A comparison of the rapid shallow breathing index and complexity measures during spontaneous breathing trials after cardiac surgery

Purpose

Extubation failure is associated with worse outcomes. Physicians use respiratory parameters to help them to decide to extubate or not. The purpose of this study is to determine if novel measures of respiratory physiology such as complexity and variability can identify patients who will tolerate extubation.

Methods

Eighty-three patients who required reinstitution of mechanical ventilation after extubation (Extub-Fail) were matched to 83 patients who successfully tolerated extubation (Extub-Success) and to 83 who failed a spontaneous breathing trial (SBT-Fail). Patients were compared using interbreath intervals and tidal volumes using means, SDs, measures of complexity, spikiness, and rapid shallow breathing index (RSBI).

Results

From SBT-Fail to Extub-Fail to Extub-Success, the interbreath intervals progressively lengthened (mean ± SD, 2.2 seconds ± 0.6 vs 2.5 ± 0.6 vs 2.7 ± 0.8; P < .001), became more variable (mean ± SD, 0.57 ± 0.13 vs 0.62 ± 0.21 vs 0.66 ± 0.23; P = .012), and became more complex. Complexity as measured by approximate and sample entropy was greater in the Extub-Success group than in the SBT-Fail group. Patients who were in the SBT-Fail group had a higher RSBI than did either of the extubated groups, but there was no difference in RSBI between Extub-Success and Extub-Fail.

Conclusions

Patients who successfully tolerate extubation have longer interbreath interval with greater complexity and variability of that series. Although the V_T was similar between the Extub-Success and the SBT-Fail groups, the Extub-Success group had greater long-term complexity with no difference in short-term complexity. This implies that the respiratory controllers are differently impacted in patients tolerating or not tolerating extubation.     

Interobserver agreement rate of the spontaneous breathing trial

Purpose

During the mechanical ventilation weaning process, the spontaneous breathing trial (SBT) is the confirmatory test of patients' capability to breathe unassisted. However, the SBT interobserver agreement rate (its reliability) is unknown, and our objective was to evaluate it.

Materials and Methods

This is a prospective, multicentric and observational study. Patients were included when the SBT criteria were fulfilled. Two physicians and 2 respiratory therapists (RTs) rated each SBT. The SBT interobserver agreement was measured using κ statistic and also the percentage of agreement with its 95% credible interval (CrI) calculated by a Bayesian inference.

Results

Ninety-three distinct physicians and 91 distinct RTs rated 130 SBTs. The κ coefficient was 0.46 for physicians and 0.57 for RT, indicating a moderate interobserver agreement rate. The percentage of agreement was 87.7% between physicians (95% CrI, 81.0%-92.3%) and 86.2% between RT (95% CrI, 79.2%-91.1%). The physicians' and RT' percentage of agreement were not statistically different (P = .71).

Conclusions

The SBT interobserver agreement rate is only moderate for physicians and RT. The percentage of agreement between 2 different SBT observers is 79.2% to 92.3%. Therefore, a relevant percentage of patients will have different extubation decisions depending on the SBT observer.     

小剂量溶栓结合PTA和支架治疗外周动脉慢性阻塞性病变

本文报告５例６支动脉阻塞经导管使用微量泵持续灌注尿激酶（５６，０００单位／小时）溶栓治疗，灌注时间５．５￣５８（平均２６）小时。阻塞位于髂外动脉２例，其中１例伴同侧股动脉阻塞；髂总和髂外动脉联合受累１例，Ｇｕｏ动脉１例；股Ｇｕｏ动脉１例。病程１￣２４（平均９．４）个月，阻塞长度８￣２５ｃｍ（平均１５．３ｃｍ），开通率达１００％。对溶栓后残存狭窄实施ＰＴＡ３例、血管内放置支架１例；随访２￣９（平均５     

A Physical Analog of the Failing Left Ventricle for In Vitro Studies of Mechanical Wall Actuation

Abstract: Mechanical repowering of a failing heart with devices or skeletal muscle could circumvent blood-pump lining problems. Requirements are complex: indefinite support with preservation of valve competence and coronary flow, avoidance of wall coaptation, and allowance of both rapid low impedance refilling and independent left and right pressures. An accurate in vitro physical failing-heart analog could facilitate the choice and screening of surgical and engineering approaches in mock circulation experiments. Prosthetic models, transplant recipient hearts, normal animal hearts, existing in vivo animal failure models, and failing cadaver hearts all have serious limitations. One hundred and four excised porcine hearts were dilated and fixed by three iterative protocols. Geometric and passive mechanical parameters were assessed and compared with targets expected for an end-stage failing heart. For Protocol 3, Subgroup 2 (reinforcing valve support, dilatation by compliant ventricular balloon, and ethyl alcohol fixation), the left ventricular shape and capacity (ellipsoid, 201–377 ml/500 g of heart weight), passive valve function, wall flexural rigidity ( Et ³ range 0.101-0.331 Nm), and refilling mechanics (99 ± 17.46 ml during 200–400 ms at ≤ 10 mm Hg transmural gradient) were all within goal criteria.     

Long-Term Ventricular Wall Actuation: Can and Should It Be Systematically Explored?

Abstract: Hearts fail because myocardial power fails. Assist, support, or replacement devices fail, at least in part, because their blood-contacting surfaces fail. Mechanical repowering of a failing heart might circumvent these difficulties by preserving a largely healthy endocardium while correcting the basic deficit, power. Any serious consideration of doing this though must confront some difficult requirements. Effective indefinite support must be coupled with preservation or restoration of valve competence, coronary flow, rapid low-impedance refilling and independent left and right pressures; the avoidance of wall coaptation; hardware that fits in the available space; and unless muscle powered, adaptability to a deliverable form of power. Despite earlier intense interest in acute mechanical devices and later empiric study of muscle wraps, little systematic methodical work has been done on elucidating and meeting these practical requirements. Concerted efforts toward developing research tools and techniques for their study and then finding mechanisms to meet them could well yield one or more effective modalities that circumvent a major obstacle to the indefinite mechanical treatment of heart failure     

呼气末正压呼吸和同步间歇指令通气对肺心病患者血气和血流动力学影响的比较研究

对比研究了呼气末正压呼吸（ＰＥＥＰ）和同步间歇指令通气（ＳＩＭＶ）对肺心病患者血气、血流动力学和氧运输的影响。８例患者应用７ｃｍＨ＿２ＯＰＥＥＰ３０分钟后，生理分流明显减少（Ｐ＜０．０５），动脉血氧分压平均升高０．４ｌｋＰａ，但伴混合静脉血氧分压降低（Ｐ＜０．０５）。９例患者应用ＳＩＭＶ３０分钟后，肺血管阻力下降（Ｐ＜０．０５），心脏指数和混合静脉血氧分压明显升高（Ｐ＜０．０５和Ｐ＜０．０１）。提示肺心病患者应慎用ＰＥＥＰ，不可避免时，应与ＳＩＭＶ合用。     

肾透析患者桡动脉-头静脉人工造瘘通道阻塞的溶栓再通术

目的：探讨血液透析患者自体血管瘘道(桡动脉与头静脉侧端吻合)阻塞后用SP微导管的同轴导管技术微创的处理方法。方法：总结5例内瘘闭塞的肾透析患者，行血管造影诊断及介入溶栓治疗。其中4例右侧、1例左侧桡动脉-头静脉人工造瘘堵塞，经皮右股动脉或肱动脉穿刺插管，送入headbunt经左或右锁骨下动脉至人工造瘘的桡动脉阻塞端，再送入SP微导管进行血栓溶栓术及导丝穿刺血栓松解术。全过程2～4h，实际溶栓时间50min～2h。结果：4例患者再通术成功，1例因狭窄而未通，无严重并发症发生。结论：采用SP微导管的同轴导管技术行肾透析惠者的桡动脉-肘正中静脉人工内瘘阻塞的溶栓及血栓松解术简便、安全、有效而且微创。     

双相正压通气模式和周期性同步强制式通气模式在冠状动脉旁路移植术后的应用比较

目的　比较在冠状动脉旁路移植术 (CABG)后应用双相正压气道通气 (BiPAP)模式和周期性同步强制式通气 (S IMV)模式对血流动力学和呼吸氧合参数的影响。方法　 2 6例术前无其他合并症及手术顺利的CABG患者随机均分为先实施BiPAP模式组和先实施S IMV模式组 ,在术后早期镇静未醒情况下 ,分别在原有呼吸模式和改换相应呼吸模式的 1h后 ,以及再次更换回原有呼吸模式 1h后 ,监测血流动力学、血气分析及其他呼吸参数。结果　两组患者中 ,用BiPAP模式时气道吸气峰压均明显低于用S IMV模式 (P <0 .0 5 ) ,但血流动力学、血气分析及其他呼吸参数的差异无显著性。结论　与S IMV模式相比 ,BiPAP模式可显著降低气道吸气峰压 ,对血流动力学和血气无影响 ,这种模式在CABG术后应用是安全的。     

New experimental procedures to evaluate the biomechanical properties of healing canine medial collateral ligaments

Both clinical and animal studies have indicated that early mobilization and exercise may improve the healing of injured medial collateral ligaments (MCLs). To investigate these effects, transected canine MCLs were subjected to three different treatment regimens: (a) no surgical repair with 6 weeks mobilization; (b) surgical repair with 3 weeks immobilization followed by 3 weeks remobilization; and (c) surgical repair with 6 weeks immobilization. After sacrifice, knee laxity was measured in a newly designed varus-valgus (V-V) laxity device. Each knee was tested subsequently in tension to determine the structural properties of the femur-MCL-tibia complex (FMTC) and the mechanical properties of the healing MCL substance. It was found that the V-V laxity increased for all experimental knees, but that early mobilization enhanced joint stability. The structural properties of the FMTC and the mechanical properties of the MCL substance were also lower than the contralateral controls. Again, the early mobilization groups had better results.     

Intravascular hemolysis in patients with normally functioning mechanical heart valves in mitral position

Objective Traumatic intravascular hemolysis has been recognized as a potentially serious problem after heart valve replacement. Chronic subclinical hemolysis in these patients with normally functioning valvular mechanical or biologic prostheses rarely develop decompensated anemia. This prospective study evaluates the presence and severity of hemolysis in patients with normally functioning mitral prosthetic valves. Methods In this prospective study 78 patients with normally functioning mitral prosthetic valves were evaluated for hemolysis postoperatively on 7^th,30^th and 180^th days by clinical evaluation, transthoracic echocardiography, hemoglobin, serum lactic dehydrogenase (LDH), and reticulocyte count. Data was statistically analysed with paired t test and variance test. Results LDH was elevated in almost all the patients with mechanical valve replacement. None had significant anemia. All the evidence of hemolysis was not observed in any of the recipients. There was no statistically significant difference in the degree of hemolysis among the recipients of various tilting disc valves. There was no significant correlation between the severity of hemolysis and cardiac rhythm or the size of valve. The recipients of bileaflet valve had significantly more severe hemolysis than those of tilting disc valves. Conclusions Almost all the recipients of mechanical mitral valves had increased LDH values at the follow up. However none had decompensated anemia during 180 days follow up. Bileaflet valves cause more hemolysis than tilting ones. Recipients of Chitra TTK valve prosthesis showed least hemolysis.