机械通气撤机诱发急性心功能障碍的研究进展

机械通气撤机失败在ICU患者中并不少见,约25%伴有COPD和(或)左心疾病的患者虽然通过了自主呼吸试验(spontaneous breathing trial,SBT),但仍撤机失败[1].目前对撤机失败原因的研究主要集中在呼吸功能障碍方面,而在呼吸系统机械力学正常但心脏储备功能较差的患者中,撤机诱发的急性心功能障碍可能是撤机失败的主要原因[2,3].     

肺联合膈肌超声在预测有创机械通气撤离中的价值

目的探讨肺联合膈肌超声对有创机械通气患者撤机结局的预测价值。方法本研究为病例对照研究。采用非随机抽样的方法, 选取2020年1月至2021年12月湖南省人民医院86例有创机械通气患者, 撤机拔管前行自主呼吸实验(SBT), SBT通过后使用床旁超声进行肺和膈肌功能评估, 记录患者的肺部超声评分(LUS), 膈肌功能如呼气末膈肌厚度(DTee)、膈肌增厚分数(DTF)。撤机拔管后分撤机成功组(71例)和撤机失败组(15例), 通过比较2组的LUS、DTee、DTF的差异, 寻找预测撤机相关危险因素。运用受试者工作特征曲线比较各危险因素在SBT后的曲线下面积(AUC)以及敏感度和特异度, 并建立多指标组合模型以提高预测准确性。结果撤机成功组SBT后LUS低于撤机失败组, 而DTee、DTF高于撤机失败组, 差异均有统计学意义(P值均<0.05)。SBT后LUS增加(OR=0.636, P=0.005)、DTee变薄(OR=1.881, P=0.037)、DTF下降(OR=1.558, P=0.017)为撤机失败的独立危险因素。LUS、DTee和DTF预测机械通气患者撤机成功的AUC值...     

自主呼吸试验前后下腔静脉变异度对呼吸衰竭合并心功能不全患者撤机失败的预测价值

目的评价自主呼吸试验(SBT)前后下腔静脉变异度(△DIVC)对呼吸衰竭合并心功能不全患者机械通气后撤机失败的预测价值。方法选取2016年11月至2018年2月在徐州市中心医院ICU进行机械通气的呼吸衰竭合并心功能不全患者120例。患者30 min SBT成功后拔管,48 h内不需要再次气管插管和无创呼吸机辅助为撤机成功组(n=62);30 min SBT失败或者SBT成功后拔管,但48 h内需要再次插管或无创呼吸机辅助为撤机失败组(n=58)。分别在SBT前和30 min后记录并比较2组患者的临床特征及△DIVC。采用SPSS 17.0软件统计分析。根据数据类型,组间比较采用独立样本t检验、Mann-Whitney U检验或χ~2检验。采用多因素logistic回归法分析影响撤机失败的独立危险因素。利用受试者工作特征(ROC)曲线评估△DIVC对撤机失败的预测价值。结果 2组患者在慢性呼吸疾病、急性生理学和慢性健康状况评价Ⅱ(APACHEⅡ)评分、第1次插管到拔管的持续时间和血红蛋白水平方面比较差异有统计学意义(P0.05)。与撤机成功组比较,撤机失败组患者在SBT前及30 min后二氧化碳分压和N端脑钠肽前体显著升高,左室射血分数(LVEF)显著降低,差异有统计学意义(P0.05);在SBT后30 min,撤机失败组患者△DIVC较撤机成功组显著升高,差异亦有统计学意义(P0.05)。多变量logistic回归分析显示,LVEF(OR=1.204,95%CI 1.133～1.381;P=0.015)和SBT后30 min的△DIVC(OR=1.450,95%CI 1.102～2.026;P=0.009)是患者撤机失败的独立危险因素。SBT后30 min的△DIVC预测患者撤机失败的ROC曲线下面积为0.905,最佳截断点0.27,灵敏度为82.4%,特异度为94.4%。LVEF预测患者撤机失败的曲线下面积为0.806,最佳截断点为42.0%,灵敏度为54.5%,特异度为86.8%。结论 SBT 30 min后的△DIVC对于呼吸衰竭合并心功能不全患者撤机失败具有较高的预测价值。     

膈肌功能对慢性阻塞肺疾病加重期插管患者撤机的指导价值分析

目的探讨膈肌功能对慢性阻塞性肺病加重期(AECOPD)插管患者撤机的指导价值。方法选取行机械通气并考虑撤机的AECOPD插管患者为研究对象,根据患者撤机成功与否分为撤机成功组与撤机失败组。具备撤机条件后行自主呼吸试验(SBT)30 min,监测SBT 0、5、30 min时膈肌电活动(Edi)、呼吸浅快指数(f/Vt)及口腔闭合压(P0.1)。结果 37例患者纳入本研究,其中撤机成功组25例,撤机失败组12例。撤机失败组患者血Pa CO2高于另一组患者(P0.05)。撤机成功与失败组患者的年龄、Pa O2、MAP等各方面均无显著差异(P0.05)。SBT 30 min时两组患者Edi均显著高于SBT 0 min;在SBT 30 min撤机成功组Edi低于撤机失败组,以Edi12V为临界值,撤机失败预测的灵敏度为100.0%和特异度为66.7%。在SBT 5、30min时撤机成功组患者f/Vt较撤机失败组低,两组患者P0.1无明显差别(P0.05)。结论 Edi对AECOPD患者撤机具有良好的预测价值。     

脉搏灌注指数和脉搏灌注变异指数在机械通气患者撤机中的应用

目的 观察脉搏灌注指数（PI）和脉搏灌注变异指数（PVI）在机械通气患者撤机中的应用效果。方法 选取116例准备撤机的机械通气患者,通过撤机筛查后采用T-管模式进行自主呼吸试验（SBT）,以患者拔管后自主呼吸时间超过48 h为撤机成功,根据撤机结果将患者分为撤机成功组（90例）和撤机失败组（26例）,使用脉搏血氧仪Radical-7监测SBT前和SBT结束时患者PI、PVI,计算SBT前后PI和PVI的变化（ΔPI、ΔPVI）,利用ROC评估SBT前PI、PVI及ΔPI、ΔPVI对机械通气患者撤机结果的预测价值。结果 与撤机失败组比较,撤机成功组SBT前PVI、SBT后PI、SBT后PVI、ΔPI、ΔPVI增加（P均<0.05）。当SBT前PVI>14.0%时,其预测机械通气患者撤机成功的灵敏度为86.1%,特异度为79.2%,AUC为0.860,95%CI为0.766～0.953;当ΔPVI>10.5%时,其预测机械通气患者撤机成功的灵敏度为91.7%,特异度为83.3%,AUC为0.905,95%CI为0.831～0.978;当ΔPI>12.5%时,其预测机...     

浅快呼吸指数指导AOPP患者撤机的临床研究

目的探讨浅快呼吸指数(light fast breathing index RSBI)作为急性有机磷中毒(acute organophosphate poisoning,AOPP)患者撤机的临床价值。方法重症医学科20例机械通气的AOPP患者均通过了1h的自主呼吸实验(spontaneous breath-ing test SBT),记录了2个时期的RSBI:SBT前、SBT1h,同时记录年龄、性别、APACHEⅡ评分、撤机前30min的动脉血气分析及胆碱酯酶活力(choline esterase vigo CHE)。结果 15例AOPP患者成功撤机,5例患者撤机失败,在成功和失败两组年龄、性别、A-PACHEⅡ评分无明显差异(P>0.05),CHE有明显差异(P<0.05),以RSBI≤105 bpm/L为标准预测撤机成功的灵敏度和特异度分别为:SBT前SBT1 92.8%、10.2%,SBT1h的RSBI预测撤机成功的灵敏度和特异度分别为93.6%、40.5%。SBT1h的RSBI与CHE联合预测撤机成功的灵敏度和特异度分别为90.5%、75%。结论 SBT1h的RSBI预测AOPP撤机成功的准确性高于SBT前,其与CHE联合评价将提高预测撤机成功的准确性。     

SBT联合BNP监测对COPD患者拔管结局的预测价值

目的探讨自主呼吸试验(SBT)联合脑钠肽(BNP)预测慢性阻塞性肺疾病(COPD)患者拔管结局价值.方法选择2016年1月至2018年12月广东同江医院重症监护室收治的需要行有创机械通气的COPD呼吸衰竭患者80例,根据最终成功拔管与否分为拔管成功组和拔管失败组.分别记录SBT试验前及通过SBT试验2h后患者BNP、血气分析结果,比较SBT前后BNP差值△BNP和△BNP的受试者工作特征曲线及曲线下面积.结果(1)SBT前,2组BNP水平差异无统计学意义(t=0.040,P>0.05),SBT后,拔管失败组BNP水平高于拔管成功组(t=23.458,P<0.05).(2)SBT前,2组pH、动脉血二氧化碳分压、动脉血氧分压差异均无统计学意义(t=1.030、0.481、0.585,P值均>0.05),SBT后,拔管失败组pH、动脉血氧分压低于拔管成功组(t=5.678、2.012,P值均<0.05),动脉血二氧化碳分压高于拔管成功组(t=5.098,P<0.05).(3)△BNP AUC大于SBT前BNP和SBT后BNP,△BNP的cut-off值为45 ng/L,特异度为95.66%,敏感度为83.32%,预测脱机后拔管失败准确率为93.11%.结论对于COPD合并心功能不全患者,达到撤机标准后,在进行SBT基础上评价SBT前后△BNP水平可有效预测COPD合并心功能不全患者撤机拔管成功率,可在临床广泛推广使用.     

不同撤机方式在COPD机械通气患者的临床观察

目的:观察慢性阻塞性肺疾病(COPD)急性加重期接受有创机械通气患者采用2种撤机决策(临床医生经验与自主呼吸试验)的临床疗效。方法:将94例COPD急性加重期且需要有创机械通气的患者,按照PaCO2水平应用分层随机化法分为自主呼吸试验(SBT)组和临床医生经验(DED)组各47例,2组均给予常规基础治疗。每日对2组患者进行撤机筛选试验,完成筛选试验的SBT组患者行SBT后实施撤机;完成筛选试验的DED组患者,由科室呼吸治疗小组根据临床经验决定是否撤机。观察病死率、住ICU时间、有创机械通气时间、脱机成功率、呼吸机相关性肺炎(VAP)发生率、2次插管率、SBT组SBT终止原因等。结果:SBT组患者住ICU时间、有创机械通气时间、病死率及VAP发生率均明显高于DED组患者(均P<0.05)。DED组患者脱机成功率显著高于SBT组(P<0.05)。DED组患者2次插管率略高于SBT组患者,但差异无显著性(P>0.05)。结论:SBT有可能导致撤机延迟,增加有创机械通气时间,应重视COPD加重期有创机械通气撤机决策中医生临床经验的重要性,提高撤机成功率。     

浅快呼吸指数指导缺血性脑卒中患者撤机的临床观察

目的探讨浅快呼吸指数(RSBI)指导缺血性脑卒中患者撤机的临床价值。方法前瞻性研究,入选在重症医学科进行有创机械通气24 h 40例缺血性脑卒中患者,根据撤机结果将患者分为成功组26例,失败组14例。应用低水平压力支持通气法进行自主呼吸实验(SBT),40例患者均通过了1 h的自主呼吸实验,记录SBT前和SBT1h、SBT1.5h及SBT2h的RSBI,同时记录年龄、性别、APACHEⅡ评分、撤机前30 min的血气分析。结果成功组和失败组年龄、性别、GCS评分、APACHEⅡ评分无明显差异(P0.05),失败组合并冠心病比例较成功组明显升高(P0.05)。以RSBI≤105 bpm/L为标准预测撤机成功的灵敏度和特异度分别为:SBT前93.8%、10.6%,SBT1 h 100%、40.24%、SBT1.5 h 98.2%、38.7%SBT2 h 96.3%、38.2%。结论SBT1 h的RSBI预测缺血性脑卒中患者撤机成功的准确率高。动态观察RSBI对缺血性脑卒中患者成功撤机有一定的预测价值。     

血浆BNP对慢性阻塞性肺疾病有创机械通气撤机的指导价值

目的探讨撤机前后血浆BNP水平及其变化对慢性阻塞性肺疾病(简称慢阻肺)患者有创机械通气撤机的指导价值。方法回顾性调查满足条件的70例患者,测定患者开始有创机械通气时,自主呼吸试验(SBT)前、后的血浆BNP水平,分别标为(BNP 0、BNP 1、BNP 2),SBT前、后的血浆BNP水平差值(ΔBNP),并根据患者撤机结局分为撤机成功组与撤机失败组。绘制ROC曲线,分析血浆BNP水平对慢阻肺患者撤机结局的预测价值。结果 70例患者中,成功撤机52例,撤机失败18例。BNP 0、BNP 1、BNP 2预测慢阻肺患者撤机失败的AUC分别为0.6079、0.8568、0.9081,ΔBNP预测撤机失败的AUC为0.9466。结论血浆BNP水平对预测慢阻肺患者撤机结局有指导价值,其中ΔBNP预测慢阻肺患者撤机结局的价值最大。     

自主呼吸试验在机械通气脱机过程中的应用

目的 自主呼吸试验(SBT)作为程序化拔管步骤在机械通气脱机过程中的应用.方法 程序化拔管患者行前瞻性研究,非程序化拔管患者行回顾性分析,比较两组机械通气时间、呼吸机相关性肺炎(VAP)发生率、48 h复插管率、住ICU天数及ICU病死率.对于程序化拔管组患者,比较SBT成功与SBT失败、拔管成功与拔管失败组SBT前后监测指标的变化.结果 程序化拔管组较非程序化拔管组机械通气小时数(经Ln数据转换后)缩短(4.01±0.71 vs 4.51±0.85,P<0.05).住ICU天数(经Ln数据转换后)缩短(1.86±0.82 vs 2±48±0.92±P<0.05),VAP发生率及48 h复插管率差异无统计学意义.程序化拔管组SBT成功与SBT失败患者SBT前后心率、呼吸频率、浅快呼吸指数(f/Vt)、PaC_2的变化差异有统计学意义;而拔管成功与拔管失败患者SBT前后监测指标的变化差异无统计学意义.5例拔管失败患者中3例由于痰液引流障碍导致48 h内复插管.结论 程序化拔管可缩短机械通气时间.减少住ICU天数,不增加48 h复插管率.SBT前后心率、呼吸频率、f/Vt、PaCO_2变化对于判断SBT是否成功较其他指标更为重要.对于拔管后可能存在痰液引流障碍的患者需谨慎拔除气管插管.     

Automatic tube compensation-assisted respiratory rate to tidal volume ratio improves the prediction of weaning outcome

OBJECTIVE: To assess whether the respiratory rate to tidal volume ratio (RVR) measured while receiving automatic tube compensation (ATC) [RVRATC] would have a better predictive value as a weaning measure than unassisted RVR. DESIGN: Prospective cohort study. SETTING: General ICU of a tertiary-care university hospital. PATIENTS: Forty-three patients who received mechanical ventilation for > 24 h and were considered ready for weaning. INTERVENTIONS: All patients underwent a 60-min spontaneous breathing trial (SBT) [positive end-expiratory pressure of 5 cm H(2)O; ATC, 100%]. Patients tolerating the trial (n = 35) were extubated immediately. The following parameters were measured at the onset and end of the SBT: RVR, RVRATC, peak airway pressure (Paw), airway occlusion pressure, and minute ventilation. The outcome measure was successful extubation (ability to maintain spontaneous breathing for > 48 h). MEASUREMENTS AND RESULTS: Median age was 55 years (range, 25 to 88 years), median APACHE (acute physiology and chronic health evaluation) II score was 15.5 (range, 3 to 29), and median duration of mechanical ventilation prior to the SBT was 7 days (range, 1 to 40 days). Extubation was successful in 25 patients (72%). There were no significant differences in baseline characteristics between patients successfully extubated (group 1) and those requiring reintubation. On multivariate analysis, RVRATC measured at 60 min (RVR(60)ATC) was most predictive of successful extubation (p = 0.03). The area under the receiver operator characteristic curve was also highest for RVR(60)ATC (0.81 +/- 0.03) as compared to RVR (0.77 +/- 0.03), RVRATC (0.75 +/- 0.04), and RVR measured at 60 min (0.69 +/- 0.05). The ratio of RVR(60)ATC to Paw was the best predictor (0.84 +/- 0.02). CONCLUSIONS: RVRATC measured at the end of the SBT was the best predictor of successful extubation. A new ratio (ratio of RVRATC to Paw) was most predictive and deserves further study.     

自主呼吸试验在撤离呼吸机中的作用

目的 探讨自主呼吸试验(SBT)在机械通气的撤离、拔除气管插管过程中的作用.方法 采用前瞻性随机对照方法,选择67例机械通气超过48 h的患者,当所有患者达到撤离呼吸机状态时将其随机(采用从密封信封中抽取随机号的方法)分为自主呼吸试验组(SBT组,35例)和无自主呼吸试验组(NO-SBT组,32例)两组.SBT组患者顺利通过SBT后随即拔除气管插管,NO-SBT组患者在达到撤离呼吸机条件后,不进行SBT,即拔除气管插管.以拔除气管插管的成功率作为评判的主要指标,成功的标志为拔除气管插管后能维持自主呼吸48 h以上.两组均数的比较采用两个独立样本的t检验,频数的比较采用X~2检验.结果 两组患者在拔除气管插管前的一般状况、呼吸生理和血流动力学等指标比较差异无统计学意义;年龄、性别、气管插管的口径、疾病的严重程度和疾病种类相似,机械通气的时间比较差异尢统计学意义.两组各有3例患者再次气管插管(X~2=0.013,P=0.908).两组患者拔除气管插管后,需无创辅助通气的患者NO-SBT组为5例,SBT组为4例(X~2=0.253,P=0.727).两组患者医院内病死率[N0-SBT组为12.5%(4/32),SBT组为9.7%(3/35),X~2=0.311,P=0.600]差异无统计学意义.结论 SBT可能不是拔除气管插管前的必需过程.     

Minute ventilation recovery time: a predictor of extubation outcome

STUDY OBJECTIVES: To determine if minute ventilation (E) measured as a trend following the final weaning trial prior to extubation may identify patients ready for extubation and be useful as a predictive measure of extubation outcome. DESIGN: Prospective observational study. SETTING: Community hospital medical/surgical ICU. PATIENTS: Sixty-nine patients receiving mechanical ventilation enrolled in an ICU weaning protocol who underwent planned extubation during 6 months of prospective evaluation. The failed extubation group included patients reintubated within 7 days. Patients were excluded if they received ventilation by noninvasive mask, bilevel positive airway pressure, tracheostomy, or were self-extubated. INTERVENTIONS: Patients tolerating a spontaneous breathing trial (SBT) and ready for planned extubation were placed back on their pre-SBT ventilator settings for up to 25 min, during which respiratory parameters were recorded. Respiratory parameters (respiratory rate, tidal volume, E, rapid shallow breathing index [f/VT]) were obtained at three time points: baseline (pre-SBT), posttrial (immediate conclusion of SBT), and recovery (return to baseline). Patients were assumed to recover when E decreased to 110% of the predetermined baseline. MEASUREMENTS AND RESULTS: Fifty-nine patients were successfully extubated, and 10 patients required reintubation after 2.5 +/- 2.6 days (mean +/- SD). Both groups were similar in age, comorbid status, primary diagnosis, APACHE (acute physiology and chronic health evaluation) II score, mode of weaning, and SBT length (p > 0.1). Respiratory parameters measured were similar at all three time points studied (p > 0.1). E recovery time of successful extubations was significantly shorter than failed extubations (3.6 +/- 2.7 min vs 9.6 +/- 5.8 min, p < 0.011). Multiple logistic regression adjusted for age, sex, and severity of illness revealed that E recovery time was an independent predictor of extubation outcome (p < 0.01). The area under the receiver operating characteristic curve for E recovery time (0.85 +/- 0.07) was larger than that for baseline E, posttrial E, posttrial f/VT, or PaCO(2). CONCLUSIONS: E recovery time is an easy-to-measure parameter that may assist in determining respiratory reserve. Preliminary data demonstrates that it may be a useful adjunct in the decision to discontinue mechanical ventilation.     

Predictors of extubation outcome in patients who have successfully completed a spontaneous breathing trial

BACKGROUND: After patients recovering from respiratory failure have successfully completed a spontaneous breathing trial (SBT), clinicians must determine whether an artificial airway is still required. We hypothesized that cough strength and the magnitude of endotracheal secretions affect extubation outcomes. METHODS: We conducted a prospective study of 91 adult patients treated in medical-cardiac ICUs who were recovering from respiratory failure, had successfully completed an SBT, and were about to be extubated. A number of demographic and physiologic parameters were recorded with the patient receiving full ventilatory support and during the SBT, just prior to extubation. Cough strength on command was measured with a semiobjective scale of 0 to 5, and the magnitude of endotracheal secretions was measured as none, mild, moderate, or abundant by a single observer. In addition, patients were asked to cough onto a white card held 1 to 2 cm from the endotracheal tube; if secretions were propelled onto the card, it was termed a positive white card test (WCT) result. All patients were then extubated from T-piece or continuous positive airway pressure breathing trials. If 72 h elapsed and patients did not require reintubation, they were defined as successfully extubated. RESULTS: Ninety-one patients with a mean (+/- SE) age of 65.2 +/- 1.6 years, ICU admission APACHE (acute physiology and chronic health evaluation) II score of 17.7 +/- 0.7, and duration of mechanical ventilation of 5.0 +/- 0.5 days were studied over 100 extubations. Sixteen patients could not be extubated, and 2 patients underwent two unsuccessful extubation attempts, for a total of 18 unsuccessful extubations. Age, severity of illness, duration of mechanical ventilation, oxygenation, rapid shallow breathing index, and vital signs during SBTs did not differ between patients with successful extubations vs patients with unsuccessful extubations. The WCT result was highly correlated with cough strength. Patients with weak (grade 0 to 2) coughs were four times as likely to have unsuccessful extubations, compared to those with moderate-to-strong (grade 3 to 5) coughs (risk ratio [RR], 4.0; 95% confidence interval [CI],1.8 to 8.9). Patients with moderate-to-abundant secretions were more than eight times as times as likely to have unsuccessful extubations as those with no or mild secretions (RR, 8.7; 95% CI, 2.1 to 35.7). Patients with negative WCT results were three times as likely to have unsuccessful extubations as those with positive WCT results (RR, 3.0; 95% CI, 1.3 to 6.7). Poor cough strength and endotracheal secretions were synergistic in predicting extubation failure (Rothman synergy index, 3.7; RR, 31.9; 95% CI, 4.5 to 225.3). Patients with PaO(2)/fraction of inspired oxygen (P:F) ratios of 120 to 200 (receiving mechanical ventilation) were not less likely to be successfully extubated than those with P:F ratios of > 200, but those with hemoglobin levels < or = 10 g/dL were more than five times as likely to have unsuccessful extubations as those with hemoglobin levels > 10 g/dL. CONCLUSIONS: After patients recovering from respiratory failure have successfully completed an SBT, factors affecting airway competence, such as cough strength and amount of endotracheal secretions, may be important predictors of extubation outcomes. Also, a majority (89%) of medically ill patients with P:F ratios of 120 to 200 (four of five patients with P:F ratios from 120 to 150), values sometimes used to preclude weaning, were extubated successfully.     

Changes of heart rate variability during ventilator weaning

STUDY OBJECTIVES: Despite the recognition that ventilator weaning is associated with a change in autonomic nervous system activity, there has not been any report concerning the change of heart rate variability (HRV), a reliable method to detect autonomic nervous system activity, in patients during weaning. The aim of this study was to investigate the change of autonomic nervous system activity during ventilator weaning by HRV analysis. DESIGN: Prospective study. SETTING: A 16-bed medical ICU of a tertiary university hospital. PATIENTS: Twenty-four patients receiving mechanical ventilation were included. Twelve patients with successful extubation after a spontaneous breathing trial (SBT) [T-piece trial] were classified as the success group; otherwise, the patients were placed in the failure group. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: Variables, including the total power (TP), and the high-frequency (HF) and low-frequency (LF) components of HRV, were measured in three phases: assist/control mandatory ventilation, pressure support ventilation (PSV), and SBT. While shifting from PSV to SBT, the HRV components decreased significantly in the failure group (TP, p = 0.025; LF, p = 0.007; HF, p = 0.031), but not in the success group. CONCLUSIONS: By HRV analysis, reduced HRV and vagal withdrawal of the autonomic nervous system activity are the main changes in patients with weaning failure.     

The early phase of the minute ventilation recovery curve predicts extubation failure better than the minute ventilation recovery time

STUDY OBJECTIVES: To determine, in patients who had successful outcomes in spontaneous breathing trials (SBTs), whether the analysis of the minute ventilation (Ve) recovery time obtained by minute-by-minute sequential monitoring after placing the patient back on mechanical ventilation (MV) may be useful in predicting extubation outcome. DESIGN: Twelve-month prospective observational study. SETTING: Medical-surgical ICU of a university hospital. PATIENTS: Ninety-three patients receiving > 48 h of MV. INTERVENTIONS: Baseline respiratory parameters (ie, respiratory rate, tidal volume, and Ve) were measured under pressure support ventilation prior to the SBT. After tolerating the SBT, patients again received MV with their pre-SBT ventilator settings, and respiratory parameters were recorded minute by minute. MEASUREMENTS AND RESULTS: Seventy-four patients (80%) were successfully extubated, and 19 patients (20%) were reintubated. Reintubated patients were similar to non-reintubated patients in baseline respiratory parameters and baseline variables, except for age and COPD diagnosis. The recovery time needed to reduce Ve to half the difference between the Ve measured at the end of a successful SBT and basal Ve (RT50%DeltaVe) was lower in patients who had undergone successful extubation than in those who had failed extubation (mean [+/- SD] time, 2.7 +/- 1.2 vs 10.8 +/- 8.4 min, respectively; p < 0.001). Multiple logistic regression adjusted for age, sex, comorbid status, diagnosis (ie, neurocritical vs other), and severity of illness revealed that neurocritical disease (odds ratio [OR], 7.6; p < 0.02) and RT50%DeltaVe (OR, 1.7; p < 0.01) were independent predictors of extubation outcome. The area under the receiver operating characteristic curve for the predictive model was 0.89 (95% confidence interval, 0.81 to 0.96). CONCLUSION: Determination of the RT50%DeltaVe at the bedside may be a useful adjunct in the decision to extubate, with better results found in nonneurocritical patients.     

单一剂量右美托咪定在慢性阻塞性肺病患者撤机中的应用

目的:研究应用单一剂量右美托咪定对慢性阻塞性肺病(COPD)患者拔除气管插管期间的影响。方法:选择COPD合并呼吸衰竭经呼吸机治疗后欲拔除气管插管的40例患者,分为观察组和对照组,各20例。观察组患者拔管前予以0.5μg/kg负荷剂量的右美托咪定,10min注射完毕后开始拔管。监测并记录2组患者用药前(T0)、拔管前(T1)、吸痰后(T2)、拔管后(T3)、拔管后5min(T4)、拔管后10min(T5)、拔管后30min(T6)的呼吸、心率、收缩压、动脉血二氧化碳分压(PaCO2)、氧分压(PaO2)和24h内重插管上机例数。结果:2组患者用药前一般资料和生命体征及血气之间无显著差异;用药导致观察组患者SBP、HR下降,但不影响RR、PaCO2、PaO2;此剂量用药不能完全抑制拔管时吸痰所造成的交感兴奋,但可以减轻幅度,减少再插管率。结论:0.5μg/kg负荷剂量的右美托咪定用于COPD患者脱机时拔管,心血管稳定性较好,在不影响患者呼吸的前提下,有效减轻患者拔管时的血流动力学剧烈变化和继发的二氧化碳潴留及低氧血症,并可能减少由此引发的脱机失败。     

Extubation failure in a large pediatric ICU population

OBJECTIVE: To review a large population of children receiving mechanical ventilation to establish a baseline rate of extubation success and failure and to identify those characteristics that place a patient at greater risk of failing planned extubation. DESIGN: Retrospective chart review. SETTING: University-affiliated children's hospital with a 20-bed pediatric ICU. PATIENTS: All 632 patients receiving mechanical ventilation during the 2-year period from July 1, 1996, to June 30, 1998. METHOD: Patients receiving mechanical ventilation were identified via a computerized database. Charts were reviewed of all patients who were reintubated within 72 h of extubation. MEASUREMENTS AND RESULTS: There were 548 planned extubation events, of which 521 were successful. Twenty-seven patients failed planned extubation at least once; only the first attempt at extubation was included in the analysis. The failure rate of planned extubations was 4.9%. Including only patients who had received mechanical ventilation for > 24 h before extubation, the failure rate was 6.0%. For patients intubated > 48 h, the failure rate was 7.9%. The patients who failed extubation were found to be significantly younger and to have received mechanical ventilation longer than those who succeeded, in both the analysis of all patients receiving mechanical ventilation and the subgroup of those receiving mechanical ventilation > 24 h. When only patients who had received mechanical ventilation for > 48 h were analyzed, the difference in age was no longer significant, but the duration of ventilation before extubation was still significantly longer for those who failed. CONCLUSION: We determined the overall failure rate of planned extubations in a large population of pediatric patients to be 4.9%. Those patients who were younger and had received mechanical ventilation longer were more at risk for extubation failure.