title: Integrative Physiology-Coupled Pilot-Centered Flight Simulation
Creators: name: Harrison, Shawn C.
Publisher: name: Old Dominion University Libraries
Year: 2022

description: Maintaining the pilot’s physiological performance envelope within the limits of human capabilities may be crucial for avoiding hazardous physiological episodes in fighter aircraft that compromise safety. The main physiological episode of interest is impaired pilot respiration, better known as hypoxia caused by a high fraction of inspired oxygen (FiO2) at high altitudes and variation in accelerative gravitational forces (g-forces). Integrated into fighter aircraft is an Onboard Oxygen Generating System (OBOGS) developed to mitigate the necessity of gaseous and liquid oxygen cannisters [1]. OBOGS act as a life support in hypoxic environments by providing oxygen-rich air, thereby oxygenating the bloodstream [2] [3]. In theory, this prevents conditions such as hypoxia and decompression sickness. However, unexplained physiological episodes have still occurred despite pilot training and safety checklists [4].

This research focuses on coupling FlightGear and Pulse Physiology Engine (Pulse) simulations to recreate and understand hypoxic events related to a combination of high g-forces and high FiO2. Pulse is an integrative human physiology simulator that simulates conditions during disease, trauma, and treatment [5]. FlightGear is an open-source flight simulator with a variety of aircraft flown in dynamic flight environments [6]. Global data is shared between Pulse and FlightGear by creating interdependency between the two applications known as coupling. The internet protocol, Transmission Communication

Protocol (TCP), used for coupling, allows data transmission from FlightGear in the form of packets that can be received by Pulse during communication. By coupling interactive simulations based on FlightGear and Pulse, hypoxia was recreated from two scenarios: simulated accelerative atelectasis, achieved by using high g-forces output from FlightGear with a modified Pulse tension pneumothorax scenario, and the combination of high gforces and high FiO2, based on a prototype OBOGS simulation.

Each scenario resulted in hypoxic events after executing three consecutive simulations, validated by the ratio mismatch of pulmonary ventilation (𝑉 ̇A) and perfusion (𝑄̇) rates, 𝑉 ̇A /𝑄̇, due to a reduction in ventilation. During homeostasis, the average 𝑉 ̇A /𝑄̇ ratio from Pulse is approximately 1.0. When analyzing hypoxia based on high g-forces only and based on the combination of high g-forces and high-FiO2, hypoxia occurs for each scenario after executing the training route due to the 𝑉 ̇A /𝑄̇ ratio falling below 1.0, thereby causing a 𝑉 ̇A /𝑄̇ mismatch. For cases of high g-force only, hypoxia occurs between 86 – 96 seconds for a simulated male physiology and 69 – 71 seconds for a simulated female with a standard deviation of 5.51 and 1.15, respectively. For cases of high g-forces and high- FiO2, hypoxia occurs between 88 – 95 seconds for the male and 70-72 seconds for the female with a standard deviation of 3.79 and 1.0, respectively. Eventually, a detailed atelectasis simulation founded on multi-physics finite elements (FE) is planned in future work, where real-time efficiency is feasible through a deep neural network implementation trained on FE experiments. Using neural networks based on biometrics and preexisting health conditions, if any, will result in the development of a predictive analytics model to determine if pilots are susceptible to hypoxia prior to flight.