physiological rationale and current evidence for therapeutic

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AACN Advanced Critical CareVolume 20, Number 3, pp.228–240

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 ill

patients, and therapeutic positioning is

important to prevent further complications

and to improve patient outcomes. Nurses

use therapeutic positioning to prevent com-

plications of immobility. This article reviews

therapeutic positions including stationary

positions (supine, semirecumbent with head

of bed elevation, lateral, and prone) and

active repositioning (manual, continuous

lateral rotation, and kinetic therapy). The

physiological rationale and current evidence

for each position are described. Applicable

evidence-based practice guidelines are sum-

marized. Special considerations for thera-

peutic positioning of critically ill obese and

elderly 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 including

altered 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, MD

21201. She is also Associate Professor, Trauma/Critical Care/

Emergency Nursing Masters Program, University of Maryland,

School of Nursing, Baltimore ([email protected]).

Tim Meyenburg is Clinical Nurse II, Surgical ICU, University

of Maryland Medical Center, Baltimore.

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VOLUME 20 • NUMBER 3 • JULY–SEPTEMBER 2009 POSITIONING

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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�.12–14 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 30�to 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-Fowler’s 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-Fowler’s 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 Institute aswell as other national educational programsreported that they maintained the HOBelevations 30� to 45� most of the time. Morethan 85% of the respondents reported thatthey maintain HOB elevations 30� to 45 fortheir patients 86% of the time.30 The VAPPractice Alert was recently revised to includeadditional sources of evidence and the levelsof evidence to support the Practice AlertStatements.

The VAP Practice Alert Audit Tool containsmethods to estimate HOB elevation (Figure 1).

Figure 1: Methods for Estimating HOB Elevation.HOB indicates head of bed elevation. Reprintedwith permission from the American Association ofCritical-Care Nurses.115

• Use the built-in angle measurement for HOB elevation ifavailable.

• Use a simple protractor positioned on the horizontalframe of the bed and the frame of the backrest at thepivot point of the backrest.

• Calculate the angle of the backrest elevation by mea-suring the length of the backrest from the pivot area (A on diagram below) to the top of the backrest (B). Thenmeasure from the top of the backrest (B) straight down tothe horizontal frame of the bed (C). Divide the distancefrom B to C by the distance from A to B and take the arcsine of that product. Angle of backrest � arc sine of (A to B)/(B to C).

Example: The angle of backrest elevation for a backrest (A to B) which is 32 in, which is 16 in above the frame (B to C), is equal to the arc sine of32/16 � 30 degrees.

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Stationary Lateral PositionsThe decision to place critically ill patients inthe left or right lateral decubitus position isbased on relevant lung pathology and hemo-dynamic stability. Studies have shown thatwhen patients with unilateral lung disease(pneumonia, atelectasis) are placed with theconsolidated lung in the dependent position,there is a mismatch of ventilation to perfusionthat results in hypoxemia.31–36 Placement of thediseased lung in the dependent lateral positionresults in greater perfusion to a diseased poorlyventilated lung and impairs gas exchange.Therefore, patients with unilateral lungpathology should be placed in a lateral posi-tion with the “good” lung down. Even thoughthis is the golden rule for patients with unilat-eral disease, there are contraindications to thisposition in certain lung pathologies. For exam-ple, in patients with pulmonary abscesses orpulmonary hemorrhage, it is important tokeep the affected lung in the dependent posi-tion so that drainage will not migrate towardthe healthy lung.37,38 In addition, patients withinterstitial emphysema should be placed withthe affected lung in the dependent position toprevent hyperinflation.38

Although there is evidence to support lat-eral positioning in patients with unilateralpulmonary disease, less is known about theeffects of lateral positioning on oxygenationin patients with bilateral pulmonary disease.At 10 to 30 minutes after a lateral positionchange, cardiac output and heart rate maynot be the same as in the supine position, butthese changes in most mechanically venti-lated patients are not clinically significant.39–43

Early evidence demonstrated that cardiovas-cular changes can be highly individualizedand may be most prominent in patients withlow cardiac output and in patients who arehypothermic and/or receiving vasoactivemedications.41 More recent evidence suggeststhat lateral positioning of critically illpatients who are hypoxemic or have low car-diac output does not further endanger tissueoxygenation.44

Prone PositionResearch demonstrates that prone positioningin critically ill patients with acute lung injuryand/or ARDS improves pulmonary gasexchange45,46 and reduces the rate of VAP.47,48

The physiological mechanisms responsible forimprovement in pulmonary gas exchange have

not been fully elucidated. Possible mechanismsmay include better drainage of pulmonarysecretions,45 reopening of atelectactic units inthe dorsal regions of the lungs,49 and minimiz-ing ventilator-induced lung injury.50 The opti-mal response and beneficial effect of pronepositioning may occur during the early edema-tous phase of ARDS when atelectasis and lungedema predominate.51 Despite these improve-ments in pulmonary gas exchange, 2 recentstudies reported no survival benefit for the useof the prone position in ARDS.48,52 The ration-ale for this lack of a survival benefit is not clearbut it should be noted that the average range oftidal volume given to patients in these studieswas 9 mL/kg, which may have contributed toventilator-induced lung injury.53

Alsaghir and Martin54 recently conducted asystematic review and meta-analysis to assessthe effect of the prone position, as compared tothe supine position, on improvement in oxy-genation, number of days on the ventilator, VAP,and mortality. They included 5 randomized con-trolled trials (n � 1316) comparing greater than6 hours of prone position in adult patients withARDS. Prone positioning showed significantand persistent improvement in PaO2/FIO2 in allphases of ARDS (Table 3). However, significantstatistical heterogeneity of treatment effect wasfound, meaning that the results were highly vari-able across studies. Sources of clinical hetero-geneity included when proning was initiated andthe duration of the prone position. Treatmenteffect heterogeneity may mask substantial bene-fit for some, little benefit for others, and harmfor a few.58 There were no significant differencesin number of days on mechanical ventilation orthe incidence of VAP (Table 3). Although no sig-nificant difference in short-term or long-termmortality was reported, a couple of studiesshowed that prone position significantlyreduced mortality in patients with higher illnessseverity (Table 4). Future randomized controlledtrials focusing on early initiation of the proneposition while controlling for time in the proneposition are warranted.

Currently there are no clinical practiceguidelines that recommend the use of pronepositioning to decrease VAP. However, recentguidelines released by the Society of CriticalCare Medicine recommend prone positioningin patients with ARDS who require potentiallyinjurious levels of FIO2 or have elevated plateaupressures, who are not at high risk for adverseconsequences of positional changes, in facilities

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that have experience with such practices.19

Adverse consequences include dislodgement ofthe artificial airway and enteral feeding tubes,loss of venous access, development of facialedema and pressure ulcers, and difficultieswith cardiopulmonary resuscitation. Potentialcontraindications to the use of the prone posi-tion, as summarized by Ball and colleagues,59

are listed in Table 5.For critical care units that use prone posi-

tioning, evidence-based guidelines for bedsidenurses should be in place. These guidelinesshould include indications and contraindica-tions, preprone assessment and safety prac-tices, strategies for placing the patient in theprone position, assessment guidelines for mon-itoring patient response to the prone position,and limb positioning while in the prone posi-tion. The reader is referred to several pub-lished clinical practice guidelines on the use ofprone positioning in critically ill patients.59–61

Active RepositioningHealthy individuals change positions, even dur-ing sleep, approximately every 12 minutes.62 A

variety of sensory cues prompt a change in bodyposition. These sensory cues prevent detrimen-tal effects of prolonged periods of immobility.Individuals who have neurological or sensori-motor impairments must rely on others to repo-sition them to prevent hazards of immobility.

Manual RepositioningRepositioning is conceptualized as turning thepatient from side to side when lying in bed oron a similar surface.63–65 Within this context,the patient is placed in a side-lying positionwith the pelvis rotated approximately 30�from the supine position.65 The current stan-dard of care is to reposition patients every 2 hours. This standard is based on 2 studiesconducted in the early 1960s in healthy indi-viduals.66,67 Repositioning every 2 hours is thenursing standard for all immobilized criticallyill patients as documented in nursing text-books68,69 and national guidelines.70 A survey ofICU physicians revealed that 83% of respon-dents agreed that the standard of ICU care isto turn patients every 2 hours.71 However, aprospective longitudinal observational study

Table 3: Results of Meta-analysis on Effects of Prone Positioning on PaO2/FIO2, Days onMechanical Ventilation, and Incidence of Ventilator-Associated Pneumoniaa

Number Weighted Mean Outcome Variables of Studies n Difference 95% CI References

PaO2/FIO2 (12 h–2 d) 4 866 51.5 6.95–96.05 48, 55–57

PaO2/FIO2 (4 d) 3 754 43.87 13.86–73.88 48, 56, 57

PaO2/FIO2 (10 d) 4 833 24.89 15.3–34.48 48, 52, 56, 57

Days on mechanical 2 831 �.42 d �1.56 to 0.72 48, 56

ventilation

Incidence of VAP 3 967 0.78% 0.40–1.51 48, 56, 57

Abbreviations: CI, confidence interval; n, sample size; PaO2/FIO2, ratio of partial pressure of oxygen in arterial blood to the fraction of inspired

oxygen; VAP, ventilator-associated pneumonia.aData are from Alsaghir and Martin.54

Table 4: Results of Meta-analysis on Effects of Prone Positioning on Mortalitya

Outcome Variables Number of Studies n Odds Ratio 95% CI References

ICU mortality 3 466 0.79 0.45–1.39 52, 55, 57

28- to 30-day mortality 3 1231 0.95 0.71–1.28 48, 52, 57

90-day mortality 4 1271 0.99 0.77–1.27 48, 52, 56, 57

Mortality with SAPS II �50 2 113 0.29 0.12–0.70 52, 57

Abbreviations: CI, confidence interval; ICU, intensive care unit; n, sample size; SAPS, Simplified Acute Physiology Score.

aData are From Alsaghir and Martin.

54

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conducted at 3 ICUs in 2 states demonstratedthis standard was not met.71 In this same study,74 patients were observed for an average of7.7 hours. Ninety-seven percent of the patientsdid not receive the minimum standard of bodyrepositioning every 2 hours. About half (47%)of the observed patients were in the supineposition for 4 to 8 hours, and 23% of thepatients were not repositioned for more than 8hours. A more recent study in 40 ICUs in theUnited Kingdom revealed similar findings:Patients were in the supine position for 46%of the observations, with an average time of4.85 hours between turns.72 If repositioningevery 2 hours is the standard of care, theseresults prompt the question, why is the stan-dard not being met?

There has been limited investigation intothe reasons why patients are not repositioned.Nurses in long-term care facilities were sur-veyed and said the chief reasons for not rou-tinely repositioning patients were lack ofspecific assignment to the task and a lack oftime and staff.73 Although there have been nostudies published that explain why criticallyill patients are not repositioned every 2 hours,lack of time and staff are the most likelyexplanations. Additional factors may includepatient intolerance, hemodynamic instability,and pain. Evidence exists to support thatrepositioning critically ill patients is painful.In AACN’s Thunder Project II, a study of6201 critically ill patients revealed that turn-ing was the most painful routine procedureperformed for adults.74 A smaller, but morerecent, study found similar results as criticallyill patients reported turning to be the mostpainful routine procedure they experienced.75

This study and others highlight the problem:Not all patients receive preemptive pain reliefbefore repositioning.76,77

Strategies to remind staff of the need to turn,such as playing music over the intercom whenpatients are to be turned and posting signs ondoors alerting staff of patient pressure ulcerrisk, have been implemented with some short-term success.78 The reality is that rigid turningschedules in the ICU are difficult to maintainbecause of treatments, therapies, diagnostictests, procedures, and nursing care that requirethe patient to be in a supine position.

Although the initial question may be to askwhy the standard of every 2-hour turning isnot met, perhaps the real question should be,does repositioning every 2 hours impact

Table 5: Potential Contraindications toProne Positioning

Cardiovascular

Hemodynamic instability

Mean arterial pressure � 60 mm Hg or systolic

blood pressure � 90 mm Hg, regardless of

fluid resuscitation or inotropes

Recent cardiopulmonary arrest

Short-term bleeding

Ventricular assist devices

Intra-aortic balloon pump

Recent cardiothoracic surgery/unstable mediastinum

Trauma

Head injury

Spinal cord precautions/injury

Multiple trauma

External pelvic fixation or pelvic fractures

Rib fractures

Traction

Neurological

Increased intracranial pressure

Seizures

Head and neck

Increased intraocular pressure

Maxillofacial surgery

New tracheostomy (�24 h)

Respiratory

Asthma

Open chest

Abdominal

Recent abdominal surgery

Recent stoma formation

Open abdomen

Large abdomen

Musculoskeletal

Kyphoscoliosis

Advanced osteoarthritis

Rheumatoid arthritis

Others

Pregnancy (second/third trimester)

Weight � 135 kg

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patient outcomes? The optimal interval forturning acutely or critically ill patients is notknown. Only one study examined this issue.Defloor and colleagues79 investigated theeffects of different turning intervals in a ran-domized controlled trial involving patients in11 long-term care facilities. They found thatturning patients every 4 hours combined withthe use of a specialized foam mattress signifi-cantly reduced the incidence of pressure ulcerscompared with turning every 2 hours on stan-dard hospital mattresses. It would be difficultto advocate turning patients every 4 hoursrather than every 2 hours based on this 1 studybecause there were several methodologicalissues with this study including lack of alloca-tion of interventions, inadequate blinding ofparticipants and data collectors, and lack of anintent to treat analysis.

Rotation TherapyRotation therapy, including continuous lateralrotation therapy (CLRT), involves the use ofspecialized beds to mechanically turn thepatient from side to side. CLRT uses continuousturning of a patient up to 40� on each side with6 to 8 turns an hour. The bed frame rotates thepatient from side to side. Research demon-strates that patients must be rotated at least 18hours a day to achieve maximum benefit.80–85

Four systematic reviews and meta-analyseshave shown that rotation therapy decreasesthe relative risk of VAP but has no benefit onreducing ICU length of stay or decreasing mor-tality.81,86,87 Several methodological issues usedin these studies must be highlighted. Manystudies lack (or at least did not report) the useof rigorous methods to ensure adherence tomanual turning routines in the control groups.It is not apparent that manual turning wasstrictly monitored or enforced.71 Given theresults of 2 studies that revealed critically illpatients were not turned every 2 hours,71,72

rotation therapy studies may have been com-paring specialty beds with a control group thatwas not turned adequately. Therefore, thereduction in VAP with the use of rotation ther-apy may actually be due to being turned,rather than the specialty bed itself. Futurestudies need to include protocols that demon-strate strict adherence to manual turning.

Despite the number of studies published onrotation therapy, it remains unclear whichpatients are the best candidates for this ther-apy. This may be in part because few studies

have attempted to elucidate the underlyingphysiological mechanisms by which rotationtherapy may decrease the development of VAP.Bein and colleagues88 investigated the effects ofcontinuous rotational therapy on ventilation-perfusion in 10 patients with ARDS. By usingthe inert-gas elimination technique, they foundthat 20 minutes of rotation improved gasexchange by decreasing low ventilation toperfusion lung units. They also found thatpatients with more severe ARDS did notimprove oxygenation (PaO2/FIO2) with rotationtherapy than did patients with less severe dis-ease. They speculated that these results weredue in part to the pathophysiological changeswith ARDS over time as the lung evolves froma wet, heavy, atelectatic lung to a brittlefibrotic lung. In the early stage of ARDS,rotation therapy may be effective in alteringthe distribution of ventilation and perfusion.However, late ARDS pathophysiological changesrender position changes ineffective. Furtherstudies are needed to explain the physiologicalbasis of rotation therapy.

Current clinical practice guidelines by theCenters for Disease Control and Preventionmake no recommendations for the use of rota-tion therapy for the prevention of VAP in criti-cally ill and immobilized patients.18 However,more recent guidelines published by the Cana-dian Critical Care Society recommend clini-cians consider the use of kinetic beds toprevent VAP.21

Positioning of the Critically Ill Obese PatientObesity is defined as a body mass index (BMI;weight [kg]/height [m2]) greater than or equalto 30.89 According to recent data from theCenters for Disease Control and Prevention,more than 20% of American adults are obeseand the number is expected to increase.90 Con-sequently, as the general population of obeseindividuals has increased, so too has the popu-lation of critically ill obese patients. Position-ing these patients can be challenging.Currently, most positioning interventions forobese patients are only modifications of thoseused for nonobese patients.91,92

A task force of the National Association ofBariatric Nurses developed best practices forsafe handling of obese patients.93 These guide-lines recommend the establishment of unit-based multidisciplinary bariatric task forces toidentify high risk tasks and to outline solutions

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especially for repositioning patients in bed.Caregivers must be knowledgeable about avail-able technology to assist with positioning, howto access it quickly, and the weight capacity ofbeds and reclining chairs. The VISN 8 Web siteof the Department of Veterans Affairs has avaluable resource available on its Web site,94

the “Safe Bariatric Patient Handling Toolkit,”that contains assessment criteria, algorithms,equipment lists, and a policy template. A taskthat is challenging and places caregivers at highrisk for injury is repositioning an obese patientup in bed for turning to the side. The use ofmanufactured slings can greatly reduce theserisks and allow for repositioning the obesepatient while in bed. An algorithm on reposi-tioning obese patients in bed (side to side, up inbed) can be helpful for critical care nurses whocare for these patients (Figure 2).

Positioning Obese Patients to PromoteAdequate OxygenationIn obese individuals, there are structural andfunctional changes that impact ventilation. ABMI greater than 30 kg/m2 is directly associ-ated with reductions in all lung volumes, par-ticularly in expiratory reserve volume andfunctional reserve capacity.95 Adipose tissuedeposits in the abdomen, diaphragm, andintercostal muscles can prevent proper chestwall expansion and diaphragmatic excur-sion.91 The airway may be narrowed from adi-pose tissue deposits in the upper airway, whichcan complicate airway management. Thesestructural changes may lead the obese patientto experience a hypoventilation syndromewith chronic hypoxia or obstructive sleepapnea.91 Obese patients are at risk for moreventilator days than are nonobese patients andare more likely to aspirate gastric secretionsbecause of increased gastric secretions, upperairway changes, and poor lung volumes.96

These patients are at greater risk for the devel-opment of atelectasis and pneumonia fromshallow breathing patterns.92 Head of bed ele-vation of at least 30� improves ventilatoryeffort and tidal volume in patients with largeabdomens and reduces the incidence of aspira-tion in mechanically ventilated patients.97

However, this HOB elevation is often associ-ated with the patient “sinking” to the foot ofthe bed (Figure 2). This requires additionalpersonnel to help reposition the patient to thehead of the bed. Useful strategies to counteractthis problem may include the use of an

adjustable footboard against which the patientcan push to move up in the bed, and an over-bed trapeze that the patient can grasp to lever-age into a higher position.98

Special care must be taken when placing theobese patient with large pendulous abdomensin a lateral position. If allowed to hang overthe side of the bed, they can have the effect ofpulling the patient off the bed via gravity.99

Care must also be taken, in both men andwomen, to protect the breasts from compres-sion injury.

The effects of the prone position in obesepatients have not been thoroughly examined.The process of placing the obese patient in thisposition presents challenges and safety risks forthe patient as well as members of the health careteam. Adequate numbers of staff and appropri-ate equipment that can tolerate the weight shiftsof obese patients are required.98 A recent casestudy of an obese patient with ARDS reportedthat the prone position improved alveolar venti-lation.100 Rossetti and colleagues101 in a studyconducted on ICU patients with ARDS foundthat patients with increased body weight hadgreater improvement in oxygenation than didthose with less weight. Further research is neces-sary to strengthen and to support the use of theprone position for obese patients.

There are specific mattress products thatoffer CLRT for obese patients. These productsreduce friction and shear and provide for turn-ing to maximize respiratory function.92,98 Theyinclude air mattresses that have multiple airchambers that inflate and deflate to laterallyrotate the patient. One example of this is thePlexus TruTurn Elite Therapeutic Turning Mat-tress (Gaymar Industries, Orchard Park, NewYork). Nurses should be cognizant of avoidingthe use of the term “big boy bed” as this anunnecessary assault on the patient’s dignity.94

Positioning Obese Patients to Promote Skin IntegrityObese patients are more susceptible to pres-sure ulcers than are nonobese patients for avariety of reasons including poorly vascular-ized adipose tissue, additional mass and skinsurface area, limited mobility, improper equip-ment, and inadequate staff members and staffwho lack training in caring for obese patients.Standard hospital beds may not provideenough pressure relief for the obese patient ormay be so narrow that the rails cause pressureagainst arms, legs, and hips.102 Properly sized

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Figure 2: Bariatric Reposition in Bed: Side to Side and Up in Bed. From the Safe Bariatric Patient HandlingToolkit (www.visn8.med.va.gov/patientsafetycenter/safePTHandling/toolkitBariatrics.asp).

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equipment reduces the risk of pressure ulcersthrough pressure reduction and promotion ofindependence, decreases staff workload, andincreases satisfaction of the obese patient.103 Airand foam matrix mattresses minimize frictionand shear and therefore reduce the developmentof pressure ulcers.91,92,98,104,105 Appropriate bedframes can be selected for safe mobilization andpositioning of the bedridden patient. Trapezesare useful for patient positioning because theyallow patients to participate in their own care,reduce the number of staff required for transfer,and reduce the risk of friction and shear withrepositioning.102 A bariatric ceiling lift with aseated sling can be used to transfer patientsfrom bed to chair if the patient cannot fully orpartially assist.

A multidisciplinary team effort is requiredto determine which positioning interventionsare required for critically ill obese patients.This team effort should be expanded toencourage proper interventions to ensuresafety for the patient and caregivers.92,98,104 Aprospective, cross-sectional descriptive studyreported that at least 2 staff members wereneeded to assist with positioning, and thosewith a BMI greater than 40 kg/m2 were mostlikely to need at least 4 staff for positioning.98

On the basis of these results, the investigatorsrecommend using BMI as a trigger for order-ing rented or stored equipment to promotetimely arrival and intervention.

Positioning of the Critically Ill Elderly PatientThe overall mortality rate for critically illpatients older than 65 years is higher thanthat for patients younger than 45 years(36.8% vs 14.8%, respectively).106 Causes forincreased mortality include acute respiratoryfailure, use of mechanical ventilation, anddevelopment of complications.107 Pressureulcers can increase an elderly patient’s chancesof mortality in an ICU by 2 to 4 times.108

Regarding such staggering differences in mor-tality statistics, these numbers are compelling,particularly when they can be addressed, inpart, by patient positioning.

Positioning Elderly Patients to Promote Adequate OxygenationThere are structural and functional changesthat occur with aging that impact ventilationand increase the risk of respiratory failure andVAP including reduction in expiratory force,

diminished respiratory muscle strength, poormucociliary clearance, increased upper airwaycolonization, swallow dysfunction, and dimin-ished respiratory muscle strength. Elevation ofthe HOB should be at least 30� to minimize theincidence of VAP16 and to improve oxygena-tion.109 In a study of healthy elderly patients,Hardie and colleagues110 found that oxygena-tion was better in the sitting position than inthe supine position; however, further studies incritically ill patients showing the same resultsare needed.

Positioning Elderly Patients to Promote Skin IntegrityCritically ill elderly patients are at high risk forthe development of pressure ulcers.108,111 Fur-thermore, and ironically, some research sug-gests that obesity can reduce the incidence ofpressure ulcers in elderly populations whencompared with optimal weight patients andunderweight patients.112 The authors of the pre-ceding study postulate that adipose tissue couldpotentially provide a type of subcutaneouscushion dispersing pressure over more tissue.This research illustrates the point that it isimperative to provide individualized care to theelderly critical care patient when addressingrisks for pressure ulcer development. Evidenceexists to support the use of interventions forgeneral patient populations to address theserisks, such as patient turning in bed, CLRT,and positioning on a specialty surface113,114;however, research into the elderly population’sresponse to these interventions is lacking.

Age-related decreased peripheral perfusionto the lower extremities in the elderly is a riskfactor for the development of pressure ulcerson the heels of elderly patients on bed rest.Cushioning devices, such as foam heel protec-tors and pillows, are important in the preven-tion of heel ulcers.

SummaryNurses use clinical judgment based on physio-logical and scientific evidence to position criti-cally ill patients to prevent complications ofimmobility and to achieve optimal patient out-comes. Therapeutic positioning in stationarypositions is done to optimize ventilation andperfusion and to promote effective pulmonarygas exchange. In patients with unilateral dis-ease, optimal gas exchange occurs when thepatient is placed with the “good lung down.”Less physiological and scientific evidence exists

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for optimal positioning of patients with bilat-eral disease. More research is needed. Strongevidence exists that HOB elevation preventsVAP. More research is needed to identify theoptimal degree of HOB elevation that prevents VAP and development of pressureulcers. Although research has demonstratedthat prone positioning in patients with ARDSimproves pulmonary gas exchange, the exactphysiological mechanisms responsible forimprovement in pulmonary gas exchange havenot been elucidated. Even though prone posi-tioning optimizes oxygenation, the use of this position has not been shown to impactmortality. The current standard of repositioningpatients is every 2 hours, yet there is little physi-ological or scientific evidence to support thisstandard. Furthermore, it appears that the stan-dard is often not met. Research is needed toprovide evidence that turning frequencyimpacts outcomes. Research has shown thatrotation therapy decreases VAP. However,methodological issues arise because of lack ofrigorous methods to assess adherence to groupassignments in randomized controlled trialscomparing rotation therapy with conventionalturning methods. More research is needed tounderstand physiological and scientific basis ofoptimal positioning in select critically ill patientpopulations, such as obese and elderly patients.

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CE Test Questions

Physiological Rationale and Current Evidence for Therapeutic Positioning of Critically Ill PatientsObjectives:Upon completion of this article, the reader will be able to:

1. Understand the role of therapeutic repositioning in preventing complications and improving critically ill patient out-

comes.

2. Describe the physiological rationale for stationary and active repositioning.

3. Recognize special considerations for therapeutic repositioning of critically ill obese and elderly patients.

1. What complication of bed rest is caused by diminished

baroreceptor activity?

a. Hypoxemia

b. Venous thromboembolism

c. Syncope

d. Atelectasis

2. How does prolonged placement in the supine position

affect patients with diseased lungs?

a. They have a normal ventilation/perfusion ratio.

b. They develop alveolar dead space.

c. They have a high ventilation/perfusion ratio.

d. They develop an intrapulmonary shunt.

3. What head of bed (HOB) elevation do multiple clinical

practice guidelines recommend for critically ill

patients in the semirecumbent position?

a. 10 to 25 degrees

b. 30 to 45 degrees

c. 50 to 65 degrees

d. 75 to 90 degrees

4. Which is a contraindication to HOB elevation?

a. Enteral nutrition

b. Mechanical ventilation

c. Hypertension

d. Ischemic stroke

5. What is a possible risk of HOB elevation above

30 degrees?

a. Low sacral tissue interface pressures

b. Pressure ulcers

c. Aspiration pneumonia

d. Ventilator-associated pneumonia (VAP)

6. A patient with which diagnosis should be positioned

with the unaffected lung in the dependent position?

a. Pneumonia

b. Interstitial emphysema

c. Pulmonary abscess

d. Pulmonary hemorrhage

7. Which position improves pulmonary gas exchange in

patients with acute lung injury and/or acute respiratory

distress syndrome?

a. Supine

b. Semirecumbent with HOB elevation

c. Left lateral decubitus

d. Prone

8. According to Alsaghir and Martin, what is an effect of

prone positioning?

a. Decreased number of mechanical ventilation days

b. Decreased VAP incidence

c. Improved PaO2/FIO2

d. Decreased mortality

9. Which is a potential contraindication to prone

positioning?

a. New tracheostomy (�24 h)

b. Weight of 130 kg

c. Systolic blood pressure of 100 mm Hg

d. Mean arterial pressure of 70 mm Hg

10. In AACN’s Thunder Project II, what was the most

painful routine procedure performed in adults?

a. Endotracheal tube suctioning

b. Arterial blood gases

c. Turning

d. Venipuncture

11. In addition to expiratory reserve volume, what lung

volume is primarily reduced in patients with a body

mass index greater than 30 kg/m2?

a. Functional reserve capacity

b. Forced vital capacity

c. Inspiratory reserve volume

d. Residual volume

12. What structural and functional change of aging

increases the risk of respiratory failure and VAP?

a. Increased expiratory force

b. Swallow dysfunction

c. Decreased upper airway colonization

d. Increased respiratory muscle strength

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physiological rationale and current evidence for therapeutic

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