Exercise Limitation Imposed by an Approved Air Purifying Respirator (APR)
Technical Report,01 Apr 2007,01 Dec 2009
Navy Experimental Diving Unit Panama City
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In this IRB-approved study, 31 subjects exercised with and without an approved air purifying respirator APR. A commonly used gas mask was used in both standard and slightly altered configurations in Phase1 the filter was loaded for a pressure drop simulating dust loading, and in Phase 2 the inlet pathway in the mask was modified. Phase 1 exercises were short fire hose drag or long duration incremental-load treadmill running, ladder climbing, and self-paced box lifting. Phase 2 exercise was incremental and endurance treadmill running. Parameters measured and calculated included breathing frequency, tidal volume, respiratory duty cycle, mask pressure, resistive effort WOBVT, minute ventilation VE, peak inspiratory flow Vi peak, rate of O2 uptake VO2, inhaled and exhaled CO2, and heart rate. With a standard APR, breathing difficulty caused 22 of 30 subjects to stop incremental running,14 of 15 to stop endurance runs, and 1 of 15 to stop climbing 6 of 15 with the loaded filter. With the standard APR, duration of incremental treadmill running dropped 14 from that with no APR, running endurance time decreased 57, and climbing endurance dropped by 20. The standard APR did not affect load lift and transfer or fire hose drag performance, but the number of boxes moved decreased 8 with the loaded filter, and five subjects complained of breathing resistance during recovery from the hose drag. Without an APR, the highest sustained VE exceeded 150 Lmin, and Vi was recorded at 434 Lmin. With an APR, VE decreased 14 to 26 relative to that without an APR at the same workload. Peak attainable VO2 was reduced 15, and VO2 at end running endurance decreased 15 to 18. Because required inspiratory pressures from laminar and turbulent flow were so high at the necessary Vi, inspiratory WOBVT was excessive.