Can We Achieve Semirecumbency?
Can We Achieve Semirecumbency?
Abstract & Commentary
By Saadia R. Akhtar, MD, MSc, Idaho Pulmonary Associates, Boise, is Associate Editor for Critical Care Alert.
Dr. Akhtar does research for Eli Lilly.
Synopsis: This prospective multi-center randomized trial determined that the target head-of-bed elevation of 45° for ICU patients was difficult to achieve, and that lower levels (up to 28°) did not reduce rates of ventilator-associated pneumonia.
Source: van Nieuwenhoven CA, et al. Feasibility and effects of the semirecumbent position to prevent ventilator-associated pneumonia: a randomized study. Crit Care Med. 2006;34:396-402.
A prospective, multi-center randomized trial was performed to determine the feasibility of the semirecumbent position (goal, head of bed elevation [HOB] 45°) and its impact on the incidence of ventilator-associated pneumonia (VAP). Four ICUs in the Netherlands participated. Over a 2-year period, all patients who were intubated within 24 hours of ICU admission anticipated to require > 48 hours of mechanical ventilatory support, and, without contraindication to positioning as per the study protocol, were eligible. Selective digestive decontamination and continuous subglottic aspiration were not used. Usual demographic, severity-of-illness and outcome data were collected. All patients received stress gastritis prophylaxis until initiation of enteral feeding (via nasogastric tube). Angle of HOB above horizontal was monitored by a continuous computerized recording system that measured every 60 seconds for the first week. Patient position was adjusted as needed by research nurses 2-3 times a day and bedside labels reminded all caretakers of goal position. Deviation from randomized position was defined as a change of > 5°. VAP was diagnosed by standard CDC criteria and confirmed with quantitative cultures of bronchoscopic lavage; blinded investigators reviewed data and classification of VAP. Appropriate power calculations, intent-to-treat analysis and other usual standard statistical methods were used.
The study enrolled 221 patients and there were no significant differences in baseline characteristics or outcomes between the 2 positioning groups. A similar number of patients in each group required ventilation < 48 hours; ICU and hospital length of stays and mortality were also comparable. Mean HOB elevation was 9.8-14.8° for the supine/standard care group and 23.1°-29.2° for the semirecumbent (goal 45°) group. The latter group had HOB <40° 85% of the time. There was no difference between the 2 groups in the number of patients with clinically suspected or microbiologically confirmed VAP; the latter occurred in 10.7% of the semirecumbent group and 6.5% of the supine/standard care group. There was also no difference within each group in VAP risk relative to the degree of HOB elevation. The authors found no associations between VAP and diagnosis, severity of illness, age, gender, enteral feeding or length of sedation but did find an association with presence of infection at admission and with specific hospital.
Commentary
Aspiration of gastroesophageal contents may be one mechanism for development of VAP and it has been clearly shown that endotracheal aspiration of gastric contents is greater in the supine vs semirecumbent position.1 The one and only randomized trial of semirecumbent (45°) vs supine (0°) patient positioning was a single center study that was stopped early for the marked (78%) reduction in VAP.2 Since then, patient positioning has been an important part of the recommended strategies for prevention of VAP.3,4 It is a cheap and, in theory, easily applicable measure with no apparent downsides.
van Nieuwenhoven et al's study questions the feasibility and value of semirecumbent positioning for VAP prevention. It differs significantly from Drakulovic et al's work.2 The present authors defined 'supine' as usual care (found to be HOB elevation about 10°) vs. a predefined level (0° in the prior study). In addition, they used a computerized recording device to measure position continuously (as opposed to just once a day), providing more accurate and detailed data. Finally, it is important to note that their recorded rates of VAP are lower overall than in the prior study.
The issue of feasibility is what drew me to this study initially, as in my personal experience it continues to be a struggle to consistently maintain semirecumbency (45°) for patients in the ICU despite repeated education and clear protocols. The reasons are not entirely clear and were not detailed in this publication either: they may include disbelief in prior data, patient request (for those awake and able to communicate this), hemodynamic instability, the need to change position for nursing care/procedures/ therapies and then forgetting or neglecting to return to prior position, perceptions about patient comfort, concerns about skin care or other.
Some institutions have 'compromised' and set HOB ≥ 30° (instead of 45°) as the goal, with the assumption that there will be some benefit in terms of prevention of VAP even at this level. The current study suggests that although this level of HOB elevation may be achievable, it does not appear to reduce VAP incidence compared to usual care. This is a reminder of the important concept that in order to attain the benefits noted in a particular study, one must follow the study protocol. To paraphrase a former mentor: "If a well-designed study demonstrates that a triple chemotherapy combination regimen improves mortality, you aren't going to pick only 1 of those drugs to give to your patients—the same principle is true of any clinical study protocol."
What about the fact that the authors found no difference in VAP incidence in their supine and semirecumbent positioning groups? The study's findings may be interpreted in several ways, such as: any elevation of HOB above 0° may significantly reduce incidence of VAP (perhaps 10° is as good as 45°); a specific threshold difference in elevation of HOB may be needed before a reduction in VAP rate is seen (about 20° may not be enough); usual ICU care has changed enough in the past 5-10 years that VAP rates are already lower and a larger sample size would be needed to appreciate smaller differences.
I suggest that because patient positioning continues to be a 'free' intervention that may have significant benefit, we should continue to try to implement Drakulovic and colleagues' work more exactly until a confirmatory study is completed.
References
- Torres A, et al. Pulmonary aspiration of gastric contents in patients receiving mechanical ventilation: the effect of body position. Ann Intern Med. 1992:116:540-543.
- Drakulovic MB, et al. Supine body position as a risk factor for nosocomial pneumonia in mechanically ventilated patients: A randomized trial. Lancet. 1999:354:1851-1858.
- Dodek P, et al. Evidence-based clinical practice guideline for the prevention of ventilator-associated pneumonia. Ann Intern Med. 2004:141:305-313.
- Hess DR. Patient positioning and ventilator-associated pneumonia. Respir Care. 2005:50:892-898.
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