Web page on Queues in Health Care


1)   Accumulating Priority Queue Health care systems set delay limits for patients to be seen based solely upon clinical need. The idea behind the APQ is that these targets may not be met when using a classical priority queue service discipline, in which a customer of higher priority is always seen before one of lower priority. The APQ philosophy is that the priority when selecting the next patient for treatments should, in many cases, reflect both the patient’s acuity and how long they have waited. The work we have completed on the APQ enables a health care decision maker to do just that, with the goal being to better comply with the clinical delay limits.

i)   London Free Press Article: Geeks speed hospital wait times

ii)   Western News Article: New findings mean more flexibility in the delivery of timely health care

iii)   Open Access Article: Waiting time distributions in the accumulating priority queue


2)   Inequity in Transplant Wait Times Many transplant waiting lists work on the basis of blood type compatibility. ABO-compatible transplantation allows organs of one blood type (most commonly the universal donor blood type O) to be given to a compatible donor group. This leads to longer wait times for O recipients, who require O organs. ABO-identical transplantation insists that all organs should go to patients of the same blood type. This leads to unacceptably long wait times for patients of the less frequent blood types, B and AB, which represent 9% and 3% respectively of the Canadian blood mix. We have proposed the following approach to aim for comparable wait times for recipients  of all blood groups.

i)   London Free Press Article: Blood types affect transplant wait times

ii)   Open Access Article: A queuing model to address waiting time inconsistency in solid-organ transplantation

iii)   Click HERE to view the research poster on “Addressing Waiting Time Inconsistencies due to ABO Status in Transplantation


3)   Short Stay Units / Medical Assessment Units and their impact on Emergency Department Flow   One of the major causes of ED / ER congestion is the lack of a suitable ward bed at time of transfer, due to overcrowded wards. Various hospitals have tried to respond to this by developing specialized units where some or all urgent  ED patients can go. Generically, Short Stay Units are places where all ED patients to be admitted can go, until such time as an appropriate ward bed becomes available. Medical Assessment Units try to identify patients possessing certain predictable characteristics, for whom a 24-to-36 hour stay may preclude the need for admission, and a chance for observation and intervention in the interim.

The problem of the connectedness of the Emergency Department, Acute Care wards, Rehabilitation Facilities  and Long-term Care is well known, and often leads to patients waiting upstream in an inappropriate bed for downstream facilities. In Canada, these are known as “Alternative Level of Care” (ALC) patients. Mike Carter, Greg Zaric and I wrote an article regarding ALC titled ‘Downstream bottlenecks: The hidden cause of ER congestion’ in the March 2011 issue of Western News.

i)   PLEASE NOTE: An open access article regarding Short Stay Units will be posted here soon.

ii) Western News Article: Downstream bottlenecks: The hidden cause of ER congestion (see page 5)


I am a queueing theorist with particular interest in health care wait times, both in their own right, and as a field motivating further research developments in queues (such as the Accumulating Priority Queue (APQ) topic below). My research works both from the health care problem to find a specific solution, as exemplified by my work on inequity in transplant wait times, as well as from the theoretical end, as with the APQ. For those interested in the basics of how queueing theory can help one understand health care wait times, I have prepared two videos: one in English (et l’autre en français) on key principles of system congestion. These links can be found below.

Photo courtesy of Research to Reality (R2R)

          courtesy of Research to Reality (R2R)


VIDEO: How Queueing Theory Can Improve Wait Times (La théorie des files d'attente et son impact sur les temps d’attente)

                 English version: https://www.youtube.com/watch?v=SRqI_Ntrcnc

                 Voici la version originale en français: https://www.youtube.com/watch?v=KNLxLWV_IYM