therapeutic goal cannot, or is unlikely, to be achieved within the framework of the ICU, it is possible to not start (withhold) or to end (withdraw) the therapy. For example, a decision to withdraw ventilation or dialysis may be acceptable if there is little or no expected benefit. 1 Such decisions should be made in a team with the involvement of the patient and relatives. Intensive care teams around the world have adopted these standards over the past decades and have found ways to implement them, often with input from clinical ethicists.
In crisis situations, such as pandemics, the admission and decision-making processes can change significantly if there are insufficient resources for care, as each decision taken for one patient may affect the decision-making for other patients. Triage in crisis situations comprises the selection of patients who will receive treatment, meaning that those not selected may not receive treatment from which they could benefit. The basic values underlying triage decisions in crisis situations generally include prioritization of medical urgency, capacity to benefit and fairness. 2 For COVID-19, various guiding principles have been suggested, in particular the maximization of benefit and justice, including considerations such as treating people equally, promoting instrumental value, and giving priority to the worst-off. 3 Triage decisions thus include medical factors, such as the severity of the health condition and likely outcome, as well as fairness in resource allocations and ethical issues.
Maximizing benefit under conditions of scarcity can mean different things: it could refer to saving as many people as possible, to saving the greatest possible number of life years, or to saving the greatest amount of quality-adjusted life years (QALYs), with the resources available. Depending on which criterion is applied, resource allocation will look quite different. Saving as many life years as possible would favour young people, whereas maximizing QALYs would favour those with a capacity to lead long, healthy, independent lives.
Maximizing benefit gives back a sense of control in a desperate situation: although it may be impossible to help all patients, it is still possible to save those who will benefit most. 4 The application of this guiding principle is not straightforward, however, and depends not only on how the medical assessment of benefit and its probability are operationalized but also on sociocultural and ethical norms concerning which benefits matter. 5 Defining benefit for application in triage in a pandemic, for instance, requires weighing short-term against longterm prognosis, including the impact of age and comorbidities as potential triage criteria. The question of whether people who are of instrumental value (e.g. healthcare workers) should be prioritized 6 is an additional consideration compatible with the overall idea of maximizing benefit. In order to enable the necessary therapeutic decisions to be made consistently and fairly, criteria for maximizing benefit in triage situations must be clearly and transparently defined.
Although the focus here is on triage, it is important to note that in crises such as the SARS-CoV-2 pandemic, benefit can most effectively be maximized not at the level of triaging those who have fallen seriously ill but at the population level, where disease prevention in the general and vulnerable populations, and in the healthcare workforce is key. This includes ensuring that measures are in place to protect the most vulnerable in society, who have often traditionally been marginalized or in whom the social determinants of health have enhanced their vulnerability, as well as to support treatment teams with appropriate protective equipment (PPE) and potential prioritization for vaccinations, if available. A reward for individual commitment, such as prioritization of vaccination for healthcare workers, or allocation of the most effective masks (FFP2, N95) to those with greater exposure to respiratory droplets, can motivate people to contribute in a crisis. 7
The principle of justice in triage can be understood to mean that all patients with a comparable prognosis should have equal access to necessary medical care in the event of a crisis, based on predefined medical and ethical criteria. There is some controversy as to how to proceed in a next step, regarding the allocation of limited therapy to patients with the same prognosis. Whereas some have argued for a 'first come, first served' rule, others favour a lottery or randomization in order to avoid disadvantaging those who arrive later for reasons that are beyond their control (e.g. a delayed diagnosis). 8
Other criteria for distribution, such as preferential treatment based on merit, are often rejected based on objections such as arbitrariness and the societal implications of connecting survival to certain distinctions or social roles. 9 Giving priority to the worst-off, another potential distribution criterion, is hard to reconcile with the idea of maximizing benefit, assuming the worst-off are not or at least less likely to benefit. Triaging guided by benefit maximization would rather favour the group that is severely affected and needs treatment urgently but is still well enough to be likely to profit from treatment. In fact, the conventional triaging process (e.g. in mass disaster) explicitly advocates excluding those who are least likely to benefit from treatment as well as those not in urgent need of care if resources are constrained.
Whereas justice in general invokes equality, meaning that everyone should receive the same treatment, equity-another concept relevant to triage-emphasizes the need to avoid discrimination, and to address 'remediable differences among groups of people, whether those groups are defined socially, economically, demographically or geographically or by other means of stratification'. 10 Equity may mean different treatment for different needs, which is challenging to achieve in the context of triage, where advanced age and comorbidities may impact survival and benefit maximization.
Given the multitude of potential criteria for operationalizing justice in concrete allocation decisions, procedural approaches have been suggested, to work towards a consensus that is acceptable to all those affected by the decisions to be taken. 11
Overall, two major principles constitute the normative basis of triage guidelines: benefit maximization and justice. For the purpose of our analysis we will focus on equity and fair process, and list any additional considerations mentioned in the guidance texts. 12
Italy was one of the first countries to experience a large number of patients who were critically ill at the same time, which led to a shortage of ventilators and intensive care resources. 13 Although there may be nuances to this claim and more evidence is needed, access to ventilation therapy in COVID-19 was by default perceived as a matter of life or death, so that scarcity of respirators and ICU beds received special attention. 14 In the initial stages, overwhelmed by the acute crisis, care allocation decisions had to be taken in the absence of formal triage guidelines. This led to much distress on the part of individual clinicians and teams who continuously had to make alloca- In the following, we identify and explore ethically relevant similarities and differences among the guidelines as well as some inconsistencies (see Table 1 
Reference to the principle of justice can be found in all guidance. The principle of equality is invoked by stipulating that triage decisions should apply to all patients with the same prognosis, with or without COVID-19. In a pandemic with a mass influx of sick people and limited resources, consideration must be given to how to treat people equally. 37 Equitable access to healthcare is described in the sense that there should be no discrimination, i.e. no unjustified unequal treatment, on grounds of characteristics such as age, race, sexual orientation, disability or socio-economic status. depending on the extent of scarcity. In order to continually adapt treatment strategies to current resources and to an individual patient's condition, regular re-evaluation is recommended in all documents.
Various scores are recommended to assess mortality risk and to estimate the probability of survival of the acute event. Some guidance texts use the sequential organ failure assessment score (SOFA) score (DEU, ZAF), while others discuss or reject the SOFA score be- 
All guidance documents agree that age as a criterion alone, despite its objectivity, is not enough for a triage decision. Age must be correlated with comorbidities and prognosis. However, the Italian recommendations comment that an age limit 'may ultimately need to be set' for intensive care therapy. The Swiss guidance also stipulates that in the event of an absolute scarcity of intensive care capacities (where no free ICU beds are available), people over 85 years of age should not be admitted to the ICU. Prioritization of younger patients over older patients is described in the guidance from Australia/New Zealand, South Africa and Canada in cases of similar ranking, as a 'tiebreaker'. 
All guidance documents mention that the patient's wishes regard- 
All guidance discusses the possibility that, depending on the prevalent resource constraints, therapy may need to be restricted.
Withholding some treatment does not mean withholding all therapy, and even intubation with ventilation does not mean that survival is guaranteed. The decision for or against artificial ventilation is also based on knowledge of the potential benefits and harms for a given individual. Some texts explicitly mention futility as a criterion for re- 
With the exception of the Belgian recommendations, which stress the avoidance of disproportionate care and the maximization of ICU capacity as a key concern, guidance documents focus on maximizing 
Professional societies have done a remarkable job in coming up with guidance so quickly. Some inconsistencies, tensions and vagueness remain, partly in controversial areas such as the role of age as prognostic factor for short-and/or long-term survival, or determining membership of a priority group or criteria to be used as a tie- Hardly any of the guidance documents mention age as a hard criterion for triage decisions, and all aim to avoid discrimination.
However, most documents cite long-term prognosis as a decision criterion for triage, which inherently include age and comorbidities as important contributing factors. The frailty scale-a measure of comorbidities in the elderly-is recommended as a tool to establish prognosis by various guidelines. Taking into account comorbidities favours not only younger over older patients but also non-disabled over disabled people. In addition, the social determinants of health place people with lower socio-economic status and certain ethnic groups at a double disadvantage, as they not only suffer more often from comorbidities but also are affected by increased exposure to and mortality from COVID-19. 48 There is therefore a clear tension between maximizing benefits and aiming at non-discrimination of groups who are characterized by more fragile health. Focusing on short-term survival as a first-order criterion and invoking other criteria that are more susceptible to systematically disadvantaging certain patient groups (such as long-term survival) could ease tensions in cases of a tiebreak.
Another interesting finding is the absence of explicit quality of life considerations among (benefit-maximizing) triaging criteria, which are mainly focused on survival in many guidance texts. This is understandable given the intention to avoid discrimination, which a quality of life criterion would likely imply. At the same time, it can be expected that prospective quality of life after an ICU stay would be a key criterion for individuals in their decision-making for or against ICU treatment, and this would also affect benefit-maximization strategies. The consideration of advance directives in the triage process may be a way to address this discrepancy.
Some guidance mentions the prioritization of health workers as an ethical principle, not only with a view to their instrumental value but also as a matter of reciprocity, acknowledging their readiness to help others. This statement should be critically reviewed with regard to justice and the principle of treating everyone equally, as non-health professionals may have exposed themselves in an altruistic manner but would not get preferential medical treatment. 
We gratefully acknowledge the Käthe-Zingg-Schwichtenberg Fond of the Swiss Academy of Medical Sciences, which supports Susanne
Jöbges' work at the interface of ethics and intensive care.
The authors declare no conflict of interest. 