title: Subjective assessment of backrest elevation: magnitude of error.
abstract: BACKGROUND
  Backrest elevation, defined as the angle of the backrest height above the horizontal position, is a common nursing intervention that is often used by subjective visual estimation in critically ill patients.
  
  
  OBJECTIVE
  The aim of the study was to describe the magnitude of error during the subjective assessment of backrest elevation.
  
  
  METHODS
  This prospective study was conducted in a sample of 160 subjects: 97 registered nurses, 48 undergraduate nursing students, and 15 nursing assistants. Data were collected by recording the degrees of backrest elevation identified by the subjects through an individual random presentation of the selected study angles of 20 degrees, 30 degrees, 35 degrees, 40 degrees, and 45 degrees. A measurement instrument was developed for determination of the angles.
  
  
  RESULTS
  Of the 800 investigated angles, 14.9% were estimated accurately, 61.6% were overestimated, and 23.5% were underestimated, with an error average of 8 degrees (+/-13.5 degrees). It was determined that the larger the angle estimated, the greater the average error. A statically significant difference (P <or= .001) was found between the actual degree of backrest elevation and the estimated backrest elevation for 20 degrees, 40 degrees, and 45 degrees with the exception of 30 degrees and 35 degrees, which had similar averages of error. Years of critical care experience did not significantly influence the magnitude of error.
  
  
  CONCLUSIONS
  The results indicate that the subjective assessment of backrest angle may result in errors that may potentially compromise the patient's condition and supports the need for a more objective method for determining backrest angle.
authors.affiliation: Nursing Department, Federal University of São Paulo, UNIFESP, São Paulo City, Brazil.
authors.forename: Maria Angélica S
authors.initials: MA
authors.lastname: Peterlini
authors.forename: Patrícia K
authors.initials: PK
authors.lastname: Rocha
authors.forename: Denise M
authors.initials: DM
authors.lastname: Kusahara
authors.forename: Mavilde L G
authors.initials: ML
authors.lastname: Pedreira
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000328:Adult; D001513:Beds; D003422:Critical Care / Q000379:methods*; D016638:Critical Illness / Q000451:nursing*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011187:Posture; D011446:Prospective Studies