Tidal volume and peak pressure limitation in patients at risk of ARDS

 

 

There is no outcome benefit for tidal volume and peak pressure limitation in patients "at-risk" of ARDS Level of Evidence 1-

 

Citation/s:
Stewart TE et al. Evaluation of a ventilation strategy to prevent barotrauma in patients at high risk for acute respiratory distress syndrome. N Engl J Med 1998;338:355-61

Lead author's name and fax: Stewart T

 

Three-part Clinical Question:

1.      The patients- High risk for ARDS (2 or more of Sepsis; Gastric aspiration, pulmonary contusion, multiple transfusion, multiple fractures, pneumonia, inhalation injury, burns, acute pancreatitis, drug overdose or shock and PaO2 / FiO2 ratio < 250mmHg with PEEP of 5cmH2O

2.      The treatment- Limited ventilation strategy- Tidal volume less than or equal to 8ml/kg and PIP less than or equal to 30cmH2O

3.      The outcome- In hospital mortality

Search Terms: Respiratory distress syndrome; acute Treatment- Ventilation Limited to Human and AIM journals

 

The Study:
Double-blinded randomised controlled trial with intention-to-treat.

The Study Patients: At risk for ARDS- PaO2 / FiO2 ratio < 250mmHg and two risks factors as above

Control group (N = 60; 60 analysed): Peak inspiratory pressure < 50cmH2O Tidal volume 10-15ml/kg (ideal body weight) Assist-control mode of ventilation with decelerating wave form flow PEEP- 5-20cmH2O according to algorithm RR- 5 to 35 PaCO2 35-45mmHg

Experimental group (N = 60; 60 analysed): Peak inspiratory pressure < 30cmH2O Tidal volume < or equal to 8ml/kg, Assis control mode of ventilation and decelerating wave form flow PEEP- 5-20cmH2O according to algorithm RR 5-35 PaCO2 35-45

The Evidence:

Outcome	Time to Outcome	CER	EER	RRR	ARR	NNT
Mortality	in hospital	0.467	0.500	-7%	-0.033	-30
	95% Confidence Intervals:			-45% to 31%	-0.212 to 0.146	NNT = 7 to INF; NNH = 5 to INF
Barotrauma	ICU	0.067	0.100	-49%	-0.033	-30
	95% Confidence Intervals:			-197% to 98%	-0.132 to 0.066	NNT = 15 to INF; NNH = 8 to INF

 

Comments:

 

1. Do the methods allow the adequate testing of the hypothesis- There may be a problem regarding whether the control and treatments groups were similar with regard to mean tidal volume (7 vs 10ml/kg) and mean peak pressures (24 vs 31 cmH2O) which may stop us from adequately testing the hypothesis.

2. Do the statistical tests correctly test the results to allow differentiation of statistically significant result- Yes

3. Are conclusions valid in light of results- they have concluded that they did not show a difference in mortality and suggested that the treatment and control groups may not have been sufficiently different to test the hypothesis. They also state that they did not test all aspects of lung protection

4. Did results get omitted, and why- No

5. Did they suggest areas of further research- Yes, to study the role of lung protective ventilation strategies in patient prone to lung over-distension and other therapies in lung protection

6. Did they make recommendations based on results and were they appropriate- Yes, they suggested that although this study shows a negative outcome further work is required

7. Is this study relevant to my clinical practice- Yes, similar group of patients to what may be seen in Scottish ICU’s

8. What level of evidence does this study represent- Level 1 negative

9. What grade of recommendation can I make on this result alone- Grade A

10. What grade of recommendation can I make when this study is considered along with other available evidence- Grade A

11. Should I change my practice because of these results- No

12. Should I audit my current practice because of these results- Yes
    
    

Appraised by: Brian H Cuthbertson, University of Aberdeen, Aberdeen; Wednesday, May 22, 2002
Email: b.h.cuthbertson@abdn.ac.uk
Kill or Update By: 22nd May 2004

 

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