Marie-Léandre Gomez
email: gomez@essec.edu

Marie Kerveillant
email: kerveillant@essec.edu

Matthieu Langlois
email: matthieu.langlois@me.com

Nicolas Lot
email: nicolas.lot@edf.fr

Mathieu Raux
email: mathieu.raux@aphp.fr

Organizational innovation under constraints: the case of Covid patients' flow management in Parisian Hospitals

The COVID crisis has put hospitals under great stress over the past two years and some institutions came close to their breaking points. This has often forced decision makers and the entire institutions to change their practices and the organization of the hospitals in order to continue operating despite limited resources. It has also led some hospitals to develop and implement organizational innovations. This article is based on a qualitative case study analyzing the case of a crisis unit that has implemented various innovative medical and organizational actions in order to manage the flow of resuscitation covid patients in a large group of hospitals in Paris. This team has implemented a new evaluation scale of resuscitation needs in order to better manage quantitatively and qualitatively the patients' flow; it has defined medical criteria to select the patients eligible for transfer; it has organized one hundred patients

Organizational innovation under constraints: the case of Covid patients' flow management in Parisian Hospitals

transfers to other hospitals' intensive care units, in and out of the region, involving private hospitals and private ambulances for a new collaboration.

The case allows us to understand innovation in the midst of an extreme situation, when material and human resources are highly constrained, and with very strong time pressure. We highlight the importance of implementing flexible organizational processes and staffing the crisis team with physicians and nurses with specific and complementary skills and experience in flow management and crisis situations.

Introduction

Most innovations in hospitals take place over long periods of time, whether they are scientific innovations, innovations in patient care 1 , or managerial innovations [START_REF] Swan | Mobilizing knowledge in healthcare: challenges for management and organization[END_REF] . The COVID crisis has put hospitals under great stress over the past two years and some institutions came close to their breaking points. This has often forced decision makers and the entire institutions to change their practices and the organization of the hospitals in order to continue operating despite limited resources. We have identified a case of innovative organization in Parisian hospitals (APHP), corresponding to significant organizational breakthroughs, which have made it possible to temporarily modify practices in the hospitals concerned and to stimulate collective dynamics that are essential in times of uncertainty and tension. These innovations have made it possible, at a given moment, to provide a new and disruptive solution to the problems encountered. They deal with the flow of patients in intensive care, at the heart of the COVID crisis. We analyze this case trying to answer the following research question: how to develop and implement organizational innovations under strong resource and time constraints?

The case presented here allows us to understand this issue in the midst of an extreme situation: the COVID crisis, when material and human resources were highly constrained, and with very strong time pressure. We highlight the importance of implementing flexible organizational processes and of carefully staffing the crisis team with doctors and nurses having complementary competences, and in accordance with the needs of the situation. In particular, we stress the unusual and fruitful integration of a tactical physician within the team.

In the first part, we define crises and extreme situations in hospitals and refer to the first analyses conducted on managerial and hospital innovations during the Covid crisis. Then, in the second part, we present the empirical study. In the third part, we analyze the factors that enabled these innovations and discuss their contribution to a better understanding of hospital innovation.

Innovation in crisis times and extreme situations

What is commonly referred to as "COVID crisis" is actually both a crisis and, above all, an extreme situation according to the criteria proposed by management research. A crisis is characterized by an exceptional, sudden and rapidly escalating event that leads to the development of a process of high turbulence [START_REF] Roux-Dufort | Is Crisis Management (Only) a Management of Exceptions?[END_REF] . Faced with a crisis, teams often find themselves stunned and saturated, and find it very difficult to grasp the event as it is happening [START_REF] Wolbers | Introducing a Fragmentation Perspective on Coordination in Crisis Management[END_REF] . Disasters can then occur, when teams are unable to grasp the meaning of the situation, they often fail to interpret the course of the event [START_REF] Weick | The Collapse of Sensemaking in Organizations: The Mann Gulch Disaster[END_REF] .

In order to deal with the crisis, there is the need to "change the software" 6 , to move from a paradigm of operational routine to a paradigm of attention to the signals, even weak ones, sent by actors but also by the external environment. Teams must be prepared to demonstrate acute situational awareness and to operate with a high degree of autonomy and flexibility while remaining finely coordinated with their networks and the rest of the organization. [START_REF] Weick | Managing the Unexpected: Sustained Performance in a Complex World[END_REF] In the context of the covid crisis, the interviews conducted with professionals in the sector [START_REF] Dumez | Le système hospitalier français dans la crise Covid-19[END_REF] show all the experiences of these professionals in the face of the first wave and note the difficulties in interpreting and qualifying the crisis: the suddenness of the deterioration and the acuteness of the situation; its unexpected nature; the difficulty in framing it and the unpreparedness of the minds which made it difficult to understand the crisis; there was a need for strong and adequate leadership [START_REF] Abdi | Role of hospital leadership in combating the COVID-19 pandemic[END_REF] .

The crisis is an abnormal situation, not meant to last. However, the "Covid crisis" started in French hospitals in mid-February 2020 and lasted several months before slowing down and starting up again, with a long-time span. Therefore, its characteristics lead us to turn to the literature on extreme situations to refine our understanding of the "Covid crisis".

An extreme situation is highly exceptional, evolving, uncertain, and risky [START_REF] Lièvre | Management of Extreme Situations[END_REF] . Major crises can be part of it. However, some organizations evolve permanently in extreme situations, such as polar expeditions, air force aerobatic teams, or police intervention teams. Operating in extreme contexts does not necessarily mean that teams are regularly confronted with a crisis. However, these teams require heightened vigilance to detect problems as early as possible, frequent training practices and significant improvisational and adaptive skills [START_REF] Bouty | Coordination in extreme situations[END_REF] . Given their high reliability and low accident rate, they can be considered as high reliability organizations or HROs [START_REF] Adrout | Interagir pour improviser en situation de crise. Le cas de la canicule de[END_REF] . For some HROs, the extreme situation can mostly be interpreted as a necessary control of risk. The risk is at the same time carried by the technicality, the procedures and the human being. The organization of an operating room must therefore be an HRO in order to avoid accidents and any form of crisis, but also to find agile responses in the event of a problem. This is the case of Trauma centers, also presented as fast-responses organizations operating in extreme situations [START_REF] Faraj | Coordination in Fast-Response Organizations[END_REF] . These organizations facing extreme situations can be sought as laboratories for innovation.

Extreme situations are then experienced rather as phases of intense experimentation, involving risks and a lot of uncertainty, but which are an obligatory passage to accomplish technological or human feats. This is for instance the case of the first heart transplants. Teams that have prepared themselves for a long time, having evolved in these unknown situations, draw an undeniable benefit afterwards: the extreme situation can be considered as a formidable moment of individual and collective learning.

Many observers consider that hospitals do not have enough of a crisis management culture.

They are less prepared for crises than organizations in other sectors, according to the very words of the medical directors of crisis of the Paris Area hospitals [START_REF] Riou | Retour d'expérience sur la direction médicale de crise à l'Assistance publique-Hôpitaux de Paris pendant la crise Covid-19[END_REF] . This situation is longstanding and predates the COVID, as shown by the difficulties faced by hospitals in the Paris' region during the 2003 heat wave, and the different ways in which they improvised to deal with the urgency of this crisis [START_REF] Adrout | Interagir pour improviser en situation de crise. Le cas de la canicule de[END_REF] .

In the context of the first wave of Covid 19, hospitals and especially resuscitation and intensive care departments had local responses, often very different from one institution to another.

Facing an unprecedented situation requiring the absorption of an unusual flow of patients in a very short time, many hospitals were forced to rethink their organization and managerial practices. As the adaptation of the usual methods appeared to be ineffective, these establishments or services were placed in a mode of "forced innovation" [START_REF] Nobre | L'hôpital pendant la Covid-19 : innovations, transformations et résiliences[END_REF] and created new regulation devices; reorganized patient reception by differentiating Covid and non-Covid patient flows; transformed beds in other departments into Covid + units; transferred patients in other regions; built military field hospitals… In healthcare crisis management, disaster physicians have always been at the forefront. Disaster physicians are specialist doctors dealing with and preventing collective emergencies, disasters and exceptional health situations, particularly in the field of emergency assistance and care for victims. They are in the frontline after earthquake, terrorist attacks, massive flow of refugees.

They can be specialists in emergency medicine, surgeons, anesthesia-resuscitation, … with a specific complementary training for collective emergencies. Among disaster physicians, tactical physicians are those doctors integrated in the intervention forces of the police, the army, the fire brigades. In the performance of their duties, a fundamental activity is to coordinate and collaborate with other medical services, especially hospital services, particularly in preparation [START_REF]Service Medical du Raid. Tactical emergency medicine: lessons from Paris marauding terrorist attack[END_REF] . During terrorist crises, particularly when attacks are carried out on several sites at the same time, or during natural or industrial disasters, all the emergency services work at the same time, and in parallel with the fire department, police and hospital structures [START_REF] Dulion | Gestion de crise intrahospitalière face à la menace terroriste[END_REF] .

Coordination must therefore be total with a global strategy, not focused on upstream or downstream but on the entire upstream flow, in situ capacity and downstream flow. These medical teams face process discontinuity, increasing ambiguity of decisions, important interdependencies, which make coordination within the team and between teams and sites more complex, and finally a global understanding away from cleavages and self-sufficient management [START_REF]Service Medical du Raid. Tactical emergency medicine: lessons from Paris marauding terrorist attack[END_REF] .

On the other hand, tactical physicians continue to practice a more traditional medical activity in hospitals, military, public and private medical structures. Thus, several hospitals have atypical profiles of tactical doctors or nurses within their team. Tactical doctors can thus maintain their conventional medical practice but also remain in phase with the organization of hospital services and culture. Some hospital services have developed new practices in crisis management thanks to the participation of these physicians. In the context of the covid crisis, these physicians were particularly mobilized, as presented in the case hereafter.

Dynamo case

This case was selected among various cases of organizational innovation in French hospitals, as a paradigmatic case with insightful elements [START_REF] Stake | The art of Case Study Research[END_REF] . It advances our understanding of organizational innovation under time and resources constraints. We adopted an interpretativist [START_REF] Sandberg | How do we justify knowledge produced within interpretive approaches?[END_REF] approach, based on the representation that the actors make of reality.

The context: Paris Sorbonne hospitals resuscitation for Covid patients

Paris Sorbonne hospitals are part of the global Paris Hospital (Assistance-Publique des Hôpitaux de Paris). Paris Sorbonne groups seven hospitals in Paris : Tenon, Saint-Antoine, Rothschild, Armand Trousseau, Charles Foix, and La Pitié-Salpêtrière University Hospital.

On March 19th 2020, the Crisis Medical director was appointed for all Paris hospitals and, under his responsibility, the Crisis Medical director for the Paris Sorbonne hospitals. This director had a long experience on Crisis management since Paris 2015 terrorist attacks: he had been setting up procedures and training on crisis management with police tactical doctors. He requested the head of the police tactical forces with whom he had collaborated for years to coordinate a group in charge of managing, optimizing and accelerating the flow of "Covid+" patients: i.e. those presenting signs of major severity and requiring heavy resuscitation. The objective was to guarantee the quality of care for all Covid+ patients requiring intensive care and therefore to be able to accommodate a much larger number of patients than the available places in the intensive care unit allowed. This crisis unit was not foreseen in any plan built before the crisis. Two other anesthetic-resuscitation doctors and two head nurses, specialized in the coordination for organ transplants, joined the unit. They decided to call this unit Dynamo, referring to the operation to evacuate British troops from European soil in June 1940 [START_REF] Langlois | Cellule de coordination des flux sortants des réanimations en période de Covid 19[END_REF] .

One author participated in the unit observed. Another author was involved in the governance of crisis management in this hospital. Other authors completed interviews via zoom or face-toface and followed crisis unit meetings during which the use of this unit was pushed. The median age of the patients proposed for transfer was 62 years.

Dynamo team and organizational innovation under constraints of time and resources

Dynamo was activated on

In order to maintain a permanent capacity for patients requiring resuscitation and to guarantee the quality of care for all Covid+ patients, the hospital crisis unit decided to create a flow between the resuscitation units, which was completely new for the departments involved. It was based on the principle that not all Intensive Care Units have the same level of expertise. Indeed, recently transformed units cannot reach in a few days the same performance as a multipurpose resuscitation team, expert in respiratory distress syndrome. Therefore, the hospital crisis unit team has proposed that patients whose clinical condition does not require the highest level of expertise, because it has improved for example, be transferred to less specialized units. As the crisis medical director summarizes, the idea was to "fit a 10-litre can into a 5-litre can". Thus, the strategy of the Dynamo cell was to organize a flow of patients within the intensive care unit, so as not to reach the breaking point and thus have to exclude certain patients from care.

To do this, the hospital crisis unit decided to sequence the resuscitation pathway into three different levels, from traditional heavy resuscitation (intubation, artificial respirator, possibly dialysis, patient on the stomach, etc.), to lighter resuscitation, especially for patients who are improving significantly. The criteria to be eligible for transfer were: intubated for at least 48 hours, no prone position for at least 24 hours, Fi02<60%, hemodynamic support by noradrenaline <1mg/h. Outside of a crisis situation, the patient is managed in the same place for the entire resuscitation course. Sequencing this resuscitation course has made it possible to direct patients requiring lighter resuscitation to adapted structures, freeing up, in turn the heaviest resuscitation places, which are also the rarest. The Dynamo unit had to have reliable information, in real time, on all the heavy resuscitation beds in its area. This information needed to be permanently updated, as some acute care beds were being transformed. Dynamo mobilized the intensive care units, recovery units and operating rooms of hospitals and private clinics in the Ile-de-France region in order to keep the heavy intensive care beds available for patients who absolutely needed them. The aim was to avoid saturation, and always have some of the heaviest beds available for the highest critical incoming patients. As a matter of fact, Dynamo had to closely follow the evolution of the patient flow in order to anticipate the demand and always preserve some beds. Medical logic and the interest of the patients always came first, but the optimization of flows was also an undeniably important factor, enabling to take more patients in need of care.

Actually, at the worst moment of this first wave, Dynamo succeeded in always keeping at least one bed available for the heaviest level of resuscitation. It avoided the hospitals of the zone being saturated.

The challenge of this dynamo cell was also to find a solution to accelerate the downstream flow of patients in intensive care, without consuming additional logistical and human resources. "We had to be creative: the transfers were carried out with the resources available: anesthetists, surgeons, etc. and most of the time we called on a private ambulance company, which is not our usual practice". Dynamo therefore coordinated the flows between four types of teams, different for each transfer: the requesting department, the transfer teams (which it formed adhoc according to availability and needs, each day), the transfer vector (mainly ambulance, train or air for 14 patients), the receiving department. As reported by one of the nurses: "after two days, we perfectly mastered the process. It's simple, we had a request form, two vector filesone for the ambulance and one for the team providing the transport -and one form for the recipient. We had one form for the ICU with the medical criteria. We validate, determine the appropriate time and place, and then create the bridge between the two, generally we find a private ambulance. Then we put two doctors in it for transport".

Results

The main destination for transferred patients was the temporary resuscitation service created inside La Pitie-Salpétrière hospital (37%); then, the adult resuscitation service created inside the resuscitation service at pediatric Trousseau hospital (6%); then, the private hospital Geoffroy St Hilaire (5,5%). 69% of the transfers were sent to public hospitals, 26% to private hospitals, 5% to private non profit structures. 13% of the patients have been sent outside the Parisian area, in public hospital in Western France, with specific transfers in high-speed trains, aircraft or helicopter. No major incident occurred during the transfers.

The rejected demands were due to a deterioration of patient's health (22 cases), the difficulty to find a place for a patient with a need for persistent hemodialysis (7 cases) or with major overweight (4 cases).

As the crisis medical director summarizes: "Thanks to their capacity for innovation and their ability to work outside the box, [the doctors] were able to find solutions where there were only problems. Thanks to Dynamo, more than a hundred patients were safely transferred to resuscitations and continuous monitoring units outside the perimeter of AP.Sorbonne University's resuscitations, freeing up as many beds to accommodate patients there, [which helped] to protect the front line and ensure access to care for all patients who came to our hospitals".

The principle of Dynamo organization was to operate in a fluid, non-hierarchical way, with real-time information: reliable information on the occupation of the different intensive care units, communication between the different interlocutors, including those outside the public system such as the private ambulance drivers and some local private clinics which participated by creating intensive care units. In order to be easily reachable by all the resuscitation services, Dynamo created a unique email address and a dedicated phone number and the team used an Excel file to report information about patients' transfers. The two computers of the team were linked to the information systems of the Paris hospitals. A very concise transfer request form was created and made available to all the departments concerned.

A team with complementary skills

The dynamo unit included three doctors and two experienced nurses. The two nurses were initially transplant coordinating nurses and in charge of organizing organ transplants. They were therefore used to making a lot of calls at short notice and had connections with different departments. They are used to talking with doctors, presenting patients' cases, understanding the patients' pathology and detecting whether they meet the criteria for discharge and transfer.

They were particularly efficient for this type of job and managed to establish good relationships with the medical teams involved. They indeed hold important relational skills and know how to talk to various interlocutors (family, legal, medical). Finally, they have managed to build up a network of relationships with downstream structures and trust was created through repeated phone contacts and evidence that they were keeping their word: "They saw that the patients we presented to them had the criteria we had announced. And we promised to take them back if their condition deteriorated."

The two nurses were in charge of the secretarial and administrative work and had a lot of autonomy: they were able to organize everything by themselves and the doctors only intervened for the strategy and when there were medical discussions about the patients. The two nurses were not themselves the initiators of the innovations brought about by Dynamo, but they facilitated them because they understood the spirit of Dynamo. They also provided solutions and ideas thanks to their tactical autonomy. The context was very chaotic and the whole team had to be agile in such a context. Transfers were decided at the last minute and the nurses had to work outside the process, which they did.

The dynamo unit also included three anesthetists: the tactical physician; another physician who had an experience of overload in intensive care and hospital crisis and the Parisian hospital environment (APHP); the intern who had a good knowledge of the management of patients in the ICU, and of the skills of the doctors who were going to take charge of the patients.

The physicians' main task was to facilitate the flow of patients taking into account organizational and medical parameters. They were also in charge of medical assessments of the patients before their transfer and the staffing of the doctors who were going to do the transfers. They received the assessment files from the requesting intensive care units and sorted the patients (eligibility, feasibility, health status, stability of the patients, level of care needed) with a medical arbitration each time to evaluate in which intensive care unit they should be transferred.

As exposed by a physician, referring to WW2 Dynamo: "Dynamo works like an airport control tower, which finds, or even prepares, as many small airports as possible to allow planes that are not used to landing there". As a consequence, this strategy of sequencing the resuscitation pathway doubled the natural flow to resuscitation, a valuable gain in the midst of the Covid-19 crisis when resuscitation slots were saturated.

In our analysis, we consider that this innovative process could be designed and implemented thanks to the complementarity of the Dynamo cell members. Beyond their medical competence, they held complementary managerial and organizational skills. The two anesthetic-resuscitation doctors brought their knowledge of the APHP services and medical teams. The two nurses, specialized in transplants, are used to working with strong time constraints, and to dealing with various departments, which enhanced their relational and communication skills. This was essential in implementing efficient relations with the downstream units. Last but not least, the tactical doctor incorporated into the Dynamo team played a key role. He translated some of the disaster medicine principles into the hospital context. This could have been perceived as not acceptable by the head of the various resuscitation departments without the five-year collaboration between his tactical group and the anesthesia and critical care department from Paris Sorbonne hospitals. As the head of the medical team of a French police special forces unit, he had strong experience in patients flow management under strong constraints.

Translating experience from tactical medecine

Counter terrorism special forces unit of the French Police has had operational medical support since 1993. The physicians who make up this tactical emergency medical service combine regular medical activity in emergency or intensive care unit departments with tactical medicine activity within the special forces.

Entering a space under terrorist attacks supposes to overcome some mental boundaries -on top of physical and social ones -as very few people can cope with such a distressing and stressful situation and keep their ability to act in a coordinated and consistent manner. In a way, these tactical physicians are trained to ascribe meaning to unknown and chaotic spaces as they sensorially move across them. The training that they get is just not about learning patterns or sequences of actions. Rather, it is to sense and response to what is being felt and learned in situ as they move across an unfamiliar space.

Tactical Emergency physicians are completely integrated in the special operations forces group. They share the trainings and the intervention. Tactical physicians' main task is to take care of any injured police officers of the unit, or victims of the attacks like a Mass Casualty event. They are equipped with ballistic protection and have specific equipment for intervention: flexible stretchers, triage tools, hemorrhage, and blast advanced medical equipment, etc… These medical team played a decisive role in the organization of the wounded rescue during mass casualties attacks in France. They have taken the necessary decisions to optimize evacuation to "traditional" rescue services, which are not allowed to enter the fire zone. Making decisions is commonplace for a doctor specializing in life-threatening emergencies, but making them in constrained, complex and "out of the box" situations is the specific challenge of these tactical emergency physicians. Tactical medicine is necessarily agile and disruptive because it is confronted with extremely rapid changes in the initial context, a lack of resources and information on the situation, strong security issues that impose themselves on any "standard" emergency care procedure, etc.

Tactical emergency physicians have a key competence in the management of patient flows. In disaster medicine, as in tactical medicine, managing the flow of victims is key. Teams try at all costs to avoid reaching the saturation point of the care capacity, which leads to disorganization, creates enormous stress and loss of chances for many victims. The management of flows in degraded conditions is one of the key subjects of reflection and learning for these medical specialties. These doctors have developed a strong expertise in flow management and know how to manage them in a global and dynamic way. They continuously balance the incoming flow of victims (by distributing them to the different points of care), the capacity (human factors and material resources, for example by increasing capacity by asking police officers to help with stretching, by transforming veterinary resuscitation equipment for humans), and the outgoing flow (for example by organizing transfers, and sometimes, during certain major crises, by discharging patients with little chance of survival). This flow management is very different from hospital practices, which are not used to a massive flow of patients in trauma and intensive care units. The contribution of tactical doctors is a key for the teams who need to find new solutions that are appropriate to the human and material situation of the hospital and avoid the structure breaking point.

In Dynamo case, the tactical doctor knew the members of the teams and the hierarchy of the services thanks to the five-year collaboration with the newly appointed medical crisis director, at that time head of anesthesia and critical care service. They have designed and organized training sessions for several years, under the patronage of the Deans and heads of departments, which has enabled them to gradually make hospital teams understand how they function in the midst of a crisis, and what support the hospital could provide. As a matter of fact, by incorporating a tactical physician, the Dynamo unit could benefit from his competence in managing the flow of patients, and his ability to mobilize different frames, to propose a new organization, with a new way to evaluate the acuity of resuscitation patients and involving private hospitals and ambulances.

Discussion

This case shows what organizational innovation can be amid an extreme situation. In the midst of the COVID crisis, the Dynamo cell has worked as a small community of practice, with doctors and nurses having strong and complementary skills. This has led to design and implement an innovative process. The first innovation was from the hospitals' medical crisis director who appointed a physician who did not hold a full-time position, to lead the group.

Then, tactical medicine principles translated into hospital context, have allowed for real innovation, by managing the situation they were confronted with in a disruptive manner. Each member of the team brought skills and contributed to the success of this innovation: capacities for thinking outside the box and knowledge of private structures (tactical doctor), knowledge of the internal structure (anesthetist), knowledge of the network of anesthesia interns (second doctor), relational skills to interface with structures outside the hospital (nurses).

While there have been other reported cases of transforming acute care beds into resuscitation beds and transfers to private hospitals, this case is unique in the implementation of a new resuscitation scale and the leadership of the unit to an external doctor. It corresponds to fast and frugal innovation [START_REF] Sandberg | How do we justify knowledge produced within interpretive approaches?[END_REF] , which "does not mean low quality but instead means the ability to provide safe healthcare in the best way possible under given circumstances and constraints."

Beyond the various advantages listed above for the patients and the stability of their condition, in a context of scarce resources, the optimization of medical teams and equipment is essential.

Dynamo was launched when it was impossible anymore for the SAMU to handle patient transfers because of their major involvement in primary care. It also relieved the services from the search of downstream beds, saving them precious time and energy. The teams were led to develop an unprecedented solution, by conducting a real investigation logic [START_REF] Lorino | Pragmatism and organization studies[END_REF] : the search for possible solutions, elaborate them progressively by developing the steps, the conditions, by looking for innovative tracks in the different registers of action that tactical medicine or disaster medicine may have listed, but also allow themselves to conceive solutions out of the box, to evaluate them by dialoguing with colleagues and non-medical staff; progressively build an action plan involving remote hospitals, physicians and transporters, and have the capacity and legitimacy to have it accepted and implemented. Previous work on extreme situations has mainly shown creativity and organizational innovation outside of a crisis phase, or a phase of high risk, during the preparation phases [START_REF] Schakel | To the edge and beyond: How fast-response organizations adapt in rapidly changing crisis situations[END_REF] . In crisis, or in the operational critical phase, the actors focus on coordination and the choice of predefined action sequences. It shows the importance of sensemaking in healthcare emergency settings and highlights the key role of coordination practices. This case also highlights some of the conditions that facilitate the transition from invention (i.e. the new idea) to innovation (i.e. the implementation of the idea). By constantly striving to make sense of it in relation to the need, the Dynamo cell members have allowed the initial idea to be appropriated by all the partners. This appropriation gives meaning and efficiency to the novelty, allows it to be made one's own and to build a usefulness in relation to a project. However, this process requires the abandonment of certain ideas: this was the case for the Dynamo cell as with the transport of patients in buses, for example. During the discussions, these ideas were considered as being too "out of step" with current practices. This case reminds us that any innovation must be confronted with the social order, but cannot be built against practices, at the risk of being dogmatic and not very effective 26 .

The diffusion of innovations depends on the capacity to connect the members of the network (here upstream structures, downstream structure, ambulance, doctor, surgeon, etc.) around the resolution of the critical situation. The success of this linkage was based on social dynamics: the personal networks that the physicians had established with the hospital's internal ICU prior to the crisis were mobilized, thus facilitating the recruitment of patients who were discharged and the physicians who provided transport. The articulation with the external services benefited from the personal affinities that the nurses managed to build, at a distance, with the downstream intensive care units, through their daily exchanges, their kindness and above all the respect of the given word. All in all, the technical and relational skills of the members supported the necessary process of translation, making it possible to gather around the same objective the various entities constituting the innovation network [START_REF] Latour | Reassembling the social. An Introduction to Actor-Network-Theory[END_REF] .

Finally, the case shows the importance of the temporal dimension in crisis and extreme situations. During the Covid crisis hospitals faced a double temporal challenge, as they were running both a marathon and a sprint [START_REF] Garg | Hospital Medicine Management in the Time of COVID-19: Preparing for a Sprint and a Marathon[END_REF] . Tactical physicians, trained and accustomed to dealing with these different temporalities, allowed the hospital teams in which they were integrated to be able to modify their organization and implement innovative modalities designed to deal with these disruptive situations. It opens avenues to further better link temporal and spatial perspectives in healthcare management, and in particular to enrich our views on patients' flows [START_REF] Barros | Improving service in an emergency department by designing the health production flow[END_REF] .

According to the Dynamo cell members, they acknowledge that they would have been more efficient if they could have better communication processes between the various partners. Some partner institutions were private, other public, other non-profit. There was no unified communication network, nor practices. They had no specific time to join or dedicated instant message system. They sometimes lost time to get in touch with the right people. They also acknowledge that they would have needed to interact more and in an easier mode with the medical crisis direction and the regional health authorities, to better organize in advance, according to the forecasts, and better coordinate with other types of regional actors.

The Dynamo cell was ready to re-activate during the two following Covid waves in Paris area, under the demand of the medical crisis director, but with different nurses as transplants did not stop during the following waves. However, it was not needed, as the hospitals could manage differently the patients' flow: the forecasts were more reliable, and the medical crisis direction could better help to organize. However, anesthesiologists, emergency doctors and nurses have learnt that thinking out of the box and agility was not easy in traditional hospitals services, and that this had to be learnt and prepared. They raised their concern for the possibility to face other crisis in the future and the need to better organize.

The Dynamo experience was short in time. It emerged through specific circumstances: previous collaboration between tactical forces and the hospital; the availability of the tactical doctor and the transplant nurses. Of course, this specific encounter cannot happen strictly everywhere. However, it shows that thinking out of the box, mobilizing resources outside the traditional set, can help to change rapidly and efficiently.

Practical implications

The case analyzed here suggests practical implications. First, regarding crisis and extreme situations in hospitals, it highlights the importance of flow management and the key role of hybrid teams with tactic physicians who have both competences in crisis management and in more classical medicine. While these physicians are not always part of the traditional hospital organization, they can bring their experience and knowledge in crisis management by being integrated into the crisis organization. Moreover, Dynamo unit, incorporated into a larger crisis organization, shows the role of agile and decentralized teams. It reminds that, despite what has been planned or prepared for crisis management, the organization must be adapted to the specificities of the crisis, its rhythm and pace. Improvisation is not disorganization. It is a way to keep flexibility, to adapt existing routines and procedures to the situation, and to be able to innovate under time pressure and resource constraints. To be able to innovate, propose and implement relevant solutions, the crisis units must be composed of members trusting each other, and acknowledged as legitimate by the rest of the people with whom they will interact, in particular the heads of the medical departments more impacted by the crisis. More generally, regarding the ability to innovate in the healthcare sector, this case sheds the light on the role of communities of practices [START_REF] Nicolini | Communities of Practice and Situated Learning in Healthcare[END_REF] with practitioners with different backgrounds and mixing physicians, nurses, paramedics, or other persons with specific competences that may enhance the hospital's perspectives.

Last, the case of Paris Sorbonne hospitals confirms the importance of preparing heads of departments and head nurses to crisis management. The training to crisis this hospital has developed could ease the department's doctors for disruptive solutions.

  March 27, 2020, through April 22, 2020. It operated 7 days a week during business hours. It received 149 requests for patients' transfers and accepted 105. The peak in the number of requests occurred on April 1 st , with 19 transfers made for 23 requests.


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come

Deep-learning-based 3D lesion segmentation on whole-body [18F]-FDG PET images including automated quality control: method and external validation

Kibrom Girum, Louis Rebaud, Anne-Ségolène Cottereau, Thibault Escobar, Jérôme Clerc, Laetitia Vercellino, Olivier Casasnovas, Franck Morschhauser, Catherine Thieblemont and Irene Buvat Introduction: Reliable and automatic lesion segmentation might facilitate the investigation of prognostic image-based biomarkers by reducing the delineation time and inter/intra-observer variability. This work proposes an artificial intelligence (AI) pipeline to automatically detect and segment metabolically active lesions on [18F]-FDG PET images in 3D. Importantly, an associated quality control (QC) method is developed to detect possibly unreliable segmentations. Image-based biomarkers extracted by nuclear medicine experts and the proposed AI are compared.

Methods: This was a retrospective analysis of muti-center multi-trial Diffuse Large B-Cell Lymphoma patients. We used the [18F]-FDG PET/CT of 287 patients from the REMARC (NCT01122472) cohort to train and cross-validate the AI method and evaluated it on the PET/CT of 174 LNH073B (NCT00498043) patients. All lesions on the PET/CT scans were delineated by experts using a semi-automated procedure, providing the lesions' "mask". The 3D PET image was projected into coronal and sagittal maximum intensity projection (MIP) images. The coronal and sagittal MIP of the lesion mask obtained from the experts were also calculated. The AI method was trained to segment the lesion areas on the sagittal and coronal PET images (Girum et al., J Nucl Med, 2022). A robust postprocessing algorithm was developed to reconstruct the 3D segmentations by exploiting the lesion areas identified by the AI on the sagittal and coronal MIP and the SUV values from the 3D PET images.The segmented masks on the coronal and sagittal MIP images were inserted at the location of the coronal and sagittal planes corresponding to the MIP values. The regions where the coronal and sagittal insertions coincided were considered seed voxels for the 3D segmentation. The minimum SUV values of each cluster of seed voxels were obtained and used as a local SUV threshold to refine the 3D segmentation.

For QC, we retrieved a sagittal MIP segmentation from the coronal MIP segmentation by projecting the segmented SUV values in the coronal PET MIP into sagittal PET MIP. The ratio between the number of pixels in the retrieved sagittal MIP segmentation and the number of pixels in the AI sagittal MIP segmentation was calculated and called the confidence score. Total metabolic tumor volume (TMTV), tumor dissemination (Dmax), and total lesion glycolysis (TLG) extracted by the AI method in 3D were measured and compared with the corresponding values obtained by nuclear medicine experts.

Results:

The concordance index (C-index) between the AI and expert-based TLG, Dmax, and TMTV were 0.905, 0.800, and 0.865 respectively on the REMARC cohort. The timedependent areas under the ROC curves for progression-free survival (PFS) from the expert segmentation were TMTV: 0.67 (Confidence interval (CI): 0.60-0.73), Dmax: 0.65 (CI: 0.58-0.72), TLG: 0.65 (CI; 0.56-0.73), and from the AI segmentation were rTMTV: 0.65 (CI: 0.58-0.72), rDmax: 0.65 (CI: 0.58-0.72), rTLG 0.63 (CI: 0.56-0.70). The hazard ratio between the expert and AI-driven features were similar. The C-index on the LNH073B between the AI and expert-based TLG, Dmax, and TMTV were respectively 0.915, 0.814, and 0.874. Patients' classifications into three-risk groups using the tumor burden (TMTV and TLG) and dissemination (Dmax) biomarkers were predictive, and the expert and AI-driven features agreed. Interestingly, the cut-off values obtained on the expert-based biomarkers can be directly applied on the AI-based biomarkers (Figure 1). The mean QC of the detected lowquality segmentations (QC < 0.6) was 0.35 (±0.196 standard deviation), against a mean QC of 0.933 (±0.072) for all other cases.

Conclusions:

The proposed fully automatic [18F]-FDG lesion detection pipeline enabled calculating prognostic image-based biomarkers (TMTV, Dmax, and TLG) that had similar prognostic values compared to when those biomarkers were calculated by the experts. The AI results were associated with a confidence score that could make them reliable and suitable for clinical practice.


Marcin Trzmielewski
email: marcin.trzmielewski@univ-montp3.fr

Claudio Gnoli
email: claudio.gnoli@unipv.it

Representing and organizing everyday medical terminology and conceptualization in a general faceted classification: towards a reconciliation between epistemological and ontological approaches

Keywords:

published or not. The documents may come

Representing and organizing everyday medical terminology and conceptualization in a general faceted classification: towards a reconciliation between epistemological and ontological approaches

Introduction

In information science, we may distinguish two approaches to the organization of knowledge. The first one, the ontological approach, "concerns the nature of the known things, especially in terms of the general categories to which they may belong" (Gnoli 2008, 139). Such approach leads designers of knowledge organization systems (KOS) to focus on "issues like the subdivision of a class into kinds and parts, or the acknowledgment that a given concept consists of a process or a static entity" (Ibid.). Facet analysis [START_REF] Raghavan | NeurOn. Modeling ontology for neurosurgery[END_REF] and automatic terminology processing [START_REF] Muresan | Inducing terminologies from text: A case study for the consumer health domain[END_REF][START_REF] Choi | Supporting better treatments for meeting health consumers' needs: extracting semantics in social data for representing a consumer health ontology[END_REF] fit into this approach and are often used to organize medical knowledge [START_REF] Trzmielewski | Vers l'élaboration d'un système d'organisation des connaissances en allergologie : l'analyse des documents et des pratiques informationnelles des acteurs[END_REF]). The second onethe epistemological approach, "is about how humans know the world through their sense organs, and how they process knowledge according to categories both innate and culturally biased" (Gnoli 2008, loc. cit.). Methods such as analysis of context [START_REF] Huber | Social Constructs and Disease: Implications for a Controlled Vocabulary for HIV / AIDS[END_REF], analysis of practices [START_REF] Iyer | Medical ontology: Siddha System of Medicine[END_REF]) and domain analysis [START_REF] Hjørland | The classification of psychology: A case study in the classification of a knowledge field[END_REF], are connected to such approach and are mobilized as well to organize knowledge in medicine [START_REF] Trzmielewski | Vers l'élaboration d'un système d'organisation des connaissances en allergologie : l'analyse des documents et des pratiques informationnelles des acteurs[END_REF]. As "knowledge is both epistemological and ontological, as it passes through human perception by its very nature, but also refers to real objects of the world having some intrinsic structure" (Gnoli 2008, loc. cit.), some reconciliation between the ontological and the epistemological approaches should be sought. In the present article, we search for such reconciliation, by assessing the possibility to represent and organize everyday terminology and conceptualization of allergology professionals in a general KOS. We reuse contextualized and bottom-up terminological data, and we apply it in the third version of Integrative Levels Classification (ILC), which is a general classification with main classes and facet categories developed in a top-down way.

We will begin with a presentation of the ALLERGIDOC and ILC projects. Then, we will indicate our theoretical framework and methodology. Finally, we will present and discuss our results, and we will provide some perspectives for future development of our study project as well.

ALLERGIDOC and Integrative Levels Classification projects

Allergy is a major health issue in our society in terms of care and prevention. In France, allergy or allergology, the domain that studies and treats allergies, was only recognized as a specialty in its own right in 2017 [START_REF] Demoly | L'allergologie ? Désormais une spécialité médicale universitaire[END_REF], and there is no KOS that might be used by professionals in this domain for their activities of processing and search for information (Trzmielewski 2019). This situation led Trzmielewski to cooperate with the Allergy Unit of the University Hospital of Montpellier to develop the ALLERGIDOC 1 project, aiming to create an ontology to represent and organize allergy knowledge and support clinical, research and education activities of allergy professionals, based on information indexing, searching, and classification tasks.

In numerous cases, medical KOSs have been designed through techno-centric approaches, which have led designers to pay less attention to the human and social aspects. To distinguish ALLERGIDOC work from other works on design of medical KOSs, Trzmielewski constructed a first version of this ontology through a contextualist approach, relying on the study of information practices of allergology professionals, and on the analysis of documents used by these employees in their daily activities. For further information on this project, consult [START_REF] Trzmielewski | Vers l'élaboration d'un système d'organisation des connaissances en allergologie : analyse des documents et des pratiques informationnelles des acteurs[END_REF][START_REF] Trzmielewski | Vers l'élaboration d'un système d'organisation des connaissances en allergologie : l'analyse des documents et des pratiques informationnelles des acteurs[END_REF].

The Integrative Levels Classification (ILC) is a general faceted classification being developed progressively since 2004 by an international team of knowledge organization specialists led by Gnoli. The ILC research project takes its theoretical and technical foundations from the work developed in the 1960s by the Classification Research Group in London, particularly in the persons of D. J. Foskett and D. Austin, under a NATO 2 grant. At the time this did not produce any finished system for contingent reasons, but it did leave a precious heritage of advanced techniques (freely faceted classification) that are now being implemented in ILC [START_REF] Gnoli | Classifying phenomena Part 1: Dimensions[END_REF][START_REF] Gnoli | Classifying phenomena, part 3: Facets[END_REF][START_REF] Gnoli | Introduction to knowledge organization[END_REF]. A second stable edition (ILC2) is available online (ISKO Italia 2023), also in SKOS 3 format (Binding et al. 2020). This includes 10,845 classes and facets covering the whole spectrum of knowledge broadly, plus deeper specificity in certain domains that have already been worked out in detail. A third edition (ILC3) with improvements in the consistency of facet syntax and in various classes is currently under development.

Although drawing from the heritage of bibliographic classifications such as Dewey Decimal Classification or Universal Decimal Classification, ILC is different from them in allowing to represent any combination of concepts without the ties of traditional disciplines (e.g. "Medicine"). Rather, phenomena of the world are listed in the ILC schedule according to a sequence of increasing organization, based on the theory of integrative levels introduced by [START_REF] Needham | Integrative Levels: A Revaluation of the Idea of Progress[END_REF] and formalized by [START_REF] Feibleman | Theory of Integrative Levels[END_REF]. According to this theory, when elements of a lower level (e.g.: molecules, genes) are combined, they can give rise to a new integration (e.g.: organisms), with different properties and nature: Levels thus allow to establish the sequence of phenomena through dependence relationships based on phylogenetic criteria. These are completed by inclusion relationships arranging the phenomena according to the increase in morphological specificity (e.g. m organisms are divided into mn fungi, mp plants, mq animals and so on).

a
In ILC, ordinary classes (concepts) are represented by lowercases and by terms expressed in English. Although terms are important to final users (to know with which class they are dealing), notation is even more important because it represents the actual conceptualization framework of the classification and is independent of specificities of any alphabetically expressed language. In ILC, we can represent combinations of concepts relating to any scientific domain, through the possibility of expressing relationships between any pair of classes. Relationships are expressed by digits corresponding to ten fundamental categories [START_REF] Gnoli | Classifying phenomena Part 1: Dimensions[END_REF][START_REF] Gnoli | Classifying phenomena, part 3: Facets[END_REF]: In ILC, to express subject such as "Caring adult patient suffering from cancer", class sh "healthcare" provides facets sh96 "for patient" and sh94 "healing condition". Their combination results in sh96p94nr "healthcare, for adult, healing cancer".

0 as
The ILC scheme has been tested by applying it to the organization of collections of knowledge items including bibliographic databases dedicated to folk culture and bioacoustics (Figure 1), as well as the Basic Register of Thesauri, Ontologies and Classifications (BARTOC).

FIG. 1 -Example of use of ILC in a bibliographic database on bioacoustics

As we may observe, ALLERGIDOC and ILC present two different approaches to knowledge organization, respectively epistemological and ontological. In our work, in order to take the best of both approaches, we assessed whether it is possible to integrate everyday terminology and conceptualization of allergology professionals in a general KOS such as ILC. That brought us to address a broader question, i.e. whether epistemological and ontological approaches to knowledge organization can be reconciled in the design of medical KOSs.

Theoretical framework and methodology

To collect and organize allergology terminology, we developed a mixed approach. In the first place, we mobilized an epistemological approach, by adopting a socioconstructivist perspective. Such perspective consisted in the analysis of cognitive processes that take place through mutual interactions between allergology professionals and their informational and socio-organizational environments [START_REF] Clavier | Activités informationnelles et organisation des connaissances : résultats et perspectives pour l'information spécialisée[END_REF]Weiss et al. 2018). The allergology domain was considered as "a group of people [social actors] who share common goals" (Mai 2005, 605). Thus, our concern was shifted from the "correct" representation and organization of the allergological reality to the "useful" representation of the problems encountered by these actors [START_REF] Tennis | Le poids du langage et de l'action dans l'organisation des connaissances : Position épistémologique, action méthodologique et perspective théorique[END_REF], the usefulness depending on the context of the action and interaction with the KOS. Thus, we used a bottom-up approach, oriented by information and work practices of professionals.

In the second place, we mobilized an ontological approach, by adopting a more rationalist perspective. That led us to classify allergology terminology through faculty of human reason, by using logical divisions and top-down categories of knowledge that are considered to be of general use [START_REF] Gnoli | Introduction to knowledge organization[END_REF].

Therefore, we relied our study on one hand, on the analysis of context of use of specialized knowledge [START_REF] Clavier | Activités informationnelles et organisation des connaissances : résultats et perspectives pour l'information spécialisée[END_REF], by the study of the information practices (Chaudiron and Ihadjadene 2010) of allergology professionals who seek, produce, and mobilize knowledge in the domain; and on the other hand, on the facet analysis [START_REF] Vickery | Faceted classification schemes[END_REF][START_REF] Ranganathan | Prolegomena to library classification[END_REF] of terms used by these professionals in their daily activities. Although some researchers consider facet analysis as an only rationalist technique [START_REF] Hjørland | Is Facet Analysis Based on Rationalism? A Discussion of Satija (1992), Tennis[END_REF], some specialists claim that such analysis is also connected to empirical and pragmatic aims, as it is used to organize and represent terminology that expresses the practices of health professionals [START_REF] Dousa | Epistemological and methodological eclecticism in the construction of knowledge organization systems (KOSs): the case of analytico-synthetic KOSs[END_REF][START_REF] Trzmielewski | Organization of medical knowledge: documentation techniques applied to a macro-domain underpinned by sociopolitical issues[END_REF]. Indeed, the Classification Research Group adopted facet analysis for designing special KOSs "for particular groups of users and adapted to their needs" (Vickery 1966, 10).

We started with a study of information practices, carried out by Trzmielewski in 2020-2021 in the Allergy Unit of the University Hospital of Montpellier. He elaborated 16 participants' observations of 8 journal club meetings, devoted to the presentation and critical analysis of scientific articles and conference presentations, and 8 clinical meetings focused on the presentation and analysis of patient records. He also conducted 20 interviews with professionals investigating their information and work practices.

Then, Trzmielewski manually extracted terms from the corpus of data on practices, based on the reports of the observations (in total: 19,470 words) and on the transcripts of the interviews (121,203 words). Instead of extracting terms according to their frequency in the corpus, he assessed their relevance to the domain based on his TOTh -X -knowledge in allergology, acquired during a year spent in the Allergy Unit. To organize collected terms, he performed a content analysis [START_REF] Hudon | Guide pratique pour l'élaboration d'un thésaurus documentaire[END_REF], which allowed to classify allergology terminology into thematic and user-oriented facets (Albrechstsen 1992). The content of the reports and transcripts was useful to this task because it provided contextual information that led us to know if some terms should be classified in one category or another. For example, a phrase coming from an interview: "Il y a le côté clinique, donc toute l'histoire clinique des patients, et il y a tout le côté des tests d'investigation, donc des tests cutanés, des tests de provocation", enumerating two types of allergy tests, allowed to establish a category assembling "Diagnostic method[s]" including "Tests cutanés" ("Skin tests") and "Tests de provocation" ("Challenge tests"). These facets were further validated by allergy professionals, by checking whether they are useful for document indexing and characterization of allergic cases. Therefore, these facets expressed general categories of thought of professionals from the Allergy Unit.

Finally, we represented and organized the collected terminology through a facet analysis [START_REF] Gnoli | Classifying phenomena, part 3: Facets[END_REF], which led us to integrate the terms into existing facets of ILC3. Terms reorganized in such a way were input in ILC3 MySQL database.

Results

In total we collected 4974 terms from everyday use by allergology professionals. Terms were converted to singular form, except for those terms who only make sense in plural, such as "Acariens" ("Dust mites"). Terms also were alphabetically ordered and replaced by masculine genres.

Allergology terminology is highly specialized and conveys scientific and clinical knowledge (see Table 1). We identified numerous equivalent variations, at morphological level: abbreviations ("ITO" = "Introduction de tolérance orale") and shortened forms ("Allergo" = "Allergologie"). Variations at lexical level ("Intervention curative" = "Traitement", "Prick test" = "Test cutané", "Test de souffle" = "Spirométrie") were found as well. Such synonyms were not represented in ILC3, because the classification is only available in English. However, ILC3 does allow to express equivalent terms: in the ILC3 database, mq4ipl "allergy" has its synonymic form "allergic disease" (see Figure 2).

As a consequence of ILC international target, we had to work in English. Allergology terms and facets were translated with the use of medical and general dictionaries available online.

TAB. 1 -A fragment of terminological database generated in ALLERGIDOC project FIG. 2 -A fragment of an entry representing synonyms in ILC3 database

TOTh -X -

The thematic analysis of terminological data initially brought up 17 facets. The validation of these facets led to the identification of several facets of phenomena used by allergology professionals to search for information: "Allergen", "Comorbidity", "Diagnostic method", "Disease", "Healthcare circuit", "Mechanism", "Person", "Prevention", "Quality of life", "Risk factor", "Symptom", "Treatment". These ALLERGIDOC facets have then been translated into special facets of ILC3 class sh "healthcare": sh "healthcare"

sh5 "healing stage" sh7 "by drug" sh94 "healing condition" sh942 "with concurrent condition" sh943 "caused by organic pathogen" sh946 "showing symptom" sh947 "complicated by complication" sh96 "for patient" sh97 "of treated part" sh98 "severity"

In ILC3, special facets can only be applied to a specific class, for example those for diseases including "allergy" can be applied only to m organisms, as technical phenomena such as automobiles and markets are not affected by diseases. In consequence, allergology terms are mainly part of two classes of ILC3: m "organisms" (that includes mq "animals"), where mq4ipl "allergy" is considered as a natural phenomenon; and sh "healthcare", a subclass of s "services", where sh94ipl "allergy" is a part of the medical domain. This differentiates special facets from common facets of ILC3, such as -27d "in France", that can be attached to any class. Therefore, the special facets of sh "healthcare" allow to express the medical context. As the Table 2 shows, the "Healthcare circuit" facet was translated into the class sh "healthcare", encompassing the entire health care domain. On the other hand, facets such as "Diagnostic method", "Prevention" and "Treatment" (which are generic facets in ALLERGIDOC project) became special facets classified under sh5 "healing stage" in ILC3.

ALLERGIDOC facets Special facets of ILC3

"Allergen" sh494 "caused by organic pathogen"

"Comorbidity" sh942 "with concurrent condition" "Diagnostic method" sh5 "healing stage"

"Disease" sh94 "healing condition" "Healthcare circuit" sh "healthcare" "Person" sh96 "for patient"

"Prevention" sh5 "healing stage"

"Quality of life" sh94b "wellness; well-being; quality of life" "Risk factor" sh942 "with concurrent condition"

"Symptom" sh946 "showing symptom"

"Treatment" sh5 "healing stage" TAB. 2 -Representing ALLERGIDOC user-oriented facets (on the left) through universal facets of ILC3 (on the right) Some terms representing allergology knowledge are specifically context dependent, that causes semantic variability of terminology. As suggested by professionals, terms such as "Asthma" or "Eczema" are considered at the same time as a "Disease", a "Risk factor" and a "Symptom". Instead of representing these terms by poly-hierarchies, we decided to express them with parallel facets of ILC3 (see http://www.iskoi.org/ilc/how.pdf), taken from sh "healthcare" facets. By doing so, "Asthma" considered as a healed disease was represented as sh94lhs "healthcare, of asthma", "Asthma" as a risk factor by sh942lhs "healthcare, with concurrent condition : asthma", and "Asthma" as a symptom through sh946mq(4lsh) "healthcare, showing symptom : asthma".

Furthermore, in allergology, food or drugs are considered as types of "Allergen" and not for example as products fabricated by specific firms. We represented them through free facets of ILC3, allowing to combine every pair of concepts. "Food allergen", for example, was expressed as sh94ipl9430sb "caused by food", that is a combination of two classes: sh94ipl "allergy" and sb "food", linked by facet 9430 "caused by pathogen".

Conclusion

Our results show that integration of everyday terminology and conceptual categories of health professionals can be represented and organized in a general faceted classification through special and common facets of ILC3, using bound, parallel or free syntax according to the needed meaning. The classification can manage linguistic variations in English as well. That brings us to conclude that a reconciliation between epistemological and ontological approaches to knowledge organization can be TOTh -X -reached by combination of the contextual data, as collected through the analysis of information practices, with the versatility of freely faceted systems like ILC3.

Therefore, ILC3 can be considered as a boundary object (Star 1989) that merges terminological and conceptual approaches to knowledge organization, similarly to onto-terminological systems studied and designed by the TOTh community [START_REF] Roche | Le terme et le concept : fondements d'une ontoterminologie[END_REF][START_REF] Carsenty | Role of the Corpus in Ontoterminology: the Case of the Balance of Payments[END_REF][START_REF] Sanfilippo | The structure of ill-structured solutions: Boundary objects and heterogeneous distributed problem solving[END_REF]. We suggest that such combination of approaches should be taken in consideration in the design of medical KOSs, to represent the terminology and conceptualizations used by healthcare professionals, which is necessary to support information processing and searching by final users. The 11th version of the International Classification of Diseases, for example, already integrated terminological functionalities to fulfill healthcare professionals coding needs [START_REF] Zeng | Challenges, opportunities, and approaches in a health KOS vocabulary's revisions --Insights from the 11th revision of the International Classification of Diseases (ICD-11)[END_REF].

The integration of allergy knowledge in ILC3 will soon be completed by further terms coming from different kinds of textual documents used by allergy professionals: titles and abstracts of scientific articles, messages from a general-public health forum, and clinical documents redacted in the Allergy Unit. As such documents are produced by different actorsresearchers and allergists, patients and the wider public, professionals from the Allergy Unitit will be interesting to see how terminological and conceptual varieties resulting from such complexity may be represented and organized in a general faceted classification.

209 terms came from the reports of the observations, 244 from the transcripts of the interviews, and 44 from reports of the facet validations.