The Ptolemaic theory and the Copernican theory: which is the right one in the overcrowding?

Francesco Rocco Pugliese1 MD, Claudia Cicchini2 MD, PhD

1. Medical Director of the Dept of Emergency Medicine, Sandro Pertini Hospital, Rome, Italy

2. Emergency Physician, Dept of Emergency Medicine, Sandro Pertini Hospital, Rome, Italy


Overcrowding refers to greater numbers of patients utilizing an area than that area has the capacity to accomodate. In overcrowding ED physical or personnel capacity is exceeded by the number of patients waiting to be seen, undergoing assessment and treatment, and waiting for departure. Both external and internal factors contribute to an ED environment vulnerable to patient overflow and inefficiency: whether the external or internal ones are the more important and changeable is the present dilemma.
The ED overcrowding literature was reviewed using PubMed. This article is a synthesis in support of the central role of the ED staff in reducing the ED overcrowding.
The leadership at the Department leads to the engagement of physicians and multidisciplinary frontline staff and organizational culture changes, that are critical factors for successful implementation and sustainability of the quality improvement. The need to address ED overcrowding is no longer an issue of resource management but of patient safety. ED crowding is a whole hospital problem and capacity or efficiency improvements could mitigate emergency care delays. Improvement of ED capacity is not a solution: in according to the Parkinson’s law patients expand to fill the space available and the queuing continues.


overcrowding, emergency department, throughput, length of stay.


According to Fatovich the Emergency Department (ED) overcrowding is the biggest impediment to the delivery of timely and adequate emergency care1-4 . It is associate with increased inpatient mortality, length of stay, and costs for admitted patients5,6 . It also has un emotional impact on patients and staff. Staff morale, physicians productivity and teaching time decline with increased patient volume7. Thus the research of the causes and solutions is widespread. The first step is the consensus in overcrowding definition.
Although there are several ED crowding estimation tools reporting varying levels of crowding, each has different definition of overcrowding, none of which is considered the gold standard. A review of the literature suggests that overcrowding is defined similarly across the following three ED crowding estimation toools: National Emergency Department Overcrowding Score (NEDOCS), Community Emergency Department Overcrowding Score (CEDOCS), and Severely-overcrowding Overcrowding and Not-overcrowding Estimation Tool (SONET). NEDOCS is by far widely used tool for ED crowding measurements8. However NEDOCS was derived in the moderate to high volume ED setting and its ability to determine ED crowding in a median-low volume ED has not been validated. CEDOCS was derived in ED ranging from low to high volume and has been deemed appropriate for crowding measurement across a wide range of ED annual volume, but lacks external validation9. SONET was derived using similar methods as NEDOCS and validated externally at different EDs where the same group provides administrative operation and management of the study ED10.
So far the main question has been the hospital centrality and various efforts to reduce ED overcrowding have been proposed over the years11, but many healthcare organizations experience high failure rate of sustained change execution. Is this another Ptolemaic theory?

The basic mathematical models of the universe

The Ptolemaic system is a mathematical model of the universe formulated by the Alexandrian astronomer and mathematician Ptolemy about AD 150 and recorded by him in his Almagest and Planetary Hypotheses. The Ptolemaic system is a geocentric cosmology; that is, it starts by assuming that the Earth is stationary and at the centre of the universe. The “natural” expectation for ancient societies was that the heavenly bodies (Sun, Moon, planets, and stars) must travel in uniform motion along the most “perfect” path possible, a circle. However, the paths of the Sun, Moon, and planets as observed from the Earth are not circular. Ptolemy’s model explained this “imperfection” by postulating that the apparently irregular movements were a combination of several regular circular motions seen in perspective from a stationary Earth. The principles of this model were known to earlier Greek scientists, including the mathematician Hipparchus (c. 150 BC), but they culminated in an accurate predictive model with Ptolemy. The resulting Ptolemaic system persisted, with minor adjustments, until the Earth was displaced from the centre of the universe in the 16th and 17th centuries by the Copernican system and by Kepler’s laws of planetary motion. Copernican system in astronomy is a model of the solar system centered on the Sun, with Earth and other planets moving around it, formulated by Nicolaus Copernicus, and published in 1543. It appeared with an introduction by Rhäticus as De revolutionibus orbium coelestium libri VI. The Copernican system gave a truer picture than the older Ptolemaic system, which was geocentric, or centered on Earth. It correctly described the Sun as having a central position relative to Earth and other planets. Copernicus retained from Ptolemy of Alexandria, although in somewhat altered form, the imaginary clockwork of epicycles and deferents (orbital circles upon circles), to explain the seemingly irregular movements of the planets in terms of circular motion at uniform speeds. Translating these concepts in the emergency system, until now the Hospital has been “the Earth” of the Ptolemaic theory with all the operative units revolving around it with orbital circles. Nowadays we suggest that the emergency department is “the Sun” in the middle of the system with all the remainder revolving around.

Ed setting

The main cause of ED overcrowding is hospital access block with prolonged boarding of inpatients in EDs12-14. In 2003 Asplin et al proposed a model based on three items, input, throughput and output15: the first is the excessive contemporary access of patients in the ED, the second is related to insufficient staff and/or delay in the diagnostic services, and the third is related to delayed discharges from the wards, reduction of the hospital beds and the excessive number of patients to be admitted. In our series the not urgent patients (i.e. white code) amount to 2.5% of all the patients, thus they are not the main cause of ED crowding. Actually the inability to transfer emergency patients to inpatient beds and resultant boarding of admitted patients in the ED are the root causes of ED crowding: thus the ED crowding is the symptom of a crowded hospital rather than of the inappropriate ED use. The policy of dissuading the use of ED for not urgent pathology is not decisive. The demand that seems inappropriate is actually the counterpart of a health system unfit to adapt to social modifications. When the resources are limited, the inpatient beds are a fixed resource destined to both ED patients and hospitalized patients. The priority must be for patients with major assistance needs: the ED patients need diagnostic tests and therapeutic procedures mainly in the first 24 hours, the inpatients often are waiting for home care or chronic hospitalization. Thus an equitable heath resources allocation should impose a diversion from the inpatient waiting for the discharge to the ED patient waiting for the diagnostic therapeutic procedures.
Only some of the managerial elements are controlled by the ED physicians: the use of standardized protocols, the appropriate prescriptions, the prompt activation of outpatient pathways, the correct coding of the diagnoses. Most of the protagonists of the care process are external operators under the control of decision makers who don’t consider the ED a priority. If hospital programs close bed for budgetary reasons, to allow staff vacation (seasonal closures) or because of sick calls, they do so expecting that the ED will simply hold more patients. If an inpatient discharge is delayed from 9 to 16 hours, one more ED stretcher will be blocked for the day. Actually the decision makers should be interested to reduce the long stay of patients in the ED as risk management of the patients security.
If ED boarding is an acceptable response to demand-capacity challenges, there is little need to develop real flow solutions. Solution must be searched in proactive demand-capacity planning, queue management and limiting the ED role as a capacity buffer14-16.
In the last two decades health leaders have addressed ED overcrowding by introducing flow initiatives and diversion strategies. None have had a sustained effect and shifting ED patients to strained inpatient programs has proven difficult. The rising population, age and patient complexity have created demand unmatched by new capacity. Alternative level of care patients with no viable discharge destination have increased, compromising inpatient capacity, just as boarding inpatients compromise ED capacity. When efficiency gains create capacity within a program, this tend to be allocated to mitigate internal operational pressures with only little impact on boarding delays, which is still viewed as primarily an ED problem17.
Natural variability (for example seasonal influenza) and scheduled variability (for example surgical admission clustered in first days of the week) generate large fluctuations in bed demand, aggravated by variable hospital length of stay by service and provider. Seasonal bed closures, reduced discharge rates in weekends, diminished consultant capacity and lack of palliative or long term care intake outside mean that system capacity is unmatched to patient demand. Uncontrolled variability demand and capacity create more severe and prolonged overcapacity situations during which ED boarding become extreme.
The need to manage more patients with fewer available stretchers has driven profound changes in emergency care models: almost half high-acuity patients are allocated in alternative locations, these areas are typically crowded and offer less nursing care, little monitoring, limited privacy, and often compromised patient examination, thus in a patient’s opinion this could reflect suboptimal care. After all in daily practice ED stretchers made available through process innovation are immediately occupied by boarding patients.


Up until now many administrators have come to view boarding as inevitable, a form of normalized deviance. Successful enactment of change in healthcare organizations requires persistent involvement of leadership, culture change anche physicians engagement.
The increased adverse effects due to ED overcrowding is seen in patients of different ages, with varied conditions and at all time of year, hence the need to address ED overcrowding is no longer an issue of resource management but of patient safety.
ED crowding solving is a complex enterprise, but the basis must be the view that it’s a whole hospital problem and capacity or efficiency improvements could mitigate emergency care delays. Improvement of ED capacity is not a solution: paraphrasing the Parkinson’s law, patients expand to fill all the space available and the queuing continues.


  1. Fatovich DM: Emergency medicine. BMJ 2002, 324: 958-62.
  2. Peltan ID, Bledsoe JR, Oniki TA, et al. Emergency department crowding is associated with delayed antibiotics for sepsis. Ann Emerg Med 2019; 73: 345-355.
  3. Schull MJ, Vermeulen M Slaughter G, et al. Emergency department crowding and thrombolysis delays in acute myocardial infaction. Ann Emerg Med 2004; 44:577-585.
  4. Wu D, Zhou X, Ye L, et al. Emergency department crowding and the performance of damage control resuscitation in major trauma patients with hemorrhagic shock. Acad Emerg Med 2015; 22: 915-921.
  5. Tsai MT, Yen YL, Su CM, et al. The influence of emergency department crowding on the efficiency care for acute stroke patients. Int J Qual Health Care 2016; 28: 774-778.
  6. Sun BC, Hsia RY, Weiss RE, et al. Effect of emergency department crowding on outcomes of admitted patients. YMEM 2012; 61: 505-611
  7. Derlet RW, Richards JR. Overcrowding in the nation’s emergency departments: complex causes and disturbing effects. Ann Emerg Med 2000; 35: 63-8.
  8. Weiss SJ, Derlet R, Arndahl J, et al. Estimating the degree of emergency department overcrowding in academic medical centers: results of the National ED Overcrowding Study (NEDOCS). Acad Emerg Med 2004; 11: 38-50.
  9. Weiss SJ, Rogers DB, Maas F, et al. Evaluating community ED crowding: the Community ED Overcrowding Scale study. Am J Emerg Med 2014; 32: 1357-1363.
  10. Wang H, Robinson RD, Garrett JS, et al. Use of the SONET Score to evaluate high volume emergency department overcrowding: a prospective derivation and validation study. Emerg Med Int 2015:401757. Epub 2015 June 8.
  11. Honigman L, Schuur J, Cjambers J, et al. Adoption of interventions to reduce emergency department overcrowding  from 2007 to 2010. Ann Emerg Med 2014; 64: 574-575.
  12. Moskop JC, Sklar DP, Geiderman JM, et al. Emergency department crowding, part 2 – barriers to reform and strategies to overcome them. Ann Emerg Med 2009; 53: 612-617.
  13. Villa-Roel C, Guo X, Holroyd BR, et al. The role of full capacity protocols on mitigating overcrowding in EDs. Am J Emerg Med 2012; 30: 412-420.
  14. Rabin E, Kocher K, McClelland M, et al. Solutions to emergency department “boarding” and crowding are underused and may need to be legislated. Health Aff 2012; 8: 57-66.
  15. Asplin BR, Magid DJ, Rhodes KV, et al. A conceptual model of emergency department crowding. Ann Emerg Med 2003; 42: 173-180.
  16. Innes GD. Access block and accountability failure in the health care system. CJEM 2015; 17: 171-179.
  17. Ramanujam R, Rousseau D. The challenges are organizational not just clinical. J Organiz Behav 2006; 27: 811-827.