- 11 Nov 2013
- Working Paper
Increased Speed Equals Increased Wait: The Impact of a Reduction in Emergency Department Ultrasound Order Processing Time
Executive Summary — This study of ultrasound test orders in hospital emergency departments (EDs) shows that, paradoxically, increasing capacity in a service setting may not alleviate congestion, and can actually increase it due to increased resource use. Specifically, the study finds that reducing the time it takes to order an ultrasound counter intuitively increases patient throughput time as a result of increased ultrasound use without a corresponding increase in quality of care. Furthermore, the authors show that in the complex, interconnected system or hospitals, changes in resource capacity affects not only the patients who receive the additional resources, but also other patients who share the resource, in this case, radiology. These results highlight how demand can be influenced by capacity due to behavioral responses to changes in resource availability, and that this change in demand has far reaching effects on multiple types of patients. Interestingly, the increased ultrasound ordering capacity was achieved by removing what appeared to be a "wasteful" step in the process. However, the results suggest that the step may not have been wasteful as it reduced inefficient ultrasound orders. In healthcare, these results are very important as they provide an explanation for some of the ever-increasing costs: reducing congestion through increased capacity results in even more congestion due to higher resource use. Overall, the study suggests an operations-based solution of increasing the cost/difficulty of ordering discretionary but sometimes low-efficacy treatments to address the rise in healthcare spending. Therefore, to improve hospital performance it could be optimal to put into place "inefficiencies" to become more efficient. Key concepts include:
- A process improvement can inadvertently cause an increase in demand for a service as well as associated shared resources, which results in congestion, counter intuitively decreasing overall system performance.
- While individual patients and physicians may benefit from the reduced processing time, there can be unintended consequences for overall system performance.
We exploit an exogenous process change at two emergency departments (EDs) within a health system to test the theory that increasing capacity in a discretionary work setting increases wait times due to additional services being provided to customers as a consequence of reduced marginal costs for a task. We find that an increase in physicians' capacity for ordering ultrasounds (U/S) resulted in an 11.5 percentage point increase in the probability of an U/S being ordered, confirming that resource availability induces demand. Furthermore, we find that the additional U/S demand increased the time to return other radiological tests due to the higher demand placed on radiologists from the additional U/S. Consequently, the average length of stay (LOS) for patients with an abdominal complaint increased by nearly 30 minutes, and the waiting time to enter the ED increased by 26 minutes. We do not find any indications of improved performance on clinical metrics, with no statistical change in the number of admissions to the hospital or readmissions to the ED within 72 hours. Our study highlights an important lesson for process improvement in interdependent service settings: increasing process capacity at one step in the process can increase demand at that step, as well as for a subsequent shared service, and both can result in an overall negative impact on performance.