IHMC Statement of Work.docx

Statement of Work

Investigating the impact of oxygen system warnings on hypoxia symptom reporting and cognitive performance in aircrew

Problem Statement/Knowledge Gaps:

Physiological events (PEs), which are aircraft malfunctions leading to aircrew symptoms, are a predominant safety concern for all U.S. military air forces. PEs have led to mishaps and groundings, reducing trust in aircraft reliability. Investigations into causal factors of PEs have not identified a single definitive cause but have highlighted a range of underlying contributing factors.

An issue identified during PE investigations is aircrew reporting rapid hypoxia-like symptoms despite receiving adequate oxygen levels for the cabin altitude. Notably, these symptoms occurred immediately after an onboard oxygen generating system (OBOGS) degrade warning. Investigators concluded that these hypoxia symptom reports likely stemmed from an autonomic response to physiological stress rather than actual oxygen deprivation. However, it remains unclear whether OBOGS warnings influence hypoxia reporting as isolated incidents or signal a broader issue among aircrew.

To our knowledge, no studies have investigated the effects of OBOGS warnings on hypoxia symptom reporting or cognitive performance. This study aims to address this gap by systematically evaluating the relative contributions of OBOGS warnings and hypoxic exposures on hypoxia symptom reporting and cognitive performance. The findings will offer crucial insights into the underlying factors of PEs and inform training paradigms that address the psychophysiological aspects of PEs.

Background:

Hypoxia resulting from an OBOGS malfunction has historically been considered a predominant causal factor of PEs. Aircrew have reported PEs due to hypoxia across various flight platforms, including the F-22, F-35, F/A-18, F-15, F-16, T-6, and T-45. Notably, the U.S. Navy grounded all T-45 training aircraft in 2017 due to a significant number of instructor pilots refusing to fly because of concerns with OBOGS.

In response to the surge in PE occurrences, both the U.S. Navy and Air Force initiated comprehensive reviews and established Physiological Episode Action Teams (PEAT). The Navy PEAT conducted a root cause corrective action (RCCA) investigation to identify and address the underlying causes of PEs. Their RCCA investigation concluded that the causes of PEs are multifactorial and are not attributed to any singular cause. Investigations found that OBOGS produces high-quality oxygen at or above ambient levels (i.e., 21% O2), ruling out contamination and hypoxic hypoxia as plausible causal factors of PEs. Despite these findings, aircrew still report rapid onset of hypoxia symptoms while OBOGS delivers sufficient oxygen concentrations [8,9].

One explanation for these false-positive hypoxia reports is an autonomic response to physiological stress initiated by the OBOGS degrade warning. While intended as a safety measure, the warning may inadvertently reinforce preconditioned beliefs about oxygen system issues and hypoxia, leading to an exaggerated autonomic response. These responses, driven by physiological stress in an off-nominal environment, can manifest as tachycardia (rapid heartbeat), hyperventilation (rapid breathing), and hyperhidrosis (excessive sweating). Each of these physiological responses can result in hypoxia-like symptoms, making it difficult for aircrew to distinguish between hypoxia and autonomic responses to physiological stress.

The negative preconditioned beliefs triggered by an OBOGS degrade warning may be an unintended consequence of hypoxia symptom recognition training. Hypoxia symptom recognition training educates aircrew on the signs and symptoms of hypoxia; however, there is little focus placed on recognizing other physiological causes of hypoxia-like symptoms. By associating all symptoms with hypoxia, this training could reinforce the belief that any symptoms experienced during an OBOGS degrade indicates insufficient oxygenation, even when the OBOGS delivers adequate oxygen concentrations.

Autonomic responses to an OBOGS degrade warning may represent a plausible mechanism contributing to PEs among aircrew. However, the direct impact of OBOGS degrade warnings on hypoxia symptom reporting and cognitive performance are not fully understood. To address this gap, we propose studying the individual effects of hypoxic exposures and the presence of a warning light on hypoxia symptom reporting and cognitive performance measures. This research is particularly relevant to Department of Defense (DoD) stakeholders involved in designing aircrew training programs. It may highlight the need for training paradigms that emphasize adaptive responses to critical events and improved decision-making under stress, rather than focusing solely on hypoxia symptom recognition. Additionally, the findings will aid military stakeholders and safety commands in conducting more informed aeromedical investigations into the causal factors of PEs.

Hypothesis and Specific Aims:

Research Question: How do OBOGS warnings and hypoxic exposures influence hypoxia symptom reporting and performance on the Cognitive Assessment of Aviation Performance and Evaluation of State (CAAPES)?

Hypotheses:

H1. OBOGS warnings will significantly increase the likelihood of hypoxia symptom reporting compared to hypoxic exposure alone, with each effect assessed separately.

H2. OBOGS warnings will significantly reduce CAAPES performance compared to hypoxic exposure alone, with each effect assessed separately.

Confirmatory Aims:

Aim 1. Determine how OBOGS warnings and hypoxic exposures independently influence the likelihood of hypoxia symptom reporting.

Aim 2. Quantify the impact of OBOGS warnings and hypoxic exposures on CAAPES performance.

Exploratory Aims:

Aim 3. Explore how physiological responses differ between OBOGS warnings and hypoxic exposures.

Aim 4. Rank the physiological metrics by their strength and direction of association with hypoxia symptom reporting.

Aim 5. Examine patterns in the severity and frequency of hypoxia symptoms under OBOGS warnings and hypoxic exposures.

Milestones and Deliverables:

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