Speech intelligibility while wearing full-facepiece air-purifying respirators.

Intelligible speech communication while wearing air-purifying respirators is critical for law enforcement officers, particularly when they are communicating with each other or the public. The National Institute for Occupational Safety and Health (NIOSH) requires a 70% overall performance rating to pass speech intelligibility certification for commercial chemical, biological, radiological, and nuclear air-purifying respirators. However, the speech intelligibility of certified respirators is not reported and the impact on operational performance is unknown. The objective of this effort was to assess the speech intelligibility of 12 certified air-purifying respirators and to predict their impact on operational performance. The NIOSH respirator certification standard testing procedures were followed. Regression equations were fit to data from studies that examined the impact of degraded speech intelligibility on operational performance of simple and complex missions. The impact of the tested respirators on operational performance was estimated from these equations. Performance ratings observed for each respirator were: MSA Millennium (90%), 3M FR-M40 (88%), MSA Ultra Elite (87%), Scott M110 (86%), North 5400 (85%), Scott M120 (85%), Avon C50 (84%), Avon FM12 (84%), Survivair Optifit (81%), Drager CDR 4500 (81%), Peltor-AOSafety M-TAC (79%), and 3M FR-7800B (78%). The Millennium and FR-M40 had statistically significantly higher scores than the FR-7800B. The Millennium also scored significantly higher than the M-TAC. All of the tested respirators were predicted to have little impact on simple and complex mission performance times and on simple mission success rate. However, the regression equations showed that 75% of missions that require complex communications would be completed while wearing the Millennium, FR-M40, or Ultra Elite but that only 60% would be completed successfully while wearing the FR-7800B. These results suggest that some certified respirators may have a greater impact on speech communications than others.

Unmanned assessment of respirator carbon dioxide levels: comparison of methods of measurement.

A study was performed to determine average inhaled carbon dioxide (F(I)CO2) concentrations of multiple respirators using unmanned test methods, and to compare results among test procedures to determine whether they could be used interchangeably. Respirator experiments were performed according to the National Institute for Occupational Safety and Health (NIOSH) (NF(I)CO2), standard European (ENF(I)CO2), and a modified method of the European test (BF(I)CO2) using full-facepiece air-purifying respirators and one air-purifying escape respirator. Bland-Altman statistics for determination of limits of agreement were applied to assess agreement among the various test methods. A considerable lack of agreement was found between NF(I)CO2 and ENF(I)CO2 methods and between BF(I)CO2 and NF(I)CO2 methods for average F(I)CO2. The modified EN136 method produced F(I)CO2 averages about 0.13% to 0.23% above unmodified EN136 values, but the agreement between methods was generally acceptable. These results demonstrate that NIOSH and European unmanned test methods for determining respirator average F(I)CO2 concentrations produce different results for like respirators. However, the findings suggest that the ENF(I)CO2 and BF(I)CO2 unmanned methods could be used interchangeably for quantifying respirator F(I)CO2 concentrations.

Maximum static inspiratory and expiratory pressures with different lung volumes.

BACKGROUND: Maximum pressures developed by the respiratory muscles can indicate the health of the respiratory system, help to determine maximum respiratory flow rates, and contribute to respiratory power development. Past measurements of maximum pressures have been found to be inadequate for inclusion in some exercise models involving respiration. METHODS: Maximum inspiratory and expiratory airway pressures were measured over a range of lung volumes in 29 female and 19 male adults. A commercial bell spirometry system was programmed to occlude airflow at nine target lung volumes ranging from 10% to 90% of vital capacity. RESULTS: In women, maximum expiratory pressure increased with volume from 39 to 61 cmH2O and maximum inspiratory pressure decreased with volume from 66 to 28 cmH2O. In men, maximum expiratory pressure increased with volume from 63 to 97 cmH2O and maximum inspiratory pressure decreased with volume from 97 to 39 cmH2O. Equations describing pressures for both sexes are: Pe/Pmax = 0.1426 Ln( %VC) + 0.3402 R2 = 0.95 Pi/Pmax = 0.234 Ln(100 - %VC) - 0.0828 R2 = 0.96 CONCLUSION: These results were found to be consistent with values and trends obtained by other authors. Regression equations may be suitable for respiratory mechanics models.

Effects of caffeine on performance of low intensity tasks.

31 college age men and women who consume less than three caffeinated beverages per week agreed to participate as subjects in research on the effects of acute caffeine intake on low intensity task performance. All subjects performed two randomly administered test conditions: (1) caffeine (5 mg/kg) and (2) placebo on separate visits following an initial 1-hr. orientation visit. Subjects were administered the beverage 30 min. prior to performing 12 separate tests assessing basic mathematics, simple response, logical reasoning, hand-eye coordination, and spatial and assembly skills. The Spielberger State Anxiety test was administered immediately after consuming the test beverage and once again at posttest. Analysis showed that caffeine did not significantly affect performance on all tests with the exception of the peripheral awareness (hand-eye coordination) test on which performance was higher after ingesting caffeine. The placebo treatment produced no effect on state anxiety, which contrasted with a significant rise in anxiety after caffeine consumption. State anxiety values were significantly greater after caffeine treatment relative to the placebo at pretest, and this difference persisted at posttest. These results demonstrated that the dose of caffeine increased scores on state anxiety for individuals who consumed less than three caffeinated beverages weekly but had very little effect on performance of low intensity tasks, except for a hand-eye coordination test involving peripheral awareness. Perhaps longer continuous performance of more demanding tasks would be more sensitive.