Yihang Liu

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.

Occupational medicine practice: one specialty or three?

Objective: To characterize education, practice, and skills of occupational physicians and to evaluate subgroups within the profession. Methods: The data for the baseline surveys of the occupational medicine practice research project were collected for a national sample of occupational physicians using paper or on-line instruments. Three subgroups were defined a priori-injury care, clinical specialist, and management/population. Results: Occupational medicine seems to include three distinct subgroups, which differ in characteristics such as patient volume, relevant clinical skills, and income source. Nevertheless, many commonalities were present across all three groups, such as emphasis on communication, OSHA, and workers compensation. Musculoskeletal and workers compensation care were most important, although there were highly significant differences among the three subgroups. Conclusions: Planning for education, certification, and organization of services should acknowledge the distinctions among the three subgroups.

Occupational medicine practice: activities and skills of a national sample.

Objective: To characterize activities and skills of occupational physicians using work diaries. Methods: A total of 260 occupational physicians from a national sample provided task/skill descriptions at approximately 25 specific times. The average percentage of activity samples using a skill and the interquartile range expressed results. Results: Clinical activities, particularly musculoskeletal, were most frequent, followed by industry and health system management. Traditional public health approaches were infrequent. Injured patients, employers, and healthy workers were the most common beneficiaries. Communication about prevention and work restrictions was frequent. Interphysician variability was high for most measures. Conclusions: Results demonstrated a dichotomy—many frequent activities/skills are associated with other specialties as well (eg, treating injury); others, albeit less frequently used, demarcate the uniqueness of occupational medicine (eg, preventive examinations, toxicology, benefiting employers or worker groups, assessing work ability, payment by employers).

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.

Value of occupational medicine board certification.

Objective: To assess the impact of occupational medicine board certification and career stage on practice characteristics. Methods: Two hundred sixty occupational medicine physicians completed a questionnaire and 25 activity log descriptions about 72 items in 9 major domains. For each item, the percentage of activities involving the item and the percentage of physicians conducting the item at least once were calculated. Results were analyzed by board certification status and career stage. Results: Board-certified physicians had more-diverse practice activities and skills. They were more involved in management and public health–oriented activities, with greater emphasis on toxicology and less on musculoskeletal disorders. The noncertified physicians received more payment from workers compensation. Early-career physicians spent more time in direct injury/illness treatment, being paid by workers compensation, and addressing musculoskeletal problems. Conclusions: Formal training confers advantages in practice diversity and population medicine orientation.

Career paths in occupational medicine.

Objective: To describe career path patterns for occupational medicine (OM) physicians. Methods: A convenience sample of 129 occupational physicians described work activities and locations at several career points up to 20 years ago, first OM position, and 10 years after expectations. Results: Clinical activities were important throughout (eg, 41% and 46% of occupational physicians reported frequently treating patients 20 years ago and currently). Practice locations changed more markedly, with increased multisite clinics and hospital/medical center-based practices. Performing mainly clinical activities in a first job increased from 82% to 97% over the past 20 years. Career transitions between clinical and nonclinical roles were common (40% of participants). Many anticipate transition to nonclinical work over 10 years. Conclusions: Activities have not fundamentally changed, but practice locations have evolved. Both clinical and management activities remain important, and path to managerial positions increasingly begins in clinical practice.

Assessing the risk of work-related international travel.

Objective: To identify factors affecting the likelihood of requiring medical services during international business trips. Methods: Data from more than 800,000 international trips and medical assistance cases provided to 48 multinational corporations in 2009. Travel destination countries were grouped into four a priori risk-related categories. Results: Travel to “low” medical risk countries in aggregate accounted for more hospitalizations and medical evacuations than travel to “high” medical risk countries. Nevertheless, the risk per trip was much higher for travel to higher medical risk countries. Conclusions: Corporations with employees on international travel should allocate sufficient resources to manage and ideally prevent medical issues during business travel. Travel medicine must focus on more than infectious diseases, and programs are necessary for both high- and low-risk regions. Improved understanding of travel-related needs determines resource allocation and risk mitigation efforts.

Country factors associated with the risk of hospitalization and aeromedical evacuation among expatriate workers.

Objective: To assess country factors associated with the risk of requiring aeromedical evacuation and hospitalization among expatriate workers and their dependents. Methods: The 2009–2010 data including 5725 aeromedical evacuations and 17,828 hospitalizations, and 2009 data of hospitalizations and aeromedical evacuations among 94,651 at-risk expatriates, were analyzed to assess 2 country risk rating tools. Each tool utilized four risk categories and reflected level of development and medical capabilities. Results: Country risk category was strongly associated with risk of evacuation and/or hospitalization for each risk rating tool (eg, 46-fold increase from lowest to highest country risk category). Conclusion: Country risk tools strongly associate hospitalization and aeromedical evacuation with country risk category, and thus can be important indicators of relative medical risk. Employers may use these results to implement targeted prevention programs to support expatriate workers and their families.

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.