Ability of the Medical Priority Dispatch System Protocol to Predict the Acuity of “Unknown Problem” Dispatch Response Levels

Abstract

Objective. To determine if Medical Priority Dispatch System's (MPDS's) Protocol 32–Unknown Problem interrogation-based differential dispatch coding distinguishes the acuity of patients as found at the scene by responders, when little (if any) clinical information is known. Methods. “Unknown problem” situations (i.e., all cases not fitting into any other chief complaint group) constitute 5–8% of all calls to dispatch centers. From the total patient encounters (n = 599,107) in the aggregate data of one year (September 2005 to August 2006), we examined 3,947 (0.7%) encounters initially coded as “unknown problem” by the London Ambulance Service Communications Center for the scene presence of cardiac arrest (CA) andparamedic-determined high-acuity (blue-in [BI]/“lights andsiren”) findings. Odds ratios (ORs) with 95% confidence intervals (95% CIs) andp-values were used to assess the degree of associations between determinant codes andcase outcomes (i.e., CA/BI). Results. Statistically significant association between clinical dispatch determinant codes andcase outcomes was observed in the “life status questionable” (LSQ; DELTA-1 [D-1]) andthe “standing, sitting, moving, or talking” (BRAVO-1 [B-1]) code pair for the CA outcome (OR [95% CI]: 0.11 [0, 0.63], p = 0.005) andfor the BI outcome (OR [95% CI]: 0.47 [0.28, 0.77], p = 0.003). The LSQ andall three code pairs (i.e., B-1; “community alarm notifications” [B-2]; and“unknown status” [B-3]) also demonstrated significant associations both with the CA outcome (OR [95% CI]: 0.43 [0.23, 0.81], p = 0.010) andwith the BI outcome (OR [95% CI]: 0.74 [0.56, 0.97], p = 0.033). All the determinant code levels yielded significant association between BI andCA cases. Conclusion. This dispatch protocol for unknown problems successfully differentiates dispatch coding of low-acuity andnon-CA patients only when specific situational information such as the patient's standing, sitting, moving, or talking can be determined during the interrogation process. Also, emergency medical dispatcher (EMD) reliance on caller-volunteered information to identify predefined critical situations does not appear to add to the protocol's ability to differentiate high-acuity andCA patients. LSQ proved to be a better predictor of both CA andBI outcomes, when compared with the BRAVO-level determinant codes within the “unknown problem” chief complaint. The B-3 (completely unknown) determinant code is a better predictor of severe outcomes than nearly all of the clinically similar BRAVO determinant codes in the entire MPDS protocol. Hence, the B-3 coding should be considered—in terms of its predictability for severe outcome—as falling somewhere between a typical DELTA anda typical BRAVO determinant code.

Key words:

• emergency medical dispatch
• emergency medical dispatcher
• dispatch protocol
• unknown problem
• dispatch outcome
• cardiac arrest
• protocol compliance