The question of who is actually responsible for the decisionmaking in intensive care is an ongoing debate in critical care medicine. Traditionally in Australia the intensive care specialist takes responsibility for all decisionmaking for the patients under their care, and refers to the primary team only for consultation on specific questions, or for specialist services (eg. angiography, surgery, endoscopy etc). This model is supported by our robust (nightmarish, exhausting, arbeit macht frei) training program which produces world-class intensive care physicians. However, the primary team's desire to have active input into the care of their patients is a source of conflict, and it must be acknowledged that many ICUs in developed countries function reasonably well without intensivists.

Question 26 from the second paper of 2007 asked the candidates what they understood by "open" and "closed" ICUs, and what are the advantages/limitations of each. As the pass rate was around 60%, most candidates understood this fairly well. This bodes well for their future practice. Australian ICUs tend to be all "closed", with the exception of private hospitals where it seems the admitting surgical specialist can make (occasionally disastrous) decisions which countermand whatever the staff intensivist has recommended, making it a de facto open model. The reason for such openness is the imbalance of power in private institutions, where the surgeons are dominant revenue-bringers. As the chief money-makers, their influence over clinical decisions tends to be more supported by the executive staff whenever a dispute arises. It is economically more sensible to jettison the troublemaking intensivist then to risk losing the surgeon.

Anyway.  As far as useful resources go, there is some material out there:

• There is a good discussion of this in LITFL
• L.I.G Worthley reflects on this in a 2007 "point of view" article - as he was the probable author of Question 26 from the second paper of 2007, this piece is worth a look.
• Pronovost (2002) - a systematic review
• J.L Vincent (2016) offers a strong argument  for closed ICU systems
• Weissman and Halpern (2016) offer an alternative view
• Guidet et al (2016) offer an analysis which cannot reach a firm conclusion, but which discusses the controversies in a non-partisan manner. For the time-poor candidate, this would the ideal single resource to read before the exam.

Oh's manual has surprisingly little to say on this matter, presumably because in the opinion of the authors the matter is settled. A paragraph is devoted to the issue on page 6, where the Pronovost (2002) review is quoted in support of thew closed model.

Definition of "open" and "closed" ICU models

• An "Open" ICU is one where specialty teams have full admitting rights and where an intensivist is merely "consulting".
• A "Closed" ICU is one where the intensivist is the admitting medical officer and the specialty teams collaborate with ICU staff.
• A "High intensity" staffing model is one which involves either a closed ICU, or a "mandatory consult" situation where the specialty teams might still have admitting privileges to the ICU but every patient must be seen by an intensivist (hence "mandatory"). An alternative is a model where some of the ICU beds are allocated as "closed" and others are "open" and cared for by the specialist teams.
• Most ICUs worldwide are closed. The open vs. closed debate is largely an American thing. In America, half of ICUs don't have any intensivist coverage. In context, this means that even large units would not meet with the CICM accreditation criteria, and would be ineligible to accept trainees for the ICU training program.
• The terms "open" and "closed" are probably misleading and inappropriate, as they imply exclusion and inclusion. Better terms might be "service" ICUs for the open model, and "specialist" ICUs for the closed model.

Advantages of a "closed" ICU

• A "high intensity" model is associated with decreased mortality and ICU length of stay.
• However, at least in the United States a "closed" model does not seem to be associated with any mortality benefit independently of a "high intensity" model (According to a 2008 study by Levy et al as well as a subsequent meta-analysis by the same author). Essentially, it does not matter who the admitting specialist is, so long as the patients have mandatory daily intensivist involvement.
• An intensivist does not need to be on site for the whole 24 hours provided they are seeing every patient daily (a "high intensity" model).
• Focused critical care skills into a critical care environment
• Better coordination of critical care services
• A more cohesive treatment strategy, with better leadership
• More efficient use of resources (some patients do not need admission to ICU, and intensivists are better at triaging these cases)

Advantages of an "open" ICU

• There is no need for an interfering intensivist, which might be favoured by specialist teams
• Primary physicians and surgeons have a better familiarity with their patients, whereas the intensivist has only met them for the first time in the context of their critical illness.
• Primary specialists carry on care after ICU admission, promoting continuity of care
• Much of the workload traditionally associated with ICU specialists in Australia can be outsourced to allied health staff (eg. respiratory care technicians manage ventilation in America because the primary physicians are unwilling or incapable of it; American nurses and physicians assistants can intubate the patients and insert central lines). This can be a cost-saving measure.
• Each time a patient enters or leaves an ICU a hand-over must take place, which is an opportunity for information to be lost or misrepresented.
• Continuity of care may result in improved patient and family satisfaction, as they end up dealing with the same familiar faces rather than having to discuss important issues with a relatively unfamiliar specialist

Evidence in support of the closed model

• Carson et al (1996) found improved outcomes when a medical ICU converted from open to closed. Specdific improvements noted were improved ratios of actual to expected mortality (i.e a crude SMR) and increased nurse confidence with clinical decisionmaking.
• Hackner et al (2009) found an improvement in mortality associated with the closed model in a medical ICU, but no difference in ICU length of stay.
• Ghorra et al (1999) found a variety of improved outcome parameters when a 9-bed surgical ICU converted to a closed model, including improved mortality and a decreased use of dopamine (this study was from the era when low-dose "renal" dopamine was in vogue).
• van der Sluis et al (2011) also found a mortality benefit when their surgical ICU converted to a closed model.

Evidence in support of the open model

• A 2008 study by Levy et al as well as a subsequent meta-analysis by the same author discovered that ICU patients who had an intensivist involved had increased mortality. A more recent (2014) analysis of mortality in 69 centres also failed to detect an improvement in mortality associated with a closed model. How did this happen?
  • The studies was limited to the US
  • Many of the ICUs only involved an intensivist if the specialty team requested their opinion
  • The patients managed by an intensivist were on average far sicker and had more procedures
  • The closed units were probably run by an "internist", i.e. a general physician with no critical care expertise. Brilli et al (2001) found that 56% of American ICUs were run by a person not certified in critical care. Now, you put some FCICMs in there and see what happens.
• Other American authors (Weissman and Halpern,  2016) has pointed out that the evidence for the superiority of a closed model is largely retrospective, and that " units that transitioned to intensivist-led models did not achieve improvements in risk-adjusted mortality in either medical or surgical units"

Some synthesis of the above

• A "closed" ICU model is clearly superior in an environment where critical care training is as evolved as it is in Australia and New Zealand.
• A collaborative approach with primary specialist teams is still essential to promote high quality patient care. In Worthley's words:

We don’t have‘his’ or ‘her’ patients, we have ‘our’ patients, and in the event that the home team feels that there may be aspects of our treatment that require explanation, we are only too happy to discuss this with them — civilly."