Introduction: There are many recent articles published in scientific literature on the topic of work-related stress. However, these studies focus on the effects of stress on the workers and not on the impact that stress could have on their work performance—more specifically on the calltaker’s (emergency dispatcher (ED)) performance and consequently on the whole Emergency Medical Service (EMS).
Objective: The objective of this study was to assess whether the number of consecutive hours worked (WH) by the EMDs had an impact on their performance, in terms of case evaluations, and on the type (i.e., Advance Life Support [ALS] vs. Basic Life Support [BLS]) and methods/mode (i.e., with/without Lights and Siren [L&S]) of dispatch of emergency vehicles.
Methods: The retrospective descriptive study included cases in the Liguria EMS, Italy, database dated from January 01, 2011 to December 31, 2019. The criticality of priority codes (from the most serious to the least serious: black, red, yellow, green, and white) assigned by the EMDs during the emergency call (EMD criticality; CP) were compared with the priority codes assigned by the field responders (Responder criticality; CR). The data were then analyzed in relation to the WH and descriptive statistics such as sensitivity, relative risk, and predictive values were estimated.
Result: A total of 1,599,809 cases were analyzed. Sensitivity for patients with impaired vital functions (red codes) was 76.4% (95% CI: 75.2-77.4) with a positive predictive value of 20.3% (95% CI: 19.2-21.9) and specificity was 87.8% (95% CI: 87.1- 88.8) with a negative predictive value of 98.9% (95% CI: 98.8-99.0). The relative risk ratio (RRR) of inconsistent assessments improves in the first three WHs: -3% at the third WH (0.97, 0.96-0.99) and progressively worsens in the following hours, reaching +6% (1.06; 1.05 – 1.08) at the sixth WH. In the first three WHs, there was also an improvement in the appropriateness of the resources sent: -4% at the third WH (0.96, 0.94 – 0.98) which then progressively worsens thereafter, reaching + 11% (1.11, 1.07 – 1.14) in 7 -12 WH range.
Conclusion: The performance of the EMDs, in terms of predictive ability of the priority codes assigned, of the type of resources, and of the sending methods/mode, improved within the first three WHs, then progressively worsened up to the sixth WH. As the number of WHs increased, overtriage and dispatch of emergency vehicles with L&S also increased.
Keywords: Working hours, work shift, working-time regulation, emergency medical dispatch, field responders, patient safety, overemployment, overtriage, undertriage.

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