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Making it possible to measure knowledge, experience and intuition in diagnosing lung injury severity: a fuzzy logic vision based on the Murray score.

D'Negri CE, De Vito EL - BMC Med Inform Decis Mak (2010)

Bottom Line: Murray score is the result of an equation that gives all its variables the same linear contribution and weight and makes use of consented cut-offs.An overestimation was found in the surveyed group's interpretation of severity.FL methodology could overcome a series of restrictions that current tests have due to cut-offs.

View Article: PubMed Central - HTML - PubMed

Affiliation: Consejo Nacional de Investigaciones Científicas y Técnicas, Combatientes de Malvinas 3150, CP 1427, Buenos Aires, Argentina. cdnegri@lanari.fmed.uba.ar

ABSTRACT

Background: Murray score is the result of an equation that gives all its variables the same linear contribution and weight and makes use of consented cut-offs. Everyday physicians' vocabulary is full of terms (adjectives) like: little, small, low, high, etc. that they handle in an intuitive and not always linear way to make therapeutic decisions. The purpose of this paper is to develop a fuzzy logic (FL) vision of Murray's score variables to enable the measurement of physicians' knowledge, experience and intuition in diagnosing lung injury and test if they followed Murray's equation predictions.

Methods: For a prospective survey carried out among a team of professionals (aged 29 to 53) in a University Hospital Intensive Care Unit, twelve physicians filled in two questionnaires. In the first one they had to define the ranks which should be categorized as normal, moderate and severe for three of four Murray variables. In another questionnaire, which represented all probable combinations of those categories, they had to tick the pulmonary condition as: no injury, mild, moderate, and ARDS. This procedure gave rise to a Fuzzy Inference System designed to provide the degree of severity as sensed by the group.

Results: The survey showed fuzzy frontiers for the categories and fuzzy diagnosis. In all, 45% of the hypothetical patients (n 18,013) were equally diagnosed by the survey and Murray's equation, whereas another 51% was overestimated in one level by the survey. Physicians agreed with 96.5% of ARDS cases according to Murray's test but only 11.6% of its mild cases were equally diagnosed by the survey. Nonlinearity of the survey reasoning (high relevance to gas exchange and chest film) was apparent.

Conclusions: The contiguous categories of the variables confirm the existence of fuzzy frontiers. An overestimation was found in the surveyed group's interpretation of severity. This overestimation was mainly due to the different weight assigned to PO2/FiO2 and chest film variables. The FL approach made it possible to measure knowledge, experience and intuition as they appear in physicians' thinking. FL methodology could overcome a series of restrictions that current tests have due to cut-offs.

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Membership functions of Murray variables. (a) PO2/FiO2 functions: severe, moderate and normal (left to right). (b) Compliance functions: severely diminished, moderately diminished and normal (left to right). (c) PEEP functions: low, moderate and high (left to right). (d) Chest film functions: for 0 through 4 quadrants consolidations; vertical lines at 0, 1, 2, 3 and 4 represent Murray's values assigned to this variable. Murray bands (grey and white strips) were drawn superimposed in the first three graphs and bands' values are seen embedded in them.
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Figure 1: Membership functions of Murray variables. (a) PO2/FiO2 functions: severe, moderate and normal (left to right). (b) Compliance functions: severely diminished, moderately diminished and normal (left to right). (c) PEEP functions: low, moderate and high (left to right). (d) Chest film functions: for 0 through 4 quadrants consolidations; vertical lines at 0, 1, 2, 3 and 4 represent Murray's values assigned to this variable. Murray bands (grey and white strips) were drawn superimposed in the first three graphs and bands' values are seen embedded in them.

Mentions: Physicians were requested to fill in a form that included two questionnaires. The first one was related to the following three variables: PaO2/FiO2 ratio (values from 0 to 450 were subdivided in 9 equal segments), Compliance (values from 0 to 100 ml/cmH2O were subdivided in 10 equal segments ) and PEEP (values from 0 to 20 cmH2O were subdivided in 10 equal segments) in which they had to indicate which range was to be assigned to each of a three-category division (low, medium, high) with no overlapping and no gaps in between. Of course, coincidence among all those surveyed proved to be impossible. This fact introduces the first aspect of fuzziness: individual criteria for the above-mentioned adjectives are not unique and thus fuzzy frontiers arise. With these variables it was possible to construct nine membership functions (figure 1a, b, c) [see procedure in Appendix II (a)]. The fourth variable (chest film) strictly followed the five categories defined by Murray's score (figure 1d), [see details in Appendix II (b)].


Making it possible to measure knowledge, experience and intuition in diagnosing lung injury severity: a fuzzy logic vision based on the Murray score.

D'Negri CE, De Vito EL - BMC Med Inform Decis Mak (2010)

Membership functions of Murray variables. (a) PO2/FiO2 functions: severe, moderate and normal (left to right). (b) Compliance functions: severely diminished, moderately diminished and normal (left to right). (c) PEEP functions: low, moderate and high (left to right). (d) Chest film functions: for 0 through 4 quadrants consolidations; vertical lines at 0, 1, 2, 3 and 4 represent Murray's values assigned to this variable. Murray bands (grey and white strips) were drawn superimposed in the first three graphs and bands' values are seen embedded in them.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2991274&req=5

Figure 1: Membership functions of Murray variables. (a) PO2/FiO2 functions: severe, moderate and normal (left to right). (b) Compliance functions: severely diminished, moderately diminished and normal (left to right). (c) PEEP functions: low, moderate and high (left to right). (d) Chest film functions: for 0 through 4 quadrants consolidations; vertical lines at 0, 1, 2, 3 and 4 represent Murray's values assigned to this variable. Murray bands (grey and white strips) were drawn superimposed in the first three graphs and bands' values are seen embedded in them.
Mentions: Physicians were requested to fill in a form that included two questionnaires. The first one was related to the following three variables: PaO2/FiO2 ratio (values from 0 to 450 were subdivided in 9 equal segments), Compliance (values from 0 to 100 ml/cmH2O were subdivided in 10 equal segments ) and PEEP (values from 0 to 20 cmH2O were subdivided in 10 equal segments) in which they had to indicate which range was to be assigned to each of a three-category division (low, medium, high) with no overlapping and no gaps in between. Of course, coincidence among all those surveyed proved to be impossible. This fact introduces the first aspect of fuzziness: individual criteria for the above-mentioned adjectives are not unique and thus fuzzy frontiers arise. With these variables it was possible to construct nine membership functions (figure 1a, b, c) [see procedure in Appendix II (a)]. The fourth variable (chest film) strictly followed the five categories defined by Murray's score (figure 1d), [see details in Appendix II (b)].

Bottom Line: Murray score is the result of an equation that gives all its variables the same linear contribution and weight and makes use of consented cut-offs.An overestimation was found in the surveyed group's interpretation of severity.FL methodology could overcome a series of restrictions that current tests have due to cut-offs.

View Article: PubMed Central - HTML - PubMed

Affiliation: Consejo Nacional de Investigaciones Científicas y Técnicas, Combatientes de Malvinas 3150, CP 1427, Buenos Aires, Argentina. cdnegri@lanari.fmed.uba.ar

ABSTRACT

Background: Murray score is the result of an equation that gives all its variables the same linear contribution and weight and makes use of consented cut-offs. Everyday physicians' vocabulary is full of terms (adjectives) like: little, small, low, high, etc. that they handle in an intuitive and not always linear way to make therapeutic decisions. The purpose of this paper is to develop a fuzzy logic (FL) vision of Murray's score variables to enable the measurement of physicians' knowledge, experience and intuition in diagnosing lung injury and test if they followed Murray's equation predictions.

Methods: For a prospective survey carried out among a team of professionals (aged 29 to 53) in a University Hospital Intensive Care Unit, twelve physicians filled in two questionnaires. In the first one they had to define the ranks which should be categorized as normal, moderate and severe for three of four Murray variables. In another questionnaire, which represented all probable combinations of those categories, they had to tick the pulmonary condition as: no injury, mild, moderate, and ARDS. This procedure gave rise to a Fuzzy Inference System designed to provide the degree of severity as sensed by the group.

Results: The survey showed fuzzy frontiers for the categories and fuzzy diagnosis. In all, 45% of the hypothetical patients (n 18,013) were equally diagnosed by the survey and Murray's equation, whereas another 51% was overestimated in one level by the survey. Physicians agreed with 96.5% of ARDS cases according to Murray's test but only 11.6% of its mild cases were equally diagnosed by the survey. Nonlinearity of the survey reasoning (high relevance to gas exchange and chest film) was apparent.

Conclusions: The contiguous categories of the variables confirm the existence of fuzzy frontiers. An overestimation was found in the surveyed group's interpretation of severity. This overestimation was mainly due to the different weight assigned to PO2/FiO2 and chest film variables. The FL approach made it possible to measure knowledge, experience and intuition as they appear in physicians' thinking. FL methodology could overcome a series of restrictions that current tests have due to cut-offs.

Show MeSH
Related in: MedlinePlus