Physiological evaluation of air-fed ensembles.

The goal of this study was to evaluate the respiratory and metabolic stresses of air-fed ensembles used by workers in the nuclear, chemical, and pharmaceutical industries during rest, low-, and moderate-intensity treadmill exercise. Fourteen men and six women wore two different air-fed ensembles (AFE-1 and AFE-2) and one two-piece supplied-air respirator (SA) at rest (REST) and while walking for 6min at oxygen consumption (V.O2) rates of 1.0 (LOW) and 2.0 l min(-1) (MOD). Inhaled CO2 (FICO2), inhaled O2 (FIO2), pressure, and temperature were measured continuously breath-by-breath. For both LOW and MOD, FICO2 was significantly lower (P < 0.03) and FIO2 was significantly greater (P < 0.008) for SA compared with AFE-1 and AFE-2 in women, while in men, similar trends were observed. Significantly lower FICO2 (P < 0.009) and significantly greater FIO2 (P < 0.04) were consistently observed in AFE-1 compared with AFE-2 in men during LOW and MOD. For both men and women, average FICO2 exceeded 2.0% in AFE-2 during MOD. During LOW and MOD, average FIO2 in AFE-1 and AFE-2 dropped <19.5% in men and women. For men and women, average inhalation pressures (PIave) were significantly greater in both air-fed ensembles than SA (P < 0.001) during REST, LOW, and MOD. Inhaled gas temperature was significantly lower in SA than in either air-fed ensemble (P < 0.001). When the air supply was shut off during walking, the time taken for minimum FICO2 to reach 2.0% was <38 s for all three ensembles in both men and women, an observation that has implications for the design of emergency escape protocols for air-fed ensemble wearers. Results show that inhaled gas concentrations may reach physiologically stressful levels in air-fed ensembles during moderate-intensity treadmill walking.