PubMed · 10202896
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S Daya. 1999. Differences between crossover and parallel study designs--debate?. https://doi.org/10.1016/s0015-0282(98)00495-6
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BACKGROUND: Assisted mechanical ventilation is the mainstay of management of a variety of conditions affecting the neonate. However there are a number of potential hazards associated with this life saving intervention. New suctioning techniques have been introduced into clinical practice which aim to prevent or reduce these untoward effects. OBJECTIVES: To assess the effects of endotracheal suctioning without disconnection in intubated ventilated neonates. SEARCH STRATEGY: The review has drawn on the search strategy for the Cochrane Neonatal Review Group. A comprehensive search of MEDLINE, Cochrane Library, MEDLINE and CINAHL databases was undertaken by the reviewers. SELECTION CRITERIA: All trials utilizing random or quasi-random patient allocation in which suctioning with or without disconnection from the ventilator is compared in the neonatal population. DATA COLLECTION AND ANALYSIS: Standard methods of the Cochrane Neonatal Group were used. Each author reviewed trials for eligibility and quality and extracted data separately, then compared and resolved differences. Analysis was performed using the fixed effects model and outcomes were reported using relative risk for categorical data and weighted mean difference for outcomes measured on a continuous scale. MAIN RESULTS: Two trials (22 infants) were included in this review. The trials employed a cross-over design in which suctioning with or without disconnection was compared. Suctioning without disconnection resulted in a reduction in episodes of hypoxia (RR 0.30, 95% CI 0.11, 0.80) and a smaller percentage decrease in the TcPO2 (WMD 18.5%, 95% CI 8.11, 28.89). There were also fewer infants who experienced episodes where TcPO2 decreased by > 10% (RR 0.36, 95% CI 0.17, 0.79). Suctioning without disconnection resulted in a smaller percentage decrease in heart rate (WMD 11.53%, 95% CI 3.64, 19.43) and a reduction in the number of infants experiencing a decrease in heart rate by > 10% (RR 0.56, 95% CI 0.32, 0.99). REVIEWER'S CONCLUSIONS: Based upon the results of this review, there is insufficient evidence to decide between endotracheal suctioning with or without disconnection. There is, however, evidence of some benefit from performing suctioning without disconnection for some specific short-term outcomes. Further research should be undertaken to fully assess this practice with particular focus on extremely low birth weight infants and different modes of mechanical ventilation, and to address clinically important outcomes.
To obtain meaningful results in any clinical trial, patients need to be allocated to treatments in such a way that valid analysis can be carried out. Balancing treatment groups before analysis is carried out is more desirable than trying to compensate for incomparability at a later date. Therefore, the development of allocation procedures to produce comparable groups in which prognostic factors are equally represented is important. Minimization, a deterministic allocation method, aims to ensure balance on such factors, particularly in small trials when traditional randomization methods are likely to fail. However, views on the use of conventional analysis following minimization are divided. The use of minimization in two randomised crossover trials is described where, in addition to the comparisons between randomised treatments, it was desired to have balance between groups based on differential trial procedures. Theoretical concerns about the use of minimization are not applicable in this setting, and therefore minimization is shown to be a useful technique for obtaining balance.
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