Evaluation of Respiratory Support Devices for Use in the Hyperbaric Chamber

Abstract

The U.S. Navy has identified a need to increase the level of patient care and support in the hyperbaric environment; ventilators, cardiac monitors, and other ancillary equipment are being evaluated to meet this need. Two Penlon Oxford ventilators, MK 1 and MK 2 (Penlon Limited; Oxfordshire, UK) are the only devices used in U.S. Navy recompression chambers. The Penlon MK 1 uses a pneumatically driven, mechanically controlled valved bellows - a design that enables the device to be operated in a hyperbaric environment simply by maintaining a pneumatic supply pressure 5080 pounds per square inch gauge (pslg) greater than the bottom pressure. These units have been out of production since the early 1980s, and repair parts are increasingly difficult to obtain. To meet the need for mechanical ventilation in U.S. Navy hyperbaric chambers the Navy Experimental Diving Unit (NEDU) tested a series of commercial off-the-shelf (COTS) ventilators between 2000 and 2003. Unmanned testing, including an electrical/mechanical safety evaluation, assessed the functional characteristics of the ventilators. The ventilator controls were then tested in a manned hyperbaric chamber. In addition to meeting design safety requirements, ventilators were required to achieve a minimum flow rate of 10 liters/min (L/min) at a depth of 165 feet of seawater (fsw) under various lung-loading conditions.