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DARPA Project: Integrated Microsystems to Sense and Control Diver Physiology
Greg - 4/11/2013 3:25 PM
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Category: Educational
Comments: 4
DARPA Project: Integrated Microsystems to Sense and Control Diver PhysiologyNew SCUBA technology seems to begin with military application. The new DARPA project listed below should ultimately provide cool new high-tech gear for scuba divers.

SB131-004: Integrated Microsystems to Sense and Control Warfighter Physiology for Military Diver Operations

TECHNOLOGY AREAS: Biomedical, Sensors

OBJECTIVE: Develop an integrated microsystems platform that dynamically senses and controls warfighter physiology to enable extreme military dive operations.

DESCRIPTION: Consequences of inhaling gases at high pressure were originally encountered during undersea salvage and construction over a century ago. Empiric depth and time limits were found to reduce gas bubble formation in tissues that caused the “bends”. We continue to limit adverse physiology – now expanded to include decompression sickness (DCS), oxygen toxicity, inert gas narcosis, and high pressure nervous syndrome (HPNS) – primarily by breathing static gas mixtures at prescribed pressures and durations. Longstanding US Navy dive regulations and technologies mandate use of standard gas mixtures, rate of descent, rate of ascent, depth, and bottom time.

While dive technology has changed little in the last two decades, recent advances in applied physiology and microsystems technology could coalesce into revolutionary capability. Nitric oxide (NO) is an example of a gas that could be dynamically added to the inhaled gas mixture to improve dive operations and safety. Although trace gases such as NO were traditionally considered “poisons”, they are now known as naturally occurring biomolecules that play a critical role in cellular signaling and metabolism. Of relevance to the current topic, inhaled NO relaxes blood vessels and increases tissue perfusion with a rapid onset/offset of action. Within the Defense Advanced Research Projects Agency (DARPA) Rapid Altitude and Hypoxia Acclimatization (RAHA) program, inhaled NO was found to improve tolerance to hypoxia. In the dive environment, NO donors such as nitroglycerin also have been shown to decrease incidence of DCS. Of note, inhaled NO is Food and Drug Administration (FDA) approved for the treatment of pulmonary hypertension.

Combining the physiologic effect of inhaled gases such as NO with in vivo monitoring of pre-symptomatic risk factors such as microbubble formation could reduce the risk of adverse events such as DCS, but requires novel algorithms for dynamic control of pressure-related physiologic conditions, constant physiological feedback, and precise gas administration.

This solicitation calls for novel gas mixtures, models and algorithms that extend operational capabilities while minimizing the risk of the following:
• DCS—gas expansion injuries and bubble formation in blood and tissue caused by rapid ascent;
• oxygen toxicity—increased partial pressure of oxygen (PO2 > 1.6 ATA) resulting in seizures;
• gas narcosis—euphoria and decrement in intellectual and psychomotor performance related to the lipid solubility of the gas; and
• hypoxia—decrement in cognition and performance related to low partial pressure of oxygen. The dynamic sensing and control could include but is not limited to such gases as O2, COx, NOx, H2S, and inert gas diluent.

Additionally, this solicitation seeks to develop novel component technologies including but not limited to: chip-scale gas chromatograph / mass spectrometer (to actively and rapidly monitor inspired and expired gases/agents); capacitive micro-machined ultrasonic transducer arrays (for in vivo bubble detection and environmental monitoring); and gas/vapor control elements such as MEMS gas pumps, valves and nebulizers that could be integrated into a physiologic control system for extreme environments. Such new component technologies may also support next generation military open circuit, semi-closed circuit or close circuit rebreather systems.

The platform should enable safe operation in this representative extreme combat dive profile: (1) insertion via military free fall from 35,000 feet flight level; (2) a brief surface interval; (3) combat dive down to 200 feet sea water (FSW) for at least 120 minutes duration, surface and immediately begin a second dive of variable, increasing depth with minima at 100 FSW (for at least 10 minutes), 150 FSW (for at least 10 minutes), and 200 FSW (for at least 20 minutes) without decompression obligation; (4) brief surface interval; and (5) extraction in an unpressurized aircraft below 14,000 feet mean sea level.

PHASE I: Define the gas mixtures suitable for the representative dive profile. Explore and develop requirements for the dynamic mixed gas model and control algorithm. Develop a high level model and control algorithm, to be informed by Phase II in vivo experimentation and data collection. Select representative component microsystem technologies for proof of concept and development. Design a breadboard mixed gas platform for use in simulated dive profile(s) within a chamber. Develop the military and Occupational Safety and Health Administration (OSHA) regulatory approval plan for the component technologies and integrated device.

Phase I deliverables: A report defining (1) Opportunities and limitations of selected gases; (2) current state-of-the-art and limitations of component technologies including model/algorithm, physiologic sensors, gas sensors, and gas control components; (3) high level model and control algorithm; (4) detailed design of breadboard system; and (5) proposed animal chamber testing and regulatory approval plan.

PHASE II: Develop, demonstrate, and validate a dynamic model and control algorithm using a small animal model. Build a breadboard mixed gas system that includes the necessary control algorithm, physiologic sensors, gas sensors, and gas control components for use in chamber experiments. The breadboard system shall be demonstrated using the defined profile. At the conclusion of Phase II the performer shall provide a detailed plan for algorithm optimization, hardware miniaturization and integration into a prototype device, and transition of a man-portable prototype device into operationally relevant environments. As such, full and traceable documentation of in vivo testing that meets regulatory requirements must be provided in order to move to Phase III.

Phase II deliverables: (1) Dynamic mixed gas model and control algorithm that enables extreme combat diving with limited risk of complications; (2) breadboard system that includes the necessary algorithm, physiologic sensors, gas sensors, and gas control components; (3) prototype integrated microsystem device design; and (4) detailed regulatory approval, transition, and commercialization plan.

PHASE III: Phase III commercial application will focus on exploration and extraction of undersea oil, gas, and minerals. Improved deep water site access, operations, and safety should limit cost and environmental impact of production of natural resource necessary for US economic and military viability. Phase III military application will focus on robust military diving operations. Specific applications include expanded special operations and EOD capabilities.


Canthon - 4/26/2013 9:09 AM
Greg, may I use this article on DARPA’s SB131-004 in a newsletter our dive club has?
Greg - 4/26/2013 9:14 AM
Sure, that’s cool.
Eric_R - 4/12/2013 5:16 PM
Even if the research gets 10% of what their looking for it would be successful in my book.
Greg - 4/11/2013 3:30 PM
My favorite part is where they want the diver to be able to skydive from an altitude of 35,000 feet...then immediately scuba dive to 200 feet underwater for at least 2 hours...upon surfacing the diver must be able to complete 3 additional dives without decompression...then immediately jump on an unpressurized plane up to an altitude of 14,000 feet to fly home.

That sounds pretty hard core!