Hyperbaric Oxygen Therapy and Oxygen Compatibility of Skin and Wound Care Products.

Objective: Use test methods to assess the oxygen compatibility of various wound care products. Approach: There are currently no standard test methods specifically for evaluating the oxygen compatibility and safety of materials under hyperbaric oxygen (HBO) conditions. However, tests such as the oxygen index (OI), oxygen exposure (OE), and autogenous ignition temperature (AIT) can provide useful information. Results: The OI test measures the minimum oxygen concentration that will support candle-like burning, and it was used to test 44 materials. All but two exhibited an OI equal to or greater (safer) than a control material commonly used in HBO. The OE test exposes each material to an oxygen-enriched atmosphere (>99.5% oxygen) to monitor temperature and pressure for an extended duration. The results of the OE testing indicated that none of the 44 articles tested with this method self-ignited within the 60°C, 3 atm pressurized oxygen atmosphere. The AIT test exposes materials to a rapid ramp up in temperature in HBO conditions at 3 atm until ignition occurs. Ten wound care materials and seven materials usually avoided in HBO chambers were tested. The AIT ranged from 138°C to 384°C for wound care products and from 146°C to 420°C for the other materials. Innovation: This work provides useful data and recommendations to help develop a new standard approach for evaluating the HBO compatibility of wound care products to ensure safety for patients and clinicians. Conclusion: The development of an additional test to measure the risk of electrostatic discharge of materials in HBO conditions is needed.

The selection of skin care products for use in hyperbaric chamber may depend on flammability acceptability indices score.

PURPOSE: Current protocols call for stopping adjunctive skin care treatments during hyperbaric oxygen therapy (HBOT) because the hyperbaric environment is considered unsafe for skin care products. The elevated oxygen fraction and the increased pressure in the hyperbaric chamber dramatically increase the flammability potential of materials, leading to the need for rigorous standards to prevent flame ignition. A scientific method of evaluating the flammability risks associated with skin care products would be helpful. Several skin care products were tested, using established industrial techniques for determining flammability potential with some modification. The information obtained from these tests can help clinicians make more rational decisions about which topical products can be used safely on patients undergoing HBOT. METHODS AND MATERIALS: Wendell Hull & Associates conducted independent studies, comparing the oxygen compatibility for leading skin care products. Oxygen compatibility was determined using autogenous ignition temperature (AIT), oxygen index (OI), and heat of combustion (HoC) testing. AIT, a relative indication of a material's propensity for ignition, is the minimum temperature needed to cause a sample to self-ignite at a given pressure and oxygen concentration. OI, a relative indication of a material's flammability, is the minimum oxygen percentage that, when mixed with nitrogen, will sustain burning. HoC is the absolute value of a material's energy release when burning, if ignition occurs. Products with a high AIT, a high OI, and a low HoC are more compatible in an oxygen-enriched atmosphere (OEA). An acceptability index (AI) based on these 3 factors was calculated for the products, so the testers could rank overall material compatibility in OEAs (Lapin A. Oxygen Compatibility of Materials. International Institute of Refrigeration Commission Meeting; Brighton, England; 1973). RESULTS: Test results for the skin products varied widely. The AIT, OI, HoC, and AI were determined for each product under described circumstances. The AIT results indicate that all products in 99.5% oxygen concentration under pressure will ignite and that a pattern based on the absence or presence of petroleum-based ingredients does not seem to exist. Products containing petrolatum, mineral oil, paraffin, and paraffin wax had a HoC that equaled or exceeded the HoC of gasoline, whereas products without petroleum-based ingredients had a significantly lower HoC. The OI of skin products not containing petrolateum-based ingredients was significantly higher than the OI of products containing it. The AI values the OI as the most important value: the higher the AI, the more acceptable the product is for use with oxygen. The silicone-containing, petroleum-free products received an AI up to 25 times higher than the petrolatum-based products. These findings suggest a wide variation in the safety profiles of skin products. Skin products being considered for use in an OEA should be screened for flammability risks. This screening will allow informed decisions about the fire safety of the products. Further research is indicated.

Reflection of structural waves at a solid/liquid interface.

This paper investigates the reflection characteristics of structural or guided waves in rods at a solid/liquid interface. Structural waves, whose wavelengths are much larger than the diameter of the rod, are described in a first approximation by classical one-dimensional wave theory. The reflection characteristics of such waves at a solid/liquid (melting) interface has been reported by two different ultrasonic measurement techniques: first, measuring the fast regression rate of a melting interface during the burning of metal rod samples in an oxygen-enriched environment, and second, monitoring the propagation of the solid/liquid interface during the slow melting and solidification of a rod sample in a furnace. The second work clearly shows that the major reflection occurs from the solid/liquid interface and not the liquid/gas interface as predicted by plane longitudinal wave reflectivity theory. The present work confirms this observation by reporting on the results of some specially designed experiments to identify the main interface of reflection for structural waves in rods. Hence, it helps in explaining the fundamental discrepancy between the reflection characteristics at a solid/liquid interface between low frequency structural waves and high frequency bulk waves, and confirms that the detected echo within a burning metallic rod clearly represents a reflection from the solid/liquid interface.