SciELO - Scientific Electronic Library Online

 
vol.18 issue56Effects of motivational interviewing on cardiovascular patient adherenceCompetent trans* health care, current situation and future challenges. A review author indexsubject indexarticles search
Home Pagealphabetic serial listing  

My SciELO

Services on Demand

Journal

Article

Indicators

Related links

  • On index processCited by Google
  • Have no similar articlesSimilars in SciELO
  • On index processSimilars in Google

Share


Enfermería Global

On-line version ISSN 1695-6141

Enferm. glob. vol.18 n.56 Murcia Oct. 2019  Epub Dec 23, 2019

http://dx.doi.org/10.6018/eglobal.18.4.362201 

Reviews

Application of Nursing Activities Score (NAS) in different types of ICUs: an integrating review

Raiane Antônia Santos Nobre1  , Hertaline Menezes do Nascimento Rocha2  , Fernanda de Jesus Santos3  , Allan Dantas dos Santos4  , Rafaela Gois de Mendonça5  , Andreia Freire de Menezes4 

1Nursing student, Federal University of Sergipe. Brazil. raianenobre@hotmail.com

2Nurse. Master in Nursing. Professor at the Federal University of Sergipe. Brazil.

3Nurse. Postgraduate degree in patient safety and quality of health services by FAVENI. Brazil.

4Nurse. PhD in Nursing. Professor at the Federal University of Sergipe. Brazil.

5Nurse. Master Student of the Postgraduate Program in Nursing, Federal University of Sergipe. Brazil.

ABSTRACT

Objective

To compare the nursing workload measured by the Nursing Activities Score (NAS), between intensive care unit general adult ICU, and specialized surgical, cardiologic and trauma type.

Methods

A literature review of the integrative type was carried out, searching the databases BDENF, LILACS, MEDLINE, and SCIELO, using the descriptors nursing, Intensive Care Unit, workload and Nursing Activities Score. They met the inclusion criteria 20 articles published in the period 2007 to 2017.

Results

They show a high workload in the ICU, both in general ICUs and in all of the cited specificities, the same with a NAS score> 50.00, especially the trauma ICU, which was characterized with higher scores 72.00 and 71.3.

Conclusion

In much of the research, the average number of nursing professionals calculated by the NAS is higher than the average number of professionals required by the legislation. It was observed that even in ICUs with the same specificity it was possible to perceive large differences in the mean of the NAS score, in this way, we understand that despite having the same specificity, the profile of the patient as well as that of the institution has its peculiarities requiring time to different assistance and consequently divergences in sizing.

Palavras-chave: nursing; Intensive care unit; work load; Nursing Activities Score

INTRODUCTION

The Intensive Care Units (ICUs) arose from the need to offer a differentiated care to the critical patients in an uninterrupted manner. This intensive and specialized care requires technological resources, and that all professionals involved have a high standard of knowledge, as well as specific competencies to work in the area. With the evolution of this practice, the units were segregated in clinical, surgical, cardiological ICU, among other specialties, to attend adults, children and newborns 1

The determination of the quantity and the qualification of the nursing team are indispensable to ensure quality nursing care, especially in relation to the critically ill patient due to hemodynamic instability and service complexity. As the nurse is the member of the nursing team with greater technical and scientific preparation, an inadequate dimensioning of this professional can bring losses in the quality of care and the health of the worker, as a consequence of the work overload 2.

Currently, to offer subsidies to nurses in the dimensioning of nursing personnel, the Federal Nursing Council (COFEN) through the new resolution (COFEN) n. 543/2017 3, resolution No. 293/04, establishes and establishes parameters for sizing the minimum amount of the professional staff for health care coverage.

The Resolution of the Collegiate Board of Directors (CBD) n. 26 of May 11, 2012 can also be found which provides the minimum requirements for the operation of ICU`s, including human resources, in which it provides that the team must be quantified quantitatively according to the care profile, sector demand and current legislation 4.

The assistance to critically ill patients is a difficult task, since the service dynamics itself precludes moments of reflection on care, therapeutic behaviors among health professionals working in the sector, among other competencies. Therefore, the use of instruments capable of correctly dimensioning the professionals, provides better working conditions, consequently a more humanized and safe nursing care, both for the patient and for the nursing professional 5.

Given the need to take into account patients' individuality and differentiated time demands, some tools emerged with the objective of characterizing the nursing workload in the ICU, in order to show in a real way the nursing hours spent directly and indirectly in patient care 6.

The Nursing Activities Score (NAS) is currently one of the most important tools as an instrument for measuring the workload of nursing staff in the ICU and aims to measure the number of hours spent by the professional in the care of patients, not only tasks, but also managerial activities of nursing, as well as the time of care spent supporting the patient's family. Thus, helping in the best dimensioning of nursing professionals in the Intensive Care Unit 7.

The NAS consists of 23 items of therapeutic interventions, subdivided into seven categories: basic activities, ventilator support, cardiovascular support, renal support, neurological support, metabolic support and specific interventions. The category of basic activities includes support and care for family members, administrative activities, and other activities related to care, such as monitoring and control, hygiene procedures, mobilization and positioning8.

Each item that composes the mentioned activities is assigned a score, in which the final score represents the percentage of time spent by the nursing professional in the patient care in the last 24 hours, that is, a score of 100 means that the patient needed 100% of the work time of the nursing professional to perform their care. Turning to the assistance time provided, each NAS point equals 14.4 minutes. The total score obtained by the sum of the points is directly related to the percentage of time spent by a team professional in patient care, which can reach up to 176.8%, so a nurse or nursing technician can take care of a shift, of up to two patients whose achieved NAS was 50% 8,9.

Taking into account the information mentioned above, based on the idea that a group of patients with distinct characteristics require demands for care, planning and human resource sizing according to their specific needs, the present study aims to compare the workload of nursing measured by NAS, between general adult ICU, specialized surgical, cardiologic and trauma type. The same is justified due to the limitation of publications that carried out research on the measurement of workload of Nursing staff from the NAS, above all, comparing general and specific ICU.

METHOD

It is an integrative review in which studies related to the subject have been condensed, allowing the achievement of general conclusions.

According to Brevidelli and Sortório 10, the following steps are necessary to construct an integrative review: Identification of the theme, selection of the research guiding question, establishment of inclusion and exclusion criteria, identification and characterization of selected studies, analysis and interpretation results and presentation of the review.

For the present study, the following guiding question was elaborated: There is a difference between the nursing workload required for the care of patients in different types of ICUs from the use of NAS?

The search for literature occurred in July 2018 in the following databases: Latin American and Caribbean Literature in Health Sciences (LILACS), Medical Literature Analysis and Retrieval System Online (MEDLINE), Scientific Electronic Library Online (SCIELO) and Database of Nursing (BDENF), through an online consultation to the Virtual Health Library (VHL). The descriptors used by the classification of Descriptors in Health Science (DeCS) were: Nursing, Intensive Care Unit; Workload and Nursing Activities Score. They were used in association using the Boolean operator AND.

Original articles were available online and in full that included the proposed theme and works in which the NAS was used exclusively in ICUs, regardless of language, year of publication of the journal, and methodologies used, except for integrative reviews, filtered by title and summary, followed by careful reading and analysis of the selected studies.

RESULTS

Initially, 344 studies were found that after reading the titles and abstracts, analysis of the inclusion and exclusion criteria and duplicate articles, 110 articles were left. From these, after the thorough and thorough reading of the works, 20 publications were obtained that answered the guiding question proposed.

The selected studies are distributed in the Tables below, considering information such as authors, year, country, type of study, objectives, number of participants, ICU specificity, NAS score and results. The characterization of the works, summarized in Table 2, are distributed in order to provide a better reading of the results.

Table 1. Distribution of selected publications according to database. 

Data bases BDENF LILACS MEDLINE SCIELO TOTAL
Publications found 16 34 40 20 110
Excluded for not having free access 00 00 06 00 06
Excluded for not being in full 01 00 04 00 05
Deleted due to being repeated in other databases 14 27 18 17 76
Total of selected publications 02 07 08 03 20

Soure:(Research data, 2018)

Table 2. Summary Table with general and specialized ICU articles according to authorship, year, country, type of study, objective, number of participants, NAS score and search results. 

The selected publications occurred between 2007 and 2017, an average of 1 article per year was published, the years 2014 and 2015 presented more publications, with 6 and 3 articles respectively.

The countries where the surveys took place were Brazil, Greece, Italy, Norway, the Netherlands, Spain, Poland and Egypt. The largest number of studies was found in Brazil (17), followed by Greece (3), this number took into account the publication of Padilha 11, performed in 7 ICUs from different countries.

Regarding the specificities of the ICUs, 4 publications carried out the study in more than 1UTI with different specificities, in view of the purpose of this work, for the purpose of calculation, the results of each ICU will be analyzed in a segregated way, in this way, 14 investigations were performed in General ICU, 7 in Surgical ICU, 3 in cardiology ICU and 2 in ICU of trauma.

The publication with the largest number of participants was the Lucchini study (12), which obtained the largest sample in the general ICU (2,308), surgical ICU (1960), and cardiology ICU (1588), representing a total of 5,856 participants. In the others there was variation between 23 and 758 participants.

Among the 20 articles selected, in 17 (80%) there was a predominance of males, and three of them did not present sex as a variable in the study, ten were published in Portuguese and ten in English. It was observed that the type of research was predominant in the Cohort (9), followed by transverse (6) and observational (5) types, of which eight were prospective and 4 retrospective studies.

DISCUSSION

For purposes of analysis and discussion, the selected articles were segregated into four groups, each group represented by a specificity of ICU, so the studies were separated into: general ICU, surgical ICU, cardiac ICU, and trauma ICU.

Of the 20 selected studies 14 were carried out in General ICU, of these 14 surveys, Padilha's article 11 carried out the research in seven different ICUs, establishing a total of 20 general ICUs. It was observed that among the 20 ICUs studied, the majority (17) had a NAS score greater than 50%, with a maximum score of 101.8, a minimum of 36.1 and an overall mean of 62.6. NAS results higher than 50% show a high nursing workload and express that the professional is able to take care of only one patient per shift, especially in situations in which the leak exceeds 70% represented in the publications of Padilha, Lucchini , and Nogueira 11,12,13.

The exposed values reveal an excess of workload in the nursing professionals, especially in the nurses, since, because they are patients in critical condition, a large part of the procedures performed is exclusive to the professional nurse, not the technician. Because it is endowed with scientific knowledge, nurses have the ability to make quick decisions in the face of intercurrences, besides being responsible for all administrative matters 11,12,13.

The Gerasimou-Angelidi study 14, differed from the majority of articles performed in general ICU, was performed in Greece and presented a lower NAS score (36.1) when compared to the other studies. This was a retrospective study in which the NAS was calculated in the three shifts, obtaining morning NAS scores of 42.5, late 36.6 and night 29.1, with a mean load of 36.1, and the NAS score the reduction of the number of nurses in this shift in relation to the workload.

In all the studies, the NAS is portrayed as an important instrument for the measurement of nursing workload in the ICU, and in only two studies the NAS score was lower compared to the actual number of professionals present, evidencing a number of professionals overestimated, both in private institutions 15,16, in the others, the number of professionals present was lower than the needs proposed by the NAS. Some studies performed the prospective and retrospective application showing homogeneity in both, but the prospective NAS showed an advantage over the retrospective regarding its use for personnel sizing, since it always considers the scheduling of nursing activities 17.

Seven studies were performed in surgical ICUs in three different countries, Brazil 13,18,19,20,21, Greece22 and Italy12, only the Altafin study 19 in a private institution, three specifically in cardiac surgical ICU, two in neurological surgical ICU, and two in general surgical ICU, when we compared the NAS score we noticed a high workload in all studies, with a NAS score> 61.6 in 71% of the studies selected, presenting a minimum average of 58.1, maximum of 74.47 and a general average of 64.9.

The publication of Lucchini 12 performed in 3 different types of ICUs presented a lower NAS score (59.33) due to a progressive decrease in the number of patients attended, and reported an increase in adverse events when there was a negative difference between the available nursing team and the necessary staff according to the number stipulated by the NAS. The study by Novaretti 23 corroborates this result, since it points out the influence of the nursing workload demanded by ICU patients as a risk factor for the occurrence of adverse events and consequently exerts a negative influence on patient safety and length of stay. Only 1 publication did not demonstrate a correlation between an increase in workload and length of stay in the sector 13.

The three studies performed in cardiac ICUs 12,18,21 obtained NAS score 66.00, 58.88 and 63.51 respectively, with a general mean of 62.7, the same ones performed in ICUs of private institutions. It was possible to verify a high workload in all publications, but in a lower score when compared to other specificities, since in all the works related to the cardiology ICU, the nursing workload was measured concomitantly with other specificities of ICUs with objective of comparison. Another factor common to the studies is the male predominance, reduced hospitalization time and low mortality rate, the latter being common to the private institutions of this study. Only one publication 18 shows correlation between NAS score and residence time.

Despite the high NAS scores (63.51 and 67.65), Lucchini 12 and Coelho 18 reported adequate human resources, the studies showed a lower number of mortality than projected by mortality rates, in addition to the reduction of the time of permanence, being able to be associated to a quality nursing assistance consequence of a correct dimensioning of professionals.

Only two studies 24,25 referred to trauma ICU, with NAS scores 72.0 and 71.3 respectively, and overall mean 72.55, they showed a correlation between patient severity and workload, and higher NAS scores at the time of admission, as well as a higher incidence of patients diagnosed with multiple traumas.

Currently in Brazil, DRC n. 26 and the COFEN resolution govern the minimum quantification in the nursing team dimension 3,4. Although this study included studies carried out in other countries in which the legislation regarding nursing team size may differ, a large part of the studies carried out in Brazil have shown an overload of nursing staff due to under-dimensioning.

When comparing the number of professionals required by the NAS with that stipulated by the legislation, we noticed a very large professional gap, both in DRC No. 26 and in the COFEN Resolution, however, the latter is the one that best suits the Brazilian reality, with numbers closer to the stipulated by the NAS, besides taking into account the complexity of the patient, determining that 50% of the team is made up of nurses, since most of the procedures in critical patient care are exclusive ,15,16,17,18,19,20,21,22,23,24,25.

CONCLUSION

The results of this integrative review show a high workload in the ICU, both in general ICUs and in all of the cited specificities, the same with a NAS score> 50.00, especially the trauma ICU, the type that characterized the highest scores 72.00 and 71.3, thus a greater workload. It can be seen that private institutions have adequate nursing staff size, unlike public institutions, which directly reflects the patient's time of permanence and the clinical outcome of the patient, evidenced by the reduction in the mortality rate.

It was observed that in a large part of the research, the average number of nursing professionals calculated by the NAS is higher than the average number of professionals required by the legislation. Even in ICUs with the same specificity, it was possible to perceive large differences in the mean of the NAS score, in this way, we understand that despite having the same specificity, the profile of the patient as well as that of the institution has its peculiarities, requiring different assistance time and consequently divergences in sizing, showing that standard numbers provide inadequate sizing.

The main limitation of this study was due to the few publications on nursing workload in specialized ICUs, both in the national and international settings, which restricts the comparisons and findings presented.

REFERENCIAS

1. Carneiro TM, Fagundes NC. Absenteísmo entre trabalhadoras de enfermagem em unidade de terapia intensiva de hospital universitário. Rev de Enferm UERJ. [Internet]. 2012 jan-mar [Acesso em 10 de jul de 2018]; 20(1): 84-9. Disponível:http://www.epublicacoes.uerj.br/index.php/enfermagemuerj/article/view/3999/2769Links ]

2. Yanaba DS, Giúdice CAR, Casarin SNAC. Dimensionamento da equipe de enfermagem em unidade de terapia intensiva para adultos. J Health Scilnst. [Internet]. 2013 [Acesso em 08 de ago de 2018]; 31(3): 279-285. Disponível: http://www.unip.br/presencial/comunicacao/publicacoes/ics/edicoes/2013/03_julset/V31_n3_2013_p279a285.pdfLinks ]

3. Conselho Federal de Enfermagem. Resolução COFEN n°543/2017, Atualiza e estabelece parâmetros para o Dimensionamento do Quadro de Profissionais de Enfermagem nos serviços/locais em que são realizadas atividades de enfermagem. [Internet]. de 18 de abril de 2017. Brasília (DF): COFEN; 2017. [Acesso em 10 de ago de 2018] Disponível: http://www.cofen.gov.br/resolucaocofen-5432017_51440.htmlLinks ]

4. Agência Nacional de Vigilância Sanitária (Brasil). Resolução n° 26, de 11 de maio de 2012. Altera a Resolução RDC nº 7, de 24 de fevereiro de 2010, que dispõe sobre os requisitos mínimos para funcionamento de Unidades de Terapia Intensiva e dá outras providências. [Internet]. Diário Oficial da União. 11 mai 2012. [Acesso em 10 de ago de 2018]. Disponível: http://bvsms.saude.gov.br/bvs/saudelegis/anvisa/2012/rdc0026_11_05_2012.htmlLinks ]

5. Ferreira SC, Santos MJLO, Estrela FM. Nursing Activities Score e o cuidado em unidade de terapia intensiva. Arq Ciên Saúde. [Internet]. 2016 jan-mar [Acesso em 10 de ago de 2018]; 23(1). Disponível: http://www.cienciasdasaude.famerp.br/index.php/racs/article/download/400/165/Links ]

6. Leite IRL, Silva GRF, Padilha KG. Nursing Activities Score e demanda de trabalho de enfermagem de terapia intensiva. Acta Paul enferm. [Internet]. 2012 [Acesso em 09 de ago de 2018]; 25(6). Disponível: http://www.scielo.br/pdf/ape/v25n6/v25n6a03.pdfLinks ]

7. Camuci MB, Júlia TM, Alexandrina AMC, Maria LCCR. Nursing Activities Score: carga de trabalho de enfermagem em unidades de terapias intensives. Rev Latino-AM Enfer. [Internet]. 2014 mar-abr [Acesso em 10 de ago de 2018]; 22(2). Disponível: DOI: 10.1590/0104-1169.3193.2419 [ Links ]

8. Miranda DR, Nap R, Rijk A, Schaufeli W, Iapichino G. Nursing activities score. Crit Care Med. 2003; 31(2): 374-82. [ Links ]

9. Nunes BK, Toma E. Dimensionamento de pessoal de enfermagem de uma unidade neonatal: utilização do Nursing Activities Score. Rev Latino-AM Enfer. [Internet]. 2013 jan-fev [Acesso em 10 de jul de 2018]; 21(1). Disponível: http://dx.doi.org/10.1590/S0104-11692013000100009 [ Links ]

10. Brevidelli MM, Sertório, SCM. Trabalho de conclusão de curso, guia prático para docentes e alunos da área da saúde. 4a ed. São Paulo: 2013. [ Links ]

11. Padilha KG, SIV S, Diana S, Marga H, Francisco JCM, Hashem G. Nursing Activities Score: manual atualizado para aplicação em unidade de terapia intensiva. Rev Esc de Enferm USP. [Internet]. 2015 [Acesso em 01 de set de 2018]; 49: 131-137. Disponível: http://dx.doi.org/10.1590/S0080-623420150000700019 [ Links ]

12. Lucchini A. et al. Nusing Activities Score (NAS): 5 Years of experience in the intensive care units of na Italian University Hospital.Intensiveand Critical Care Nursing. 2014 30 (3): 152-158. [ Links ]

13. Nogueira LS, Renata ELFR, Vanessa BP, Rita CGS, Ricardo LB, Elaine MO. Carga de trabalho de enfermagem: preditor de infecção relacionada à assistência à saúde na terapia intensiva?. Rev Esc de Enferm USP. [Internet]. 2015 [Acesso em 1 de set de 2018]; 49: 36-42 Disponível: http://dx.doi.org/10.1590/S0080-623420150000700006 [ Links ]

14. Gerasimou-Angelidi S, Myrianthefs P, Chovas A, Poulos GB, Komnos A. Nursing Activities Score as a predictor of family satisfaction in an adult intensive care unit in grace. Journal of Nursing Management [internet] 2014 [Acesso em 4 de set de 2018]; 22: 151-158. Disponível: https://www.ncbi.nlm.nih.gov/pubmed/23859120Links ]

15. Conishi RMY, Gaidzinsk RR. Nursing Activies Score (NAS) como instrumento para medir carga de trabalho de enfermagem em UTI adulto. Rev Esc de Enferm USP. [Internet] 2007 [Acesso em 10 de set de 2018]; 41(3): 346-54. Disponível: http://www.scielo.br/pdf/reeusp/v41n3/02.pdfLinks ]

16. Padilha KG, Sousa RMC, Garcia PC, Bento ST, Finardi EM, Hatarashi RHK. Nursing workload and staff alocation in na intensive care unit: a pilot study according to nursing activities score. Intensive and Critical Care Nursing. [Internet] 2010 [Acesso em 10 de set de 2018]; 26: 108-113. Disponível: http://www.elsevier.com/iccnLinks ]

17. Ducci AJ, Padilha KG. Nursing activites score: estudo comparativo da aplicação retrospectiva e prospectiva em unidade de terapia intensiva. Acta Paul Enferm. [Internet] 2008 [ Acesso em 10 de set de 2018]; 21(4): 581-7. Disponível: http://dx.doi.org/10.1590/S0103-21002008000400008 [ Links ]

18. Coelho FUA, Queijo AF, Andolhe R, Gonçalves LA, Padilha KG. Carga de trabalho de enfermagem em unidade de terapia intensiva de cardiologia e fatores clínicos associados. Texto Contexto Enferm. [Internet] 2011 out-dez [Acesso em 01 de out de 2018]; 20(4): 735-41. Disponível: http://dx.doi.org/10.1590/S0104-07072011000400012 [ Links ]

19. Altafin JAM, Grion CMC, Tanita MT, Festti J, Cardoso LQT, Veiga CFF. et al. Nursing Activities Score e carga de trabalho em unidade de terapia intensiva de hospital universitário. Rev Bras Ter Intensiva. [Internet] 2014 [Acesso em 02 de out de 2018]; 26(3): 292-298. Disponível: http://dx.doi.org/10.5935/0103-507X.20140041 [ Links ]

20. Oliveira LB, Rodrigues ARB, Puschel VAA, Silva FA, Conceição SL, Béda LB et al. Avaliação da carga de trabalho no pós operatório de cirurgia cardíaca segundo o nursing activities score. Rev Esc Enferm USP. [Internet] 2015 [Acesso em 14 de set de 2018]; 49: 80-86. Disponível: http://dx.doi.org/10.1590/S0080-623420150000700012 [ Links ]

21. Siqueira EMP, Ribeiro MD, Soua RCS, Machado FS, Diccini S. Correlação entre carga de trabalho de enfermagem e gravidade dos pacientes críticos gerais, neurológicos e cardiológicos. Rev Esc Anna Nery. [internet] 2015 [Acesso em 07 de out de 2018]; 19(2): 233-238. Disponível: http://www.scielo.br/pdf/ean/v19n2/1414-8145-ean-19-02-0233.pdfLinks ]

22. Giakoumidakis K, Baltopoulos GI, Charitos C, Patelarou E, Galanis P, Brokalaki H. Risk factors for prolonged stay in cardiac surgery intensive care units. Nursing in Critical Care. [Internet] 2011 [Acesso em 07 de out de 2018]; 16(5). Disponível: doi: 10.1111/j.1478-5153.2010.00443.x [ Links ]

23. Novaretti MCZ, Santos EV, Quitério LM, Daud-Gallotti RM. Sobrecarga de trabalho da enfermagem e incidentes e eventos adversos em pacientes internados em UTI. Rev Bras Enferm. [Internet] 2014 set-out [Acesso em 01 nov de 2018]; 67(5):692-9. Disponível: http://www.scielo.br/pdf/reben/v67n5/0034-7167-reben-67-05-0692.pdfLinks ]

24. Goulart LL, Aoki RN, Vegian CFL, Guirardello EB.Carga de trabalho de enfermagem em uma unidade de terapia intensiva. Rev Eletr Enf. [Internet] 2014 abr-jun [Acesso em 01 de nov de 2018]; 16(2):346-51. Disponível em: http://dx.doi.org/10.5216/ree.v16i2.22922 [ Links ]

25. Nogueira LS, Domingues CA, Poggetti RS, Sousa RMC. Nursing workload in intensive care unit trauma patients: analysis of associated factors. Plos one. [Internet] 2014 [Acesso em 01 de nov de 2018]; 9: 112-125. Disponível: https://www.ncbi.nlm.nih.gov/pubmed/25375369Links ]

26. Campagner AOM, Garcia CR, Piva JP. Aplicação de escores para estimar carga de trabalho de enfermagem em uma unidade de terapia intensiva. Ver Bras Ter Intensiva. [Internet] 2014 [Acesso em 01 de nov de 2018]; 26(1): 36-43. Disponível: http://dx.doi.org/10.5935/0103-507X.20140006 [ Links ]

Received: February 07, 2019; Accepted: March 24, 2019

Creative Commons License Este es un artículo publicado en acceso abierto bajo una licencia Creative Commons