Meta Analysis
Prone ventilation reduces mortality in patients with acute respiratory failure and severe hypoxemia: systematic review and meta-analysis.
This review may be edited
Summary
Posted By: Gordon S Doig
E-Mail: gdoig@med.usyd.edu.au
Posted Date: 13 Dec 2010
Title: Prone ventilation reduces mortality in patients with acute respiratory failure and severe hypoxemia: systematic review and meta-analysis.
Authors: Sud S, Friedrich JO, Taccone P, Polli F, Adhikari NK, et al
Reference: Intensive Care Med. 2010 Apr;36(4):585-99. Epub 2010 Feb 4.
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Abstract: BACKGROUND: Prone position ventilation for acute hypoxemic respiratory failure (AHRF) improves oxygenation but not survival, except possibly when AHRF is severe.

OBJECTIVE: To determine effects of prone versus supine ventilation in AHRF and severe hypoxemia [partial pressure of arterial oxygen (PaO2)/inspired fraction of oxygen (FiO2) less than 100 mmHg] compared with moderate hypoxemia (100 mmHg less than or equal to PaO2/FiO2 to 300 mmHg).

DESIGN: Systematic review and meta-analysis.

DATA SOURCES: Electronic databases (to November 2009) and conference proceedings.

METHODS: Two authors independently selected and extracted data from parallel-group randomized controlled trials comparing prone with supine ventilation in mechanically ventilated adults or children with AHRF. Trialists provided subgroup data. The primary outcome was hospital mortality in patients with AHRF and PaO2/FiO2 less than 100 mmHg. Meta-analyses used study-level random-effects models.

RESULTS: Ten trials (N = 1,867 patients) met inclusion criteria; most patients had acute lung injury. Methodological quality was relatively high. Prone ventilation reduced mortality in patients with PaO2/FiO2 less than 100 mmHg [risk ratio (RR) 0.84, 95% confidence interval (CI) 0.74-0.96; p = 0.01; seven trials, N = 555] but not in patients with PaO2/FiO2 greater than or equal to 100 mmHg (RR 1.07, 95% CI 0.93-1.22; p = 0.36; seven trials, N = 1,169). Risk ratios differed significantly between subgroups (interaction p = 0.012). Post hoc analysis demonstrated statistically significant improved mortality in the more hypoxemic subgroup and significant differences between subgroups using a range of PaO2/FiO2 thresholds up to approximately 140 mmHg. Prone ventilation improved oxygenation by 27-39% over the first 3 days of therapy but increased the risks of pressure ulcers (RR 1.29, 95% CI 1.16-1.44), endotracheal tube obstruction (RR 1.58, 95% CI 1.24-2.01), and chest tube dislodgement (RR 3.14, 95% CI 1.02-9.69). There was no statistical between-trial heterogeneity for most clinical outcomes.

CONCLUSIONS: Prone ventilation reduces mortality in patients with severe hypoxemia. Given associated risks, this approach should not be routine in all patients with AHRF, but may be considered for severely hypoxemic patients.

PMID: 20130832 [PubMed - indexed for MEDLINE]

 
Are the Results Valid?
1. Did the overview address a focused clinical question?
Yes. The authors report:

A priori, we hypothesized that prone ventilation would reduce mortality in severely hypoxemic patients, defined by baseline ratio of partial pressure of arterial oxygen (PaO2) to inspired fraction of oxygen (FiO2) less than 100 mmHg, but not in patients with moderate hypoxemia (100 mmHg B PaO2/FiO2 B 300 mmHg).

2. Were the criteria used to select articles for inclusion appropriate?
Yes. The authors included all RCTs on-topic.
3. Is it unlikely that important, relevant studies were missed?
No, the authors conducted an extensive literature search. The search included MEDLINE, EMBASE and CENTRAL with hand searching of conference abstracts from key meetings (SCCM, ESICM,ACCP).
4. Was the validity of the included studies appraised?
Yes. The authors report use of blinding, maintenance of allocation concealment and report that they 'analyzed patients according the assinged group for all outcomes'.
The authors do not report whether each study reported outcomes for all randomised patients (complete follow-up).
5. Were assessments of studies reproducible?
Yes, there was complete agreement on the inclusion of studies.
6. Were the results similar from study to study?
There was no heterogeneity for the primary outcome (mortality, I2=0%). There was low heterogeneity (I2 less than 35%) for physiological outcomes.
What are the Results?
1. What are the overall results of the overview?
The use of proning demonstrated a significant reduction in mortality in severly hypoxemic patients (PaO,2/FiO2 less than 100mmHg):

risk ratio (RR)0.84, p = 0.01;

Prone ventilation also improved oxygenation by 2739% over the first 3 days of therapy.

2. How precise were the results?
The 95% confidence interval (CI) around the esitmate of mortality reduction was: 0.740.96;
Will the Results Help Me In Caring For My Patients?
1. Can the results be applied to my patient care
Yes. Although your ICU team will need to practice proning and gain experience in managing patients in this position, this technique can be applied to patients in any standard ICU.
2. Were all clinically important outcomes considered?
Yes. The authors considered mortality, physiological outcomes and harms.
3. Are the benefits worth the harms and costs?
The authors report that proning increased the risks of pressure ulcers (RR 1.29, 95% CI 1.161.44), endotracheal tube obstruction (RR 1.58, 95% CI 1.242.01), and chest tube dislodgement (RR 3.14, 95% CI 1.029.69). As team experience is gained, ICUs report a decrease in adverse event rates.

The costs of proning are marginal. The intervention requires a team of 4 people and pillows.


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Prone ventilation reduces mortality in patients with acute respiratory failure and severe hypoxemia: systematic review and meta-analysis.

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