Using ASV mode for respiratory support withdrawal in patients after posterior fossa surgery

The study gives data on how to improve the way from mechanical to spontaneous breathing in patients with weakened respiratory drive after posterior fossa tumor removal. We compared the effectiveness of two methods of weaning from mechanical ventilation in these patients. The main group consisted of 6 patients weaned from ventilator with ASV mode. The control group was made up of 10 patients weaned from ventilator with SIMV or PS modes. The duration of weaning from ventilator using ASV mode was significantly shorter than with SIMV or PS modes. During ASV ventilation spontaneous breath rate gradually increased. In all patients the level of P0,1 index representing respiratory center activity was initially lower than normal. While spontaneous breath activity increased the level of P0,1 index also gradually normalized. Plmax index (respiratory effort index) measured once a day increased as well. Weakened respiratory drive is accompanied by P0,1 and Plmax indexes' decrease in patients after posterior fossa tumor removal. ASV mode in these patients allows quicker weaning from mechanical ventilation.     

双相气道正压通气在心脏直视术后的应用

目的评价双相气道正压通气(B IPAP)模式在心瓣膜置换术后机械通气患者中的应用效果。方法80例心脏瓣膜置换术后患者随机分成2组,每组40例,分别应用B IPAP模式和同步间隙指令通气(SIMV)模式进行辅助呼吸,监测血流动力学和气道参数的变化,计算呼吸指数以及镇静剂的用量。结果B IPAP组氧合指数(440.7±55.1)明显高于SIMV组(357.5±64.3),P<0.05;B IPAP组机械通气时间为(13.1±11.1)h,SIMV组(13.0±11.0)h,差异无统计学意义;两组在镇静剂的使用率方面亦差异无统计学意义,但在用量方面B IPAP组度非合剂(哌替啶+异丙嗪)平均用量小于SIMV组(P<0.05);两组脱机过程均顺利。结论B IPAP是心脏术后患者机械通气的一种较理想模式。     

Weaning from mechanical ventilation: old and new strategies.

The strategies available for weaning patients from mechanical ventilation are many: T-piece mode, SIMV, PSV, and combinations of each. T-piece trials alternating with SIMV or AC provide periods of spontaneous breathing with rest on the ventilator. Decreasing SIMV rates gradually increases the patient's independence and spontaneous breathing; however, may result in an increased work of breathing with some systems. Alternatives such as flow-by and the addition of PSV may assist in the reduction of airway resistance. PSV weaning alone or in combination with SIMV or T-piece trials reduces work of breathing, promotes respiratory muscle training, and improves patient-ventilator interaction. Schuster states "the specific weaning technique employed is often less important than the care with which it is applied."     

压力与容量控制通气模式对危重症患者心排血指数和胸腔内血容量指数影响的比较研究

目的 比较在机械通气过程中双水平气道正压(BIPAP)与同步间歇指令通气(SIMV)两种模式对患者心排血指数(CI)、胸腔内血容量指数(ITBVI)的影响.方法 选择24例因各种原因需行有创机械通气和脉搏指示连续心排血量(PiCCO)技术监测血流动力学的患者,根据CI分为心功能正常组(9例)和心功能低下组(15例).在BIPAP模式下,调整吸气压使潮气量(VT)分别维持于6、10、15ml/kg,其他参数不变,呼吸机模式改为SIMV后,VT调节同前.以上各种条件维持20 min后测量呼吸力学及中心静脉压(CVP)、CI、ITBVI指标,试验过程中上述参数随机选择进行.结果 在心功能正常组,两种呼吸模式间CI、ITBVI、心率(HR)、平均动脉压(MAP)、平均气道压(Pmean)、内源性呼气末正压(PEEPi)的变化均无明显差异(P值分别为0.067、0.124、0.348、0.328、0.110、0.187);而外周循环阻力指数(SVRI)在10 ml/kg VT时,BIPAP模式下高于SIMV模式(P=0.030).在心功能低下组,CI、ITBVI在SIMV模式下降明显,仅在10ml/kgVT时CI差异有统计学意义(P<0.05);在6、10、15 ml/kg VT时BIPAP模式下Pmean均较SIMV模式低(P值分别为0.003、0.000、0.004);而SVRI、HR、MAP及PEEPi在不同VT水平两种呼吸模式间差异均无统计学意义.结论 两种通气模式随VT增加均可使CI、ITBVI降低.在相同VT时,压力控制模式(BIPAP)较容量控制模式(SIMV)Pmean相对低,对CI、ITBVI影响相对较小,因此,应用PiCCO监测容量变化时通气模式可影响CI、ITBVI.     

应用机械通气模式改善婴幼儿心脏手术后低氧血症的护理

目的研究应用压力控制型同步间歇指令（SIMV＋PC）加压力支持（PSV）加呼气末正压（PEEP）通气模式改善婴幼儿心脏手术后并发低氧血症的护理方法。方法对62例心脏手术后并发低氧血症患儿分为治疗组和对照组,治疗组（32例）给予SIMV（PC）＋PSV＋PEEP通气,随时调整呼吸机参数,加强呼吸道的护理。对照组（30例）采用同步间歇指令（SIMV）通气模式和常规护理。结果治疗组血氧改善快,呼吸机使用时间短,并发症少;住ICU时间缩短。治疗组1例、对照组3例死于多器官功能衰竭。结论婴幼儿心脏手术后并发低氧血症时,应用SIMV（PC）＋PSV＋PEEP模式通气,能有效改善低氧血症,减少肺部并发症,缩短呼吸机使用时间。     

两种机械通气撤机法在10 kg以下患儿心内直视术后的应用比较

目的比较SIMV模式撤机法与直接撤机法在10 kg以下患儿心内直视术后的撤机效果。方法对32例10 kg以下心内直视术后行机械通气的患儿进行回顾性分析,按照撤机方法的不同分为SIMV模式撤机组与直接撤机组。结果两组相比,撤机所需时间差异有显著性意义(P<0.05),SIMV模式撤机法所需的时间更短,并且呼吸机相关性肺炎(VAP)的发生率更低(P<0.05);两组再置管率差异无统计学意义;两种撤机方法撤机前后的心率、呼吸及血压的变化值比较差异均有显著性意义(P<0.05);两种方法撤机前后的PO2、PCO2及pH值的比较,差异均无统计学意义(P>0.05)。结论10 kg以下行心内直视术后的患儿应用SIMV法撤机能够缩短呼吸机辅助的时间和降低呼吸机相关性肺炎的发生率,效果优于直接撤机法。     

智能脱机模式与传统脱机模式在机械通气脱机过程中的比较

[目的]比较智能监护（SmartCare）脱机模式和同步间歇指令通气＋压力支持勇气（SIMV＋PSV）、PSV＋间断T形管通气（TC）三种脱机方法,探讨智能监护脱机模式是否可以缩短脱机时间和提高呼吸衰竭患者的脱机成功率.[方法]2008年2月至2009年8月本院ICU收治的各种因呼吸衰竭进行机械通气患者48例,随机分为SIMV＋PSV组、PSV＋TC组和智能监护脱机组（SC组）,进行脱机治疗.记录每位患者脱机开始时的急性生理学与慢性健康状况评分系统（APACHE-Ⅱ）评分、血气分析、脱机时间.脱机成功标准为停用呼吸机48 h以上生命体征平稳,未再进行机械通气者.[结果]SC组脱机时间比SIMV＋PSV组、PSV＋TC组短,且差异有显著性（P〈0.05）.[结论] 三种脱机方式中智能监护（SmartCare）脱机模式优于SIMV＋PSV方式和PSV＋TC方式.     

Patient-ventilator interaction during acute lung injury, and the role of spontaneous breathing: part 2: airway pressure release ventilation

Airway pressure release ventilation (APRV) and bi-level positive airway pressure (BIPAP) are proposed to reduce patient work of breathing (WOB) sufficiently and to obviate issues related to patient-ventilator synchrony, so that spontaneous breathing can be maintained throughout the course of acute lung injury (ALI). Thus, APRV/BIPAP should reduce requirements for sedation and muscle paralysis, and thereby reduce the duration of mechanical ventilation. Only 17 human, animal, or lung-model studies have examined these claims, either directly or indirectly. Most did not target patients with ALI. Studies on sedation use have serious methodological limitations. Other studies found that APRV/BIPAP either increased WOB and asynchrony, or had no effect on energy expenditure. To supplement the discussion of patient WOB during APRV/BIPAP in ALI, 4 clinical examples showed marked elevation and wide variation in patient WOB. One plausible explanation is that spontaneous breathing is superimposed upon the mechanical ventilation pattern. Thus a variety of "breathing environments" exist during APRV/BIPAP that affect patient WOB and respiratory drive differently and perhaps unpredictably. This characteristic of APRV/BIPAP makes WOB comparisons with traditional modes problematic. Furthermore, the theoretical benefits of APRV, in terms of controlling patient WOB, appear particularly limited when lung-protective ventilation is used for ALI patients with high minute ventilation demand. Future research should focus on issues of WOB and synchrony, so that reasonable ventilation protocols can be devised to test clinical outcomes against traditional modes. To date, low-level evidence suggests that promoting spontaneous breathing with APRV/BIPAP may not be appropriate in patients with relatively severe ALI/ARDS.     

低辅助通气不同通气模式对心功能低下患者血流动力学的影响

目的观察双水平气道正压(BIPAP)、压力支持(PSV)、成比例压力支持通气(PPS)3种不同通气模式对心功能正常及心功能低下患者血流动力学的影响,探讨心功能严重低下、撤机困难患者较理想的撤机方式。方法70例各种原因导致呼吸衰竭而行机械通气的患者根据撤机模式不同分为PSV组(38例)和PPS组(32例)。PPS组经治疗恢复自主呼吸后,行无创血流动力学监测,根据心排血指数(CI)将患者分为心功能正常组(CI≥2.0L·min-1·m-2)和心功能低下组(CI<2.0L·min-1·m-2),比较两组患者在BIPAP、PSV、PPS3种通气模式对血流动力学的的影响。结果1心功能正常组PSV、PPS通气模式下心排血量(CO)、CI、每搏量(SV)、肺毛细血管血流(PCBF)均显著高于BIPAP模式,PPS模式下CO、CI、SV、PCBF最高,但与PSV模式下比较差异无显著性;PPS模式下外周血管阻力(SVR)较BIPAP模式显著降低,但较PSV模式差异无显著性。2心功能低下组BIPAP、PSV、PPS通气模式下CO、CI、SV逐渐升高,3种通气模式间差异有显著性,PPS模式下CO、CI、SV最高。3心功能低下患者3种通气模式下气道峰压(Ppeak)、平均气道压(Pmean)均呈递减趋势,PSV、PPS模式下与BIPAP模式差异有显著性,PPS模式下心功能低下组Ppeak最低,与另两种模式比较差异有显著性。4PPS组带机时间较PSV组明显缩短。5心功能正常组3种模式的内源性呼气末正压(PEEPi)也呈递减趋势,PPS为最低,与BIPAP模式比较差异有显著性(P<0.01)。结论PPS通气模式对心功能严重低下的机械通气患者血流动力学影响最小,较适用于作为该类患者的撤机模式。     

Effects of patient-triggered automatic switching between mandatory and supported ventilation in the postoperative weaning period

OBJECTIVE: To compare two ventilator settings in the postoperative weaning period. Patient-triggered automatic switching between controlled ventilation and supported spontaneous breathing (Automode, AM) was compared to synchronised intermittent mandatory ventilation (SIMV) with stepwise manual adjustment of mandatory frequency according to the breathing activity. DESIGN: Prospective clinical investigation. SETTING: Eighteen-bed intensive care unit in a university hospital. PATIENTS: Forty postoperative patients with healthy lungs who had undergone brain tumour surgery. INTERVENTIONS: Randomisation either to the AM or SIMV weaning procedure after entering the ICU. MEASUREMENTS AND RESULTS: Total weaning time and number of manipulations on the ventilator were observed. Cardiocirculatory and respiratory parameters were measured consecutively at five points during the weaning period. No significant differences were seen for cardiocirculatory parameters, airway pressures and oxygenation between the two groups. There was a trend to shorter weaning times with AM (136 +/- 46 min vs 169 +/- 68 min, n.s.), the average number of manipulations on the ventilator was lower (0.55 +/- 0.69 vs 5.05 +/- 1.19,p < 0.001) and arterial partial pressure of carbon dioxide (PaCO2) levels showed fewer variations in the late phase of the weaning period (39.5 +/- 3.1 vs 38.3 +/- 7.2, p < 0.001 for differences in variance). CONCLUSIONS: Automatic, patient-triggered switching between controlled and supported mode of ventilation can be used for postoperative weaning of neurosurgical patients with healthy lungs. Compared to a SIMV weaning procedure, fewer manipulations on the ventilator are necessary and individual adaptation of ventilation seems to be more accurate.     

Weaning from mechanical ventilation

Practice guidelines on weaning should be based on the results of several well-designed randomized studies performed over the last decade. One of those studies demonstrated that immediate extubation after successful trials of spontaneous breathing expedites weaning and reduces the duration of mechanical ventilation as compared with a more gradual discontinuation of ventilatory support. Two other studies showed that the ability to breathe spontaneously can be adequately tested by performing a trial with either T-tube or pressure support of 7 cmH₂O lasting either 30 or 120 min. In patients with unsuccessful weaning trials, a gradual withdrawal for mechanical ventilation can be attempted while factors responsible for the ventilatory dependence are corrected. Two randomized studies found that, in difficult-to-wean patients, synchronized intermittent mandatory ventilation (SIMV) is the most effective method of weaning.     

Regional lung aeration and ventilation during pressure support and biphasic positive airway pressure ventilation in experimental lung injury

Introduction  

There is an increasing interest in biphasic positive airway pressure with spontaneous breathing (BIPAP+SB_mean), which is a combination of time-cycled controlled breaths at two levels of continuous positive airway pressure (BIPAP+SB_controlled) and non-assisted spontaneous breathing (BIPAP+SB_spont), in the early phase of acute lung injury (ALI). However, pressure support ventilation (PSV) remains the most commonly used mode of assisted ventilation. To date, the effects of BIPAP+SB_mean and PSV on regional lung aeration and ventilation during ALI are only poorly defined.     

同步间歇指令通气辅以压力支持治疗新生儿胎粪吸入综合征的效果与护理

目的探讨同步间歇指令通气（SIMV）联合压力支持（PS）对新生儿胎粪吸入综合征（NMAS）患儿的治疗效果及护理体会。方法将40例NMAS患儿按通气模式不同分为对照组和观察组各加例。对照组患儿接受SIMV,观察组患儿接受SIMV＋PS;观察两组患儿吸氧时间、机械通气时间及住院时间;观察治疗后平均动脉压（MABP）、平均气道压（MAP）及氧合指数（OI）的变化。结果观察组吸氧时间、机械通气时间、住院时间分别为（4．9±1．1）d,（65．7±7．0）h,（7．9±1．4）d,均低于对照组的（5．6±0．7）d,（75．1±9．2）h,（10．1±2．0）d,差异有统计学意义（t值分别为2．401,3．636,4．030;P〈0．05）;两组治疗前后MABP均较平稳;观察组治疗后36hMAP、01分别为（7．4±0．9）cmH2O,（4．7±1．8）,均低于对照组的（8．1±1．1）cmH：0,（10．1±3．4）,差异有统计学意义（t值分别为2．203,6．698;P〈0．05）。结论应用SIMV＋Ps,能改善患儿氧合,降低平均动脉压和气道压,利于早日脱机及减少通气总时间。严密观察患儿病情,做好气道护理可提高治疗效果。     

COPD呼吸机依赖患者的脱机方法研究

目的观察COPD呼吸机依赖患者采用不同脱机方法的脱机成功率。方法将39例COPD呼吸机依赖患者随机分为试验组19例和对照组20例。试验组采用间歇性停机法,对照组采用压力支持通气（PSV）＋同步间歇指令通气（SIMV）方法,比较3周内的脱机成功率。结果2周内试验组和对照组的脱机成功率分别为78．9％和35.0％,有显著性差异（P〈0．01）;3周内的脱机成功率分别为78．9％和65．0％,无显著性差异（P〉0．05）。结论COPD呼吸机依赖患者脱机时,采用间歇性停机法脱机成功率高,具有重要的临床价值。     

Airway pressure release ventilation versus assist-control ventilation: a comparative propensity score and international cohort study

Purpose

To compare characteristics and clinical outcomes of patients receiving airway pressure release ventilation (APRV) or biphasic positive airway pressure (BIPAP) to assist-control ventilation (A/C) as their primary mode of ventilatory support. The objective was to estimate if patients ventilated with APRV/BIPAP have a lower mortality.

Methods

Secondary analysis of an observational study in 349 intensive care units from 23 countries. A total of 234 patients were included who were ventilated only with APRV/BIPAP and 1,228 patients who were ventilated only with A/C. A case-matched analysis according to a propensity score was used to make comparisons between groups.

Results

In logistic regression analysis, the most important factor associated with the use of APRV/BIPAP was the country (196 of 234 patients were from German units). Patients with coma or congestive heart failure as the reason to start mechanical ventilation, pH <7.15 prior to mechanical ventilation, and patients who developed respiratory failure (SOFA score >2) after intubation with or without criteria of acute respiratory distress syndrome were less likely to be ventilated with APRV/BIPAP. In the case-matched analysis there were no differences in outcomes, including mortality in the intensive care unit, days of mechanical ventilation or weaning, rate of reintubation, length of stay in the intensive care unit or hospital, and mortality in the hospital.

Conclusions

In this study, the APRV/BIPAP ventilation mode is being used widely across many causes of respiratory failure, but only in selected geographic areas. In our patient population we could not demonstrate any improvement in outcomes with APRV/BIPAP compared with assist-control ventilation.     

Pattern of spontaneous breathing: potential marker for weaning outcome

OBJECTIVE: To quantitatively assess the spontaneous breathing (SB) pattern, during minimal ventilatory support, of patients who pass or fail weaning trials from mechanical ventilation. DESIGN: A prospective, clinical trial. SETTING: Intensive care unit of a university teaching hospital. PATIENTS: Fifty-two tracheally intubated and hemodynamically stable patients who were judged clinically ready for extubation. METHODS: Using a computerized respiratory profile monitor, continuous respiratory parameters were obtained while patients were receiving four or less synchronized intermittent mandatory (SIMV) breaths and during CPAP trials. Coefficients of variation (CV) of spontaneous tidal volumes and flows during SIMV trials as well as the entropies and dimensions of the breathing patterns during CPAP trials were used to assess the dynamical breathing behaviors of the patients who passed or failed weaning trials. MEASUREMENTS AND RESULTS: Thirty-nine extubations were successful and 13 were not. The CV of the spontaneous tidal volumes (VT) and the spontaneous peak inspiratory flows (PF), the Kolmogorov entropy and the dimension of the SB patterns were compared in the two groups. The CV of VT (9.13 +/- 4.11 vs 26.07 +/- 6.94), the CV of PF (11.63 +/- 4.18 vs 29.88 +/- 12.07), the Kolmogorov entropy (0.09 +/- 0.03 bits/cycle vs 0.39 +/- 0.09 bits/cycle), and the dimension of the SB pattern (1.33 +/- 0.07 vs 3.93 +/- 0.47) were all significantly smaller (P < 0.05) in the successfully extubated group versus the group that failed extubation. CONCLUSION: The spontaneous breathing pattern during minimal mechanical ventilatory support is more chaotic in patients who failed extubation trials compared to patients who passed extubation trials. Thus, we speculate that characterizing the SB pattern during minimal ventilatory support might be a useful tool in differentiating between extubation success and failure.     

自主呼吸试验在撤机中的应用

目的 对应用自主呼吸试验(SBT)撤机方式与逐渐降低机械通气支持水平撤机方式成功拔管的患者进行比较,以寻找最佳撤机方式.方法 选择57例机械通气患者,病情稳定后通过撤机试验前评估,然后准备撤机.采用前后对照的方法将患者分为两组,2004年6月-2005年12月的21例患者作为对照组,采用逐渐降低机械通气支持水平的撤机方式拔管;2006年1月-2007年3月的36例患者作用为试验组,采用SBT的撤机方式拔管.分别观察两组患者的机械通气时间、住重症监护病房(ICU)时间、呼吸机相关性肺炎(VAP)发生率、48 h内再插管率、ICU病死率.结果 试验组与对照组的机械通气时间分别为(59.45±37.1)h和(111.4±59.8)h(P=0.001),住ICU时间分别为(8.0±5.5)d和(15.3±14.3)d(P=0.034),VAP发生率分别为16.7%和38.0%(P=0.070),48 h内再插管率分别为19.4%和5.0%(P=0.253),ICU病死率分别为25.0%和24.0%(P=0.920).结论 SBT的撤机方式比逐渐降低机械通气支持水平的撤机方式具有机械通气时间和住ICU时间短的优点,而两组VAP发生率、48 h内再插管率、ICU病死率基本相同.     

Sevrage de la ventilation mécanique chez l’enfant (en dehors du nouveau-né)

The process of weaning from mechanical ventilation (SVM) is the same in children as in adults. In the literature, weaning and/or extubation failure rate ranges from 4.9 to 34%. So far, no weaning predictors have been demonstrated to be sufficiently accurate. Nevertheless, endurance has never been investigated in children more at risk of respiratory muscle fatigue. Criteria to determine whether patients can be considered for discontinuation have neither been validated nor adapted to the children population. The spontaneous breathing test (SBT) is the recommended screening test for weaning: nevertheless, it has never been validated and has rarely been studied in children. In infants as in children, it can be achieved with pressure support ventilation or spontaneous breathing (T piece or canopy). A standardised weaning protocol was used only twice in the pediatric literature. Impact of such protocols in shortening the duration of VM and SVM is not yet demonstrated; it must be distinguished from the impact of sedation protocols. Weaning criteria, and criteria of SBT and/or protocol tolerance are guides, but decisions to use these criterias must be individualized. In children as in adults, weaning from mechanical ventilation may depend on patient’s disease. The implementation of noninvasive ventilation in weaning protocols could modify the definitions of weaning failure and weaning success.     

Balance des fluides et sevrage de la ventilation mécanique

Volume overload is frequently encountered in intensive care unit patients, especially in patients with sepsis and/or mechanical ventilation. Volume overload is associated with a prolongation of mechanical ventilation in general and of the weaning period in particular. It is a major contributing factor to cardiovascular weaning failure, including failed spontaneous breathing trial and failed extubation. A strategy of restrictive fluid management shortens the duration of mechanical ventilation, including weaning length.     

有创-无创序贯性机械通气治疗老年肺内源性急性呼吸窘迫综合征随机对照临床研究

目的 评价有创-无创序贯性机械通气治疗老年肺内源性急性呼吸窘迫综合征(ARDS)患者的疗效及可行性.方法 32例老年肺内源性ARDS患者被随机分为序贯治疗组及常规治疗对照组,每组16例.两组均建立人工气道,以辅助/控制模式+呼气末正压(PEEP)+间隙性控制性肺膨胀(SI)方式通气24 h,随病情改善改用同步间歇指令通气(SIMV)+压力支持通气(PSV)+PEEP的方式.待"ARDS控制窗"出现,序贯组改换为无创正压通气(NIPPV),以持续气道正压(CPAP)方式通气并逐渐脱离呼吸机;对照组以SIMV+PSV+PEEP常规方式脱机.动态观察两组患者的通气及氧合指标,记录有创和总机械通气时间、呼吸机相关性肺炎(VAP)发生情况及住呼吸重症监护病房(RICU)的天数.结果 两组患者治疗前血气分析结果相仿(P均>0.05);序贯组有创通气时间[(4.6±1.0)d]、总机械通气时间[(12.7±4.0)d]、住RICU时间[(16±7)d]较对照组[分别为(21.9±9.0)d、(21.9±9.0)d、(29±13)d]明显缩短,VAP发生率[6.25%(1/16)]和病死率[25.00%(4/16)]也较对照组[分别为75.00%(12/16)、56.25%(9/16)]明显降低,差异均有统计学意义(P<0.05或P<0.01).结论 对老年肺内源性ARDS插管机械通气以ARDS控制窗为时机及时改用无创通气可显著改善其疗效.