transfer via conduction in the elements5. As mentioned in a previous paper7 the development of the 2009 model E.H. Wissler was strongly influenced by the work of Fiala et al.9,10 as Prof. Wissler states himself. This influence was also observed by the author in the code, both by the formulas / approaches chosen to model certain physiological behaviors and when comparing the physical properties used within the Wissler Thermal Model to the published values by Fiala et al. Figure 1. Graphical Representation of the Wissler Human Thermal Model B. The external Structure of the 2009 Wissler Thermal Model During the translation of the Wissler Human Thermal Model from Fortran to C# (described in an earlier paper8) the author discovered that the physical, external measurements were not simulated correctly within the model. It was found that a standard male, as described by the ICRP (International Commission on Radiological Protection) (73 [kg]; 2 International Conference on Environmental Systems 1760 [mm])11, is calculated about 115 [mm] smaller, resulting in a compressed simulated subject, as the Wissler Human Thermal Model was still predicting the weight of the simulated human correctly. This lead to the conclusion that the external build-up would need to be reworked. But since this would lead to possible changes or distortions in the (local) simulation of organs and/or tissues such as muscle, bone or fat it was decided that the entire build-up, both externally and internally would need to be reassessed, analyzed and subsequently reworked. C. Approach As stated within Ref. 7, the author realized that the Wissler Human Thermal Model, as received from E.H. Wissler in 2013, is lacking in documentation and code commenting and that a revision and optimization of the current model would be needed. Therefore the author decided to perform an in depth assessment, analysis and subsequent rework of the passive model, starting with the rework of the external build-up (body measurements), internal build-up (tissue representation at each node and therefore assessment of organ size/ weight and tissue distribution within the body and within each element of the Wissler Thermal Model), which will be published in a dedicated paper alongside this one, and the assessment of physical properties of the main tissues within the human body (paper under preparation). II. Materials, Methods and Assessment The anthropometry of the human body i.e. the knowledge of the measurements of the human body becomes very important for the construction of the human body in a human thermal simulation program. High variance in body height, weight, age and gender – to name only a few factors influencing human body measurements, causes difficulties to accurately predict body measurements of various body parts depending on the person to be simulated. There are many standards available referencing and reporting values for human body measurements such as the NASA-STd-3000, EN ISO 7250 or dIN 33402. The problem with these standards is that body measurements for all people vary a lot. Additionally, other factors such as the ethnical background may influence the ability to adapt measurements gained from a standard for a certain limited part of the population to another one. For example, the NASA-STd-3000 explicitly states: Data are provided for the 5th percentile Asian Japanese and 95th percentile White or Black American Male projected to the year 2000. This does not necessarily define the 5th and 95th percentile of the user population. The data in this document are meant only to provide information on the size ranges of people of the world. The Japanese female represents some of the smaller people of the world and the American male some of the larger.12 Values are normally available in data tables or as average values accompanied by the 5th, 50th and 95th percentile showing statistic mean and extrema for a studied population. Newer standards such as the NASA-STd-300113 refer to that “each program shall identify or develop an anthropometry, biomechanics, aerobic capacity, and strength data set for the crewmember population to be accommodated”, thereby showing the importance for program tailored data sets and information to gain specifically for the target population – as intended by the author of this paper. The current rework of the Wissler Thermal Model done by the author is intended to simulate astronauts within the V-HAB project’s simulation environment, being of various ethnicities and mainly flying in their fourth to sixth decade (only six astronauts were 60 or older during their last flight: Pavel V. Vinogradov, Gregory H. Olsen, Paolo Nespoli, Dennis A. Tito, Franklin S. Musgrave and John H. Glenn – Michael W. Mevill is not counted in as he only conducted suborbital flights with SpaceShipOne) but being selected at the age of about 30 to 35 it was decided that a large data collection would be needed. Therefore, the author searched for a dataset covering medium to well-trained humans (as e.g.
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