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Ventilation with reduced tidal volumes and peak pressures in patients with severe ARDS

 

 

No benefit could be observed with reduced tidal volume ventilation titrated to a peak pressure around 25cmH2O compared with a conventional approach in ARDS with MLIS > 2.5

Level of Evidence 1-

 

Citation/s:

Brochard L et al. Tidal volume reduction for prevention of ventilator-induced ling injury in acute respiratory distress syndrome. Am J Respir Crit Care Med. 1998;158:1831-8

Lead author's name and fax: Brochard L

 

Three-part Clinical Question:

1.      The patients- ARDS with Murray Lung Injury Score > 2.5

2.      The treatment- Pressure controlling at less than or equal to 25cmH2O and tidal volume 6-10ml/kg

3.      The outcome- Mortality

 

Search Terms: 1. Respiratory distress syndrome: adult 2. Treatment 3. Limited to Human and AIM journals

 

The Study:
Single-blinded randomised controlled trial without intention-to-treat.


The Study Patients: ARDS (Diffuse bilateral infiltrates on CXR, Arterial hypoxaemia requiring mechanical ventilation and FiO2 > 0.5 for 24 hours, and a Murray Lung Injury Score > 2.5


Control group (N = 58; 58 analysed): 1. Titration of PEEP- A PEEP trial was performed before randomisation to determine optimal level and then "total" PEEP measured by airway occlusion technique 2. Volume controlled ventilation with tidal volume of 10ml/kg up to 15ml/kg. 3. Respiratory rate adjusted to maintain PaCO2 between 38 and 42 mmHg 4. Peak airway pressure < 60cmH2O


Experimental group (N = 58; 58 analysed): 1. titration of PEEP- As control group 2. Volume controlled ventilation with tidal volume of 10-15ml/kg 3. Respiratory rate not adjusted to control PaCO2 4. Peak airway pressure < 30cmH2O

The Evidence:

 

Outcome

Time to Outcome

CER

EER

RRR

ARR

NNT

Mortality

60 day

0.379

0.466

-23%

-0.087

-11

95% Confidence Intervals:

-70% to 24%

-0.266 to 0.092

NNT = 11 to INF; NNH = 4 to INF

 

EBM summary questions:

 

  1. Do the methods allow the adequate testing of the hypothesis- Yes

  2. Do the statistical tests correctly test the results to allow differentiation of statistically significant result- Probably, but peak pressures did not significantly differ between control and experimental groups which may have reduce chances of demonstrating a significant

  3. Are conclusions valid in light of results- Yes with statement above taken into account.

  4. Did results get omitted, and why.- Unclear if intention to treat analysis or how many patients were analysed

  5. Did they suggest areas of further research- No

  6. Did they make recommendations based on results and were they appropriate- No

  7. Is this study relevant to my clinical practice- Yes, it seems to represent a similar group of severe ARDS patients to that seen in 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- Alone it makes a grade A recommendation but must be considered in light of more recent evidence supporting its hypothesis.

  10. What grade of recommendation can I make when this study is considered along with other available evidence- This study fails to show a significant improvement in mortality with tidal volume limitation. Future studies test a similar hypothesis and lead to a Grade A recommendation for tidal volume limitation in ARDS.

  11. Should I change my practice because of these results- No on the evidence of this study

  12. Should I audit my current practice because of these results- Yes, audit the tidal volume and peak pressures in your unit in light of future results.

Appraised by: Brian H Cuthbertson, Intensive Therapy Unit, Aberdeen Royal Infirmary; Tuesday, February 12, 2002
Email: b.h.cuthbertson@abdn.ac.uk
Kill or Update By: 12th February 2005

 

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