title: [The effects of high frequency oscillation ventilation on patients with acute respiratory distress syndrome: a Meta-analysis and sequential analysis of trial].
abstract: OBJECTIVE
  To evaluate the effect of high frequency oscillation ventilation (HFOV) vs. conventional mechanical ventilation (CV) on the treatment and prognosis of adult patients with acute respiratory distress syndrome (ARDS).
  
  
  METHODS
  Published articles concerning randomized controlled trials (RCTs) about the effect of HFOV vs. CV on the prognosis of adult patients with ARDS published before May 2014 were retrieved from PubMed, EMBase, Cochrane central registry of controlled trials, CNKI and Wanfang Data. The mortality and data of physiological parameters were analyzed with STATA 12.0, and the mortality rate was also analyzed by trial sequential analysis with TSA 0.9, and the line chart was drawn with Microsoft Office Excel 2003.
  
  
  RESULTS
  Seven trials with 1,731 patients met the criteria, all of them recorded the physiological parameters data, and mortality rate was mentioned in 6 trials (1,705 patients). Compared with CV, HFOV did not show any statistically significant beneficial effects on mortality [relative risk (RR)=0.93, 95% confidence interval (95%CI)=0.70-1.24, P=0.63], and other clinical outcomes, including survival without mechanical ventilation (RR=1.05, 95%CI=0.72-1.54, P=0.80), survival on mechanical ventilation (RR=1.23, 95%CI=0.65-2.35, P=0.52), or treatment failure (RR=0.89, 95%CI=0.50-1.56, P=0.67). The risk factors of adverse events including hypotension (RR=0.89, 95%CI=0.07-10.99, P=0.93), acidosis (RR=1.05, 95%CI=0.43-2.56, P=0.91), and air leakage from ventilator (RR=0.74, 95%CI=0.31-1.80, P=0.51) were similar. But the physiologic parameters of patients and parameters of ventilator in HFOV group, including oxygenation index, positive end-expiratory pressure, tidal volume, mean airway pressure, arterial pH, partial pressure of arterial carbon dioxide, fraction of inspired oxygen, ratio of partial pressure of arterial oxygen to fraction of inspired oxygen, were better than those in the CV group. Methods adapted from formal interim monitoring boundaries applied to cumulative Meta-analysis showed that the evidence failed by a considerable degree to meet the standards for forgoing studies, and the necessary sample was 3 874 patients. Trial sequential analysis also showed that the accumulated Z-score did not cross the traditional boundary (P=0.05) and interim monitoring boundaries. This result indicated that there was no significant difference between CV and HFOV on mortality before the number of needed sample reached (3,874 cases). We could not get a definitive conclusion with current evidences.
  
  
  CONCLUSIONS
  Compared with CV, the use of HFOV in ARDS was not associated with a significant reduction in mortality. But the physiologic parameters of patients in HFOV group were better than those in the CV group. More RCTs are needed to draw a definitive conclusion.
authors.affiliation: Department of Integrated Intensive Care Unit, the First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, Henan, China. Corresponding author: Sun Tongwen, Email: suntongwen@163.com.
authors.forename: Haixu
authors.initials: H
authors.lastname: Wang
authors.forename: Tongwen
authors.initials: T
authors.lastname: Sun
authors.forename: Youdong
authors.initials: Y
authors.lastname: Wan
authors.forename: Quancheng
authors.initials: Q
authors.lastname: Kan
mesh_terms: D000328:Adult; D001784:Blood Gas Analysis; D006612:High-Frequency Ventilation; D006801:Humans; D010313:Partial Pressure; D011175:Positive-Pressure Respiration; D011379:Prognosis; D012121:Respiration, Artificial; D012128:Respiratory Distress Syndrome; D012307:Risk Factors; D013990:Tidal Volume