The impact of the patient’s initial NACA score on subjective and physiological indicators of workload during pre-hospital emergency care

BACKGROUND: Excessive workload may impair patient safety. However, little is known about emergency care providers’ workload during the treatment of life-threatening cases including cardiopulmonary resuscitation (CPR). Therefore, we tested the hypothesis that subjective and physiological indicators of workload are associated with the patient’s initial NACA score and that workload is particularly high during CPR. METHODS: NASA task load index (NASA-tlx) and alarm codes were obtained for 216 sorties of pre-hospital emergency medical care. Furthermore, initial NACA scores of 140 patients were extracted from the physicians’ protocols. The physiological workload indicators mean heart rate (HR) and permutation entropy (PeEn) were calculated for 51 sorties of primary care. General linear mixed models were used to analyze the association of NACA scores with subjective (NASA-tlx) and physiological (mean HR, PeEn) measures of workload. RESULTS: In contrast to the physiological variables PeEn (p = 0.10) and HR (p = 0.19), the mental (p<0.001) and temporal demands (p<0.001) as well as the effort (p<0.001) and frustration (p = 0.04) subscale of the NASA-tlx were significantly associated with initial NACA scores. Compared to NACA = I, an initial NACA score of VI (representing CPR) increased workload by a mean of 389.5% (p = 0.001) in the mental and 345.9% (p<0.001) in the temporal demands, effort by a mean of 446,8% (p = 0.002) and frustration by 190.0% (p = 0.03). In line with the increase in NASA-tlx, PeEn increased by 20.6% (p = 0.01) and HR by 6.4% (p = 0.57). CONCLUSIONS: Patients’ initial NACA scores are associated with subjective workload. Workload was highest during CPR.