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AACN Advanced Critical CareVolume 20, Number 3, pp.228240

In the Public Domain

Physiological Rationale and Current Evidence for TherapeuticPositioning of Critically Ill Patients

Karen L. Johnson, RN, PhD

Tim Meyenburg, RN, MS, CNL

Prolonged bed rest is common in critically illpatients, and therapeutic positioning isimportant to prevent further complicationsand to improve patient outcomes. Nursesuse therapeutic positioning to prevent com-plications of immobility. This article reviewstherapeutic positions including stationarypositions (supine, semirecumbent with headof bed elevation, lateral, and prone) and

active repositioning (manual, continuouslateral rotation, and kinetic therapy). Thephysiological rationale and current evidencefor each position are described. Applicableevidence-based practice guidelines are sum-marized. Special considerations for thera-peutic positioning of critically ill obese andelderly patients are also discussed.Keywords: critically ill, positioning

A B S T R A C T

Stationary PositionsSupine PositionIn the supine position, ventilation and perfu-sion are greater in dependent areas of the lungsthan in the anterior areas. In healthy lungs,adequate matching of ventilation and perfu-sion (V/Q match) can be achieved in the supineposition. In diseased lungs, prolonged place-ment in the supine position can alter the V/Qmatch. For example, excess fluid associatedwith pulmonary edema accumulates in thedependent areas of the lungs and interferes

Multiple factors relegate critically illpatients to strict bed rest includingaltered level of consciousness, drugs that pre-vent mobility (paralytics, sedatives), trau-matic injuries, and surgical complications(open chest or abdominal cavities). However,bed rest is associated with multiple compli-cations that are well documented in the liter-ature (Table 1). Because critical care nursesare keenly aware of these complications,they use clinical judgment in their daily prac-tice to place bedridden patients in the mostoptimal position to prevent these complica-tions and to improve patient outcomes. Thepurpose of this article was to review optionsof therapeutic positioning in critically illpatients. The physiological rationale andcurrent evidence for stationary and activerepositioning are described. In addition,positioning of critically ill obese and elderlypatients is discussed.

Karen L. Johnson is Director of Nursing, Research and Evidence-Based Practice, University of Maryland Medical Center, 22 S Greene St, 7 Gudelsky, Room C728, Baltimore, MD21201. She is also Associate Professor, Trauma/Critical Care/Emergency Nursing Masters Program, University of Maryland,School of Nursing, Baltimore (kjohnson8@umm.edu).

Tim Meyenburg is Clinical Nurse II, Surgical ICU, Universityof Maryland Medical Center, Baltimore.

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with diffusion of gases across the alveolar-capillary membranes. Perfusion, however,remains constant in the dependent areas.Therefore, there is a V/Q mismatch that resultsin an intrapulmonary shunt.

The supine position results in anatomicalchanges that alter ventilation and perfusion,especially in patients with enlarged hearts. Inthe supine position, the major part of the leftlower lobe and a significant part of the rightlower lobe are located beneath the heart.6

Enlarged hearts produce an increased pleuralpressure in the dependent areas and contributeto alveolar collapse.6 Studies using isotope ven-tilation-perfusion scans in patients with car-diomegaly and no evidence of pulmonarypathology have shown a 40% to 50% reduc-tion in left lower lobe ventilation in a prolongedsupine position with no concomitant reductionin regional perfusion.7,8 Patients with acute res-piratory distress syndrome (ARDS) who aremechanically ventilated while in the supineposition develop atelectasis in the dependentareas of the lungs.9 Ventilation is impaired byairway secretions, lung edema, and cardiac andabdominal compression of the lungs while per-fusion is maintained, and this results in intra-pulmonary shunt and severe hypoxemia.10,11

Semirecumbent Position With Head of Bed ElevationHead of bed (HOB) elevation is an importantcomponent of the semirecumbent position thatmust be considered for patients who are receiv-ing enteral nutrition to prevent aspiration ofgastric contents and ventilator-associatedpneumonia (VAP). Several studies using radio-labeled enteral feeding solutions in mechani-

cally ventilated patients have reported thataspiration of gastric contents occurs to agreater degree when patients are in the supineposition than when they are in the semi-recum-bent position with the HOB elevated to 30 to45.1214 Drakulovic and colleagues15 conducteda prospective, randomized clinical trial to com-pare continuous HOB elevation of 45 to noelevation in the early mechanical ventilationperiod and found a significantly greater inci-dence of VAP in patients who did not haveHOB elevation. More recently, this work wasextended by Grap and colleagues,16 who foundthat VAP was more likely to occur in patientswho spent more initial mechanical ventilationtime with HOB elevation of less than 30.

Because of these studies, multiple clinicalpractice guidelines have stated that the semire-cumbent position with HOB elevation of 30to 45 should be used for critically ill patientsto prevent aspiration pneumonia and VAP.These guidelines include those issued by theAmerican Association of Critical-Care Nurses(AACN),17 the Centers for Disease Controland Prevention,18 the Society of Critical CareMedicine,19 the American Thoracic Society,20

and the Canadian Critical Care Society.21 Inaddition to the benefits of HOB elevation, crit-ical care nurses need to be aware of the con-traindications of this position and to applyappropriate judgment. Contraindications toHOB elevation, as identified in the AACNVAP Practice Alert Audit Tool,17 are summa-rized in Table 2.

Table 1: Complications of Bed Rest

Pulmonary1,2

Atelectasis

Pneumonia

Hypoxemia

Cardiovascular

Venous thromboembolism3

Syncope because of diminished baroreceptor activity

Skin integrity

Pressure ulcers5

Table 2: Contraindications to HOBElevation in Critically Ill Patients

Cardiovascular

Low cardiac index

Hypotension

Neurological

Ischemic stroke

Traumatic brain injury

Processes of care

Procedure in progress in which HOB elevation is inappropriate

Prone position

Medical order for no HOB elevation

Abbreviation: HOB, head of bed.

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It is important for critical care nurses to rec-ognize that HOB elevation above 30 mayincrease the risk of pressure ulcer formation.In a study of 57 patients in a surgical intensivecare unit (ICU), patients placed in semi-Fowlers position had higher sacral tissueinterface pressures when compared with thoseplaced in other positions, regardless of thetype of pressure redistribution surfaceselected.22 These results have been confirmedin a more recent study involving healthy vol-unteers. Defloor23 evaluated tissue interfacepressures and found that pressures in thesacral area were higher when the HOB waselevated to 90 than when it was elevated to60. He found that the lowest tissue interfacepressures occurred when patients were placedin a semi-Fowlers position with the HOB ele-vated up to 30 and the knees elevated to 30.The Wound, Ostomy and Continence NursesSociety recommends maintaining the HOB at30 elevation for supine positions.24 There arevery few studies to support the use of a special-ized mattress to reduce elevated sacral pres-sures caused by HOB elevation, and the resultsare inconclusive.25,26

The optimal semirecumbent HOB elevationposition that reduces the development of aspi-ration pneumonia, VAP, and pressure ulcers isnot known. Until there is further evidence,nurses must use their judgment on the HOB ele-vation that is best for each individual patient.That judgment should be guided by the level ofevidence to support the degree of HOB eleva-tion. And to that end, as Grap and Munro27

point out, the level of evidence for the use oflower HOB elevation to prevent sacral pressureulcers (1 controlled trial, at least 2 descriptivecase studies or expert opinion) is not as strongas that for HOB elevation to prevent aspirationpneumonia and VAP (clinical or epidemiologi-cal studies or strong theoretical rationale).

Although there is evidence to support HOBelevation for critically ill patients in the semi-recumbent position, HOB elevation does notappear to be routinely implemented amongintubated patients. In a pilot study in 1999,Grap and colleagues28 found that in 347 meas-urements of 52 critically ill medical patients,the mean backrest elevation was 22.9 andthat patients were in the supine position 86%of the time, despite the presence of enteralfeedings. In a subsequent study in 2003,involving 506 observations of 170 patients inseveral ICUs, the results were worse: Mean

backrest elevation was 19, 70% of thepatients were in the supine position, and intu-bated patients had lower backrest elevationsthan did nonintubated patients.29 One expla-nation for nurses not complying with HOBelevation may be the inability to accuratelyestimate backrest elevation.27

To address these issues, AACN issued aVAP Practice Alert in 2004.17 The PracticeAlert included a procedure to audit backrestelevation, suggestions for audit frequency,and a data collection tool. These efforts seemto have had a positive effect. A recent surveyof 1200 critical care nurses who attended the AACN National Teaching In