Ergonomics
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The development of physiologic monitors has contributed to the decline in morbidity and mortality in patients undergoing anaesthesia. Diverse factors (physiologic, technical, historical and medico-legal) create challenges for monitor alarm designers. Indeed, a growing body of literature suggests that alarms function sub-optimally in supporting the human operator. Despite existing technology that could allow more appropriate design, most anaesthesia alarms still operate on simple, pre-set thresholds. Arguing that more alarms do not necessarily make for safer alarms is difficult in a litigious medico-legal environment and a competitive marketplace. The resultant commitment to the status quo exposes the risks that a lack of an evidence-based theoretical framework for anaesthesia alarm design presents. In this review, two specific theoretical foundations with relevance to anaesthesia alarms are summarised. The potential significance that signal detection theory and cognitive systems engineering could have in improving anaesthesia alarm design is outlined and future research directions are suggested. ⋯ The development of physiologic monitors has increased safety for patients undergoing anaesthesia. Evidence suggests that the full potential of the alarms embedded within those monitors is not being realised. In this review article, the authors propose a theoretical framework that could lead to the development of more ergonomic anaesthesia alarms.
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Comparative Study
A biomechanical and subjective assessment and comparison of three ambulance cot design configurations.
Effects of ambulance cot design features (handle design and leg folding mechanism) were evaluated. Experienced ambulance workers performed tasks simulating loading and unloading a cot to and from an ambulance, and a cot raising task. Muscle activity, ratings of perceived exertion, and performance style were significantly affected by cot condition (p < 0.05). ⋯ Providing handle options and automatic leg folding/unfolding operation can reduce cot operator's effort and physical strain. Practitioner Summary: Paramedics frequently incur musculoskeletal injuries associated with patient-handling tasks. A controlled experiment was conducted to assess effects of ambulance cot design features on physical stress of operators, as seen through muscle activity and operator's perceptions. Differences between cots were found, signalling that intentional design can reduce operator's physical stress.
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Work-related musculoskeletal pain (MSP) risk assessments by trained observers are often used in ergonomic practice; however, the validity may be questionable. We investigated the predictive value of work-site MSP risk estimates in a prospective cohort study of 1745 workers. Trained observers estimated the risk of MSP (neck, shoulder or low-back pain) using a three-point scale (high, moderate and low risk) after observing a video of randomly selected workers representing a task group. ⋯ The results show that observers were able to estimate the risk of shoulder and neck pain, whereas they found it difficult to estimate the risk of low-back pain. Practitioner Summary: Work-related musculoskeletal pain risk assessments by observers are often used in ergonomic practice. We showed that observers were able to estimate shoulder and neck pain risk, but had difficulties to estimate the risk of low-back pain. Therefore, observers' risk estimates might provide a useful method for musculoskeletal pain risk assessments.
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To examine the effects of firefighters' self-contained breathing apparatus' (SCBA) weight and its harness design on the physiological and subjective responses, eight male students performed treadmill exercise under four conditions: the 8 kg firefighter protective clothing (PC) (Control), the PC + an 11 kg SCBA with an old harness (Test A), the PC + a 6.4 kg SCBA with an old harness (Test B) and the PC + a 6.4 kg SCBA with a new harness (Test C), at ambient temperatures (T(a)) of 22°C and 32°C. Besides highlighting the fact that a heavy SCBA had a significant effect on the oxygen consumption and metabolic rate, this experiment also found that in a T(a) of 32°C, in particular, the combined effect of 4.7 kg lighter SCBA and new harness design could reduce metabolic rate and improved subjective muscle fatigue and thermal discomfort. ⋯ An effort to alleviate the physiological and subjective burden of firefighters by reducing the weight of SCBA and by using the new harness design has provided satisfactory results in reduced oxygen consumption and in improved subjective responses in a hot air environment.
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Factors, such as high repetition, high force and gripping play a role in the development of upper extremity work-related musculoskeletal disorders. The purpose of this study was to systematically examine the effects of push load and frequency on muscle activity with and without concurrent gripping. A total of 10 men and 10 women performed a cyclic bimanual pushing task. All combinations of three push loads (1 kg, 2 kg, 4 kg), three frequencies (4/min, 8/min, 16/min) and two grip conditions (no required grip and 30% of maximum grip force) were performed in randomised order. The muscle activity of the upper arm and shoulder complex reflected both frequency and load, often with significant interactions, thus may be better described by workload, the product of force and frequency. In the forearm, muscle activities were generally low but adding a submaximal grip superseded the effects of push load, with the activity reflecting frequency and grip. ⋯ Force and frequency are important risk factors for upper extremity disorders. We found that upper extremity muscle activity responds to workload (force × frequency) in a complex way which may be superseded if a grip is present. This electromyographic study provides physiological insights to muscular loading as basis for a variety of workplace disorders.