DRAKULOVIC: Semirecumbent Position for Pneumonia Prevention (1999)

“The semirecumbent body position reduces frequency and risk of nosocomial pneumonia, especially in patients who receive enteral nutrition.”

— The DRAKULOVIC Study Group

1. Publication Details

  • Trial Title: Supine body position as a risk factor for nosocomial pneumonia in mechanically ventilated patients: a randomised trial.
  • Citation: Drakulovic MB, Torres A, Bauer TT, et al. Supine body position as a risk factor for nosocomial pneumonia in mechanically ventilated patients: a randomised trial. Lancet. 1999;354(9193):1851-1858. doi:10.1016/s0140-6736(98)12251-1.
  • Published: November 27, 1999, in The Lancet.
  • Author: Mitra B. Drakulovic, MD.
  • Funding: Not specified.

2. Keywords

Ventilator-Associated Pneumonia, Nosocomial Pneumonia, Body Position, Supine, Semirecumbent, Mechanical Ventilation, Aspiration.

3. The Clinical Question

In intubated and mechanically ventilated patients, does a semirecumbent body position (45° head elevation) compared to a supine (0°) position reduce the incidence of nosocomial pneumonia?

4. Background and Rationale

  • Existing Knowledge: Nosocomial pneumonia is a major complication in mechanically ventilated patients. Gastroesophageal reflux and aspiration of gastric contents are known risk factors. It was theorized that keeping patients in a semirecumbent (head-up) position could reduce reflux and aspiration.
  • Knowledge Gap: While the theory was plausible and supported by surrogate outcome studies (e.g., less reflux), there was no direct evidence from a randomized controlled trial to show that this simple intervention actually prevented the clinical outcome of pneumonia.
  • Proposed Hypothesis: The authors hypothesized that maintaining patients in a semirecumbent position would reduce the incidence of nosocomial pneumonia compared to the standard supine position.

5. Study Design and Methods

  • Design: A prospective, randomized, unblinded, controlled trial. The trial was stopped after a planned interim analysis because of a significant benefit in the intervention group.
  • Setting: One medical and one respiratory intensive-care unit at a tertiary-care university hospital in Spain.
  • Trial Period: Not specified, but the trial was stopped early.
  • Population:
    • Inclusion Criteria: Adult patients intubated and mechanically ventilated.
    • Exclusion Criteria: Recent abdominal or neurosurgical intervention, shock refractory to treatment, or previous intubation within 30 days.
  • Intervention: Patients were positioned in a semirecumbent position, with the head of the bed elevated to 45°.
  • Control: Patients were positioned in a completely supine position (0° elevation).
  • Management Common to Both Groups: All other aspects of care, including decisions on enteral feeding and stress ulcer prophylaxis, were at the discretion of the treating physician.
  • Power and Sample Size: An interim analysis was planned after 90 patients had been recruited. The study was stopped at this point. 86 patients were included in the final analysis.
  • Outcomes:
    • Primary Outcome: Frequency of clinically suspected nosocomial pneumonia (defined by new chest infiltrate plus clinical signs like fever, leukocytosis, or purulent secretions).
    • Secondary Outcome: Frequency of microbiologically confirmed nosocomial pneumonia (requiring positive quantitative cultures).

6. Key Results

  • Enrollment and Baseline: 86 patients were included in the final analysis (39 semirecumbent, 47 supine). The groups were well-matched at baseline.
  • Trial Status: The trial was stopped early at the interim analysis due to a significantly lower incidence of pneumonia in the semirecumbent group.
  • Primary Outcome: The frequency of clinically suspected nosocomial pneumonia was significantly lower in the semirecumbent group than in the supine group (8% vs 34%; P=0.003).
  • Secondary Outcomes: The frequency of microbiologically confirmed pneumonia was also significantly lower in the semirecumbent group (5% vs 23%; P=0.018). The combination of supine positioning and enteral nutrition was associated with the highest risk of pneumonia (50%).
  • Adverse Events: No adverse events related to body positioning were reported.

7. Medical Statistics

  • Analysis Principle: An intention-to-treat analysis was performed.
  • Statistical Tests Used: Chi-square test was used for the primary outcome. Logistic regression was used to identify independent risk factors.
  • Primary Outcome Analysis: The proportion of patients developing pneumonia was compared between the two groups.
  • Key Statistic(s) Reported:
    • Clinically Suspected Pneumonia: 8% (3/39) in semirecumbent vs 34% (16/47) in supine; P=0.003.
    • Odds Ratio for Supine Position (Multivariate): 6.8 (95% CI 1.7-26.7).
  • Clinical Impact Measures:
    • Absolute Risk Reduction (ARR) for Clinically Suspected Pneumonia: 26% (34% – 8%).
    • Number Needed to Treat (NNT): 4 (1 / 0.26). To prevent one case of clinically suspected nosocomial pneumonia, 4 patients need to be managed in a semirecumbent position instead of supine.
  • Subgroup Analyses: The analysis identified that patients receiving enteral nutrition were at particularly high risk in the supine position.

8. Strengths of the Study

  • Study Design and Conduct: This was the first randomized controlled trial to evaluate a simple, low-cost intervention on a hard clinical endpoint (pneumonia) rather than a surrogate marker.
  • Patient-Centered Outcomes: The trial focused on a clinically significant complication (pneumonia) with major implications for patient morbidity.
  • Large Effect Size: The observed reduction in pneumonia was very large and statistically robust.

9. Limitations and Weaknesses

  • Internal Validity (Bias): The trial was unblinded, which could introduce performance and detection bias. However, the use of objective criteria for microbiologically confirmed pneumonia mitigates this.
  • External Validity (Generalizability): This was a single-center study, which may limit generalizability.
  • Other: The trial was stopped early. While the effect was large, trials stopped early for benefit have a tendency to overestimate the true treatment effect.

10. Conclusion of the Authors

“The semirecumbent body position reduces frequency and risk of nosocomial pneumonia, especially in patients who receive enteral nutrition. The risk of nosocomial pneumonia is increased by long-duration mechanical ventilation and decreased consciousness.”

11. To Summarize

  • Impact on Current Practice: This was a landmark, practice-changing trial. It provided the first strong evidence for a simple, no-cost intervention that dramatically reduces the risk of ventilator-associated pneumonia. Head-of-bed elevation (30-45°) became a cornerstone of ventilator care bundles and standard practice in ICUs worldwide as a direct result of this study.
  • Specific Recommendations:
    • Patient Selection: All intubated, mechanically ventilated patients without contraindications (e.g., spinal instability, refractory hypotension).
    • Actionable Intervention: Maintain the head of the bed elevated to at least 30-45°.
    • Expected Benefit: A significant reduction in the risk of developing ventilator-associated pneumonia, with an NNT of approximately 4.
  • What This Trial Does NOT Mean: This trial does not mean that head-of-bed elevation eliminates the risk of pneumonia entirely. It is one component of a multi-faceted prevention strategy.
  • Implementation Caveats: Maintaining a 45° angle can be challenging due to patient sliding and discomfort. A target of 30° is often considered more practical and is also supported by evidence.

12. Context and Related Studies

  • Building on Previous Evidence: This trial confirmed the clinical benefit suggested by earlier studies that had only looked at surrogate markers like gastroesophageal reflux.
  • Influence on Subsequent Research: This study was so influential that it would be considered unethical to randomize patients to a flat supine position today. Subsequent research, such as the study by van Nieuwenhoven et al. (2006), has focused on the optimal angle of elevation and confirmed the challenges of maintaining a high angle of elevation consistently.

13. Unresolved Questions & Future Directions

  • Unresolved Questions: What is the optimal angle of elevation (30° vs 45°)? How can compliance with this simple intervention be improved in busy ICUs?
  • Future Directions: Research has focused on incorporating head-of-bed elevation into “ventilator care bundles” and using technology to monitor and maintain the desired position.

14. External Links

15. Framework for Critical Appraisal

  • Clinical Question: The question was highly relevant, targeting a common, costly, and morbid complication of ICU care with a simple, inexpensive intervention.
  • Methods: The randomized controlled design was appropriate. Although unblinded and stopped early, the large effect size and objective secondary endpoint provide confidence in the findings.
  • Results: The results were overwhelmingly positive, with a large and statistically significant reduction in both clinically suspected and microbiologically confirmed pneumonia. The NNT of 4 represents a highly effective intervention.
  • Conclusions and Applicability: The authors’ conclusion is strongly supported by the data. The intervention is highly applicable and generalizable to most mechanically ventilated patients. This is a classic example of a simple, evidence-based intervention that has fundamentally changed and improved critical care practice.

16. Disclaimer and Contact

This summary is provided by the Academic Committee of ESBICM (ACE) to facilitate the understanding of this study; readers are advised to refer to the original trial document for a deeper understanding. If you find any information incorrect, or missing, or it needs an update or have a request for a specific critical care trial summary, kindly write to us at academics[at]esbicm.org.

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