Modification of an automated vascular diagnostic system for hyperbaric use

Modifications of an automated, noninvasive vascular diagnostic system (VASCULAB, MedaSonics, Inc.) for measuring blood pressure and plethysmographic blood flow responses to normobaric and hyperbaric oxygenation are described. The system consisted of a pump for inflating and deflating blood pressure cuffs and a microprocessor program controller (VSC21) with ultrasound Doppler, strain-gauge plethysmograph, and chart recorder. Inclusion of the VSC21 controller in the chamber was required for performance of procedures that could not be controlled from outside the chamber. All other components were outside the chamber. For fire prevention the VSC21 controller was nitrogen-purged in an acrylic case mounted on a mobile cart. Pressure-cuff tubes were attached via adapted fittings and connectors in the cart to connector ports in the controller's front panel. Electrical power cables and instrument signal wires were routed through chamber penetrations to an electrical power source and other VASCULAB components, respectively, outside the chamber. Initially, compression of the chamber to pressures in excess of 1.68 bar disabled the VSC21, requiring removal of its front membrane panel and ventilation of its pressure-sensitive keypad switches. This allowed automated assessment of blood pressure and calf blood flow at test pressures of 1.97 and 2.96 bar.