CardiovascularHigh-flow nasal cannula oxygen therapy vs conventional oxygen therapy in cardiac surgical patients: A meta-analysis☆,☆☆
Introduction
Oxygen therapy is the main supportive treatment administered to patients with hypoxemic respiratory failure and has usually been delivered by nasal prongs, cannulas, or masks. However, the maximal flow rate that these devices delivered is limited. The maximal flow rate delivered by conventional oxygen therapy (COT) is only 15 L/min, which is far lower than the demands of patients with acute respiratory failure, and the fraction of inspired oxygen (Fio2) that finally reaches the lungs significantly decreases [1]. The use of noninvasive ventilation (NIV) for these patients is associated with improved outcomes. Nevertheless, NIV is not without its limitations. It is associated with gastric distension and often poorly tolerated. Further respiratory support, such as invasive ventilation, may be still needed [2].
High-flow nasal cannula (HFNC) oxygen therapy can deliver a humidified and heated mixture of air and oxygen at a very high flow. It can provide a maximal flow rate up to 60 L/min with a Fio2 of approximately 100% [3]. The use of a HFNC has been demonstrated to generate positive airway pressure [4], [5], ameliorate oxygenation [5], [6] and dyspnea [4], [7], reduce the work of breathing and the respiratory rate [8], [9], and improve comfort [3], [10]. These benefits are attributed to the advantages of HFNCs, including its abilities to more adequately meet the peak flow of inspiration, flush the anatomical dead space, and deliver heated and humidified mixture gas of oxygen and air, thereby promoting the mucociliary function, compared with COT [11], [12], [13].
Alveolar collapse and atelectasis are common in patients undergoing cardiac surgery who required cardiopulmonary bypass (CPB), and are major causes of complications after extubation [14], [15]. Respiratory failure due to alveolar collapse and atelectasis, as well as muscular weakness, fluid overload, increased pulmonary vascular resistances, can be observed in these patients [16].
To date, there is limited evidence on the use of high-flow oxygen therapy in patients after cardiac surgery, and some studies reported that HFNC was useful for those cardiac surgery patients [17], [18], [19]. In the present meta-analysis, we aimed to assess the efficacy and safety of HFNCs compared with COT in adult postextubation cardiac surgical patients.
Section snippets
Data sources and search strategy
We reviewed studies published in the Embase, PubMed, Cochrane Central Register of Controlled Trials, Wanfang databases, and the China National Knowledge Infrastructure. We searched all relevant articles published from inception to June 2016. We also searched the references from relevant articles for avoiding loss of studies. We used the following keywords, Emtree and MeSH terms in different combinations for the searches: “oxygen therapy”, “*Oxygen inhalation therapy”, “*Oxygen delivery
Results
The selection process for the eligible studies is shown in Fig. 1. Initially, 2339 potentially relevant records were identified. After removing duplicate records, review articles, case reports, animal studies, comments, or studies that were not randomized controlled studies, 5 studies were remained for assessment. Of these, 1 study that was about neonatal/pediatric populations, and 2 studies that did not report sufficient data, were excluded. Finally, 2 studies were included in the present
Discussion
Recently, the use of HFNC for the treatment of many diseases has gained increasing popularity [20]. The HFNC therapy is administered to patients of all age groups, such as preterm and term infants, children, and adults [21]. Previous studies have demonstrated that HFNC may generate a certain degree of positive airway pressure (due to the continuous administration of a high flow rate of gas), reduce the work of breathing [22], [23], [24], reduce blood carbon dioxide levels by flushing
Conclusions
Our meta-analysis demonstrated that HFNC could reduce the need for the escalation of respiratory support, and it could be safely administered in adult postextubation cardiac surgical patients. Further large-scale, multicenter studies are required to confirm our results.
Authors' contributions
All authors conceived the study and contributed to the study design. HYY and RZ collected data and helped extract data. YFZ and JRW performed the analyses. JRW and YFZ performed the literature review. All authors contributed to the writing of the draft and approved the final manuscript.
Acknowledgments
We acknowledge all the people who helped us.
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2020, ChestCitation Excerpt :Although previous meta-analyses have examined HFNC use in this population and found inconsistent results, we believe this may partly be explained by clinical heterogeneity. One previous meta-analysis34 examined only patients undergoing cardiac surgery, excluding those undergoing thoracic or abdominal surgery. Conversely, another35 included all patients after extubation (both critically ill and postoperative), thus combining different patient populations.
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Competing interest: The authors declare that there are no conflicts of interest.
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Funding: The authors received no specific funding for this work.