Elsevier

Annals of Emergency Medicine

Volume 54, Issue 4, October 2009, Pages 492-503.e4
Annals of Emergency Medicine

Health policy and clinical practice/original research
Crowding Delays Treatment and Lengthens Emergency Department Length of Stay, Even Among High-Acuity Patients

https://doi.org/10.1016/j.annemergmed.2009.03.006Get rights and content

Study objective

We determine the effect of crowding on emergency department (ED) waiting room, treatment, and boarding times across multiple sites and acuity groups.

Methods

This was a retrospective cohort study that included ED visit and inpatient medicine occupancy data for a 1-year period at 4 EDs. We measured crowding at 30-minute intervals throughout each patient's ED stay. We estimated the effect of crowding on waiting room time, treatment time, and boarding time separately, using discrete-time survival analysis with time-dependent crowding measures (ie, number waiting, number being treated, number boarding, and inpatient medicine occupancy rate), controlling for patient demographic and clinical characteristics.

Results

Crowding substantially delayed patients' waiting room and boarding times but not treatment time. During the day shift, when the number boarding increased from the 50th to the 90th percentile, the adjusted median waiting room time (range 26 to 70 minutes) increased by 6% to 78% (range 33 to 82 minutes), and the adjusted median boarding time (range 250 to 626 minutes) increased by 15% to 47% (range 288 to 921 minutes), depending on the site. Crowding delayed the care of high-acuity level 2 patients at all sites. During crowded periods (ie, 90%), the adjusted median waiting room times of high-acuity level 2 patients were 3% to 35% higher than during normal periods, depending on the site and crowding measure.

Conclusion

Using discrete-time survival analysis, we were able to dynamically measure crowding throughout each patient's ED visit and demonstrate its deleterious effect on the timeliness of emergency care, even for high-acuity patients.

Introduction

Length of stay is an important measure of quality of care in the emergency department (ED).1, 2, 3 Several studies have found that crowding is associated with increased ED length of stay.4, 5 Rathlev et al4 observed that daily ED length of stay was positively associated with the hospital occupancy rate and number of emergency admissions at their institution. Asaro et al5 found that at their ED, crowding factors increased wait time and boarding time but not treatment time. In contrast, Schull et al6 investigated the effect of the number of low-complexity patients on the length of stay of higher-complexity patients treated at EDs in Ontario, Canada, and found that increasing numbers of low-complexity patients did not significantly lengthen the wait time or ED length of stay of higher-complexity patients.

Many hospital-based EDs across the country have been struggling with crowding for more than a decade.7, 8 Until recently, there were few objective measures of crowding and modest evidence of the negative effects of crowding on patient care and outcomes. However, advances in crowding measures during the past 5 years have resulted in a growing number of studies that quantify the negative consequences of crowding, especially on delays in care for time-sensitive conditions.7, 9, 10, 11, 12, 13 One of the major limitations of crowding studies conducted to date is that they measure crowding in a static way, either at a point in time (eg, patient arrival) or by averaging crowding during a specific interval (eg, a shift). However, many studies have shown that crowding is dynamic and can fluctuate substantially during the course of a patient's ED stay.14, 15, 16, 17

The purpose of this study was to quantify the relationship between crowding and ED length of stay at 4 hospital EDs and to compare the effect across EDs and patient acuity levels. We measured crowding at regular intervals throughout each patient's ED stay and estimated the cumulative effect of crowding on ED waiting room time, treatment time, and boarding time, using discrete-time survival analysis, which allowed us to include time-varying crowding covariates. We stratified the analysis by shift, site, and patient acuity and determined whether crowding, adjusted for other factors, significantly delayed completion of each phase of ED care.

Section snippets

Study Design

This investigation was based on a retrospective cohort design that included all ED visits to one of 4 hospital EDs during a 1-year period. Patient visit information was abstracted from the information system of each ED and combined with inpatient medicine occupancy and ED staffing data. The institutional review board of each site approved the study by expedited review.

Setting

The selection of the 4 study sites was based on previous collaboration and feasibility of aggregating electronic medical record

Results

The patient populations of the 4 study sites differ substantially from one another, particularly in terms of insurance status, admission rate, and acuity level (Table 2). Site A treats more patients who are uninsured (37%) compared with the other sites (range 5% to 21%). Site D admits proportionately fewer patients (19%) than the other EDs (range 23% to 30%). Site D also treats fewer highly acute patients (ie, Emergency Severity Index levels 1 and 2) (13%) compared with the other sites (range

Limitations

The results of this study must be interpreted in the context of the following limitations. First, this study did not attempt to connect the different phases of care and determine how the completion of care in one phase affects the completion of care in another.

Second, our models did not include all potential covariates that affect ED length of stay, such as orders for diagnostic tests, treatments, or specialty consultations. Although overall treatment times were not significantly delayed by

Discussion

To our knowledge, this is the first study to measure crowding dynamically and to examine its effect on ED length of stay. We found that crowding was associated with substantial delays in ED length of stay across 4 ED sites. Moreover, crowding prolonged the ED length of stay of high-acuity level 2 patients. Output factors, such as the number of patients boarding and the inpatient medicine occupancy rate, were associated with large delays in ED care. Crowding negatively affected ED patients'

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    Provide feedback on this article at the journal's Web site, www.annemergmed.com.

    Supervising editor: Donald M. Yealy, MD

    Author contributions: All of the authors were involved in the study concept and design, drafting of the article, and critical revision of the article for important intellectual content. The objectives, data collection protocol, review of the analysis, and findings were discussed by teleconference calls with all of the investigators. MLM, JSD, JL, and DA were responsible for acquiring the data from their sites and obtaining institutional review board approval. RD performed the data analysis under the supervision of MLM and SLZ. However, all of the authors had input into the variables considered for the analysis and how it was conducted. MLM drafted the article, and all authors contributed substantially to its revision. MLM takes responsibility for the paper as a whole.

    Funding and support: By Annals policy, all authors are required to disclose any and all commercial, financial, and other relationships in any way related to the subject of this article that might create any potential conflict of interest. The authors have stated that no such relationships exist. See the Manuscript Submission Agreement in this issue for examples of specific conflicts covered by this statement.

    Earn CME Credit: Continuing Medical Education is available for this article at: www.ACEP-EMedHome.com.

    Publication date: Available online May 6, 2009.

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