Abstract: An assist for divers breathing a dense gas mixture reduces the fatigue otherwise caused by inspiring and expiring the dense mixture. A respiratory assist cuirasse is fitted to cover the upper abdomen and lower rib cage. The cuirasse has an outer semirigid shell and a flexible bladder inside connected to a pump module which creates positive and negative pressures inside of the covered area to assist normal breathing. A control module and sensors respond to humidity, temperature, or pressure variations in the breathing mixture and breathing apparatus to actuate the pump module. While normal breathing is being facilitated and augmented, there is a greater pulmonary flow and resultant increase in the oxygenation of the blood due to the negative pressure created by the respirator assist cuirasse. As a consequence, a diver will be able to more efficiently perform the demanding tasks during periods of heavy exertion in the cold water.