Effect Of High-flow Nasal Cannula Involved In Preoxygenation During ICU Intubation:A Systematic Review And Meta-analysis

Objective:To evaluate whether high-flow nasal cannula（HFNC）involved in pre-oxygenation can reduce desaturation during endotracheal intubation in the ICU.Methods:Searching studies from PubMed,Embase,Cochrane Clinical Trials,China Academic Journal Network Publishing Database,Wanfang Journal Paper Database,China Biology Medicine disc,China Scientific and Technical Periodical Abstracts,and Chinese Science Citation Database published from inception to Oct 31,2017concerning about high-flow nasal cannula,endotracheal intubation（ETI）and preoxygenation.We Included the relevant prospective controlled studies.Then the quality of the included literature was assessed using the Cochrane bias risk assessment tool.Thirdly,we believed that heterogeneity was significant if the I² index>50%.Then the cause of the heterogeneity would be learned and excluded.Moreover,studies would be analyzed sensitively.Using Review Manager（version 5.3）to pool data and analyze in this study.Outcome was expressed as the mean difference（MD）,relative risk（RR）,and corresponding 95%confidence intervals（CI）.Results:Finally,404 foreign studies（all in English）and 0 Chinese article were searched.397 articles were excluded based on abstracts and titles.The remaining 7articles were screened for full-text reading:2 articles were excluded because of unsuitable experimental or control groups and 1 excluded because of unpublished retrospective study.At last,3 RCTs and 1 prospective quasi-experimental before-after study were included.And a meta-analysis was performed in 4 studies（158 participants in the experimental group and 151 in the control group）.The random effect model was used in all analyzes in this study to make more conservative predictions.Overall,we can observe:（1）The combined analysis of the mean minimum SPO₂ value during ETI showed that there was no significant heterogeneity（I²=34%）.And the value between HFNC group（the experimental group）and non-HFNC group（the control group）was91.78%vs 88.71%.There was significantly statistical difference（MD=3.86%,95%CI:0.40%—7.31%,P=0.03）.（2）The heterogeneity was found when we analyze the incidence of severe hypoxemia in studies（I²=52%）.And incidence of severe hypoxemia was 14.56%VS 19.87%（HFNC group VS non-HFNC group）respectively with no significantly statistical difference（RR=0.63,95%CI:0.25-1.57,P=0.32）.HFNC did not increase severe hypoxemia during ETI comparing with other methods.Sensitive analysis supported the conclusion above as well（RR=0.91,95%CI:0.45-1.82,P=0.79,I²=25%）.（3）The heterogeneity of the complications of intubation in included studies was not obvious（I²=0%）.The incidence of the two groups were 49.53%vs 56.44%respectively.High-flow oxygenation did not increase intubation-related complications（RR=0.86,95%CI:0.68-1.10,P=0.24）.Subgroup analyzes showed that arrhythmic events（RR=0.61,95%CI:0.08-4.80,P=0.64,I²=0%）and cardiac arrest events（RR=0.32,95%CI:0.03-3.00,P=0.32,I²=0%）did not increase because of HFNC.（4）Mortality after intubation（20.29%vs 23.67%）also showed no significant statistically difference（RR=0.84,95%CI:0.55-1.28,P=0.43,I²=0%）.Conclusion:High-flow nasal cannula involved in preoxygenation improves the lowest SPO₂ value during endotracheal intubation in the ICU.More researches,especially large clinical trials,are needed to explore the use of high-flow oxygen nasal cannula in pre-oxygenation.