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Monday, 07 November 2011 19:15

Case Study: Human Error and Critical Tasks: Approaches for Improved System Performance

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Health error and critical tasks in remote afterloading brachytherapy: Approaches for improved system performance

Remote afterloading btachytherapy (RAB) is a medical process used in the treatment of cancer. RAB uses a computer-controlled device to remotely insert and remove radioactive sources, close to a target (or tumour) in the body. Problems related to the dose delivered during RAB have been reported and attributed to human error (Swann-D'Emilia, Chu and Daywalt 1990). Callan et al. (1995) evaluated human error and critical tasks associated with RAB in 23 sites in the United States. Evaluation included six phases:

Phase 1: Functions and tasks. Preparation for treatment was considered to be the most difficult task, as it was responsible for the greatest cognitive strain. In addition, distractions had the greatest effect on preparation.

Phase 2: Human-system interferences. Personnel were often unfamiliar with interfaces they used infrequently. Operators were unable to see control signals or essential information from their workstations. In many cases, information on the state of the system was not given to the operator.

Phase 3: Procedures and practices. Because procedures used to move from one operation to the next, and those used to transmit information and equipment between tasks, were not well defined, essential information could be lost. Verification procedures were often absent, poorly constructed or inconsistent.

Phase 4: Training policies. The study revealed the absence of formal training programmes at most sites.

Phase 5: Organizational support structures. Communication during RAB was particularly subject to error. Quality-control procedures were inadequate.

Phase 6: Identification and classification or circumstances favouring human error. In all, 76 factors favouring human error were identified and categorized. Alternative approaches were identified and evaluated.

Ten critical tasks were subject to error:

  • patient scheduling, identification and tracking
  • applicator placement stabilization
  • large volume localization
  • dwell position localization
  • dosimetry
  • treatment set-up
  • treatment plan entry
  • source exchange
  • source calibration
  • record-keeping and routine quality assurance

 

Treatment was the function associated with the greatest number of errors. Thirty treatment-related errors were analysed and errors were found to occur during four or five treatment sub-tasks. The majority of errors occurred during treatment delivery. The second-highest number of errors were associated with the planning of treatment and were related to the calculation of dose. Improvements of eqiupment and documentation are under way, in collaboration with manufacturers.

 

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