Myths versus facts in emergency department overcrowding and hospital access block

Drew B Richardson and David Mountain
Med J Aust 2009; 190 (7): 369-374. || doi: 10.5694/j.1326-5377.2009.tb02451.x
Published online: 6 April 2009


Overcrowding has been described as the most serious problem and most avoidable cause of harm facing our hospital systems.1 Yet, given the severity of the problem, myths are still rife about causes, effects and possible solutions for emergency department (ED) overcrowding. Finding real solutions and formulating policy cannot progress without a true understanding of the underlying issues, and this is actively hindered when myths are propagated or left unanswered by research and the facts.

Wherever human beings gather, there are fluctuations in their numbers and, if uncontrolled, these occasionally exceed the efficient maximum for a given purpose. EDs are designed largely for a continuous flow of patients, with some diagnosis and treatment provided, rather than for gathering or storage. However, even in systems designed purely for flow (such as roads) there are peaks and troughs of activity, and occupancy sometimes exceeds the number able to move safely and smoothly, leading to traffic jams.

Overcrowding to the point of dysfunction has gradually become the norm in Australasian EDs since the mid 1990s. The greatest contributing factor has been access block. This is the inability of patients who need to be admitted to the hospital to be allocated appropriate beds in a timely fashion. Additionally, there has been an increase in patient numbers, the complexity of their conditions, and the need for their admission. Demand growth has resulted from an enlarging, ageing population, expansion of diagnostic and therapeutic choices and improved survival with severe diseases. This has not been properly matched by growth in other services, especially outside working hours, further increasing the burden on EDs.

Theoretical basis of overcrowding

Queuing theory indicates that the length of a queue, and hence the waiting time to treatment, is determined by the arrival rate, the treatment and discharge (either home or admitted) rate, and the baulk rate (did-not-wait-to-be-seen rate, which is usually dependent on the length of the queue). An individual patient’s access to emergency care is dependent, first, on urgency (assuming triage to the correct queue), second, on the number of similar patients already waiting ahead, and third, on the rate and strategy of treatment. Treatment rate is dependent on staffing and on the number of patients already being treated (occupancy), which determines physical availability of resources (space and equipment) and the competing demands on staff. On a daily basis, patient flow is significantly dependent on occupancy, because even a small decrease in treatment rate is cumulative — it causes further increases in the number waiting ahead of new arrivals.

EDs can be considered as overcrowded when treatment becomes dysfunctional; that is, when the treatment rate is reduced or the quality of treatment suffers, even with optimal staffing and space. This has been termed the “cardiac analogy” model,2 where ED functional efficiency is regarded as a Starling curve (Starling’s law of the heart states that the greater the end-diastolic volume [input], the greater the stroke volume [output] up to a limit corresponding to maximum muscle stretch). In this analogy, ED functional efficiency increases to a peak, but then starts to decrease with overwhelming workload (corresponding to congestion, as in cardiac failure).

Definition of overcrowding

The Australasian College for Emergency Medicine (ACEM) defines ED overcrowding as the situation where ED function is impeded primarily because the number of patients waiting to be seen, undergoing assessment and treatment, or waiting to leave exceeds the physical and/or staffing capacity of the ED.3 Access block is quantified as the proportion of patients admitted, transferred to other hospitals, or who die in the ED who have a total ED time (arrival at triage to discharge from the ED) of more than 8 hours.3

The American College of Emergency Physicians defines crowding as the situation when the identified need for emergency services exceeds available resources for patient care in the ED, hospital, or both4 — a definition deliberately closer in spirit to that of “disaster medicine”. Most research on the subject, however, is concerned with the balance between daily fluctuations and ED occupancy, rather than the response to mass-casualty surges. However, some see overcrowding as a recurrent, common and foreseeable internal disaster. Many EDs have declared internal disasters purely because of severe overcrowding, unrelated to an external disaster.

“Crowding” might be the more descriptive term, but “overcrowding” is in common use, and researchers have used multiple definitions in attempts to quantify the phenomenon. All major recognised definitions incorporate occupancy with patients under treatment, either as an absolute figure or as a proportion of a resource, such as cubicles occupied by treated patients.5,6 Many also include subjective factors (eg, when a department “feels” overcrowded) and/or outcomes such as ambulance bypass/diversion (where ambulances are diverted away from an overcrowded ED) that are not always applicable and are modifiable by administrative, rather than actual, changes to system function.

Retrospectively identified episodes of overcrowding tend to be reliable and useful for research, but are of only limited significance in day-to-day management of EDs. However, it is clear that certain seasonal patterns (overcrowding is worse in winter than in summer) and weekly patterns (overcrowding tends to be worst on Mondays because of increased admissions for elective procedures, inadequate numbers of patients discharged over the weekend, and more urgent attendances) are fairly predictably associated with worse overcrowding. These can be used to help change hospital practice and capacity planning. Real-time assessments may be correlated with patient service (number of patients waiting correlates well with waiting time for new arrivals), but are only useful if there is a managerial commitment and capacity to intervene. Predictive algorithms based on the number being treated suffer from false positives and, again, are only justified if there are interventions available to prevent deterioration in flow.

There are multiple scales proposed and used to define overcrowding,5,6 but validation studies are difficult and many rely on ambulance diversion as an outcome measure, which is only suitable for urban centres with multiple EDs. In addition, even in areas where diversion is possible, it is used less frequently over time, as severe overcrowding at all sites makes diversion less useful. The few Australasian studies that exist have not shown these scales to be clinically useful in real time.7

Myths and facts
1. Causes of overcrowding

The single most important factor affecting ED overcrowding is the availability of sufficient inpatient beds.1,8 The number of acute-care public hospital beds in Australia per head of population decreased by 18% between the financial years 1995–96 and 2005–06,9 after even larger reductions in the preceding two decades. Although these large decreases were initially ameliorated by more efficient hospital function and shorter admissions, it is clear that in most major hospitals, occupancy levels have been driven up routinely to over 90%. These levels are known to be associated with poor hospital and system function, inefficient care and increased episodes of hospital and ED overcrowding.8 In fact, it is a universal finding that operating at full capacity for prolonged periods is inefficient and unsustainable. ED overcrowding is best seen as a marker of whole-of-hospital dysfunction that requires a whole-of-hospital or whole-of-system response.10,11 Bed availability depends not only on the physical number of beds, but also on the way the bedstock is managed (appropriate use, good flow practices),11 competing uses for beds (eg, elective versus acute care), the availability of step-down units, and appropriate community care.

Importantly, there is no evidence for the often-proposed myth of “general-practice-type” or “inappropriate” patients leading to ED overcrowding.12-14 Discretionary presentations by patients with low-complexity conditions, who might reasonably be managed elsewhere, constitute an insignificant workload in most EDs. These patients are uncommon in major EDs, and the most frequent reason for them to attend an ED is because they were referred by a GP. They rarely require admission or even use of trolleys, they use minimal ED resources (less than 3% of all costs or resources in most EDs), are easy to deal with, and do not impose on the key functions of the ED (assessment of sick patients, complex treatments and resuscitation).15,16 They may attend an ED because no other options are available and, importantly, they often feel their medical needs are urgent. They may spend a lot of time in waiting rooms, but this does not affect overall ED function. This myth is particularly problematic in that, if allowed to continue to be given credence, it continually diverts attention to solutions that cannot deal with the key issue causing dysfunction in the ED — that is, excessive numbers of admitted patients.

2. Attendances and waiting time to see a doctor

At 10:00 on 2 June and 1 September 2008, two national studies funded by the ACEM examined the point prevalence of overcrowding and access block in accredited Australian EDs. As shown in Box 1, over half the patients under treatment in non-New South Wales tertiary hospitals were waiting for beds, and 75% of those had been in the ED for more than 8 hours. Despite variation between states and hospital types (partly reflecting the size of different EDs), on average, the number of people waiting to be seen was less than the number who were under treatment and experiencing access block. If the patients experiencing access block were moved to appropriate inpatient beds, there would be more than enough staff and physical resources to treat all those waiting to be seen. The 2008 point prevalence study confirms data from previous similar studies and hospital time series17,18 showing that the problem is ubiquitous, sustained, and getting worse.

4. Telephone advice lines and general practitioner collocation

Telephone advice services are popular with patients and may decrease the demand for after-hours GP consultations in some settings,19,20 but have not been shown to reduce ED workload in Australasia.21,22 Establishment of additional GP services, even bulk-billing services near hospitals, does not significantly decrease ED workload either in theory12 or in practice.23

5. Size of emergency departments

Hospitals that provide a local service in areas in which the population is undergoing significant demographic change, such as a large ageing cohort or rapid population growth, may experience ED overcrowding simply because the numbers of patients presenting exceed appropriate ED changes and resources. However, this is rarely the major issue and is rarely reported as the main cause of ED overcrowding. Indeed, studies24 and local experiences have shown that even with very large increases in ED size (eg, doubling cubicle numbers) or function, there is more access block and overcrowding. The most plausible explanation for this is that the extra capacity in the ED allows more patients to be accommodated there awaiting inpatient beds while bed capacity in the rest of the hospital (which has not been addressed) remains unchanged.

7. Consequences of overcrowding

Adverse effects of hospital overcrowding have been described since the birth of modern medicine. In Australasia, access block was first shown to be associated with decreased ED function in 2000,25 and was defined by the ACEM in 2002.3 Worldwide, rigorously conducted studies in different centres have found an association between overcrowding and reduced access to care, decreased quality measures, and poor outcomes.26

Most important are studies, including a number from Australia, that show an increased mortality rate with increasing overcrowding.27-29 Two independent studies from different centres found about a 30% increase in overall early mortality if patients are admitted through overcrowded EDs to overcrowded hospitals.27,28 Annual excess deaths amounted to 13 in one of two hospitals in the Australian Capital Territory29 (13/(0.5 × 320 000 [population of ACT]) = ~ 8/100 000) and 120 among the three major hospitals in Perth28 (120/1.4 million [population of greater Perth] = ~ 8/100 000). Thus, a rate of 8/100 000 is conservatively estimated to correspond to 1500 additional deaths a year in Australia (similar to the road toll29), based on 2003 data. Access block has worsened since.10

Other serious problems associated with ED overcrowding include: delayed time-critical interventions and increased complications (eg, more recurrent myocardial infarctions or episodes of congestive cardiac failure); increased medical error; less frequent and less adequate pain control; prolonged hospital length of stay, further worsening the underlying cause and increased costs per stay; more legal actions and complaints; and severe problems with staff turnover and burnout. ED overcrowding causes ambulance diversion and delays to offloading ambulance patients,30,31 with both financial and service impact on prehospital care. The opportunity cost of lost ambulance resources has not been quantified but is also likely to be high.

Associations between overcrowding and outcomes demonstrated in peer-reviewed studies are shown in Box 3. While there may be some publication bias, there remain no published studies associating overcrowding with improvements in care and very few where it has no effect on care. The association between overcrowding and poor outcomes is accepted to be causative by most medical authorities and all emergency medicine colleges.

It is important to realise that ED overcrowding has serious adverse effects, because there is little incentive to fix a problem if it is not shown to have serious consequences. Routine denials in the media by politicians and bureaucrats that overcrowding has major adverse effects on patient care or outcomes shows that they do not see overcrowding as having serious consequences.


Overcrowding has changed the nature of the practice of emergency medicine. The fundamental issue is the availability of inpatient beds. There is sufficient evidence to convince reasonable authorities that the relationship between overcrowding and poorer patient outcomes is causal. Emergency physicians have a role to play in maintaining the standard of patient care in the face of overcrowding, but most of the solutions to overcrowding and resultant poor outcomes will lie outside the ED. It is vital to know what really does and does not cause access block in order to decide which solutions will work and should be concentrated on, and to avoid perpetuating the myths that abound in this area of policy debate. A summary of the myths and the corresponding facts is provided in Box 4.

3 Adverse outcomes associated with overcrowding and access block in peer-reviewed international literature



Definition of overcrowding


Process measures

Increased ambulance bypass

Emergency department access block


Ambulance delay in chest pain

Divert status (time series)


Increased “left without being seen” rate

National Emergency Department Overcrowding Scale


Staff subjective opinion


Worse waiting time performance

Emergency department access block


Emergency department flow (multiple measures)

Total emergency department boarding* time


Quality measures

Decreased patient satisfaction

Staff subjective opinion


Missed myocardial infarction

Emergency department volume


Delay to reperfusion

Ambulance network diversion (“bypass”)


Reduced adherence to myocardial protocols

Simultaneous trauma cases


Patient length of stay in the emergency department


Delay to antibiotics in pneumonia

Administrative cycle time and performance data


Emergency department occupancy and number needing admission


Multiple measures at triage


Inadequate analgesia (hip fracture)

Emergency department census (occupancy) > 120%


Lower-quality pain management

Multiple measures at triage


Worse process of pain care measures

Emergency department occupancy Emergency department boarders*


Reduced satisfaction (admitted patients)

Individual patient boarding* times


Outcome measures

Increased reinfarction rate

Patient length of stay in the emergency department


Increased incidence of pneumonia in patients who had been artificially ventilated

Patient length of stay in the emergency department


Increased admission length of stay

Patient access block


≥ 6 h in emergency department (intensive care unit survivors)


Increased short-term mortality

≥ 6 h in emergency department (intensive care unit patients)


Emergency department occupancy


Emergency department and hospital occupancy


* “Boarding” is the situation in which patients are kept in the emergency department awaiting inpatient beds.

4 Summary of the myths and facts about emergency department (ED) overcrowding

The myths

The facts

  • Drew B Richardson1
  • David Mountain2

  • 1 Emergency Department, Australian National University Medical School, Canberra, ACT.
  • 2 Department of Emergency Medicine, Sir Charles Gairdner Hospital, University of Western Australia, Perth, WA.


Competing interests:

Drew Richardson’s unit has received funding from the Australasian College for Emergency Medicine to study access block and overcrowding, and both authors have received travel assistance to speak at meetings about access block and overcrowding.

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