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PubMed2000

Fit factors for quarter masks and facial size categories.

Respirator fit testing is necessary before entering hazardous working environments to ensure that the respirator, when worn, satisfies a minimum fit and that the wearer knows when the respirator fits properly. In the many countries that do not have fit testing or total inward leakage regulations (including Korea), however, many workers wearing respirators may be potentially exposed to hazardous environments. It is necessary to suggest a useful tool to provide an alternative for fit testing in these countries. This study was conducted to evaluate fitting performance for quarter-mask respirators, and fit factors in facial size categories based on face lengths and lip lengths of the wearers. A total of 778 subjects (408 males, 370 females) were fit tested for three quarter masks: Sejin Co. SK-6 (Ulsan, Korea), Yongsung Co. YS-2010 S (Seoul, Korea), and 3 M Co. Series 7500 Medium (MN, USA) masks with a PortaCount 8020 (TSI Co., USA). A facial dimension survey of the subjects was conducted to develop facial size categories, on the basis of face length and lip length. Geometric mean fit factors (GMFFs) of Series 7500 Medium were found to be the highest of the three respirators. All of the respirators were more suitable for males than females in fitting performance. The Series 7500 Medium fitted a large number of the males tested, since the GMFFs for males were above 100 for every box of facial size categories, and high pass proportion rates were shown at an individual fit factor level of 100. The YS-2010 S provides an adequate fit for males in a limited range of facial dimensions. The Series 7500 Medium is more limited in providing adequate fit for females at specific facial dimensions than for males. For adequate fitting performance, the SK-6 is not preferentially recommended for Korean male and female workers due to low GMFFs and pass proportions. The result of this study indicates that after more accurate studies are performed, facial size categories, on the basis of facial dimensions, could be a useful tool to assist in the selection of adequately fitting respirators for workers in the countries having no fit testing requirements.

Adult↗
PubMed1997

Clinical evaluation of a topographically based contact lens fitting software.

BACKGROUND: Second generation corneal topography-based contact lens software programs attempt to fit the cornea based on topographical information rather than simulated keratometry and nomogram-based fits. The EyeSys System 2000 Pro-Fit software (Version 3.1) was clinically evaluated for efficiency in fitting rigid gas permeable (RGP) lenses on 22 normal subjects. METHODS: Balanced manifest refractions, slitlamp examinations, keratometry, computerized topographic analysis and lens fitting, and manual diagnostic RGP fitting were performed on all patients. The topographically fit eyes were compared to corresponding eyes which were manually fit with diagnostic trial lenses. Lens parameters for the topographically fit eye were chosen after an optimal fluorescein pattern was achieved by either accepting the initially recommended Pro-Fit lens or a modification. Final lens parameters were based on clinical performance. Lenses were reordered when there was a need for base curve changes of 0.1 mm or more, power alterations of +/- 0.50 D or more, or for any alteration in diameter, optic zone, or edge lift. RESULTS: Both manual and topographically fit groups achieved 17/22 (77%) eyes successfully fit without any subsequent lens modifications. Time records for the manually fit group averaged 16.5 min, whereas the topographically fit group averaged 8.0 min. CONCLUSIONS: This study reports a 51.4% reduction in chair time when using a topographically based contact lens software program while achieving the same clinical results as in traditional diagnostic RGP fitting, suggesting increased efficiency in fitting RGPs to normal eyes.

Astigmatism↗
PubMedDate not supplied

Comparison of three commercially available fit-test methods.

American National Standards Institute (ANSI) standard Z88.10, Respirator Fit Testing Methods, includes criteria to evaluate new fit-tests. The standard allows generated aerosol, particle counting, or controlled negative pressure quantitative fit-tests to be used as the reference method to determine acceptability of a new test. This study examined (1) comparability of three Occupational Safety and Health Administration-accepted fit-test methods, all of which were validated using generated aerosol as the reference method; and (2) the effect of the reference method on the apparent performance of a fit-test method under evaluation. Sequential fit-tests were performed using the controlled negative pressure and particle counting quantitative fit-tests and the bitter aerosol qualitative fit-test. Of 75 fit-tests conducted with each method, the controlled negative pressure method identified 24 failures; bitter aerosol identified 22 failures; and the particle counting method identified 15 failures. The sensitivity of each method, that is, agreement with the reference method in identifying unacceptable fits, was calculated using each of the other two methods as the reference. None of the test methods met the ANSI sensitivity criterion of 0.95 or greater when compared with either of the other two methods. These results demonstrate that (1) the apparent performance of any fit-test depends on the reference method used, and (2) the fit-tests evaluated use different criteria to identify inadequately fitting respirators. Although "acceptable fit" cannot be defined in absolute terms at this time, the ability of existing fit-test methods to reject poor fits can be inferred from workplace protection factor studies.

Aerosols↗
PubMed2004

The contribution of cardiorespiratory fitness and visceral fat to risk factors in Japanese patients with impaired glucose tolerance and type 2 diabetes mellitus.

It is still unclear as to how cardiorespiratory fitness and visceral fat accumulation contribute to coronary heart disease (CHD) risk factors in patients with diabetes mellitus. The purpose of the present study was to investigate whether cardiorespiratory fitness contributes to such risk factors independently of visceral fat accumulation. Two hundred Japanese patients (137 men and 63 women, aged 22 to 81 years) with impaired glucose tolerance (IGT) and type 2 diabetes mellitus (type 2 DM) without any intervention and pharmacological therapy participated in a cross-sectional study. The levels of fasting insulin, triglyceride (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and resting blood pressure were assessed. Maximal oxygen uptake (V.o(2max)), an index of cardiorespiratory fitness, was predicted by a graded exercise test using a cycle ergometer. Visceral fat area (VFA) was measured by computed tomography scan. The criteria for abnormalities of the risk factors were determined according to the standard values for Japanese. All subjects were divided equally into the following 3 groups according to their fitness level: low-fit (V.o(2max) < 32 mL/kg/min in men, V.o(2max) < 26 mL/kg/min in women), mid-fit (32 < or = V.o(2max) < 36 in men, 26 < or = V.o(2max) < 30 in women), and high-fit (V.o(2max) > or = 36 in men, V.o(2max) > or = 30 in women). The association between fitness level and the prevalence of abnormal values for these parameters was analyzed by a multiple logistic regression model adjusted for age and VFA. The odds ratio (OR) and 95% confidence interval (CI) for the prevalence of hyperinsulinemia were significantly lower in the mid-fit (OR = 0.35, 95% CI, 0.16 to 0.78) and in the high-fit groups (OR = 0.40, 95% CI, 0.16 to 0.98) compared with the low-fit group. In addition, ORs for the prevalence of low HDL-C in the mid-fit and high-fit groups were significantly lower (OR = 0.35, 95% CI, 0.14 to 0.86; and OR = 0.19; 95% CI, 0.08 to 0.60, respectively) than in the low-fit group. These results suggested that cardiorespiratory fitness might be one of the predictors of metabolic abnormalities, especially in patients with hyperinsulinemia and low HDL-C, independent of visceral fat accumulation in Japanese patients with IGT and type 2 DM.

Adipose Tissue↗
PubMed2002

Quantitative descriptors of corneal topography that influence soft toric contact lens fitting.

PURPOSE: Empirical soft toric contact lens fitting based on manifest refraction and keratometry often presents unanticipated fitting and power errors upon initial lens dispensing. However, corneal topography may provide features that influence soft toric lens performance, flexure, and back vertex power in situ, which may assist in improved fitting guidelines. In this study, quantitative topographic descriptors were generated and analyzed as potential variables in predicting soft toric fitting success. METHODS: One hundred five eyes of 54 patients were empirically fit with back surface toric, prism ballasted, soft contact lenses after videokeratography was performed with the EyeSys 2000 (v. 4.0) or Humphrey Atlas (v. A6) instrument. Custom software was written to generate 54 separate quantitative descriptors of shape and astigmatism from the raw data files. A logistic regression was used to determine which variables significantly contributed to a successful or failed fit. RESULTS: Two types of empirical fitting failures were identified: loose fit (n = 15) and power errors (n = 17). The following variables were associated with a fitting failure: flat simulated keratometry (SimKf2b) within the central 3 mm zone, steep simulated keratometry (SimKs2b) within the central 3 mm zone, a difference between central and peripheral flat meridian axis (DIFFAXIS), and a difference between central and peripheral astigmatism (DIFFASTIG). For fitting failures caused by power errors, a larger steep SimKs2b (p< 0.01) and smaller DIFFAXIS (p< 0.05) were associated with a failed fit. For failures caused by physical fit of a selected base curve, a smaller DIFFAXIS (p< 0.05), larger steep SimKs2b (p< 0.05), and larger DIFFASTIG (p< 0.01) were associated with a failed fit. CONCLUSIONS: Novel quantitative descriptors of corneal shape and toricity derived from topography are associated with empirical soft toric contact lens fitting failures. Future algorithms or recommendations for improved soft toric lens selection may be derived from such indices to develop a predictive model for successful soft toric lens fitting using corneal topography data.

Contact Lenses, Hydrophilic↗
PubMed2005

Aerobic fitness and neurocognitive function in healthy preadolescent children.

PURPOSE: We investigated the relationship between age, aerobic fitness, and cognitive function by comparing high- and low-fit preadolescent children and adults. METHOD: Twenty-four children (mean age = 9.6 yr) and 27 adults (mean age = 19.3 yr) were grouped according to their fitness (high, low) such that four approximately equal groups were compared. Fitness was assessed using the Fitnessgram test, and cognitive function was measured by neuroelectric and behavioral responses to a stimulus discrimination task. RESULTS: Adults exhibited greater P3 amplitude at Cz and Pz sites, and decreased amplitude at the Oz site compared with children. High-fit children had greater P3 amplitude compared with low-fit children and high- and low-fit adults. Further, adults had faster P3 latency compared with children, and high-fit participants had faster P3 latency compared with low-fit participants at the Oz site. Adults exhibited faster reaction time than children; however, fitness interacted with age such that high-fit children had faster reaction time than low-fit children. CONCLUSION: These findings suggest that fitness was positively associated with neuroelectric indices of attention and working memory, and response speed in children. Fitness was also associated with cognitive processing speed, but these findings were not age-specific. These data indicate that fitness may be related to better cognitive functioning in preadolescents and have implications for increasing cognitive health in children and adults.

Adult↗
PubMedDate not supplied

Audiometric evaluation of bilaterally fitted bone-anchored hearing aids.

Bilateral fittings of bone-anchored hearing aids (BAHA) were evaluated in 25 patients with at least 3 months experience with using two BAHAs. For all patients, air conduction hearing aids were contraindicated due to either recurrent otorrhoea or otitis externa (19 cases) or to congenital aural atresia (six cases). Candidacy for bilateral fitting was primarily based on symmetry of bone conduction thresholds. For all patients, measurements comprised sound localisation, speech recognition in quiet and in noise. In addition, in a subgroup of nine patients, release from masking for pure-tone stimuli in noise with interaural phase differences (binaural masking level difference. BMLD) was measured. The percentage of correct localisation judgments with 500-Hz and 2-kHz noise bursts increased significantly (p<0.01) from 22.2 per cent and 24.3 per cent for unilateral fittings to 41.8 per cent and 45.3 per cent for bilateral fittings, respectively. With unilateral fittings sound localisation judgments appeared to be strongly biased to the ipsilateral BAHA side. whereas with bilateral fittings, judgments were far more symmetrical. The speech reception threshold for sentences in quiet was significantly (p<0.01) better for the bilateral fittings compared to the unilateral fittings: 37.5 dBA versus 41.7 dBA. Speech recognition in noise was measured with the speech signal presented in front of the listener and a 65-dBA masking noise at either +90 degrees or -90 degrees azimuth. For noise presented at the ipsilateral side of the first fitted BAHA, the signal-to-noise ratio was significantly reduced (p<0.01) from -0.7 dB for the unilateral fitting to -4.0 dB for the bilateral fitting. The speech reception threshold in noise was not significantly different (p>0.05) for unilateral and bilateral fittings when the noise was presented at the contralateral side of the first fitted BAHA. The results for the six patients with congenital atresia are comparable with those for the other patients. So, directional hearing and speech recognition in noise improve significantly with a second BAHA. The BMLD measurements showed a significant (p<0.01) release from masking of 6.1, 6.0 and 6.6 dB for 125-Hz, 250-Hz and 500-Hz stimuli, respectively. The BMLD effect of 4.1 dB at 1,000 Hz was not significant at the 5 per cent level. The positive results with the bilateral fittings in quiet can be ascribed to increased stimulus levels due to diotic summation of signals from either side. The results for localisation, speech recognition in noise and BMLD measurements indicate that bilaterally fitted BAHAs do indeed (to some extent) result in binaural hearing.

Adolescent↗
PubMed2001

Fitting tumor control probability models to biopsy outcome after three-dimensional conformal radiation therapy of prostate cancer: pitfalls in deducing radiobiologic parameters for tumors from clinical data.

PURPOSE: The goal of tumor control probability (TCP) models is to predict local control for inhomogeneous dose distributions. All existing fits of TCP models to clinical data have utilized summaries of dose distributions (e.g., prescription dose). Ideally, model fits should be based on dose distributions in the tumor, but usually only dose-volume histograms (DVH) of the planning target volume (PTV) are available. We fit TCP models to biopsy outcome after three-dimensional conformal radiation therapy of prostate cancer using either a dose distribution summary or the full DVH in the PTV. We discuss differences in the radiobiologic parameters and dose-response curves and demonstrate pitfalls in interpreting the results. METHODS AND MATERIAL: Two mechanistic TCP models were fit with a maximum likelihood technique to biopsy outcome from 103 prostate patients treated at Memorial Sloan-Kettering Cancer Center. Fits were performed separately for different patient subgroups defined by tumor-related prognostic factors. Fits were based both on full DVHs, denoted TCP(DVH(calc)), and, alternatively, assuming a homogeneous PTV dose given by the mean dose (Dmean) of each DVH, denoted TCP(Dmean(calc)). Dose distributions for these patients were very homogeneous with any cold spots located on the periphery of the PTV. These cold spots were uncorrelated with biopsy outcome, likely because the low-dose regions may not contain tumor cells. Therefore, fits of TCP models that are potentially sensitive to cold spots (e.g., TCP(DVH(calc))) likely give biologic parameters that diminish this sensitivity. In light of this, we examined differences in fitted clonogenic cell number, N(C), or density, rho(C), surviving fraction after 2 Gy, SF(2), or radiosensitivity, alpha, and their standard deviations in the population, sigma(SF(2)) and sigma(alpha), resulting from fits based on TCP(DVH(calc)) and TCP(Dmean(calc)). Dose-response curves for homogeneous irradiation (characterized by TCD(50), the dose for a TCP of 50%) and differences in TCP predictions calculated from the DVH using alternatively derived parameters were evaluated. RESULTS: Fits of TCP(Dmean(calc)) are better (i.e., have larger likelihood) than fits of TCP(DVH(calc)). For TCP(Dmean(calc)) fits, matching values of SF(2) and sigma(SF(2)) (or alpha and sigma(alpha)) exist for all N(C) (rho(C)) above a threshold that give fits of equal quality, with no maximum in likelihood. In contrast, TCP(DVH(calc)) fits have maximum likelihood for high SF(2) (low alpha) values that minimize effects of cold spots. Consequently, small N(C) (rho(C)) values are obtained to match the observed control rate. For example, for patients in low-, intermediate-, and high-risk groups, optimum values of SF(2) and N(C) are 0.771 and 3.3 x 10(3), 0.736 and 2.2 x 10(4), and 0.776 and 1.0 x 10(4), respectively. The TCD(50) of dose-response curves for intermediate-risk patients is 2.6 Gy lower using TCP(DVH(calc)) parameters (TCD(50) = 67.8 Gy) than for TCP(Dmean(calc)) parameters (TCD(50) = 70.4 Gy). TCP predictions calculated from the DVH using risk group-dependent TCP(Dmean(calc)) parameters are up to 53% lower than corresponding calculations with TCP(DVH(calc)) parameters. CONCLUSION: For our data, TCP parameters derived from DVHs likely do not reflect true radiobiologic parameters in the tumor, but are a consequence of the reduced importance of low-dose regions at the periphery of the PTV. Deriving radiobiologic parameters from TCP(Dmean(calc)) fits is not possible unless one parameter is already known. TCP predictions using TCP(DVH(calc)) and TCP(Dmean(calc)) parameters may differ substantially, requiring consistency in the derivation and application of model parameters. The proper derivation of radiobiologic parameters from clinical data requires both substantial dose inhomogeneities and understanding of how these coincide with tumor location.

Adenocarcinoma↗
PubMed2000

Fitting a temporomandibular joint prosthesis to the skull.

Fitting a temporomandibular joint (TMJ) prosthesis to the skull by using stock prostheses seems to be an appropriate method. However, fitting the skull with one stock part requires many differently shaped parts. Therefore, we fitted the skull with two connected stock parts. The aim of the study was to test whether it is possible to achieve a close fit to the skull with this design, with a maximum of 10 different parts. The articular eminence was fitted with a gully-shaped fitting member, which was rotationally connected to a basic part that fitted to the lateral side of the TMJ. The relevant dimensions of 20 dry skulls were measured and the results were used to derive the optimal dimensions of the prosthesis parts. Prototypes were subsequently fabricated. The fit of the prototypes was tested by measuring the maximum gap between fitting member and skull. All skulls could be fit with a set of four different basic parts and three different fitting members. The average maximum gap between fitting member and skull was 0.20 mm (range 0.11-0.43 mm). It was concluded that a close fit to the skull can be achieved with two connected stock parts and with a total number of seven parts.

Feasibility Studies↗
PubMed2005

Comparison of flat and steep rigid contact lens fitting methods in keratoconus.

PURPOSE: The purpose of this article is to compare the safety and efficacy of flat- and steep-fitting rigid contact lenses in keratoconus. METHODS: The Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study is a 16-center observational study. Cross-sectional results at baseline were generated for 1091 subjects with longitudinal results from the 871 subjects who completed 8 years of follow up. RESULTS: Of the 761 rigid contact lens-wearing patients at baseline, 41% had a scar at baseline compared with 24% of the nonrigid contact lens wearers (odds ratio [OR], 2.15; 95% confidence interval [CI], 1.35-3.43; p = 0.001). Eighty-seven percent were fitted with flat-fitting lenses, whereas 13% were fitted with steep-fitting lenses. Rigid lens fitting method was also associated with incident corneal scarring. A greater proportion of the corneas wearing flat-fitting contact lenses were scarred (43% compared with 26% for the steep-fitted eyes; OR,= 2.19; 95% CI, 1.37-3.51; p = 0.001). After controlling for corneal curvature, the association of rigid contact lens fit and corneal scarring at baseline did not persist (adjusted OR, 1.20; 95% CI, 0.70-2.06; p = 0.52). Thirty-two percent of unscarred eyes at baseline fitted flat had developed an incident corneal scar by the eighth year follow-up visit compared with 14% of eyes fitted steep (OR, 2.93; 95% CI, 1.34-6.42; p = 0.007). CONCLUSIONS: The data reported here indicate that, after controlling for disease severity in the form of corneal curvature, keratoconic eyes fitted with a rigid contact lens resulting in an apical touch fluorescein pattern did not have an increased risk of being scarred centrally at baseline. This "natural history" sample cannot determine causal proof that one method of fitting lenses is safer than another. To achieve this, a randomized clinical trial is needed.

Contact Lenses↗
PubMed2003

The illusion of improved physical fitness and reduced mortality.

PURPOSE: To conduct a computer simulation to assess the effects of measurement error on prospective epidemiological studies that attribute mortality outcomes to apparent changes in the independent variable (e.g., physical fitness or activity) at baseline. METHODS: As an example, we evaluated the design of the Aerobics Center Longitudinal Study (ACLS). This study compared apparent changes in fitness between two baseline visits to mortality during a subsequent 5-yr follow-up period. Unfit men who were reclassified as fit at the second baseline examination (6.6% of sample) and fit men who were reclassified as unfit (2.3%) had follow-up mortality rates that were between those of men who were consistently classified as fit or unfit. This study design was simulated assuming that differences between baseline treadmill test durations were due to measurement error alone. Based on our own data, we estimated that repeat measurements of treadmill test duration have correlation of r = 0.89 in the absence of any real fitness change. RESULTS: There is excellent agreement between the published ACLS risk reductions and our simulated reductions for both cardiovascular disease (CVD) and total mortality. Compared with the "Unfit-->Unfit" (the referent group), the estimated relative risks from the simulations for men who were reclassified as fit (i.e., "Unfit-->Fit") were 0.57 for total mortality and 0.52 for CVD mortality, and for men who remained classified as fit ("Fit-->Fit"), they were 0.33 for total mortality and 0.20 for CVD mortality. CONCLUSION: The imprecision of the fitness measurement alone (i.e., measurement error) is sufficient to produce the reported ACLS risk reductions in initially unfit men who get reclassified as fit in a subsequent clinic visit. This statistical artifact will apply to other studies that use this design.

Adult↗
PubMed2001

Accuracy of two simple methods for the assessment of health-related physical fitness.

We have developed a useful equation for estimating health-related physical fitness age. This version of health-related fitness age was developed as an extension of the biological age index and is useful for evaluation of individual differences in functional abilities of middle-aged and older adults. This measure consists of 4 independent variables fitness (VO2 max, standing trunk flexibility, %fat, and grip strength). However, direct measurement of maximal oxygen uptake (VO2 max) is an invasive clinical procedure and not practical for large scale work. In the current study, we attempted to assess the fitness age more feasibly. We selected a questionnaire method and a 12-min. submaximal treadmill walk test as substitutes for the VO2 max test. The three fitness ages were computed for 23 Japanese men (M(age) 54.7 +/- 10.7 yr.), using actual VO2 max (actual fitness age), questionnaire VO2 max (predicted questionnaire fitness age), and treadmill VO2 max (predicted treadmill fitness age). Predicted questionnaire fitness age (61.0 +/- 10.5 yr.) and predicted treadmill fitness age (60.0 +/- 12.4 yr.) were significantly correlated with actual fitness age (60.1 +/- 12.4 yr.) (r= .96 and .97, respectively). There were no significant differences among the three indices, but there was a significant difference between actual fitness age and chronological age (p<.05). For VO+/-2 max substituting the questionnaire for the treadmill estimate is acceptable in assessing fitness age and reducing the clinical risk for middle-aged and older Japanese men.

Adult↗
PubMed2006

The 100-km ultradistance race in Hong Kong: physical fitness profile and team performance outcomes.

AIM: The aim of this study was to determine different variables leading to a successful completion of a 100-km ultradistance team event. METHODS: Regular physical activity patterns, self-perceptions of fitness level and physical fitness profile were determined in subjects (n=253) registered for Trailwalker 2000. The battery of fitness tests included cardiopulmonary fitness, flexibility, muscular strength, muscular endurance and body fat composition. RESULTS: The physical fitness data reveals that the subjects in this study have an above average fitness level compared with the norm. There was association of self-perceived fitness with physical fitness parameters (P=0) and significant correlation of the total fitness score with the completion time (P=0.02). More importantly, the team member with the lowest fitness total score was correlated with the finish time at the event (P=0). Logistic regression model identified that total fitness score and years of experience in Trailwalker were predictive of a successful completion in the event (r=0.37; P=0.007). However, the low variance suggested that the selected physical fitness tests have low prediction sensitivity to characterize the specific population in the study. CONCLUSIONS: There is a strong need to determine a combination of physical fitness tests that could accurately predict the performance of participants in the Trailwalker event.

Adiposity↗
PubMed2002

Surveying a local fitness landscape of a protein with epistatic sites for the study of directed evolution.

We present a method for analysis of a fitness landscape of a biopolymer with significantly epistatic sites. The analysis is based on a quasi-additive fitness model. The fitness model is constructed with additive terms conducted by "site-fitness" and epistatic terms conducted by "pair-fitness," where the site-fitness is a fitness contribution from an independent residue and the pair-fitness is a fitness contribution from a pair of epistatic residues. As a case study, we analyzed the sequence-fitness data for 45 clones of thermostable prolyl endopeptidase mutants. They were generated by a mutation scrambling method, which can accumulate advantageous mutations. The fitness contributions from 14 single-point mutations including E67Q and Q656R were identified by the analysis. As a result, we found that the fitness model with a significant epistatic term by a pair of the 67th site and 656th site was in good agreement with the experimental data and that the explored landscape in the binary 14-dimensional sequence space is still a mountainous landscape with twin peaks. The validity was supported by the analysis of mutant fitness distributions derived from another mutation scrambling experiment and by (3D) structural data.

Directed Molecular Evolution↗
PubMed2001

A modified protocol for quantitative fit testing using the PortaCount.

A modified quantitative fit testing method has been developed for testing half masks using the TSI PortaCount respirator fit tester. This approach focuses on shortening the time for each exercise during fit testing; however, the shortened protocol is applied only to the very good-fitting masks. For marginal-fitting masks, the testing is carried out according to the full Occupational Safety and Health Administration (OSHA) respiratory protection standard (29CFR1910.134).(1) The shortened protocol (currently not approved by OSHA) still uses all the exercises required by the OSHA standard but for a shorter time (30 seconds [s] for each exercise instead of the usual 60 s). How good the fit has to be to qualify for a shortened exercise is determined by the statistical analysis of a large data set containing pass and fail fit-test data. The statistical analysis involves calculating the sensitivity and specificity of the pass and failed fit tests on half masks. From this analysis, a multiplication factor (K) to the OSHA pass/fail criterion was developed. For a respirator to undergo the shortened protocol, the fit factor obtained during any exercise must be K times the OSHA pass/fail criterion of 100 for half masks. Hence, this approach is more conservative than fit testing protocols that involve shortened exercises regardless of the fit. Nevertheless, this approach still saves time without compromising the accuracy of the fit test expressed in terms of sensitivity and specificity. For the existing data, 85 percent of the fit tests would have been performed according to the faster test protocol while only 15 percent of the tests would have been tested according to the full-length OSHA test protocol.

Decision Trees↗
PubMed1995

Polygenic mutation in Drosophila melanogaster: the causal relationship of bristle number to fitness.

The association between sternopleural and abdominal bristle number and fitness in Drosophila melanogaster was determined for sublines of an initially highly inbred strain that were maintained by divergent artificial selection for 150 generations or by random mating for 180 generations. Replicate selection lines had more extreme bristle numbers than those that were maintained without artificial selection at the same census size for approximately the same number of generations. The average fitness, estimated by a single generation of competition against a compound autosome strain, was 0.17 for lines selected for high and low abdominal bristle numbers and 0.19 for lines selected for high and low sternopleural bristle number. The average fitness of unselected lines, 0.46, was significantly higher than that of the selection lines. The fitnesses and the relationships of bristle number to fitness in progeny of all possible crosses of high x high (H x H), high x low (H x L) and low x low (L x L) selection lines were examined to determine whether the observed intermediate optima were caused by direct stabilizing selection on bristle number or by apparent stabilizing selection mediated through deleterious pleiotropic fitness effects of mutations affecting bristle number. Although bristle number was nearly additive for progeny of H x H, H x L and L x L crosses among sternopleural bristle selection lines, their mean fitnesses were not significantly different from each other, or from the mean fitness of the unselected lines, suggesting partly or completely recessive pleiotropic fitness effects cause apparent stabilizing selection. The average fitness of the progeny of H x H abdominal bristle selection lines was not significantly different from the fitness of unselected lines, but the mean fitness of the progeny of L x L crosses was not significantly different from that of the pure low lines. This is consistent with direct selection against low but not high abdominal bristle number, but the interpretation is confounded by variation in average degree of dominance for fitness (on average recessive in the high abdominal bristle selection lines and additive in the low abdominal bristle selection lines). Neither direct stabilizing selection nor pleiotropy, therefore, can account for all the observations.

Animals↗
PubMed1999

Fit-testing for firefighters.

When fit-testing firefighters who may be required to wear an SCBA unit in the positive pressure mode for IDLH or structural firefighting applications, use these guidelines. 1. The firefighter shall be allowed to pick the most acceptable respirator from a sufficient number of respirator models and sizes so the respirator is acceptable to, and correctly fits, the firefighter. 2. Before a firefighter may be required to use the SCBA, he/she must be fit-tested with the same make, model, style, and size of respirator that will be used. If different makes, models, styles, and sizes of facepieces are used, the firefighter must be fit-tested for each. 3. Based on current interpretations and guidance, OSHA requires firefighters to be quantitatively or qualitatively fit-tested while in the negative pressure mode. 4. Quantitative fit-testing of these respirators shall be accomplished by modifying the facepiece to allow sampling inside the facepiece and breathing zone of the user, midway between the nose and mouth. This requirement shall be accomplished by installing a permanent sampling probe onto a surrogate facepiece or by using a sampling adapter designed to temporarily provide a means of sampling air from inside the facepiece. 5. Qualitative fit-testing can be accomplished by converting the user's actual facepiece into a negative pressure respirator with appropriate filters or by using an identical negative pressure air-purifying respirator facepiece with the same sealing surfaces as a surrogate for the SCBA facepiece. 6. If after passing the fit-test the firefighter subsequently determines the fit of the respirator is unacceptable, he/she shall be given a reasonable opportunity to select a different respirator facepiece and be retested. 7. The new standard requires initial and at least annual fit-testing using quantitative or qualitative fit-testing protocols. 8. Additional fit-testing may be required whenever physical changes to the employee occur that may affect respirator fit, such as facial scarring, dental changes, cosmetic surgery, or an obvious change in body weight.

Female↗
PubMed2005

Prevalence and cardiovascular disease correlates of low cardiorespiratory fitness in adolescents and adults.

CONTEXT: Population surveys indicate that physical activity levels are low in the United States. One consequence of inactivity, low cardiorespiratory fitness, is an established risk factor for cardiovascular disease (CVD) morbidity and mortality, but the prevalence of cardiorespiratory fitness has not been quantified in representative US population samples. OBJECTIVES: To describe the prevalence of low fitness in the US population aged 12 through 49 years and to relate low fitness to CVD risk factors in this population. DESIGN, SETTING, AND PARTICIPANTS: Inception cohort study using data from the cross-sectional nationally representative National Health and Nutrition Examination Survey 1999-2002. Participants were adolescents (aged 12-19 years; n = 3110) and adults (aged 20-49 years; n = 2205) free from previously diagnosed CVD who underwent submaximal graded exercise treadmill testing to achieve at least 75% to 90% of their age-predicted maximum heart rate. Maximal oxygen consumption (VO2max) was estimated by measuring the heart rate response to reference levels of submaximal work. MAIN OUTCOME MEASURES: Low fitness defined using percentile cut points of estimated VO2max from existing external referent populations; anthropometric and other CVD risk factors measured according to standard methods. RESULTS: Low fitness was identified in 33.6% of adolescents (approximately 7.5 million US adolescents) and 13.9% of adults (approximately 8.5 million US adults); the prevalence was similar in adolescent females (34.4%) and males (32.9%) (P = .40) but was higher in adult females (16.2%) than in males (11.8%) (P = .03). Non-Hispanic blacks and Mexican Americans were less fit than non-Hispanic whites. In all age-sex groups, body mass index and waist circumference were inversely associated with fitness; age- and race-adjusted odds ratios of overweight or obesity (body mass index > or =25) ranged from 2.1 to 3.7 (P<.01 for all), comparing persons with low fitness with those with moderate or high fitness. Total cholesterol levels and systolic blood pressure were higher and levels of high-density lipoprotein cholesterol were lower among participants with low vs high fitness. CONCLUSION: Low fitness in adolescents and adults is common in the US population and is associated with an increased prevalence of CVD risk factors.

Adolescent↗