Difficult weaning from mechanical ventilation: a graduated approach and teamwork

Weaning from mechanical ventilation in patients with chronic obstructive pulmonary disease (COPD) or left ventricular failure may be difficult. At the time of intubation and initiation of mechanical ventilatory support, this treatment is usually life-saving in the short term. Only later on, the condition which necessitated such support may prove irreversible. COPD patients often require positive end-expiratory pressure to enable them to trigger the ventilator comfortably. Patients with left ventricular failure need pharmacological support to reduce the circulating volume and to reduce left ventricular afterload because the ventilatory support itself reduces both left ventricular preload and afterload. Gradual withdrawal of pressure support and gradually increasing periods of T-piece weaning are probably equally effective. New methods have been described but have not yet been tested in randomized controlled trials. More important than the method of weaning is the presence of qualified and dedicated nursing support. Not all patients can be weaned; for most of those who cannot, prospects are grim. These patients require optimal palliative support with recognition of their autonomy.     

Investigating the weaning process in past populations

The 19th century St. Thomas'Anglican churchyard in Belleville, Ontario, Canada is associated with a large and well-preserved infant skeletal collection (n = 149) and good-quality parish records that document interments in the graveyard (1821-1874). By using a combination of historical demographic and stable nitrogen isotope analyses on the parish records and skeletal remains, respectively, a general pattern of extended nursing for about 14 months, introduction of foods other than breast milk by around 5 months of age, and variation in breast-feeding and weaning behaviours were detected for St. Thomas' infants. The results demonstrate that it is possible to go beyond the concept of weaning age to explore the weaning process in past populations when appropriate and large samples of documentary and skeletal data are available.     

Noninvasive ventilation for postoperative support and facilitation of weaning

Noninvasive ventilation includes continuous positive airway pressure with mask, positive pressure ventilation with mask, and negative pressure body ventilation. Noninvasive ventilation is a ventilatory support mode intermediate in both effectiveness and potential complications between oxygen administration and intubation with mechanical ventilation. The advantages, disadvantages, and experimental results of the use of noninvasive ventilation in patients who have been extubated following recovery from surgery and subsequently experience respiratory difficulties are discussed. In general, noninvasive ventilation seems to provide useful ventilatory support in about three of four patients in whom it is tried. In addition, the use of noninvasive ventilation as an aid to weaning of patients from mechanical ventilation is discussed. This use of noninvasive ventilation has not yet been extensively reported, although it appears to be potentially useful.     

Psychophysiologic predictors of weaning from mechanical ventilation in chronic bronchitis and emphysema

This study identified psychophysiologic variables related to successful weaning in 27 ventilator-dependent patients with chronic bronchitis and emphysema (CBE) from two long-term care pulmonary-specialty hospitals in South Central Florida. Subjects were studied from admission until weaning occurred (successful weaning without mechanical ventilation) or until they were transferred without being weaned or died (unsuccessful weaning). The study subjects, 15 males and 12 females, ranged in age from 56 to 89. Baseline data on the variables (age, mastery, hope, social support, dyspnea, and rapid shallow breathing index [RSBI]) were not statistically significant by gender. The logistic regression model identified mastery and RSBI to be the best predictors of successful weaning (model chi 2 = 16.33, df = 2, and p value = .0003; prediction rate 82%).     

Successful weaning from mechanical ventilation in an aged subject with severe apneas due to brain damage

A 73-year-old male was admitted to Tokyo University Hospital due to cardiac arrest secondary to ventricular arrhythmias. Although the patient survived after cardiopulmonary resuscitation, he needed mechanical ventilation. When we tried to wean the patient from mechanical ventilation, we found that he suffered from frequent sleep apneas of over 40 times/hour. To evaluate the severity and frequency of the apneas, we performed polysomnographic study on the patient under assist ventilation. The polysomnographic study revealed that frequency of apneas was very high but the magnitude of desaturation was not so severe during the night. Since we confirmed the lowest SaO2 in this patients was over 90% during day and night, we tried to wean from the patient from the ventilator again and succeeded. The clinical application and usefulness of nocturnal ventilatory monitoring for patients with mechanical ventilation was discussed.     

Oxygen cost of breathing and weaning process in newborn infants

Newborn infants may have a high oxygen cost of breathing (OCB) at the time of being weaned from mechanical ventilation. We hypothesized that this increase in oxygen consumption (V'O2) could be reduced by using certain weaning ventilatory modes. We designed a study to assess V'O2 during three weaning ventilatory modes: patient triggered ventilation, synchronous intermittent mandatory ventilation (SIMV) and continuous positive airway pressure in 16 newborn infants before being weaned from mechanical ventilation In seven infants whose OCB was high. V'O2 was not significantly different between CV and PTV (8.9+/-0.6 versus 9.5+/-0.8, respectively) whereas it tended to increase to 10.8+/-1.1 mL x min(-1) x kg(-1) during SIMV and increased significantly to 11.9+/-0.8 mL x min(-1) x kg(-1). In the other nine infants whose OCB was normal, no significant variation of V'O2 was observed. Patient triggered ventilation was a weaning ventilatory mode that significantly reduced the increase in oxygen consumption observed in infants with a high oxygen cost of breathing, as compared to synchronous intermittent mandatory ventilation or continuous positive airway pressure. Further investigations in newborn infants with a high oxygen cost of breathing should be performed prior to routine use of patient triggered ventilation.     

集束化护理对严重脓毒症患者早期脱机的影响

目的 探讨集束化护理对严重脓毒症患者早期脱机的影响.方法 将2010年收住ICU18岁以上的严重脓毒症患者设为实验组,其采用集束化护理的方法,把2009年收住ICU18岁以上的严重脓毒症患者设为对照组,其采用常规护理方法.观察2组患者28d内机械通气时间及脱机再次应用呼吸机的情况,2组比较采用χ2检验.结果 实验组28d内机械通气时间较对照组缩短,实验组脱机后再次应用呼吸机的人数比对照组少,差异具有统计学意义(P＜0.05).结论 集束化护理能明显缩短脓毒症患者的机械通气时间,减少再次使用呼吸机,提高护理质量,缩短住ICU时间.     

Gastric intramucosal pH: an indicator of weaning outcome from mechanical ventilation in COPD patients

The aim of this study was to determine whether gastric intramucosal pH (pHim) and/or gastric intramucosal carbon dioxide tension (PCO2,im) measured by tonometry can be used to predict the success of weaning in chronic obstructive pulmonary disease (COPD) patients. Twenty six consecutive COPD patients, undergoing mechanical ventilation for acute respiratory failure and satisfying the criteria of weaning from mechanical ventilation with nasogastric tonometer in place, were studied. Arterial blood gas values and PCO2,im were measured 24 h before (H-24), just before (H0), and after 20 min of a weaning trial on T-piece (H20min). Weaning failure was defined as the development of respiratory distress and/or arterial blood gas impairments during the first 2 h of spontaneous breathing on T-piece, or reintubation within 24 h after extubation. Between the weaning failure (n = 6) and weaning success (n = 20) groups, there were no differences in blood gas analysis readings at H-24 and H0 before the weaning period, age, Simplified Acute Physiology Score (SAPS) on admission, SAPS on the day of weaning trial, and duration of ventilation. Clinical status, tonometric and arterial gasometric data were similar at H-24 and H0 in all patients. During mechanical ventilation, pHim was < or = 7.30 in patients who failed weaning and > 7.30 in patients who were successfully weaned (p < 0.001; 100% sensitivity and specificity). The threshold value for PCO2,im of 8.0 kPa (60 mmHg) represents a clear demarcation with respect to outcome before the weaning trial. PCO2,im values during mechanical ventilation are significantly different (p < 0.001) between patients who were successfully weaned and those who were not (6.9 +/- 0.9 vs 9.9 +/- 1.1 kPa (51.9 +/- 6.7 vs 74.3 +/- 8.0 mmHg, respectively)). At H20min, pHim and PCO2,im were still statistically different between the weaning failure and the weaning success group. We conclude that measurement of gastric intramucosal pH (or gastric intramucosal carbon dioxide tension) represents a simple and accurate index to predict weaning outcome in chronic obstructive pulmonary disease patients before attempting weaning.     

Clinical characteristics, respiratory functional parameters, and outcome of a two-hour T-piece trial in patients weaning from mechanical ventilation

The discrepancy in results from different studies regarding outcome of weaning from mechanical ventilation may be due to several factors such as the differences in patient populations and weaning indexes used. In order to analyze the clinical characteristics and weaning indexes in patients undergoing a 2-h T-piece weaning trial and the relationship between the etiology of acute respiratory failure (ARF) and the outcome of this weaning trial, we prospectively studied 217 patients receiving mechanical ventilation who met standard weaning criteria. Successful weaning occurred in 57.6% (125 of 217) of patients: 13 of 33 (39.4%) patients with chronic obstructive pulmonary disease (COPD), 27 of 46 (58.7%) neurologic patients, and 85 of 138 (61.6%) patients with ARF. Ventilatory support was reinstituted in 31.8% (69 of 217) patients: 20 of 33 (60.6%) of patients with COPD, four of 46 (8.7%) neurologic patients, and 45 of 138 (32.6%) patients with ARF (p < 0.001). Reintubation was required in 23 of 148 (15.5%) patients: 15 of 42 (35.7%) neurologic patients, and eight of 93 (8.6%) patients with ARF, whereas no patient with COPD was reintubated (p < 0.001). Using a discriminant analysis, the following variables were selected as the best predictors of outcome: (1) in the whole population, days of mechanical ventilation before weaning trial (DMV), frequency-to-tidal volume ratio (f/VT), maximal inspiratory pressure (MIP), airway occlusion pressure (P0.1), maximal expiratory pressure (MEP), and vital capacity (VC); (2) in patients with ARF, DMV, P0.1/MIP, MIP, f/VT, and age; (3) in patients with COPD, f/VT, P0.1, P0.1/MIP, MIP, age, and DMV; (4) in neurologic patients, MIP, MEP, and f/VT.P0.1. Using these predictors, 74.6% of the whole population, 76.1% of patients with ARF, 93.9% of patients with COPD, and 73.9% of neurologic patients were accurately classified as weaning successes or failures. The highest rate of reintubation occurred in neurologic patients. In this group, the ability to cough and clear respiratory secretions, objectively reflected by MEP, may help in clinical decision-making.     

A regional weaning center for patients requiring mechanical ventilation: an 18-month experience

This report reviews the outcomes of patients on mechanical ventilation admitted to a new regional weaning center. We reviewed the records of 47 patients admitted to the weaning center over an 18-month period. All patients had a tracheostomy, were ventilator dependent, and considered difficult to wean by their referring physician. The mean days of ventilator dependence prior to transfer to our facility was 86 days, with a range of 21 to 332 days. Patients were admitted to a 12-bed weaning unit at our chronic disease and rehabilitation hospital and assessed by a multi-disciplinary team of physicians, nurses, and therapists. Thirty patients were successfully weaned from prolonged mechanical ventilation and subsequently discharged from our unit. These data indicate that the majority of difficult to wean patients admitted to our regional weaning center were successfully liberated from prolonged mechanical ventilation.     

通风输送过程高浓度粉尘沉积特性

粉尘沉积是通风输送过程的常见现象,严重时常堵塞管路,本文以实验研究为手段,探讨高浓度粉尘在通风输送过程的沉积特性。得出水平直管内粉尘的沉积受风速主导,较大风速湍流强度大,边界层厚度薄,有利于外流区粉尘的悬浮和边界层内粉尘的再次悬浮;水平90°弯管内粉尘沉积具有区域性,弯头上游以有序沉积为主,弯头下游由于气流边界层分离产生了漩涡区使沉积量急剧减少,弯头外侧由于流动偏移对壁面的冲刷使粉尘沉积几率降低,而弯管内侧由于边界层分离和部分粉尘随气流的偏移使沉积量最小;水平三通管内粉尘沉积主要受支管角度与流速影响。通风输送高浓度粉尘的合适取值为:水平直管和90°弯管风速应不低于17 m/s,水平三通角度30°~45°,支管风速不超过主管。     

网络言论自由的时代价值及规范化路径

网络言论自由在监督公共权力、约束私人行为、汇集社情民意等方面具有重要的时代价值.与此同时,网络言论自由也存在损害公民的隐私权、名誉权、生活安定权等实然弊端.推行信息公开、健全财产公示制度、依法规制网络言论自由权、加强网络文明建设,是网络言论自由规范化的有效路径.     

Determination of mixing time in BOF process by a cold model study

Mixing time in a BOF process has been studied using a 1/14 water-air model. The study shows that for a simulated cold model, mixing time is independent of jet Froude number. For a partially simulated model, mixing time was found to be inversely proportional to square root of bath height to diameter ratio. This is in agreement with the similarity condition.     

Psychotherapy process as a function of the time segment sampled.

Employed a content analysis of individual psychotherapy tapes of 25 female undergraduates to determine the relative frequencies of certain response measures during the 1st, 2nd, 3rd, 4th, and 5th 10-min segments of the therapeutic hr. An attempt was made to test the assumption made by many investigators that the occurrence of a given phenomenon is evenly distributed over the course of therapy. Results indicate that such an assumption is grossly inaccurate given variables appeared consistently more frequently in certain segments of the hr. than they did in others. It is suggested that examining the variable where it occurs most often will increase the power of future investigations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Right ventricular function during weaning from mechanical ventilation after coronary artery bypass grafting: effect of volume loading

The inter-incisal distance and dimension of the interdental papilla between the mandibular incisors were examined in cyclosporin A (CSA) fed rats over 6 weeks. Rats in the test group received CSA daily in mineral oil by gastric feeding (30 mg/kg body weight); the control group received mineral oil only. The inter-incisal distance and gingival dimensions, including bucco-lingual width and vertical height, were assessed biweekly from alginate impressed stone models. Animals were sacrificed at the end of the study and tissue sections were obtained from the anterior region of the mandible for histopathological evaluation. Both the inter-incisal distance and the dimension of the interdental papilla were significantly greater in CSA-exposed animals compared to control. The significant alteration appeared earlier in the papillary dimensions than that in the interdental distance. Particular histopathological alterations of the soft and hard tissues of the periodontium were observed in CSA-exposed animals. Within limitations of the study, we suggest that the CSA-induced gingival overgrowth may offer an active force contributing to observed tooth movement, however, remarkable alveolar remodeling should be considered as an undetermined factor for the movement.     

Time to clozapine response in a standardized trial

OBJECTIVE: The authors sought to determine the time to clozapine response in treatment-refractory patients with schizophrenia. METHOD: Antipsychotic response to a clozapine trial was examined in 50 treatment-refractory schizophrenic inpatients. Subjects were treated with clozapine for at least 12 months, regardless of response status, according to a standardized, increasing dose protocol. Behavioral changes were measured through monthly assessments with the Brief Psychiatric Rating Scale. RESULTS: Thirty-four subjects (68%) met clinical response criteria by the end of the trial. Response was achieved at a mean dose of 468 mg/day (SD = 168). The dose of 30 (88%) of the responding patients was 600 mg/day or less. The mean time to response was 82 days (SD = 100, range = 10-401). It took an average of 60 days (SD = 87) for subjects to reach the dose at which clozapine response was achieved. Once this dose was reached, the average response time was 17 days (SD = 14, range = 2-56). All 34 subjects who responded met criteria within 8 weeks of a clozapine dose escalation. No late response was found in the remaining 16 subjects despite a mean follow-up period of 75 weeks (SD = 50). CONCLUSIONS: In this study, all patients who responded to clozapine did so within 8 weeks of a change in dose. Thus, there appears to be little clinical gain in prolonging exposure to clozapine beyond 8 weeks at any particular dose if no response is seen.