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[JAMA读者来信]:自主呼吸试验与成功拔管
2019年12月02日 研究点评, 进展交流 暂无评论

Comment & Response November 5, 2019

Spontaneous Breathing Trials and Successful Extubation

Jan O. Friedrich, Karen E. A. Burns

JAMA. 2019;322(17):1716. doi:10.1001/jama.2019.14217

To the Editor 

The results of the randomized clinical trial reported by Dr Subirà and colleagues compared a less demanding spontaneous breathing trial (SBT) of 30 minutes of pressure support ventilation (PSV) with a more demanding 2-hour T-piece SBT and showed a higher successful extubation rate favoring the less demanding test without a higher need for reintubation.1 In this trial, clinicians, who were not blinded to treatment assignment, made greater use of prophylactic respiratory interventions in the PSV group (24.7%) (8.9% noninvasive ventilation [NIV] + 15.8% high-flow nasal cannula [HFNC]) compared with the T-piece group (18.7%) (5.9% NIV + 12.8% HFNC). This analysis is limited to prophylactic use and not total use of NIV and HFNC after extubation. Moreover, it assumes that individual patients were treated prophylactically with either NIV or HFNC but not both.

Subirà医生及其同事报告的随机临床试验比较了需求较少的自主呼吸试验(SBT)即30分钟压力支持通气(PSV)与需要更高的2小时T管SBT,结果显示,需求较少的试验拔管成功率较高,再插管率并不增加。这项临床试验的试验分组未对临床医生设盲,因此临床医生在PSV组更多采用了预防性呼吸干预(24.7%) (8.9% 无创通气 [NIV] + 15.8% 高流量鼻导管 [HFNC]) 而T管组仅为 (18.7%) (5.9% NIV + 12.8% HFNC)。这一分析仅限于预防性使用而未包括拔管后所有的NIV和HFNC的使用。然而,这一分析假设患者分别预防性使用NIV或HFNC而非两者都是用

It is important to distinguish between prophylactic use of respiratory support interventions and total use of NIV and HFNC that also includes use of NIV and HFNC for postextubation respiratory failure. The authors reported postextubation use of respiratory support interventions for respiratory failure in aggregate across both treatment groups but not separately by treatment group. Consequently, whether increased use of NIV and HFNC may have been required after extubation to avoid reintubation in the PSV group is not clear. These results are important as clinicians may need to be prepared to make greater use of prophylactic respiratory interventions after extubation when using a less demanding PSV rather than a more demanding T-piece SBT technique. To provide more guidance for clinicians, it would be helpful to know the total number of patients in the PSV vs T-piece groups who actually used NIV or HFNC after extubation, either prophylactically or for postextubation respiratory failure.

区分预防性使用呼吸支持治疗与NIV/HFNC的全部使用非常重要,因为后者还包括使用NIV/HFNC治疗拔管后呼吸衰竭。作者报告了两个治疗组整体用于治疗拔管后呼吸功能衰竭使用呼吸支持措施的情况,但未分组报告数据。因此,PSV组NIV/HFNC的使用增加是否源于拔管后避免再次插管并不清楚。这些结果非常重要,因为在采用需要较少的PSV而非需要更多的T管SBT后,一旦能够拔管,临床医生可能需要准备更多使用预防性呼吸治疗措施。了解PSV组与T管组患者拔管后NIV或HFNC的实际使用情况,对临床医生有更多的指导意义。

Comment & Response November 5, 2019

Spontaneous Breathing Trials and Successful Extubation

Jordi Mancebo, Ewan Goligher, Laurent Brochard

JAMA. 2019;322(17):1716-1717. doi:10.1001/jama.2019.14226

To the Editor 

Dr Subirà and colleagues evaluated 2 types of SBTs to evaluate readiness for extubation, a short-duration (30-minute) PSV strategy compared with a long-duration (2-hour) T-piece strategy, and found higher extubation rates with the PSV strategy (82.3% vs 74.0% at 72 hours; 92.5% vs 84.1% after the first SBT), with no difference in reintubation rates within 72 hours of extubation (11.1% vs 11.9%).1 Surprisingly, patients underwent their first SBT when the pretest probability of successful separation from the ventilator was already extremely high (as indicated by the success rate of the trial). When the pretest probability is high, any test or strategy having a risk of false-negative results (ie, predicting failure in a patient who could be extubated) will compromise predictive performance, whereas the risk of false-positive results (ie, predicting success in a patient who cannot be extubated) will be almost nonexistent.2 The design of this study put the T-piece group at higher risk of false-negative results than the PSV group.3,4 The results were therefore expected, as predicted by Bayes’ theorem.2 The relevant question for clinical practice is why the authors included patients at a late stage when the pretest probability of extubation was already high. Moreover, the absence of differences in length of stay in the intensive care unit casts doubt on any inference that the 30-minute PSV strategy meaningfully accelerated liberation from mechanical ventilation.

Subirà医生及其同事评价了两种SBT方式对拔管可行性的判断,其中一种为短时间(30分钟) PSV策略,另一种为较长时间 (2小时) T管策略。结果发现,PSV策略拔管率较高 (72小时 82.3% vs 74.0%; 首次SBT后 92.5% vs 84.1%),而拔管后72小时内再次插管率无差异 (11.1% vs 11.9%)。奇怪的是,患者进行首次SBT时其成功脱离呼吸机的验前概率即已很高 (如拔管成功率提示)。当验前概率很高时,任何具有假阴性结果风险 (即对于成功拔管患者预测拔管失败) 的检验或策略都可能影响预测准确性,而假阳性结果风险 (即对于不能拔管患者预测拔管成功) 几乎不存在。这项研究的实验设计将T管组较PSV组置于更高的假阴性风险。因此,这一结果正如Bayes定理所预期。与临床实践相关的问题是,作者为何在晚期纳入患者,此时验前概率已非常高。而且,ICU住院日没有差异的事实,使得人们对于30分钟PSV策略加快脱机进程的推断产生了质疑。

The authors also mentioned that “…a prespecified interim analysis was performed…showed a nonsignificant difference in primary outcome between groups and…the investigators decided to complete the estimated sample enrollment.” Because the study was not blinded and the use of prophylactic NIV or HFNC after extubation was left to the discretion of attending physicians, it would be important to know how the primary outcome (successful extubation) and baseline characteristics and interventions differed between the first interim 500 patients (in whom no differences were found in the primary outcome) and the second cohort that led to the significant difference in the primary outcome.

作者还提到,“...进行了预先确定的中期分析...结果显示,两组间主要预后指标没有显著差异...研究者决定完成预计的样本量。”因为研究并未设盲,拔管后预防性使用NIV或HFNC由主治医生决定,因此,了解第一次中期分析时500名患者的主要预后指标(成功拔管)与基线特征和干预措施之间的差异(主要预后指标没有差异),以及后续队列(主要指标差异显著)相应指标的差异非常重要。

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