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American Journal of Critical Care. 2002;11: 34-37
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Nurses’ Accuracy in Estimating Backrest Elevation

By Amy Dillon, RN, MS, ACNP, Cindy L. Munro, RN, PhD, ANP and Mary Jo Grap, RN, PhD, ACNP. From Winston-Salem Cardiology Associates, Winston-Salem, NC (AD), and Virginia Commonwealth University School of Nursing, Midlothian, Va (CLM, MJG).


   Abstract
Top
 Abstract
Background and Significance
 Statement of the Problem
 Research Methods
 Results
 Discussion
 References
 
• Background Positioning patients is a key component of nursing care and can affect their morbidity and mortality. The Centers for Disease Control and Prevention recommend that patients receiving mechanical ventilation have the head of the bed elevated 30°to 45°to prevent nosocomial pneumonia. However, use of higher backrest positions for critically ill patients is not common nursing practice. Backrest elevation may be affected by the accuracy of nurses’ estimates of patients’ positions.

• Objectives To determine the difference between nurses’ estimates of bed angles and measured bed angles and to describe the relationship between nurses’ characteristics and the accuracy of their estimates.

• Methods A convenience sample of 67 nurses attending the 1999 American Association of Critical-Care Nurses National Teaching Institute and Critical Care Exposition in New Orleans, La. Each subject provided demographic information and estimated 3 bed angles. The angles were preselected by using a random number table. Summary statistics were used and were categorized according to the demographic information provided by participants. Estimated angles were correlated with measured angles, and accuracies in estimating angles were correlated with demographic characteristics.

• Results Nurses were accurate in estimating bed angles (correlation, 0.8488). Demographic information, including sex, age, years of practice, years of critical care practice, basic education, highest educational level, and present position had no relationship to accuracy.

• Conclusions Nurses are able to estimate backrest elevation accurately. Other explanations are needed to understand why recommendations for backrest elevation are not used in practice.

Positioning patients is a key component of nursing care and can affect morbidity and mortality of critically ill patients. Nurses’ selection of backrest position can have an important effect on the patients’ well-being. However, the accuracy of nurses’ estimates of backrest elevation has not been studied. Accuracy in estimating backrest elevation could affect the extent to which nurses can position patients as intended. Thus, congruence of nurses’ estimates of backrest elevation and measurements of backrest elevation are important topics in nursing research.


   Background and Significance
Top
 Abstract
 Background and Significance
Statement of the Problem
 Research Methods
 Results
 Discussion
 References
 
The supine position is an independent risk factor for mortality in patients receiving mechanical ventilation1,2 and in all intensive care patients.3 Kollef3 found that mortality in the intensive care unit (ICU) was greater for supine patients (30.2%) than for semire-cumbent patients (8.9%). Similarly, Torres et al4 found that semirecumbency during the period between extubation and reintubation increased the risk of nosocomial pneumonia in patients who needed reintubation. Height of backrest position and time spent supine are both critical factors in the occurrence of aspiration, which increases the risk of pneumonia in patients receiving mechanical ventilation.5 Aspiration can occur even when the cuff of the endotracheal tube is inflated.6 Use of Fowler’s position (head of bed 45°or higher) reduces the frequency of gastric aspiration and, therefore, ventilator-associated pneumonia.1,5,7 Ventilator-associated pneumonia is a common cause of morbidity and mortality in ICUs.

One reason for use of lower backrest positions in critical care units may be hemodynamic monitoring. However, published reports support use of higher backrest positions for specific procedures such as measuring hemodynamic parameters. Extensive research8–12 with both healthy and critically ill persons has shown that reproducible measurements of pulmonary artery and wedge pressures are obtained with backrest elevations ranging from 0°to 60°Accurate measurements of cardiac output are obtained with backrest elevations ranging from 0°to 30°.9,10,13,14

The recommendations of the Centers for Disease Control and Prevention for prevention of nosocomial bacterial pneumonia in patients receiving mechanical ventilation include elevating the head of the bed at an angle of 30°to 45°, provided that doing so is not contraindicated.15 Two studies3,5 provided empirical evidence that specifically related the effect of backrest positions to the occurrence of ventilator-associated pneumonia, although backrest positions were assessed for only a short period. Use of lower backrest positions (<30°) appears to be common in critical care units, yet description of the frequency of such use is based on limited, cross-sectional data.16 Descriptions of positioning of critically ill patients over time have not been reported.

However, use of higher backrest positions (45°or greater) for critically ill patients is not common nursing practice. Evans16 did a descriptive study to determine how nurses position critically ill patients and whether severity of illness influenced choice of position. The position of the patients was described at a single point, between 4 and 72 hours after admission to the ICU. Evans found that 48% of 113 patients were in the back-lying position (27% right side, 25% left side) and that mean backrest elevation was 23°. A significant negative correlation (r = –0.41) was found between severity of illness (Acute Physiology and Chronic Health Evaluation II score) and degree of elevation. Evans concluded that nurses primarily use supine positions or positions with little backrest elevation for critically ill patients. However, no data were reported on time of day, hemodynamic or ventilatory status, or use of nutritional support during the data collection period—factors that might affect decisions on positioning patients.

To determine the usual bed elevation and backrest position in a medical ICU and the relationship of those factors to hemodynamic status and enteral feeding, Grap et al17 randomly obtained 347 measurements of backrest elevation. Mean backrest elevation was 22.9°, and 86% of the subjects were supine. Level of backrest position was associated with systolic (r = –0.04, P = .49), diastolic (r = 0.01, P = .83), or mean arterial (r = –0.01, P = .84) blood pressure. Backrest elevation did not differ significantly between patients who were receiving enteral feedings and patients who were not (P =.23) or between patients receiving intermittent nutrition and patients receiving continuous nutrition (P =.22).

Use of higher levels of backrest elevation is minimal and is not related to use of enteral feeding or to hemodynamic status. The rationale for using lower backrest positions for critically ill patients may be based on convenience, patients’ comfort, usual patterns in the unit, or nurses’ ability to estimate backrest elevation accurately. However, no data exist on what nurses intend with regard to backrest elevation for patients. Possibly, backrest elevation is affected by accuracy of nurses’ estimates of patients’ positions.


   Statement of the Problem
Top
 Abstract
 Background and Significance
 Statement of the Problem
Research Methods
 Results
 Discussion
 References
 
The specific aims of this project were (1) to determine the difference between nurses’ estimates of bed angles and measured bed angles and (2) to describe the relationship between nurses’ characteristics and the accuracy of their estimates of bed angles.

Backrest position is affected by many factors, including nurses’ decisions, nurses’ accuracy, and patients’ characteristics. Nurses’ decisions about positioning are based on the nurses’ knowledge of common practice and the current literature. For example, it is common knowledge among nurses that the backrest should be elevated during tube feedings to reduce the risk of aspiration. Nurses’ accuracy in estimating back-rest elevation affects the backrest position. What looks like 45°to one nurse may look like 30°to another, thus altering consistency in patients’ care. This accuracy could be affected by nurses’ characteristics, including years of practice or practice setting. The third attribute that affects backrest position is the actual patient. Patients’ characteristics, including hemodynamic stability, affect the position of the backrest.

The focus of the research reported here was nurses’ accuracy in estimating backrest elevation. Because the effects of nurses’ decisions or patients’ characteristics on backrest position were not considered, an empty bed was used. Use of an empty bed helped focus the results solely on the accuracy of the nurses’ estimates without the addition of extraneous factors.


   Research Methods
Top
 Abstract
 Background and Significance
 Statement of the Problem
 Research Methods
Results
 Discussion
 References
 
The study used a convenience sample of nurses attending the National Teaching Institute conference of the American Association of Critical-Care Nurses. This national critical care conference is the premier showcase for nursing research and practice in critical care. The research reported at the conference is important to the nursing community, especially critical care nurses. Participants for our study were recruited at the exhibit hall at the Kinetic Concepts, Inc (San Antonio, Tex) and Stryker Medical (Kalamazoo, Mich) exhibit booths. Kinetic Concepts Inc and Stryker Medical are manufacturers of beds used in ICUs. The bed used for the study was a Stryker Medical Apex bed.

The bed angles were selected by using a random number table. Increments of 5°were used. The bed angle was measured and set by using the protractor method described by Grap et al.17 The subjects provided demographic information.

The researcher set the bed angle and asked the subjects to estimate the angle. Subjects recorded their responses on the data sheet. The process was repeated 2 more times, for a total of 3 observations of 3 different bed angles. This process provided 201 observations for analysis. The subjects’ responses were self-recorded as a range.

The decision to ask nurses to estimate within a range rather than to estimate an exact number reflects our belief that accuracy within a 5°range is more important in the clinical setting than is absolute accuracy to a specific number. That is, ability to accurately estimate an angle as being in the range of 40°to 45°would enable a nurse to comply with the recommendations of the Centers for Disease Control and Prevention, even if the nurse could not distinguish accurately between 40°and 41°. Data were entered into a JMP (SAS Institute, Cary, NC, 1999) database for statistical analysis.


   Results
Top
 Abstract
 Background and Significance
 Statement of the Problem
 Research Methods
 Results
Discussion
 References
 
A total of 67 nurses who attended the 1999 National Teaching Institute conference participated in this study. A majority of the participants were female. Ages of participants were representative of the working population of critical care nurses and ranged from 25 to 60 years. The majority of the subjects presently worked full-time in critical care. Descriptive data are summarized in Table 1Go.


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  		Table 1 Demographic characteristics of the sample

 
Correlations between subjects’ demographic data and their accuracy in estimating bed angles are given in Table 2Go. The overall correlation between the real angle and the estimated angle was 0.8488. No significant correlation was found between the accuracy of estimation and the demographic characteristics. Sex of the subject did not have an effect; male participants had a mean difference between estimated and actual angle of 6.67° (SD, 4.78°), and female participants had a mean difference of 7.44° (SD, 5.29°). Age, years of nursing practice, educational level, years in critical care, and years in present position were not associated with the accuracy of the estimate of bed angle.


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  		Table 2 Correlation of major demographic variables with accuracies in estimating angles

 

   Discussion
Top
 Abstract
 Background and Significance
 Statement of the Problem
 Research Methods
 Results
 Discussion
References
 
The high correlation between nurses’ estimates and measured angles indicates that nurses can estimate bed angles accurately. Interestingly, this accuracy is not affected by any of the demographic information that we obtained, including years in nursing or years in critical care. Thus, time spent in the clinical setting does not affect the ability to estimate the position of the bed accurately. Our results suggest that nurses’ accuracy in estimating the angle of the head of the bed does not play a role in backrest position. This conclusion further suggests that the accuracy of nurses’ estimates is not the primary reason why nurses are not elevating the head of the bed to the 30°to 45°that is recommended. Therefore, patients’ characteristics, nurses’ decisions, or both affect backrest position.

Our findings indicate that nurses do not need additional assistance to estimate bed angle accurately. Although patients’ characteristics cannot be modified to a great extent by bedside nurses, nurses’ decisions can be modified. Thus, efforts to change patients’ positioning will need to focus on changes in nurses’ decisions about positioning. Several approaches might be useful. First, increased emphasis should be placed on the risks associated with supine, flat positioning, and the benefits of backrest elevation must be communicated more clearly to practicing nurses. Second, increasing nurses’ awareness of their positioning decisions might encourage conscious selection of backrest elevation. Nurses’ awareness might be increased by having bed angle routinely documented on the critical care flow sheet. Such documentation could enhance responsibility for positioning. This routine documentation could be facilitated by design of critical care beds; several manufacturers include digital readout of backrest elevation as a feature. In-service training programs could be designed to improve the use of optimal positioning practices.

Advanced practice nurses have an important role in ensuring that patients are appropriately positioned. First, advanced practice nurses can serve as role models of expert practice; thus, advanced practice nurses’ decisions on positioning can have a beneficial effect on the practices of other nurses. Second, many advanced practice nurses have opportunities to provide formal staff education. Inclusion of appropriate positioning of patients in critical care in-service education could improve practice. Last, advanced practice nurses can be involved in research. Additional nursing research is needed to demonstrate the effects of nurses’ decisions about positioning on patients’ outcomes and to examine the effectiveness of strategies to change nursing practice related to positioning.


   ACKNOWLEDGMENTS
 
We thank Sigma Theta Tau, Gamma Omega Chapter, for sponsoring this research project. We also thank Kinetic Concepts, Inc (San Antonio, Tex) and Stryker Medical (Kalamazoo, Mich) for their assistance at the convention. Both companies were very helpful in finding a suitable bed for the project and in encouraging people to become subjects. These companies’ dedication to nursing research is appreciated.

To purchase reprints, contact The InnoVision Group, 101 Columbia, Aliso Viejo, CA 92656. Phone, (800) 809-2273 or (949) 362-2050 (ext 532); fax, (949) 362-2049; e-mail, reprints{at}aacn.org.


   REFERENCES
Top
 Abstract
 Background and Significance
 Statement of the Problem
 Research Methods
 Results
 Discussion
 References
 

  1. Kollef MH. Ventilator-associated pneumonia: a multivariate analysis. JAMA. 1993;270:1965–1970.[Abstract]
  2. Craven DE, Kunches LM, Kilinsky V, Lichtenberg DA, Make BJ, McCabe WR. Risk factors for pneumonia and fatality in patients receiving continuous mechanical ventilation. Am Rev Respir Dis. 1986;133:792–796.[Medline]
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M. J. Grap, C. L. Munro, R. S. Hummel III, R.K. Elswick Jr, J. L. McKinney, and C. N. Sessler
Effect of Backrest Elevation on the Development of Ventilator-Associated Pneumonia
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