Scientific literature: mechanical ventilation

As a special service to our readers, International Hospital presents a few recent literature abstracts chosen by our editorial board as being particularly worthy of attention.

A review of oral preventative strategies to reduce ventilator-associated pneumonia.

Andrews T, Steen C. Nurs Crit Care 2013; May18(3):116-22. Epub 2013 Jan 30.

This article evaluates the evidence for and efficacy of the use of mechanical hygiene and chlorhexidine in the prevention of ventilator-associated pneumonia (VAP). Search strategies included primary research articles; randomized controlled trials; systematic reviews and excluded quasi-experimental trials and opinion articles. VAP is the commonest infection found in critically ill patients who are mechanically ventilated. It is associated with increased mortality, increased length of stay in intensive care and increased costs. VAP is a health care-associated infection consistent with the presence of an endotracheal tube and mechanical ventilation for greater than 48 h. Efforts aimed at reducing infection rates include oral decontamination and mechanical hygiene to control the bacteria responsible, since there is an association between changes in bacteria found in the oropharynx and its development. Tooth brushing and the use of an oral antiseptic such as chlorhexidine gluconate are increasingly recommended in ventilator care bundles.
While there have been a number of studies conducted evaluating the efficacy of both approaches, there is limited evidence to support their use. The frequency of oral decontamination and mechanical hygiene interventions have not been established and chlorhexidine 2% seems to be more effective compared to weaker concentrations, but data is mainly confined to patients following cardiothoracic surgery.

Non-invasive positive pressure ventilation for treatment of respiratory failure due to severe acute exacerbations of asthma.

Lim WJ, Mohammed Akram R, Carson KV, Mysore S, Labiszewski NA, Wedzicha JA, Rowe BH, Smith BJ. Cochrane Database Syst Rev. 2012; Dec 12:12:CD004360.

Because of sub-optimal long-term care and delays in obtaining help during acute exacerbations, the mortality and morbidity related to asthma is still a major health concern. There is reason to believe that non-invasive positive pressure ventilation (NPPV) could be beneficial to patients with severe acute asthma; however, the evidence surrounding the efficacy of NPPV is unclear, despite its common use in clinical practice.
The objectives were to determine the efficacy of NPPV in adults with severe acute asthma in comparison to usual medical care with respect to mortality, tracheal intubation, changes in blood gases and hospital length of stay.
The search method consisted of a search in the Cochrane Airways Group Specialized Register of trials (July 2012). Following this, the bibliographies of included studies and review articles were searched for additional studies (July 2012). Included were randomized controlled trials of adults with severe acute asthma as the primary reason for presentation to the emergency department or for admission to hospital. Asthma diagnosis was defined by internationally accepted criteria. Studies were included if the intervention was usual medical care for the management of severe acute asthma plus NPPV applied through a nasal or facemask compared to usual medical care alone. Studies including patients with features of chronic obstructive pulmonary disease (COPD) were excluded unless data were provided separately for patients with asthma in studies recruiting both COPD and asthmatic patients. Five studies on 206 participants contributed data, while one study was available in abstract form only and was not fully incorporated into this review. For the primary outcome of endotracheal intubation there were two studies that contributed data: two intubations were needed in 45 participants on NPPV and no intubations in 41 control patients (risk ratio 4.48; 95% CI 0.23 to 89.13). There were no deaths in either of these studies. Length of hospital stay was reported in two studies, though meta-analysis was not possible. Hospitalisation was reported in one small study, in which there were three admissions out of 17 on NPPV and 10 admissions out of 16 in control patients (RR 0.28, 95% CI 0.09, 0.84).
This review of studies has highlighted the paucity of data that exist to support the use of NPPV in patients in status asthmaticus. As such this course of treatment remains controversial despite its continued use in current clinical practice. Larger, prospective randomized controlled trials of rigorous methodological design are needed to determine the role of NPPV in patients with asthma.