Breathing Impedance of the Mark VIII and Mark XI Semi-Closed Underwater Breathing Apparatus

A diver breathing with an underwater breathing apparatus will have his ventilatory capability degraded by an inherent breathing impedance in the equipment used. The impedance of both the equipment and the diver's respiratory system will increase as ambient pressure increases. There is little information available concerning the deleterious physiological effects imposed on the diver breathing with an underwater breathing apparatus. A paucity of information delineating bioengineering specifications for breathing resistance in underwater breathing apparatus exists. This study was undertaken to measure the breathing resistance encountered by an exercising subject using a semiclosed underwater breathing apparatus. Objectives of the study were: delineation of physiological effects imposed by equipment resistance in the presence of gases of normal and increased density; development of techniques to evaluate breathing resistance in diving equipment; tenative establishment of specifications for engineering design of diving equipment in terms of breathing resistance. All objectives of the study were attained.