Serial Diaphragm Ultrasonography to Predict Successful Discontinuation of Mechanical Ventilation

Introduction

Diaphragm excursion and contraction velocity measured using ultrasonography have been used to assess diaphragm function. We aimed to evaluate the performance of diaphragm ultrasonography during weaning from mechanical ventilation (MV).

Methods

Diaphragm ultrasonography was performed on 73 mechanically ventilated patients who were being considered for extubation on three separate occasions: (1) on assist control mode (A/C) during consistent patient triggered ventilation, (2) following 30 min during a spontaneous breathing trial (SBT), (3) 4–24 h following extubation. Right hemidiaphragm excursion and contraction velocity were measured on A/C, during SBT, and following extubation. These measurements were correlated with the outcome of extubation.

Results

Twenty patients failed extubation: 6 of whom required re-intubation and 14 of whom required non-invasive ventilatory support. During SBT, the mean diaphragm excursions were 1.7?±?0.82 cm in the group who failed extubation compared to 2.1?±?0.9 cm in the group who were successfully extubated (p?=?0.06). To predict successful extubation, a decrease in diaphragm excursion of <?16.4% between A/C and SBT had a sensitivity of 84.9% and a specificity of 65%. The area under curve (AUC) for receiver operative characteristics for above cut-off was 0.75. Diaphragm contraction velocity performed poorly in predicting weaning outcome.

Conclusions

Diaphragm excursion measured during SBT is an imperfect predictor of the outcome of extubation. Maintenance of diaphragm excursion between A/C and SBT has good performance characteristics by AUC analysis. Diaphragm contraction velocity has poor ability to predict outcome of extubation.

     

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.     

Continuous monitoring of oxygen consumption in patients undergoing weaning from mechanical ventilation

BACKGROUND: The extubation or discontinuation of mechanical ventilatory support (MVS) is only the final step in the weaning process, and an improvement in the efficiency of the weaning process is required for more successful extubation or discontinuation of MVS. OBJECTIVE: To evaluate whether continuous monitoring of oxygen consumption (VO2) using the metabolic gas monitor is a useful predictor of failure to tolerate a weaning trial of reduced MVS. METHOD: Twenty adult patients meeting the criteria for weaning, who required MVS > or = 7 days and who were previously deemed to have failed weaning by their attending physicians. A weaning trial was defined as a 30-min period during the strengthening training of our standardized weaning protocol. The average VO2, respiratory rate (RR), tidal volume (TV), minute ventilation (VE) and energy expenditure (EE) were recorded in respiratory muscles for a stable period of 20 min at rest and for the last 5 min of the trial. Subsequently, the oxygen cost of breathing (OCOB), the ratio of respiratory frequency to tidal volume (f/VT), DeltaRR, DeltaTV, DeltaVE, and DeltaEE were calculated. RESULTS: Two hundred and eight weaning trials, including 145 successful trials and 63 failed trials from 20 patients were evaluated. In nonparametric analysis, a statistical difference in OCOB, DeltaRR, and DeltaEE was found between successful and failed weaning trials, while no statistical differences were found for the other parameters. An OCOB < 30% was the most accurate predictor of outcome of a weaning trial, and an f/VT < 105 was the least accurate. In a multiple logistic analysis, the OCOB revealed the highest odds ratio among all parameters. CONCLUSIONS: Measuring the OCOB was clinically beneficial in avoiding the induction of an excessive movement load on the respiratory muscles. In patients treated with MVS, continuous monitoring of VO2 is a useful to predict success or failure of trials attempting to reduce MVS.     

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.     

Cough peak flows and extubation outcomes

BACKGROUND: Semiobjective methods of quantifying cough strength and endotracheal secretions have been demonstrated to predict extubation outcomes of patients who have passed a spontaneous breathing trial (SBT). HYPOTHESIS: Cough strength, measured by voluntary cough peak expiratory flow (PEF), and endotracheal secretions, measured volumetrically, predict extubation outcomes of patients who have passed an SBT. Patient population: Critically ill patients admitted to the medical ICU of a 300-bed community teaching hospital. METHODS: All patients who passed an SBT and were about to be extubated were studied. The best of three cough attempts, measured with an in-line spirometer, and the average hourly rate of suctioned secretions prior to extubation were recorded with other weaning parameters and demographic data. RESULTS: Ninety-five patients were studied before and after 115 extubations. There were 13 unsuccessful extubations. There were no differences in age, gender, duration of intubation, or APACHE (acute physiology and chronic health evaluation) II scores between successful and unsuccessful extubations. The magnitude of endotracheal secretions was not associated with outcomes. The PEF of patients with unsuccessful extubations was significantly lower than that of those with successful extubations (64.2 +/- 6.8 L/min vs 81.9 +/- 2.7 L/min, p = 0.03). Patients with unsuccessful extubations stayed longer in the ICU than those with successful extubations (11.7 +/- 2.1 days vs 5.3 +/- 0.4 days, p = 0.009). Those with PEF 相似文献   

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.     

Carbon dioxide recruitment threshold as a predictor of successful weaning in chronic obstructive pulmonary disease patients: A pilot study

Abstract Several methods have been used to predict successful weaning and extubation among chronic obstructive pulmonary disease (COPD) patients. The objective of this study is to determine whether carbon dioxide recruitment threshold (PCO₂RT) can be used as adjunct to conventional weaning parameters to predict early weaning and successful extubation. Twelve COPD patients who were ready to be extubated based on conventional weaning parameters were divided into group A ( n = 7) and group B ( n = 5). Group A were those patients with better weaning parameters and hence a higher probability of successful extubation as compared to group B. Carbon dioxide apnoeic threshold (PCO₂AT) was obtained by hyperventilating the patient using an increment of two breaths per min until apnoea occurs. At this point, the PCO₂AT or the PaCO₂ during said apnoeic period was recorded. A dead space of 150 cc is then added to the circuit until the patient starts to breathe as evidenced by the sensitivity trigger indicator. The PCO₂ obtained at this period is termed PCO₂RT. After weaning for 30 min on a T-tube, another arterial blood gas is determined and this is called the PCO₂SB or the CO₂ level after 30 min on spontaneous breathing. If the PCO₂SB-PCO₂RT difference is high with a sensitivity of 85.71% and specificity of 100% vs sensitivity of 57.14% and specificity of 60% using the conventional weaning parameters. Thus an increase in PCO₂SB at 30 min T-tube is indicative of impending respiratory pump failure and that other causes of failure to wean must be investigated.     

心肺联合超声在先天性心脏病婴儿术后机械通气脱机评估中的临床价值

目的:探讨心肺联合超声(CPUS)在先天性心脏病(先心病)婴儿术后机械通气脱机评估中的临床应用价值.方法:选取2020年2～6月在中国医学科学院阜外医院经外科手术治疗先心病婴儿109例,平均年龄(0.70±0.25)岁,平均体重(7.48±1.49)kg.达到临床脱机标准后进行心肺联合超声检查,记录肺超声评分、左心室射...     

Konno-Mead analysis of ribcage-abdominal motion during successful and unsuccessful trials of weaning from mechanical ventilation

Respiratory muscle fatigue is considered a common cause of weaning failure but its detection is hampered by the lack of a satisfactory diagnostic test. Abdominal paradox has been proposed as a valuable clinical index of fatigue and thus its presence may lead to curtailment of weaning trials. However, sensitivity and specificity of this sign as a predictor of weaning outcome is unknown. We hypothesize that abnormal ribcage-abdominal (RC-Ab) motion is a common finding in the early stages of weaning and its presence does not inevitably imply an unsuccessful weaning outcome. We tested this hypothesis in patients undergoing a weaning trial: one group had a successful weaning outcome and were extubated (n = 10) and the other group failed the trial (n = 7). Normal RC-Ab motion was separately characterized in 17 healthy subjects. Employing a calibrated respiratory inductive plethysmograph, quantitative assessment of asynchrony and paradox was obtained by computing several indices from series of breaths at fixed time periods using the Konno-Mead method of analysis. During the weaning trial, both groups of patients displayed significant increases in asynchrony and Ab paradox compared to normal values. As a group, patients who failed the trial displayed significantly greater asynchrony and paradox of the RC and Ab than patients with a successful outcome. However, there was considerable overlap between the individual patients in the 2 study groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Decline in diaphragm thickness and clinical outcomes among patients with sepsis

BackgroundThe decline in the diaphragm thickness is common among patients with sepsis. The purpose of this study is to examine the relationship between the decline in diaphragm thickness as assessed by ultrasonography and various outcomes in septic patients.MethodsThis prospective study included patients with sepsis whose diaphragm thickness was measured during inspiration (DTinsp) and expiration (DTexp) using ultrasonography on days 1, 3, 5, 7, 10, and 14 of admission in the ICU and thereafter weekly measurements until discharge or death.ResultsThe study included 70 (45 male) patients with sepsis [mean (SD) age = 55.91(14.08) years]. The mean (SD) DTinsp and DTexp (mm) on day-1 were 2.84 (0.32) and 2.33(0.27), respectively. During the hospital stay, there was a decline in DTinsp and DTexp. The decline in DTinsp and DTexp on days 3, 5, and 7 was significantly higher among patients with difficult weaning, non-survivors, and worse 90-day outcomes. Early decline (from day-1 to day-3) in diaphragm thickness predicted difficult weaning, in-hospital mortality, and worse 90-day outcome.ConclusionsAmong patients with sepsis, the decline in diaphragm thickness detected by ultrasonography is associated with worse in-hospital and short-term post-discharge outcomes. The role of early decline in diaphragm thickness on ultrasonography as a marker of worse outcomes needs further evaluation.     

探讨浅快呼吸指数指导COPD患者撤机的临床价值

目的评价浅快呼吸指数（rapid-shallow-breathing index,RSBI）作为COPD患者撤机的临床价值。方法呼吸重症监护病房的20例机械通气的COPD患者,均通过了1h的自主呼吸实验（spontaneous breathing trial,SBT）。记录两个时期的RS-BI：SBT前、SBT1h。同时记录年龄、性别、APACHEⅡ（acute physiology and chronic health evaluationⅡ）评分、撤机前的动脉血气分析。结果 16例COPD患者成功撤机,4例患者撤机失败。在成功和失败两组间年龄、性别、APACHEⅡ评分无明显差异（P〉0.05）,PaCO2（partial pressure of carbon dioxide in arterial blood）有明显差异（P〈0.05）。以RSBI≤105bpm/L为标准预测撤机成功的灵敏度和特异度分别为：SBT前RSBI93.8%、10%;SBT1h的RSBI93.8%、45.5%。SBT1h的RSBI与PaCO2联合预测撤机成功的灵敏度为89.5%,特异度为78%。结论 SBT1h的RSBI预测COPD患者成功撤机的准确性高于SBT前,其与PaCO2联合评价将提高预测撤机成功的准确性。     

A pilot study to investigate any relationship between sustained maximal inspiratory pressure and extubation outcome

OBJECTIVE: To establish whether any relationship exists between extubation outcome and sustained maximal inspiratory pressures (SMIP). DESIGN AND SETTING: Prospective clinical study in the 7-bed general intensive care unit of a university hospital. SUBJECTS: Twenty-seven intubated adults who were deemed ready for extubation were enrolled. MEASUREMENTS: Standard respiratory parameters and inspiratory muscle function data (ie, SMIP and peak maximal inspiratory pressures [MIP]) were recorded before extubation. RESULTS: SMIP was found to be significantly greater in those who were successfully extubated than in those who underwent a failed extubation (P <.01). Receiver operating characteristic curves for SMIP data indicated that a cutoff point of 57.5 pressure time units would give a sensitivity and specificity of 1.0 for extubation outcome prediction. Peak MIP was also significantly greater in those successfully extubated (P =.04); a cutoff point of 17.5 cm H(2)O gave a sensitivity of 1.0 and a specificity of 0.5. CONCLUSIONS: In this study, peak MIP was not specific enough to be clinically useful as a predictor of extubation outcome. SMIP was associated with extubation outcome with equally high sensitivity and specificity and may therefore have a role in outcome prediction.     

Tracheal occlusion pressure: a simple index to monitor respiratory muscle fatigue during acute respiratory failure in patients with chronic obstructive pulmonary disease

STUDY OBJECTIVE: To assess respiratory muscle fatigue in acute respiratory failure in patients with chronic obstructive pulmonary disease and evaluate its influence on weaning patients from mechanical ventilation. DESIGN AND PATIENTS: We studied the time course of tracheal occlusion pressure (P0.1) and high-to-low ratio of the diaphragmatic electromyogram in 16 patients in acute respiratory failure with chronic obstructive pulmonary disease. METHODS: All patients were intubated and studied during a 15-minute weaning period from ventilation. Minute ventilation (VE), arterial blood gases, P0.1 and high-to-low ratio of the diaphragm were measured every day from the onset to the end of acute failure (before extubation) at 5 and 15 minutes into the weaning period. The diaphragmatic electromyogram was recorded with an esophageal electrode and the high-to-low ratio of the electrical signal analyzed to assess diaphragmatic fatigue. MEASUREMENTS AND MAIN RESULTS: In all patients P0.1 was markedly increased (7.1 +/- 2.4 cm H2O, mean +/- SE) on the first day of acute failure and did not change during weaning. In 11 patients, P0.1 had decreased to 4.7 +/- 1.8 cm H2O (P less than or equal to 0.002) before extubation (which was done after 5 to 9 days). In these patients, the high-to-low ratio of the diaphragm decreased rapidly-during the first minutes of weaning on the first day of acute failure and remained low throughout weaning, whereas before extubation no decrease in high-to-low ratio was seen during weaning. In 5 patients, P0.1 did not change significantly from the onset of acute failure and the high-to-low ratio remained low before extubation. These 5 patients had to be reintubated within 2 to 6 days. In both groups of patients, VE did not change significantly from the first to last day of acute failure (10.3 +/- 3 compared with 10.7 +/- 2.1 min-1), whereas blood gases during room air breathing improved significantly from the first to last day of acute failure, respectively, in each group (arterial oxygen pressure [PaO2], 33.5 +/- 1.5 compared with 44 +/- 9 mm Hg (P less than or equal to 0.05) and PaO2 56 +/- 2.3 compared with 49 +/- 2 mm Hg (P less than 0.005). CONCLUSIONS: Extubation should not be done in patients with respiratory muscle fatigue despite improvement in arterial blood gases and clinical status; and P0.1 provides a valid and simple index to assess the likelihood of respiratory muscle fatigue.     

生理呼吸功作为呼吸机撤离指标的临床研究

目的评价生理呼吸功（ＷＯＢｐｈｙ）对机械通气患者撤机的指导意义。方法监测患者呼吸功（ＷＯＢｔ）和器械导致的附加功（ＷＯＢｉｍｐ）推算ＷＯＢｐｈｙ。不符合常规撤机标准者，以ＷＯＢｐｈｙ＜０．７０Ｊ／Ｌ为撤机标准，观察是否撤机成功。结果４１例患者中２８例符合常规撤机标准（常规组），拔管后１例再插管。１３例患者不符合常规撤机标准（非常规组），但ＷＯＢｐｈｙ均低于０．７０Ｊ／Ｌ全部拔管，其中１例再插管。非常规组ＷＯＢｔ（１．３７±０．５０Ｊ／Ｌ）和ＷＯＢｉｍｐ（０．８２±０．３７Ｊ／Ｌ）与常规组（０．９６±０．３８和０．５５±０．２７Ｊ／Ｌ）比较，差异均有显著性。但两组比较ＷＯＢｐｈｙ差异无显著性。结论以ＷＯＢｐｈｙ＜０．７０Ｊ／Ｌ作为撤机标准是安全的，有利于及时撤机拔管。     

Time course of expiratory flow limitation in COPD patients during acute respiratory failure requiring mechanical ventilation

STUDY OBJECTIVES: (1) To determine the incidence of expiratory flow limitation (FL) at ICU admission, at the time of extubation, and at ICU discharge in intubated patients with COPD receiving mechanical ventilation for acute respiratory failure (ARF); and (2) to assess the feasibility of inspiratory capacity (IC) as an indication of pulmonary dynamic hyperinflation in this setting. DESIGN: Prospective, observational pilot study with physiologic measurements performed at ICU admission and during the weaning process driven by the clinician. A 60-min T-tube trial was initiated once criteria for weaning were present. The decision to extubate or reventilate patients was made by the clinician at the end of this session. Assessment of failure or success of T-tube trials was performed independently. SETTING: A 25-bed ICU of a tertiary teaching university hospital. PATIENTS: Over a 13-month period, 25 intubated patients with COPD receiving mechanical ventilation for ARF were included. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: At ICU admission, FL assessed by the negative expiratory pressure test was measured under passive ventilatory conditions at the baseline ventilatory settings, on zero end-expiratory pressure, and in a semirecumbent position. During weaning, FL, respiratory pattern, and IC were measured during T-tube trials, before extubation, 1 h after extubation, and at ICU discharge. At ICU admission, 24 of 25 patients presented FL with, on average, 73 +/- 22% of the tidal volume. Ten patients were unavailable for follow-up due to death (n = 6) unplanned extubation (n = 3), or refusal (n = 1), so that only 15 patients completed the whole protocol (all 15 patients were extubated). For these 15 patients, the incidence of FL was 93% at ICU admission, 47% before extubation, and 40% at ICU discharge. IC was significantly greater at ICU discharge than before extubation (36 +/- 11% predicted vs 44 +/- 12% predicted, p < 0.01) and in successful T-tube trials compared with unsuccessful T-tube trials (38 +/- 13% predicted vs 24 +/- 8% predicted, p < 0.01). CONCLUSIONS: The incidence of expiratory FL is high in patients with COPD receiving mechanical ventilation, and is reduced during aggressive therapy when the patient is placed on mechanical ventilatory support and the time that weaning begins during the ICU stay. IC was lower in patients in whom weaning was unsuccessful. Further large-scale studies are required to confirm these preliminary results.     

Effect of early application of biphasic positive airway pressure on the outcome of extubation in ventilator weaning

Extubation failure is significantly associated with increased morbidity and mortality in mechanically ventilated patients. In respiratory distress after extubation, non-invasive positive pressure ventilation (NIPPV) has been suggested to avoid the complications of invasive mechanical ventilation. The purpose of this study was to evaluate the effect of early application of NIPPV on extubation outcome. We conducted a prospective study in 93 extubated patients with a mean age of 72.7 +/- 14.7 years (range, 24-93). Elective extubation was performed in 56 patients and unplanned extubation occurred in 37 patients. After extubation, patients randomly received either biphasic positive airway pressure (BIPAP) therapy (n = 47) or unassisted oxygen therapy (n = 46). Non-invasive positive pressure ventilation was delivered via face mask in BIPAP group. Of the 93 extubated patients, 73 (78.5%) were successfully extubated, and 20 (21.5%) had to be re-intubated. There were no significant differences in age, sex, pre-extubation blood gas data between re-intubated patients and those who were not re-intubated. While seven of the 46 patients in the unassisted oxygen therapy group required re-intubation, 13 of the 47 BIPAP-treated patients also required re-intubation. This difference was not statistically significant. The postextubation respiratory management, BIPAP or unassisted oxygen therapy, did not correlate with the extubation outcome, but the elective extubation had significantly better outcome than unplanned extubation. Patients with excessive bronchial secretions and intolerance to the equipment are poor candidates for NIPPV. We conclude that early application of BIPAP support did not predict a favourable extubation outcome. Our experience did not support the indiscriminate use of NIPPV to facilitate ventilator weaning.     

Capnometric recirculation gas tonometry and weaning from mechanical ventilation

The aim of this study was to describe changes in regional intramucosal PCO(2) (Pr(CO(2)) measured with capnometric recirculation gas tonometry [CRGT]) in patients with acute respiratory failure, who proceed from mechanical ventilation to weaning. In addition, we compared the predictive power for the weaning outcome of CRGT measurements obtained during mechanical ventilation to the frequency/ tidal volume (f/VT) ratio. A total of 24 patients (31 weaning trials) were included in the study, but four of the 24 patients (17%) were excluded because of extubation failure. Of the remaining 27 weaning trials in 20 patients, 12 (44%) were unsuccessful. Changes observed in patients with weaning failure (increase in Pr(CO(2)) from 60.4 +/- 15.0 mm Hg in mechanical ventilation to 67.4 +/- 21.0 mm Hg, in weaning) were significantly different (p = 0.046) from those observed in patients with weaning success (fall in Pr(CO(2)) from 61.5 +/- 15.0 mm Hg in mechanical ventilation to 56.3 +/- 16.7 mm Hg in weaning). However, absolute values of Pr(CO(2)) were not significantly different between patients with weaning success and failure, neither during mechanical ventilation (success, 61.5 +/- 15.0 versus failure, 60.4 +/- 15.0 mm Hg, p = 0.848) nor during weaning (success, 56.3 +/- 16.7 versus failure, 67.4 +/- 21.0 mm Hg, p = 0.135). The best single predictor for weaning outcome was the f/VT ratio measured early during weaning (area under the curve: 0.844 +/- 0.081; adjusted odds ratio for threshold value 相似文献   

Is airway occlusion pressure useful to predict successful weaning from mechanical ventilation in patients with acute respiratory failure?

The purpose of this study was to evaluate whether airway occlusion pressure (P0.1) would be a useful predictor for successful weaning in mechanically ventilated patients with acute respiratory failure. We studied 23 marginal weaning candidates. Fourteen patients were able to be weaned from the ventilator, and 9 patients were not able to be weaned. P0.1 and other respiratory parameters were measured just prior to weaning and at the end of weaning or at the time of discontinuation of weaning. The mean value of P0.1 in the failed group was higher than that in the successful group both before and after weaning periods. However, P0.1 varied widely among patients and did not separate the failure group from the success group because of overlap between the two. There were significant differences between the two groups of the conventional weaning parameters, such as respiratory rate, minute ventilation, PaO2, and oxygen equivalent. We conclude that P0.1 is helpful to predict successful weaning. However, it can not be used as a single parameter for weaning because of the wide variations of absolute values among patients with acute respiratory failure.