The effects of manual hyperflation using self-inflating manual resuscitation bags on arterial oxygen tensions and lung compliance - Ameta-analysis of the literature

Abstract

The self-inflating manual resuscitation bag (MRB) is a modality which is commonly used by physiotherapists to manually hyperinflate the lungs of mechanically ventilated patients. There is limited scientific evidence to support its therapeutic use and the literature is not in agreement as to the effects of manual hyperinflation. A meta-analysis of the current research on humans has been conducted to investigate the effects of this modality on arterial oxygen tensions and lung compliance. All published studies evaluating the effects of manual hyperinflation (or bagging) on arterial oxygen tensions and/or lung compliance on mechanically ventilated patients have been retrieved. Only studies which reported results in terms of mean values and standard deviation or standard error of the mean could be used in this analysis. Eleven studies were identified between the time period 1968 -1995. Seven of these studies fitted the inclusion criteria. The mean and standard error of the mean values for arterial oxygen tensions (Pa02) and lung compliance (CL) have been used to calculate the 95% confidence intervals and these results were plotted on a graph. A comparative analysis has been performed on the results of the seven studies. A generally non-significant association between bagging and the Pa02 and CL values was demonstrated. Great discrepancies were identified in the designs of the seven included studies. Since the seven studies included in this meta-analysis show an overall non-significant association, it is reasonable to assume that the therapeutic value of the self-inflating manual resuscitation bag is questionable. The studies presented such divergent designs that they do not offer conclusive evidence. More standardized, multi-centre studies are required to clarify the therapeutic value of this modality. Other methods of recruiting the lungs of critically ill patients during and after physiotherapy intervention, need to be explored.