The use of inductive plethysmography in the study of the ventilatory effects of respirator wear

The authors recently developed an ambulatory system, in which a self-contained respiratory inductive plethysmograph (RIP) was used, to measure noninvasively the volume and time components of breathing. Since it does not use nasal or oral devices, such a system is particularly suitable for use in studying the effects of respiratory protective masks on respiratory parameters. In order to validate this portable system, 22 healthy subjects were exercised on a treadmill; RIP and pneumotachographic minute ventilation measurements were compared. A short, graded submaximal exercise protocol was run 3 times by each subject under each of the following conditions: no oral mouthpiece; oral mouthpiece with pneumotachograph; and wearing an industrial protective mask (half facepiece, twin cartridge). Chest and abdominal RIP signals, a time signal and either a pneumotachograph or heart-rate signal were recorded on a small cassette recorder worn at the belt. The data tapes were later edited and analyzed by computer. Data from 5 subjects were excluded because of equipment malfunction. The average error in RIP-measured ventilation compared to values simultaneously measured by a pneumotachograph in the 17 remaining subjects over all exercise levels was -3.16%. Marked variability (SD = 11.26%), however, was found in individuals at different exercise levels and especially between subjects. Use of a respirator was associated with a decreased respiratory frequency, an increased tidal volume and minute ventilation, and an unchanged heart rate. At present, the portable RIP system has substantial variability that limits its ability to measure ventilation accurately.     

Noninvasive measurement of respirator effect at rest and during exercise

Ventilation and respiratory timing during rest and exercise were measured in normal volunteers by pneumotachograph and by respiratory inductive plethysmography (RIP) to determine if RIP is accurate and to determine if the usual methods of ventilation measurement during respirator research lead to artifacts. Data were collected with a mouthpiece, a sham mouthpiece, and no mouthpiece. A dead space and inspiratory resistance load similar to respirators were employed also. The study showed that no significant artifact is produced, particularly during exercise, by measurements using a mouthpiece. RIP is sufficiently accurate and precise for use in unobtrusively measuring ventilation during respirator studies when traditional methods cannot be used.     

Prediction of respiratory distress during maximal physical exercise: the role of trait anxiety.

Industrial respirators offer protection for men and women who are required to work in toxic and oxygen-deficient environments. Major advances continue to be made with respect to improved face mask designs and modes of protection, yet only recently have efforts been directed toward the development of criteria for use in evaluating individuals' psychological fitness to wear respirators. The purpose of the present investigation was to confirm (i.e., replicate) an earlier finding, using a simplified protocol, that an individual's tendency to experience respiratory distress during exercise can be predicted. In the present experiment, an independent sample of 38 subjects underwent a maximal exercise test. It was predicted that subjects with elevated trait anxiety scores would experience respiratory distress when required to perform heavy physical exercise using a full-facepiece, air-line supplied, pressure-demand respirator. The prediction of respiratory distress was accurate in 34 of 38 cases (89.5%). It was concluded that an objective measure of trait anxiety can be used to identify those individuals who are most likely to experience distress while performing maximal physical exercise and using a pressure-demand respirator.     

Effects of industrial respirator wear during exercise in subjects with restrictive lung disease

Few studies have examined the response of individuals with restrictive lung disease (RLD) to respirator wear. Such information should be of theoretical and practical interest when the need to determine fitness to wear respirators is considered. Seventeen females performed progressive submaximal treadmill exercise. Twelve control subjects with total lung capacity (TLC) = 5.71 +/- .19L (mean +/- SEM) and DLCO = 25.8 +/- 1.0 mL/min/mmHg were compared to five RLD subjects with TLC = 3.70 +/- 0.22 and DLCO = 14.5 +/- 0.7. Mean age, height and weight were similar. Separate exercise trials were performed with no added resistance (NAR), and with 5 cm H2O/L/sec inspiratory and 1.5 cm H2O/L/sec expiratory resistance (R2) to stimulate widely used respiratory masks. Comparisons of exercise data were made at an oxygen consumption of 0.8 L/min. With NAR, RLD subjects had significantly higher minute ventilation (VE) (29.0 vs. 21.2 L/min for controls), higher respiratory rate (RR), and lower tidal volume (VT). Heart rate, end-tidal PCO2 (PETCO2), and mouth pressure swing (Poral) were not different from control values. With R2 compared to NAR, the controls had reduced RR and VE; and increased VT, PETCO2, and Poral. While changes with R2 for the RLD subjects were in the same directions as controls, only the increase in Poral was statistically significant. Analysis of the differences showed that none of the changes with R2 in RLD subjects was different from control changes except for the greater increase in Poral and the smaller increase in VT. The former was explained by the RLD subjects' higher VE and flow rates, and the non-linear nature of R2 at higher flow rates.(ABSTRACT TRUNCATED AT 250 WORDS)     

Exploring respiratory protection practices for prominent hazards in healthcare settings

The use of respiratory protection, an important component of personal protective equipment (PPE) in healthcare, is dependent on the hazard and environmental conditions in the workplace. This requires the employer and healthcare worker (HCW) to be knowledgeable about potential exposures and their respective protective measures. However, the use of respirators is inconsistent in healthcare settings, potentially putting HCWs at risk for illness or injury. To better understand respirator use, barriers, and influences, the National Institute for Occupational Safety and Health (NIOSH) Health and Safety Practices Survey of Healthcare Workers provided an opportunity to examine self-reported use of respirators and surgical masks for targeted hazards. The hazards of interest included aerosolized medications, antineoplastic drugs, chemical sterilants, high-level disinfectants, influenza-like illness (ILI), and surgical smoke. Of the 10,383 HCWs who reported respiratory protection behaviors, 1,904 (18%) reported wearing a respirator for at least one hazard. Hazard type, job duties, site characteristics, and organizational factors played a greater role in the likelihood of respirator use than individual factors. The proportion of respirator users was highest for aerosolized medications and lowest for chemical sterilants. Most respondents reported using a surgical mask for at least one of the hazards, with highest use for surgical smoke generated by electrosurgical techniques and ILI. The high proportion of respirator non-users who used surgical masks is concerning because HCWs may be using a surgical mask in situations that require a respirator, specifically for surgical smoke. Improved guidance on hazard recognition, risk evaluation, and appropriate respirator selection could potentially help HCWs better understand how to protect themselves at work.     

Individual factors in the choice of respiratory protective devices

Federal regulations recognize the need to determine whether individuals are physically able to perform their job while wearing respirators. A variety of safety and workplace factors should also be considered at the time that a respiratory protective device is evaluated for use by a particular worker. In most negative pressure respirators, inspiratory resistance constitutes the major load on the respiratory system. In normals, the major load to the cardiovascular system occurs with heavy, self-contained respirators. In the absence of objective guidelines for the use of respirators by impaired workers, careful examination and conservative clinical judgement, and the willingness to re-assess choices must form the basis of respirator selection.     

Simulated workplace protection factors for half-facepiece respiratory protective devices

This study investigates two different methods (random effects model and 5th percentile) for determining the performance of three types of respiratory protective devices (elastomeric N95 respirators, N95 filtering-facepiece respirators, and surgical masks) during a simulated workplace test. This study recalculated the protection level of three types of respiratory protective devices using the random effects model, compared the two methods with each other and the APF of 10 for half-facepiece respirators, and determined the value of each of the fit test protocols in attaining the desired level of simulated workplace protection factor (SWPF). Twenty-five test subjects with varying face sizes tested 15 models of elastomeric N95 respirators, 15 models of N95 filtering-facepiece respirators, and 6 models of surgical masks. Simulated workplace testing was conducted using a TSI PORTACOUNT Plus model 8020 and consisted of a series of seven exercises. Six simulated workplace tests were performed with redonning of the respirator/mask occurring between each test. Each of the six tests produced an SWPF. To determine the level of protection provided by the respiratory protective devices, a 90% lower confidence limit for the simulated workplace protection factor (SWPF(LCL90%)) and the 5th percentile of simulated workplace protection factor were computed. The 5th percentile method values could be up to seven times higher than the SWPF(LCL90%) values. Without fit testing, all half-facepiece N95 respirators had a 5th percentile of 4.6 and an SWPF(LCL90%) value of 2.7. N95 filtering-facepiece respirators as a class had values of 3.3 and 2.0, respectively, whereas N95 elastomeric respirators had values of 7.3 and 4.6, respectively. Surgical masks did not provide any protection, with values of 1.2 and 1.4, respectively. Passing either the Bitrex, saccharin, or Companion fit test resulted in the respirators providing the expected level of protection with 5th percentiles greater than or equal to 10 except when passing the Bitrex test with N95 filtering-facepiece respirators, which resulted in a 5th percentile of only 7.9. No substantial difference was seen between the three fit tests. All of the SWPF(LCL90%) values after passing a fit test were less than 10. The random model method provides a more conservative estimate of the protection provided by a respirator because it takes into account both between- and within-wearer variability.     

Review of respirator performance testing in the workplace: issues and concerns.

Performance capability of respirators has traditionally been evaluated by testing components of the respirator (e.g., filter efficiency), facepiece fit, total inward leakage, or some other measure of performance evaluated under laboratory conditions. In recent years, increased emphasis has been placed on development of test methods suitable for evaluating respirator performance in the workplace. The goal of such testing is to evaluate the level of protection provided by respirators in the work environment. The AIHA Respiratory Protection Committee believes that workplace testing of respirators has the potential to be an excellent tool for increasing knowledge about the effectiveness of respiratory protection. However, a number of technical issues remain to be addressed before optimal test protocols and data analysis methods can be defined. The progress made to date in workplace testing will be reviewed, and broader discussion about key elements that must be considered when developing guidelines for testing respirators in the workplace will be initiated.     

Respiratory protection: associated factors and effectiveness of respirator use among underground coal miners

BACKGROUND: We investigated factors associated with the use of respiratory protection and explored the effectiveness of respirators among coal miners. METHODS: Between 1987 and 1992, respiratory symptoms, smoking, lung function, and dust exposures were assessed longitudinally among 185 underground bituminous coal miners. Self-reported use of respiratory protection was expressed as mean percent time wearing a respirator. RESULTS: Miners' respirator use increased with mean dust concentration, but decreased with tobacco consumption. Increasing age was associated with greater respirator use. Miners who had respiratory symptoms at the initial survey subsequently reported greater use of respirators. A significant protective association was found between the miners' respirator use and FEV(1) levels at both the initial and follow-up surveys. CONCLUSIONS: These results provide additional evidence that respirator use is protective of lung health. When respiratory protection programs are developed, factors that may affect respirator use behavior, such as age, smoking, and respiratory symptoms, should be considered. Future studies of respiratory health will need to consider workers' use of respiratory protection.     

Evaluation of the efficiency of respiratory protective equipment based on the biological monitoring of styrene in fibreglass reinforced plastics industries

The purpose of the present study was to determine the efficiency of respiratory protective equipment in a fibreglass reinforced plastic factory by comparing results of environmental and biological monitoring of exposure to styrene. Five factories including 39 workers were investigated. Three types of respiratory protective equipment were tested: one was a half-mask air-purifying respirator equipped with a cartridge for organic solvents, another was a disposable gauze respirator impregnated with charcoal filter, and the third was a dust-proof respirator. The frequency of cartridge exchange of a half-mask respirator was twice a day only at one factory, and that was less than once a month at other factories. The site concentrations exceeded 20 ppm at 10 of the 82 sampling points (12.2%), and 22 of the 39 workers' (56.4%) personal exposure exceeded 20 ppm which is the current occupational exposure limit recommended by the Japan Society for Occupational Health. The efficiency of disposable gauze respirators and dust-proof respirators was low or rather zero. The average efficiency of half-mask respirators in which cartridges were exchanged twice a day and once a month was 83.6% and 46.6%, respectively. There was a significant disparity in the efficiency of the respirator depending on the frequency of cartridge exchange (p<0.05). Overall this study showed that even though a half-mask respirator is used and its cartridge is exchanged every half a day, workers exposed to a styrene concentration at or over 122 ppm are expected to inhale more than 20 ppm of styrene.     

Using respirators and goggles to control exposure to air pollutants in an anatomy laboratory

BACKGROUND: Engineering or administrative methods are often insufficient or impractical to control exposure to chemicals in anatomy laboratories. This study explored the feasibility of wearing one or a combination of respirators and goggles used as personal protective equipment (PPE) to control exposure in one such laboratory. METHODS: A group of 28 subjects were briefly trained in wearing PPE, fit-tested, and asked to complete a questionnaire regarding their subjective reaction after wearing the assigned PPE ensemble while working in the laboratory. The subjects' exposure to formaldehyde was also measured and generally exceeded the recommended limits. RESULTS: When a full-face respirator or the combination of a half-mask respirator and goggles was worn, a majority of subjects reported no odor problem and no irritation to eyes or upper respiratory system. Subjects accepted the PPE to certain degrees, but those using respirators encountered difficulties communicating with others. CONCLUSIONS: The combination of a half-mask respirator and goggles was the most feasible ensemble to control exposure to air pollutants in an anatomy laboratory.     

Workplace protection factor measurements on powered air-purifying respirators at a secondary lead smelter--test protocol

A study was conducted at a secondary smelter to evaluate the workplace performance of the 3M Model W-344 and Racal Model AH3 powered air-purifying respirators ( PAPR ) equipped with helmets and high efficiency filters. The research protocol developed for obtaining leakage measurements in the field provides for proper respirator fitting, use, wear, maintenance and worker supervision, all of which are problems commonly associated with data acquisition when field testing respirators. The protocol proved to be very workable, even though it required extensive worker and equipment monitoring. Based upon the successful implementation of this protocol, the performance of these PAPRs should be indicative of their best performance under the workplace conditions experienced in this study. This research protocol is proposed as a model for conducting field studies on other types of respirators as well as the basis on which to develop new and improved field test procedures. The results of one such study are presented in a comparison paper.     

The physiological cost of wearing a disposable respirator

In order to gain an understanding of the physiological stresses imposed by the wearing of a single-use disposable respirator, a series of experiments was done to measure the cardiopulmonary effects of wearing the respirator (heart rate, respiratory rate, and blood pressure); resistance to breathing while wearing a respirator; and heat stress imposed by the use of a respirator (changes in inspired and expired air temperature). Ten men, ages 24 to 35, of varying fitness levels, served as volunteers in the studies. All the men exercised on a treadmill both with and without 3M Model 8715 disposable respirators. Workloads corresponding to light, moderate, and heavy levels were calculated for each volunteer based on his maximal oxygen uptake. As work intensity increased, an increase in breathing resistance was found. Peak resistances were in the range of +/- 2 cm water. Work-intensity level increases in respiratory rates were found with and without the respirators, but the respirator use trial had a significantly increased respiratory rate. Heart rate also showed a dose-related increase as work intensity increased and was significantly greater in the respirator trials at heavy levels of work and during recovery. Systolic blood pressure showed a biphasic response to respirator use, being significantly lower at rest and higher at high levels of work. Diastolic blood pressure changes were less dramatic but were elevated in the respirator trials. Clinically important increases in blood pressure were found in two volunteers when respirators were worn. Air temperatures immediately anterior to the face were, on average, 7.5 degrees C higher in the respirator trials.(ABSTRACT TRUNCATED AT 250 WORDS)     

Respiratory protection and the risk of Mycobacterium tuberculosis infection

Tuberculosis (TB) can be transmitted to susceptible healthcare workers via inhalation of droplet nuclei carrying viable Mycobacterium tuberculosis bacilli. Several types of respiratory protective devices are compared with respect to efficacy against droplet nuclei penetration: surgical masks, disposable dust/mist particulate respirators (PRs), elastomeric halfmask respirators with high-efficiency (HEPA) filters, and powered airpurifying respirators (PAPRs) with elastomeric halfmask facepieces and HEPA filters. It is estimated that these devices permit, respectively, 42%, 5.7%, 2%, and 0.39% penetration of droplet nuclei into the facepiece. More limited data for the disposable HEPA filtering-facepiece respirator suggest that it would allow droplet nuclei penetration of 3% or less, similar to the value estimated for the elastomeric halfmask HEPA filter respirator. Because a respirator wearer's cumulative infection risk depends on the extent of droplet nuclei penetration, the cumulative risk will differ, given use of these different respirators. Hypothetical but realistic “low-exposure” and “high-exposure” scenarios are posed that involve, respectively, a 1.6% and a 6.4% annual risk of infection for healthcare workers. For the low-exposure scenario, the 10-year cumulative risks given no respirators versus surgical masks versus disposable dust/mist PRs versus elastomeric halfmask HEPA filter respirators versus HEPA filter PAPRs are, respectively, 15%, 6.7%, 0.94%, 0.33%, and .064%. For the high-exposure scenario, the 10-year cumulative risks for no respirator use versus use of the same four types of respirators are, respectively, 48%, 24%, 3.7%, 1.3%, and 0.26%. The use of disposable HEPA filtering-facepiece respirator should permit cumulative risks close to those estimated for the elastomeric halfmask HEPA filter respirator. It is concluded that when an infectious TB patient undergoes a procedure that generates respiratory aerosols, and when droplet nuclei source control is inadequate, healthcare workers attending the patient may need to wear highly protective respirators, such as HEPA filter PAPRs.     

Workplace protection factors of HSE approved negative pressure full-facepiece dust respirators during asbestos stripping: preliminary findings

This research was designed to evaluate the workplace protection factors of Health and Safety Executive Approved, negative pressure full-facepiece dust respirators, during asbestos stripping. A standard method to measure the concentration of asbestos fibres inside full-facepiece respirators has been developed and the workplace protection factors have been calculated from the data obtained. The respirators in this study are approved for use by the Health and Safety Executive in concentrations of up 900 times the Control Limit [HEALTH AND SAFETY EXECUTIVE, Guidance Note EH 41 (1985)] but the preliminary test results suggest that this level is inappropriately high for this type of respiratory protective equipment.     

Discomfort and exertion associated with prolonged wear of respiratory protection in a health care setting

The nature of discomfort and level of exertion associated with wearing respiratory protection in the health care workplace are not well understood. Although a few studies have assessed these topics in a laboratory setting, little is known about the magnitude of discomfort and the level of exertion experienced by workers while they deliver health care to patients for prolonged periods. The purpose of this study was to determine the magnitude of discomfort and level of exertion experienced by health care workers while wearing respiratory protection for periods up to 8 hr when performing their typical occupational duties. This project was a multiple cross-over field trial of 27 health care workers, aged 24-65, performing their typical, hospital-based occupational duties. Each participant served as his/her own control and wore one of seven respirators or a medical mask for 8 hr (or as long as tolerable) with interposed doffing periods every 2 hr. Self-perceived discomfort and exertion were quantified before each doffing: self-perceived level of discomfort using a visual analog scale, and self-perceived level of exertion using a Borg scale. Overall, and as would be expected, discomfort increased over time with continual respirator use over an 8-hr period. Interestingly, exertion increased only marginally over the same time period. The relatively low level of exertion associated with eight respiratory protective devices, including models commonly used in the U.S. health care workplace, is not likely to substantially influence workers' tolerability or occupational productivity. However, the magnitude of discomfort does appear to increase significantly over time with prolonged wear. These results suggest that respirator-related discomfort, but not exertion, negatively influences respirator tolerance over prolonged periods. Discomfort may also interfere with the occupational duties of workers.     

Effective factors on not using the N95 respirators among health care workers: Application of Fuzzy Delphi and Fuzzy Analytic Hierarchy Process (FAHP)

Using respiratory protective equipment (RPE) including N95 respirators is one of the most important ways to protect health care workers (HCWs) against respiratory hazards. The aim of this study was to identify and prioritize the problems and obstacles in using N95 respirators among HCWs in Iran. In this cross‐sectional study, problems and obstacles in using N95 respirators were identified and ranked by experts, using Fuzzy Delphi and Fuzzy Analytic Hierarchy Process (FAHP). Additionally, HCWs were asked to give their opinions about obstacles in using N95 respirators in order to form an opinion. Of 15 important obstacles in using N95 respirators identified by Fuzzy Delphi method, 6 factors were entered into the FAHP model: heat around the face, inaccessibility to respirator, difficulty breathing, pressure on the nose, trouble communicating with patients and colleagues, and no one does it. Identified problems and obstacles in using N95 respirators could be controlled during the selection of respirators, as well as by training and administrative measures.     

Physiologic and subjective effects of respirator mask type.

The effect of alternate airflow path designs on full-face mask air-purifying respirators was assessed in 14 healthy volunteers during submaximal exercise. Respirator designs included no respirator (N), full-face mask, dual-cartridge with no nasal deflector (FN), full-face mask respirator with nasal deflector (FD), and a powered air-purifying respirator (PA). Physiologic effects were measured by using respiratory inductive plethysmography and subjective responses by two visual analog scales. There were significant effects of airflow path design upon the physiologic parameters of ventilation, tidal volume, and mean flow rate. There were no significant physiologic or subjective differences between the full-face mask respirators with and without the nasal deflector in place. The PA had less physiologic impact than the nonpowered models but did not show significant subjective benefit. The study suggests that both subjective and objective physiologic responses must be utilized in assessing respirator design.     

The effect on heart rate and facial skin temperature of wearing respiratory protection at work

Twelve New Zealand workers from a range of occupations were studied to investigate the effect of wearing air-filtering respiratory protection on heart rate (HR) and facial skin temperature (Tlip and Tcheek) whilst working. All variables were measured continuously during simulated and actual work. The former allowed physiological measurements to be undertaken during the physical activities carried out during the work task without respirators and without exposure to hazardous airborne substances. Mean heart rates in subjects moving without respirators ranged from 75 to 94 beats/min and from 77 to 98 beats/min during respirator use at work. Mean skin temperature under the mask (Tlip) increased in 11 of the 12 subjects while using respirators (range 1.2-4.8 degrees C) but Tcheek only increased in four (range 0.6-1.5 degrees C). The use of simulated work tasks in the experiment was a compromise. The heart rate data from the real and simulated work indicated that effort and workload, though not identical, were similar. The increase in skin temperature under the mask may account for the reluctance of individuals to wear respiratory protection at work. This region of the face is very thermosensitive.     

A method for evaluating aerosol leakage through the interface between protective suits and full-face respirators

Military personnel and first responders use a range of personal equipment including protective suits, gloves, boots, and respirators to prevent exposure of their skin and airways to hazardous chemical, biological, radiological, and/or nuclear substances. Although each individual item of personal protective equipment is well tested against existing standards, it is also necessary to consider the performance of the interfaces between items in terms of prevention from exposure, and the protection system as a whole. This article presents an aerosol challenge method for assessing the performance of the interface between a respirator and the hood of a protective suit. The interface is formed between the sealing strip of the hood and the surface of the respirator's outer sealing area and is affected by how well the sealing strip can cover and adapt to the sealing area. The method evaluates the leakage of particles of different sizes into the hood via the interface by particle counting at sampling points around the respirator's perimeter. Three different respirators were tested together with a single hood having a tight-fitting seal. The method variation between measurements was low but increased appreciably when the protective ensemble was re-dressed between measurements. This demonstrates the difficulty of achieving a reliable and reproducible seal between respirator and hood under normal conditions. Different leakage patterns were observed for the three respirators and were linked to some specific design features, namely the respirator's sealing area at the chin and its width at cheek level. Induced leak experiments showed that to detect substantial particle leakage, channels at the hood-respirator interface must be quite large. The method outlined herein provides a straightforward way of evaluating hood-respirator interfaces and could be useful in the further development of personal protective equipment.