THE PREDICTION OF RECOMMENDED ENERGY-EXPENDITURE FOR AN 8-H WORK-DAY USING AN AIR-PURIFYING RESPIRATOR

Thirty railway workers executed maximal, or near maximal, stress tests with and without the use of a half mask air-purifying respirator (Spa sciani 85 A1 P1) fitted with two combined filters for simultaneous pro tection from organic vapours and particulate matter. The pressure-flow characteristics of inspiratory and expiratory resistance at airflows in the range 0-90 1. min-1 were established by a continuous flow metho d on one test mask. Significant differences were found by paired 1-tes t between the two exercises (with and without use of mask), showing re duced values with use of the mask, for breath frequency, ventilation r ate, oxygen uptake, carbon dioxide production, maximal oxygen uptake, percentage of maximal voluntary ventilation used at the maximal exerci se ventilation. No significant differences were found for tidal volume , respiratory quotient, heart rate, systolic blood pressure, oxygen up take at anaerobic threshold, and duration of exercise. The predicted e nergy expenditure recommended for an 8 h work shift, corresponding to 40% of maximal oxygen uptake, is found to be reduced working with resp irator and is significantly different from that observed during stress test without mask. The average ventilation rate at this workload is b elow 25 l. min-1, with predicted inspiratory mouth pressure equal to, or less than, 20 mm H2O. This maximal inspiratory mouth pressure is pr oposed as a safety limit for prolonged work using a respirator, with a recommended energy expenditure close to 40% of maximal oxygen uptake.