Physiologic Effects from Using Tight- and Loose-Fitting Powered Air-Purifying Respirators on Inhaled Gases, Peak Pressures, and Inhalation Temperatures During Rest and Exercise.

The goal of this investigation was to evaluate the physiologic stresses of powered air-purifying respirators (PAPRs) used by workers in many industries (e.g., health care, automobile repair, public safety, building trades, etc.) during rest and three levels of energy expenditure. Twelve men and twelve women wore one tight-fitting and three loose-fitting PAPRs at rest (REST) and while walking for four minutes at oxygen consumption (V̇O2) rates of 1.0 l·min-1(LOW), 2.0 l·min-1 (MODERATE), and 3.0 l·min-1 or maximum (HIGH). Minimum inhaled carbon dioxide concentration (FICO2), maximum inhaled oxygen concentration (FIO2), peak inhalation pressure, and end inhalation temperature were measured continuously breath-by-breath. Repeated measures analysis of variance found that neither the main effect of gender, nor any interactions involving gender were significant. The highest minimum FICO2 among PAPRs occurred for MODERATE and HIGH energy expenditures while wearing the loose-fitting PAPR with the largest dead space. The lowest maximum FIO2 was observed during HIGH intensity energy expenditure also for the loose-fitting PAPR with the largest dead space. Among all PAPR models, peak inhalation pressures were negative at V̇O2 > LOW, suggesting that peak inhalation flow was greater than blower flow. Results using the variables reported here suggest that PAPRs used at various levels of energy expenditure may be tolerated among healthy workers. Further research is needed to determine the source of supplemented air when inhalation flow exceeds blower flow.

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.