Siddharth Bansal

Multidomain subjective response to respirator use during simulated work

Objective: Evaluate subjective tolerance to respirator use outside of traditional industrial settings by users including persons with mild respiratory impairment. Methods: The response to respirator use (half face mask dual cartridge and N95) was measured during eight types of work activities as well as in an exercise laboratory setting. The 43 research subjects included persons with mild respiratory impairments. Multiple domains of subjective response were evaluated. Results: Mixed model regression analyses assessing the effect of respirator type and task type showed: 1) most tolerated respirator use well; 2) half face mask respirators typically had greater adverse impact than N95 types; 3) multiple subjective outcomes, rather than only comfort/breathing impact, should be measured; and 4) rated subjective impact during work activities is less than in exercise laboratory settings. Conclusions: The results suggest that respirator use may be feasible on a widespread basis if necessary in the face of epidemic or terror concerns.

Respirator Physiological Effects under Simulated Work Conditions

This study compared the physiological impacts of two respirator types in simulated work conditions. Fifty-six subjects included normal volunteers and persons with mild respiratory impairments (chronic rhinitis, mild COPD, and mild asthma). Respiratory parameters and electrocardiogram were measured using respiratory inductive plethysmography while performing eight work tasks involving low to moderate exertion using two respirators: (1) a dual cartridge half face mask (HFM) respirator, and (2) the N95. Mixed model regression analyses evaluating the effect of task and respirator type showed that task affected tidal volume, minute ventilation, breathing frequency and heart rate; all were greater in heavier tasks. Although respirator type did not affect respiratory volume parameters and flow rates, the HFM led to increase in the inspiratory time, reduction of the expiratory time, and increase in the duty cycle in comparison with the N95. The magnitude of differences was relatively small. The results suggest that most individuals, including persons with mild respiratory impairments, will physiologically tolerate either type of respirator at low to moderate exertion tasks. However, because effective protection depends on proper use, differences in subjective effect may have greater impact than physiological differences. Using respirators may be feasible on a widespread basis if necessary for maintaining essential services in the face of widespread concern about an infectious or terrorist threat.

Anxiety During Respirator Use: Comparison of Two Respirator Types

Anxiety may interfere with proper respirator use. This study directly compares the effect of two types of respirators—elasto- meric half-face mask with dual-cartridges (HFM) and N95 filtering facepiece—on anxiety levels. Twelve volunteers with normal or mildly impaired respiratory conditions performed a series of simulated work tasks using the HFM and N95 on different days. The State-Trait Anxiety Inventory (STAI) measured state anxiety (SA) before and during respirator use. STAI also measured trait anxiety (TA), a stable personal characteristic. The effect of the respirator was measured as the difference between SA pre-use and during use. Work with HFM was associated with an increase in SA (2.92 units, p < .01), whereas work with the N95 had no observed effect. Anxiety should be considered in the selection of the best respirator for a user. Impact on anxiety should be considered for respirator design and certification purposes, particularly if the device is to be widely used in workplace and community settings.

Respirator physiologic impact in persons with mild respiratory disease

Objective: To assess whether mild respiratory disease affects physiologic adaptation to respirator use. Methods: The study compared the respiratory effects of dual cartridge half face mask and filtering facepeice (N95) respirators while performing simulated-work tasks. Subjects with mild chronic obstructive pulmonary disease (n = 14), asthma (n = 42), chronic rhinitis (n = 17), and normal respiratory status (n = 24) were studied. Mixed model regression analyses determined the effects of respirator type, disease status, and the respirator-disease interactions. Results: Respirator type significantly affected several physiologic measures. Respirator type effects differed among disease categories as shown by statistically significant interaction terms. Respiratory timing parameters were more affected than ventilatory volumes. In general, persons with asthma showed greater respirator-disease interactions than chronic obstructive pulmonary disease, rhinitis, or healthy subjects. Conclusions: The effects of respirator type differ according to the category of respiratory disease.

Respirator Impact on Work Task Performance

Objective: Respirators are used to maintain work performance and protect against inhaled toxins. The study compared the effects of two commonly used respirator classes—dual cartridge half face mask (HFM) and filtering face piece (N95)—upon work productivity. Methods: 107 volunteers performed eight simulated work tasks when using the HFM and N95 respirators. Tasks included several body positions, exertion levels, and concentration requirements. Objective measures of accuracy and speed were developed for each task. Scores for each task were based on the subjects rank among all subjects. Results: All subjects were capable of performing the tasks. There were no statistically significant differences between respirator types in either task performance metric. Conclusions: Productivity impact can be measured effectively and should be considered as part of respirator design testing and when selecting the optimal respirator for a worker.

Progression from beryllium exposure to chronic beryllium disease: an analytic model.

Background Understanding the progression from beryllium exposure (BeE) to chronic beryllium disease (CBD) is essential for optimizing screening and early intervention to prevent CBD. Methods We developed an analytic Markov model of progression to CBD that assigns annual probabilities for progression through three states: from BeE to beryllium sensitization and then to CBD. We used calculations of the number in each state over time to assess which of several alternative progression models are most consistent with the limited available empirical data on prevalence and incidence. We estimated cost-effectiveness of screening considering both incremental (cost/case) and cumulative program costs. Results No combination of parameters for a simple model in which risk of progression remains constant over time can meet the empirical constraints of relatively frequent early cases and continuing development of new cases with long latencies. Modeling shows that the risk of progression is initially high and then declines over time. Also, it is likely that there are at least two populations that differ significantly in risk. The cost-effectiveness of repetitive screening declines over time, although new cases will still be found with long latencies. However, screening will be particularly cost-effective when applied to persons with long latencies who have not been previously screened. Conclusions To optimize use of resources, the intensity of screening should decrease over time. Estimation of lifetime cumulative CBD risk should consider the declining risk of progression over time.

How Frequently Should Workplace Spirometry Screening Be Performed?: Optimization Via Analytic Models

BACKGROUND Our objective was to determine how to select the optimal frequency of workplace spirometry screening using diacetyl-exposed workers as an example. METHODS A Markov model was constructed to assess the likelihood of progressing from healthy status to early or advanced disease, starting from four different exposure levels, and performing longitudinal or cross-sectional interpretation of spirometry results over time. Projected outcomes at 10 years were evaluated to inform the optimal frequency of workplace spirometry testing. RESULTS The optimal screening interval depends on the population risk and is highly sensitive to the real-life impact (utility) associated with false-positive results (eg, related to the availability of alternative work). Screening interval is particularly important for high-risk individuals with rapid transition from early to advanced disease, where the 10-year prevalence of advanced disease would be reduced from 5.3 to 2.5% using a 6-month interval rather than a 12-month interval. Longitudinal test interpretation, based on observing trends within each person over time, is marginally preferable to traditional cross-sectional spirometry interpretation. CONCLUSIONS There is no single best screening interval. For high-risk populations, annual testing may be too infrequent.

Subjective response to respirator type: effect of disease status and gender.

Objective: To assess the effect of respirator type and user characteristics (eg, health status) on the subjective response to respirator use. Methods: The subjective responses for multiple domains were evaluated in 104 volunteers performing work tasks in a simulated work environment. Each used a dual cartridge half face mask and a filtering facepiece (N95) respirator. The study population was recruited to include four groups (normal respiratory status, mild asthma, chronic obstructive pulmonary disease, or chronic rhinitis). Mixed model regression analyses determined the effects of respirator type, disease, gender, and age. Results: Half face mask produced more adverse subjective response than the N95 for most scales. There were significant interactions such that disease status modified the effect of respirator type. In general, women reported greater adverse ratings than did men. Conclusions: The effect of respirator type depends on disease status. Respirator design evaluation panels should include persons with mild respiratory disease.