Physiological effects of pressure demand masks during heavy exercise

Inward leakage in a respiratory protective device may constitute a health hazard. The pressure demand system causes a slightly positive pressure in the facepiece throughout the breathing cycle, so that any insufficient seal in such a system will result in an outward leakage. One question is whether this positive pressure will influence work capacity. Five subjects worked until exhaustion on a bicycle ergometer with four different breathing equipments: two masks with positive pressure (0.5 kPa and 0.8 kPa) and two mouthpieces without positive pressure, one control and one with high resistance. No difference in endurance time was found. Heart rate, oxygen consumption, rated perceived exertion and blood lactate at breaking point did not show any significant changes. The high resistance mouthpiece, -1.1 kPa to +1.3 kPa, at breaking point, did reduce minute ventilation by 21% and end tidal PCO2 was increased by 16% without any influence on work performance.