TECHNOLOGY AREAS: Biomedical

The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), which controls the export and import of defense-related material and services. Offerors must disclose any proposed use of foreign nationals, their country of origin, and what tasks each would accomplish in the statement of work in accordance with section 3.5.b.(7) of the solicitation.

OBJECTIVE: To develop an approach to non-invasively monitor and measure the formation of nitrogen bubbles both in the bloodstream and in tissue, for the purpose of generating data to better characterize and qualify the physical etiology of decompression sickness (DCS) and revolutionize treatment of DCS.

DESCRIPTION: DCS is caused by the formation of small bubbles in the bloodstream and has long been a major concern in any activity requiring significant change in the ambient environmental pressure. As such, DCS is a significant hazard to Navy divers and astronauts. Currently, bubbles may be detected using Doppler ultrasound. However, Doppler has several disadvantages as a detection technique in that Doppler is sensitive to motion and bubbles have to be greater than 80 �m in diameter. In addition, Doppler data is very subjective and very difficult to standardize.

Currently, divers rely on decompression tables which are designed to decrease the incidence of DCS. Since the tables are based on reducing the statistical risk for an individual based on a population-based norm, there is no allowance to individualize preventive measures. Thus, a diver may have to undergo several hours of decompression when perhaps one hour of decompression would have worked. This detail becomes more salient when divers do not have access to a recompression chamber and have to undergo in water decompression. This significantly increases the risk to the divers, especially in times of turbulent sea state. In addition to divers, astronauts may suffer DCS during extra-vehicular activity (EVA) in space suits pressurized to only a third of an atmosphere. In fact, most astronauts undergo a lengthy oxygen pre-breathe before EVA. Thus, both activities suffer significant decreases in work efficiency in their respective environments. Despite over a century of dealing with DCS, tabular decompression tables remain statistical and experiential�and in fact, the appropriate decompression time can vary from person to person, and from time to time within a given individual.
The U.S. Navy is interested in developing an approach to monitor and measure non-invasively the formation of nitrogen bubbles both in the bloodstream and in tissue, for the purpose of generating data to better characterize and qualify the physical etiology of DCS and perhaps enhance treatment strategies. A body of anecdotal evidence suggests that reducing the number of tissue micronuclei by various pre-breathe strategies might greatly reduce the risk of DCS. Alternatively, detecting the quantity and/or size of micronuclei may predict the risk of DCS. An improved method to monitor/detect formation of bubbles would lead to a new tool in the prevention, detection and treatment of DCS.

PHASE I: Provide initial development effort that demonstrates capabilities of proposed bubble imaging system. This phase would provide key information about the uses and limitations of the system.

PHASE II: Use instrument/algorithms to correlate amount/size of bubbles with clinical signs of DCS. Other areas of research would be detection of what tissues contain bubbles and if tissue bubbles appear before intravascular bubbles. This phase would involve animal trials.

PHASE III: Determine the capability to detect bubbles in humans and correlate amount/size of bubbles with clinical signs of DCS and generally characterize the pathophysiology of DCS in humans. This phase would concentrate on hardening the equipment/standard operating procedures so that the device could be used by surface supplied divers undergoing in water decompression. Since surface supplied divers have a connection to the surface, telemetry of data would not be necessary. However, cables and couplings would need to operate in a sometimes challenging environment.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: This technology would be of interest to not only the military diving community and NASA, but also commercial (underwater construction and oil companies) and the large recreational diving communities.

REFERENCES:
1. Acta Astronaut. 2005 May-Jun; 56(9-12):1041-7.

KEYWORDS: DCS; bubble detection; micronuclei; tissue bubble