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© SICS EBM Group 2004
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PEEP in ARDS
Lead author's name and fax: R.G. Brower
Three-part Clinical Question: 1. Patients: ALI / ARDS (according to international criteria) 2. Intervention. High versus low PEEP 3. Outcomes. Death and other clinical outcomes
Search Terms: ALI, ARDS, PEEP, Outcomes
The Study: Single-blinded, Randomised trial with intention-to-treat. The study was terminated after scheduled interim analysis suggested no treatment benefit. The Study Patients: ALI / ARDS according to international criteria who have been intubated for < 36 hours.
Control group (Low PEEP) (N = 273; 273 analysed): Ventilated and managed according to ARDSnet ventilatory strategy including PEEP algorhythm (ARDSnet, NEJM 2000;342:1301-8) (PEEEP = 8.4 +/- 2.9 cmH2O)
Experimental group (High PEEP) (N = 276; 276 analysed): Initially ventilated and managed according to ARDSnet ventilatory strategy including PEEP algorhythm (Amato, NEJM 1998;338:347-54) (PEEP = 12.2 +/- 3.5). However after 171 patients had been enrolled in the trial the difference in mean PEEP levels between the two groups were less than expected. The higher-peep strategy was therefore modified to increase the difference in mean peep between the two patient groups. (PEEP = 13.6 +/- 3.5)
The Evidence:
EBM Comments: 1. Do the methods allow the adequate testing of the hypothesis? Changes made to the “High PEEP” algorithm during study was not ideal but probably did not change the result. It is interesting to note that differences between PEEP levels between groups was not clinically significant perhaps suggesting that this study did not adequately test the hypothesis. There were also differences between baseline parameters that could explain some of the results (age and PaO2/FiO2 ratio) although the authors claim that there were allowances made for these differences in the statistical analysis. 2. Do the statistical tests correctly test the results to allow differentiation of statistically significant result? Yes, they appear to so. 3. Are conclusions valid in light of results? They conclude that “In patients with acute lung injury and ARDS who receive mechanical ventilation with lower tidal volumes and inspiratory pressures, raising PEEP to levels that exceed those used in our lower-PEEP strategy does not improve important clinical outcomes”. Allowing for the above points this seems a reasonable conclusion. 4. Did results get omitted, and why? No, all patients were analyzed. 5. Did they suggest areas of further research? No. 6. Did they make recommendations based on results and were they appropriate? They stated that: “this finding further emphasizes the value of a strategy that uses lower tidal volumes and inspiratory pressures than were used in the past”. Which seems reasonable if you take into account some authors concerns about the ARDSnet study findings. 7. Is this study relevant to my clinical practice? Probably, as they include ALI / ARDS with similar severity of illness but have a differing racial mix and age mix from Scottish ICU’s. 8. What level of evidence does this study represent? Level 1+ 9. What grade of recommendation can I make on this result alone? Grade B 10. What grade of recommendation can I make when this study is considered along with other available evidence? Grade B 11. Should I change my practice because of these results? If you are using ARDSnet ventilation you can continue doing this. As there is clinical equipoise you can also change to the High PEEP strategy, although there is no specific reason to do so. 12. Should I audit my current practice because of these results? Yes, if you use ARDSnet ventilation you should probably audit your strategy, results, outcomes and specifically your PEEP use.
Appraised by: Dr BH Cuthbertson, ICU, Aberdeen Royal Infirmary, Aberdeen; 23rd August 2004Email: b.h.cuthbertson@abdn.ac.uk Kill or Update By: 21st August 2007
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