Spontaneous Breathing Trial In Patients Research Articles

PREDICTING POST-EXTUBATION RESPIRATORY FAILURE AFTER MYOCARDIAL INFARCTION USING THE RAPID SHALLOW BREATHING INDEX AND LUNG ULTRASOUND SCORE

The Rapid Shallow Breathing Index (RSBI) has been hypothesized to have discriminating power for categorizing patients at higher risk of post-extubation respiratory failure (RF). Hence aim of this study was to determine the predictive value of RSBI for post-extubation RF in patients after acute myocardial infarction (AMI). Consecutive, intubated patients admitted post-revascularization were included. RSBI and lung ultrasound score (LUS) were measured and post-extubation RF within 48 hours was recorded. RF was observed in 36.3% (78/215) patients. For the prediction of RF, RSBI and LUS had area under the curve of 0.670 and 0.635, respectively. The sensitivity, specificity, negative predictive value, and positive predictive value of RSBI >50.5 were 75.6%, 54.7%, 79.8%, and 48.8% respectively, while, the accuracy measures for the combination of RSBI with LUS >1.5 were 44.9%, 84.7%, 73.0%, and 62.5% respectively. Combined RSBI and LUS measured during spontaneous breathing trial in patients after an AMI, have high predictive abilities for identifying post-extubation RF.

Evaluation of the Integrative Weaning Index for Predicting the Outcome of Spontaneous Breathing Trial in Patients with Cirrhosis on Mechanical Ventilation: A Pilot Study.

Objective:Studies on mechanical ventilation in patients with cirrhosis have focused mainly on survival, as the disease is considered to carry a poor prognosis. The process of weaning in these patients has never been studied. With improving survival, it would be ideal to study the weaning indices that could add experience in clinical management. The integrative weaning index is known to predict weaning failure, even in those who tolerate the spontaneous breathing trial. However, it has been evaluated mainly in patients with chronic obstructive pulmonary disease. Our aim is to study the integrative weaning index in predicting the outcome of the spontaneous breathing trial in patients with cirrhosis undergoing mechanical ventilation.Methods:Adult cirrhotic patients requiring mechanical ventilation for the first time were enrolled. Twenty-seven patients were found eligible for weaning. After the decision to wean, the patients were put on pressure support mode of ventilator followed by spontaneous breathing trial using T-piece for 2 hours.Results:The study population was divided into two groups: successful spontaneous breathing trial group (Group S) and unsuccessful spontaneous breathing trial group (Group U) based on the outcome of the breathing trial. The mean respiratory rate was significantly lower in Group S as compared to Group U. The compliance of the respiratory system and integrative weaning index were found to be significantly higher in Group S. An integrative weaning index of 28 mL/cmH2O breaths/min/L was found to be a good predictor of weaning success.Conclusions:Our results demonstrate that weaning from mechanical ventilation is possible in critically ill patients with cirrhosis. An integrative weaning index of 28 mL/cmH2O breaths/min/L could be a successful predictor of weaning from mechanical ventilation.

Frequent tracheal suctioning is associated with extubation failure in patients with successful spontaneous breathing trial: a single-center retrospective cohort study

BackgroundExtubation failure, i.e., reintubation in ventilated patients, is a well-known risk factor for mortality and prolonged stay in the intensive care unit (ICU). Although sputum volume is a risk factor, the frequency of tracheal suctioning has not been validated as a predictor of reintubation. We conducted this study to examine whether frequent tracheal suctioning is a risk factor for reintubation.Patients and methodsWe included adult patients who were intubated for > 72 h in the ICU and extubated after completion of spontaneous breathing trial (SBT). We compared the characteristics and weaning-related variables, including the frequency of tracheal suctioning between patients who required reintubation within 24 h after extubation and those who did not, and examined the factors responsible for reintubation.ResultsOf the 400 patients enrolled, reintubation was required in 51 (12.8%). The most common cause of reintubation was difficulty in sputum excretion (66.7%). There were significant differences in sex, proportion of patients with chronic kidney disease, pneumonia, ICU admission type, the length of mechanical ventilation, and ICU stay between patients requiring reintubation and those who did not. Multivariate analysis showed frequent tracheal suction (> once every 2 h) and the length of mechanical ventilation were independent factors for predicting reintubation.ConclusionWe should examine the frequency of tracheal suctioning > once every 2 h in addition to the length of mechanical ventilation before deciding to extubate after completion of SBT in patients intubated for > 72 h in the ICU.

Integrative weaning index as a predictor of weaning success

ObjectiveThis study aimed to evaluate the power of integrative weaning index (IWI) in predicting the success rate of spontaneous breathing trial (SBT) in the mechanically ventilated patients.BackgroundThe use of weaning predictive indicators can avoid early extubation and wrongful prolonged mechanical ventilation. This study aimed to evaluate the effectiveness of IWI in predicting the success rate of SBT in patients under mechanical ventilation.Patients and methodsIn this prospective study, 120 patients undergoing mechanical ventilation for more than 48 h were enrolled. Before weaning initiation, the IWI was calculated and based on the defined cutoff point (≥44), the success rate of SBT was predicted. If they were in the normal range besides the patient's tolerance, the test was considered a success. The result was then compared with the IWI and further analyzed.ResultsThe SBT was successful in 96 (80%) and unsuccessful in 24 (20%) cases. The difference between the true patient outcome after SBT, and the IWI prediction was 0.833 according to the Kappa agreement coefficient (P < 0.001). Moreover, regarding the predictive power, IWI had high sensitivity (96.87%), specificity (95.83%), positive and negative predictive values (98.8 and 88.5%), and accuracy (96.7%).ConclusionThe IWI as a more objective indicator has acceptable accuracy and power for predicting the SBT result.

Role of a successful spontaneous breathing trial in ventilator liberation in brain-injured patients.

Spontaneous breathing trials (SBTs) have been shown to improve outcomes in critically ill patients. However, in patients with brain injury, indications for intubation and mechanical ventilation are different from those of non-neurological patients, and the role of an SBT in patients with brain injury is less established. The aim of the present study was to compare key respiratory variables acquired during a successful SBT between patients with successful ventilator liberation versus failed ventilator liberation. In this prospective study, patients with brain injury (≥18 years of age), who completed a 30-min SBT, were enrolled. Airway pressure, flow, esophageal pressure, and diaphragm electrical activity (ΔEAdi) were recorded before (baseline) and during the SBT. Respiratory rate (RR), tidal volume, inspiratory muscle pressure (ΔPmus), ΔEAdi, and neuromechanical efficiency (ΔPmus/ΔEAdi) of the diaphragm were calculated breath by breath and compared between the liberation success and failure groups. Failed liberation was defined as the need for invasive ventilator assistance within 48 h after the SBT. In total, 46 patients (51.9±13.2 years, 67.4% male) completed the SBT. Seventeen (37%) patients failed ventilator liberation within 48 h. Another 11 patients required invasive ventilation within 7 days after completing the SBT. There were no differences in baseline characteristics between the success and failed groups. In-depth analysis showed similar changes in patterns and values of respiratory physiological parameters between the groups. In patients with brain injury, ventilator liberation failure was common after successful SBT. In-depth physiological analysis during the SBT did not provide data to predict successful liberation in these patients. The trial was registered at ClinicalTrials.gov (No. NCT02863237).

Diaphragm Function Assessment During Spontaneous Breathing Trial in Patients with Neuromuscular Diseases.

IntroductionThe optimal time to discontinue patients from mechanical ventilation is critical as premature discontinuation as well as delayed weaning can result in complications. The literature on diaphragm function assessment during the weaning process in the intriguing subpopulation of critically ill neuromuscular disease patients is lacking.MethodsPatients with neuromuscular diseases, on mechanical ventilation for more than 7 days, and who were ready for weaning were studied. During multiple T-piece trials over days, diaphragm function using ultrasound and diaphragm electrical activity (Edi peaks using NAVA catheter) was measured every 30 min till a successful 2 h weaning.ResultsA total of 18 patients were screened for eligibility over 5-month period and eight patients fulfilled the inclusion criteria. Sixty-three data points in these 8 subjects were available for analysis. A successful breathing trial was predicted by Edi reduction (1.22 μV for every 30 min increase in weaning duration; 0.69 μV for every day of weaning) and increase in diaphragm excursion (2.81 mm for every 30 min increase in weaning duration; 2.18 mm for every day of weaning).ConclusionThe Edi and diaphragm excursion changes can be used as additional objective tools in the decision-making of the weaning trials in neuromuscular disease.Electronic supplementary materialThe online version of this article (10.1007/s12028-020-01141-9) contains supplementary material, which is available to authorized users.

T-piece versus pressure-support ventilation for spontaneous breathing trials before extubation in patients at high risk of reintubation: protocol for a multicentre, randomised controlled trial (TIP-EX)

IntroductionIn intensive care unit (ICU), the decision of extubation is a critical time because mortality is particularly high in case of reintubation. To reduce that risk, guidelines recommend to systematically...

Brain natriuretic peptide to predict successful liberation from mechanical ventilation in critically ill patients: a systematic review and meta-analysis

BackgroundPredicting successful liberation from mechanical ventilation (MV) in critically ill patients is challenging. Brain natriuretic peptide (BNP) has been proposed to help guide decision-making for readiness to liberate from MV following a spontaneous breathing trial (SBT).MethodsWe performed a systematic review and meta-analysis of randomized and prospective observational studies that measured BNP levels at the time of SBT in patients receiving MV. The primary endpoint was successful liberation from MV (absence of reintubation or non-invasive ventilation at 48 h). Statistical analyses included bi-variate and Moses-Littenberg models and DerSimonian-Laird pooling of areas under ROC curve (AUROC).ResultsA total of 731 articles were screened. Eighteen adult and 2 pediatric studies were fulfilled pre-specified eligibility. The measure of the relative variation of BNP during SBT (ΔBNP%) after exclusion of SBT failure by clinical criteria in adults yielded a sensitivity and specificity of 0.889 [0.831–0.929] and 0.828 [0.730–0.896] for successful liberation from MV, respectively, with a pooled AUROC of 0.92 [0.88–0.97]. The pooled AUROC for any method of analysis for absolute variation of BNP (ΔBNP), pre-SBT BNP, and post-SBT BNP were 0.89 [0.83–0.95], 0.77 [0.63–0.91], and 0.85 [0.80–0.90], respectively.ConclusionThe relative change in BNP during a SBT has potential value as an incremental tool after successful SBT to predict successful liberation from MV in adults. There is insufficient data to support the use of BNP in children or as an alternate test to clinical indices of SBT, or the use of ΔBNP, BNP-pre, and BNP-post as an alternate or incremental test.Trial registrationPROSPERO CRD42018087474 (6 February 2018)

The evolution of diaphragm activity and function determined by ultrasound during spontaneous breathing trials

PurposeRapid shallow breathing index (RSBI) is a commonly used index for predicting the outcome of spontaneous breathing trial (SBT). Ultrasound is a non-invasive technique for assessing diaphragm activity and function. This study aimed to investigate changes in diaphragm activity during SBT, and to compare diaphragm function between patients with and without SBT success. Materials and methodsForty-five patients undergoing SBT were enrolled. Thickening fraction of the diaphragm was assessed during tidal breathing (TFditidal), and RSBI was measured during 30 min of SBT. Diaphragm function measured by maximum TFdi (TFdimax) and diaphragmatic excursion (DEmax) was also evaluated. ResultsTFditidal and RSBI significantly increased during SBT (TFditidal0vs. TFditidal30 = 29.8 ± 13.8 vs. 37.4 ± 13.0%; p < .001, and RSBI0vs. RSBI30 = 64.8 ± 25.9 vs.70.8 ± 29.1 breaths/min/L; p = .034). In SBT failure (n = 13), there was no significant difference in TFditidal compared to SBT success, except at the beginning of the trial (p = .043); however, RSBI significantly increased throughout SBT. No differences in TFdimax or DEmax were observed between groups. ConclusionsPatient inspiratory efforts significantly increased during SBT. TFditidal measured by diaphragm ultrasound could not distinguish between patients with SBT success and failure. RSBI was significantly higher during SBT in patients with SBT failure.

Electrical impedance tomography for predicting failure of spontaneous breathing trials in patients with prolonged weaning

BackgroundSpontaneous breathing trials (SBTs) on a T-piece can be difficult in patients with prolonged weaning because of remaining de-recruitment phenomena and/or insufficient ventilation. There is no clinically established method existent other than experience for estimating whether an SBT is most probably beneficial. Electrical impedance tomography (EIT) is a clinical useful online monitoring technique during mechanical ventilation, particularly because it enables analysis of effects of regional ventilation distribution. The aim of our observational study was to examine if EIT can predict whether patients with prolonged weaning will benefit from a planned SBT.MethodsThirty-one patients were examined. Blood gas analysis, vital parameter measurements, and EIT recordings were performed at three time points: (1) baseline with pressure support ventilation (PSV) (t0), (2) during a T-piece trial (t1), and (3) after resumption of PSV (t2). Calculation of EIT parameters was performed, including the impedance ratio (IR), the tidal variation of impedance (TIV), the changes in end-expiratory lung impedance (ΔEELI), the global inhomogeneity index (GI), and the regional ventilation delay (RVD) index with use of different thresholds of the percentage inspiration time (RVD40, RVD60, RVD80). The predictive power of the baseline GI with regard to clinical impairment of an SBT was analyzed by means of ROC curves. Clinical deterioration was assumed when tidal volume was decreased by at least 20 ml after the T-piece trial, measured at t2.ResultsPartial pressure of arterial oxygen significantly decreased at t1 (71 ± 15 mmHg) compared with t0 (85 ± 17 mmHg, p < 0.05) and t2 (82 ± 18 mmHg, p < 0.05). The IR trended toward higher values during t1. At t1, TIV and ΔEELI significantly decreased. The GI was significantly increased at t1 (t0 59.3 ± 46.1 vs t1 81.5 ± 62.5, p = 0.001), as were all RVD indexes. Assuming a GI cutoff value of >40, sensitivity of 85% and specificity of 50% were reached for predicting an increased future tidal volume.ConclusionsEIT enables monitoring of regional ventilation distribution during SBTs and is suitable to estimate whether an SBT probably will be beneficial for an individual patient. Therefore, the application of EIT can support clinical decisions regarding patients in the phase of prolonged weaning.

Studying the Power of the Integrative Weaning Index in Predicting the Success Rate of the Spontaneous Breathing Trial in Patients under Mechanical Ventilation.

Background and Aims:The use of weaning predictive indicators can avoid early extubation and wrongful prolonged mechanical ventilation. This study aimed to determine the power of the integrative weaning index (IWI) in predicting the success rate of the spontaneous breathing trial (SBT) in patients under mechanical ventilation.Materials and Methods:In this prospective study, 105 patients undergoing mechanical ventilation for over 48 h were enrolled. Before weaning initiation, the IWI was calculated and based on the defined cutoff point (≥25), the success rate of the SBT was predicted. In case of weaning from the device, 2-h SBT was performed and the physiologic and respiratory indices were continuously studied while being intubated. If they were in the normal range besides the patient's tolerance, the test was considered as a success. The result was then compared with the IWI and further analyzed.Results:The SBT was successful in 90 (85.7%) and unsuccessful in 15 (14.3%) cases. The difference between the true patient outcome after SBT, and the IWI prediction was 0.143 according to the Kappa agreement coefficient (P < 0.001). Moreover, regarding the predictive power, IWI had high sensitivity (95.6%), specificity (40%), positive and negative predictive values (90.5% and 60), positive and negative likelihood ratios (1.59 and 0.11), and accuracy (86.7%).Conclusion:The IWI as a more objective indicator has acceptable accuracy and power for predicting the 2-h SBT result. Therefore, in addition to the reliable prediction of the final weaning outcome, it has favorable power to predict if the patient is ready to breathe spontaneously as the first step to weaning.

Spontaneous Breathing Trials in Patients Managed with a Sedation Protocol or a Sedation Protocol with Daily Interruption

Spontaneous Breathing Trials in Patients Managed with a Sedation Protocol or a Sedation Protocol with Daily Interruption

Utilization of Spontaneous Awakening Trials in Mechanically Ventilated Patients

SESSION TITLE: Mechanical Ventilation and Respiratory Failure Posters SESSION TYPE: Original Investigation Poster PRESENTED ON: Wednesday, October 28, 2015 at 01:30 PM - 02:30 PM PURPOSE: The purpose of this study is to establish current duration of time from intubation to first spontaneous awakening trial (SAT) and variables that may be associated with decreased likelihood of implementation of this intervention. These results will inform a clinical trial designed to increase adherence to daily spontaneous awakening and spontaneous breathing trials in patients with acute respiratory failure. METHODS: Patients from Northwestern Memorial Hospital (NMH), a tertiary academic medical center in Chicago, Illinois, and Northwestern Lake Forest Hospital, a community hospital affiliated with NMH located in an affluent suburb of Chicago, were included. Patients were excluded if they were less than 18 years of age at intubation, on the ventilator less than 12 hours, had a tracheostomy at time of hospital admission, suffered cardiac arrest immediately prior to or during their admission, were transitioned to comfort-focused care, or were managed on continuous intravenous sedation for alcohol withdrawal or delirium tremens. Based on power calculations, we collected data from the first 377 patients who were intubated in the intensive care units and met our inclusion criteria from June 23, 2013, to October 11, 2013. RESULTS: In our sample, mean age at intubation was 60.6 years, 153 (40.6%) were women, and 214 (56.8%) self-identified as white or Caucasian, 100 (26.5%) as black or African-American. Out of the 377 patients included in the analysis, 39 (10.3%) were never started on sedative infusions and of those who were started on infusions of sedatives (narcotics, benzodiazepines, and/or propofol), median time to first SAT (defined as at least 4 hours off all sedative infusions) was 40.6 hours. Of the patients started on sedative infusions, 270 (79.9%) did not receive an SAT within the first 24 hours of intubation. CONCLUSIONS: Median time to first SAT was substantially longer than recommended by most professional organizations and only a small number of patients had an SAT within the first 24 hours of intubation. CLINICAL IMPLICATIONS: Daily SATs are associated with reduced duration of mechanical ventilation and intensive care unit stay, and this data gives us evidence that adherence to this best practice is low and helps inform the design of a novel intervention to improve these rates. DISCLOSURE: The following authors have nothing to disclose: Margaret Ragland, Shayna Weiner, Curtis Weiss No Product/Research Disclosure Information

Different spontaneous breathing trials in patients with atrial fibrillation

IntroductionWeaning from mechanical ventilation is one of the most important and challenging problems for most intensive care unit (ICU) patients. Spontaneous breathing trial (SBT) is the most common method used to evaluate patients’ ability to breathe by themselves and plays an important role in decision making for weaning. The aim of our study was to investigate the effect of different methods of SBT in respiratory care unit (RCU) patients with atrial fibrillation (AF) on weaning outcome. MethodsWe retrospectively analyzed different methods of SBT in patients with and without AF. We enrolled RCU patients who required mechanical ventilation and had undergone transthoracic echocardiography from January 2011 to January 2012. ResultsThere was a higher SBT passing rate among AF patients who received pressure support ventilation (PSV) trial than in those who received T-piece trail (92.5% vs. 73.1%, p=0.041). The weaning rates between these two groups were not significantly different (83.8% vs. 94.7%, p=0.403). Total ventilator days were longer in T-piece group than in PSV group (median 40.0, IQR: 18.2–125.1 days vs. 33.0, IQR: 29.6–51.0 days respectively, p=0.580), but this difference was not statistically significant. These results were not found in patients without AF. ConclusionsThe use of PSV trial might be considered first instead of T-piece trial for SBT when AF patients were ready to wean.

Trend analysis of rapid shallow breathing indices during spontaneous breathing trial may improve predictive accuracy of extubation success

To determine the respiratory indices capable of improving predictive accuracy of extubation success through serial measurements of during spontaneous breathing trial (SBT) in automatic tube compensation (ATC) pattern of mechanical ventilation. For this prospective observational study, patients ventilated over 48 hours were enrolled according to the weaning criterion and underwent a 60 minutes spontaneous breathing trial (SBT) in ATC pattern (ATC = 100%, FiO2 = 0.4, PEEP = 0 cm H2O, PS = 0 cm H2O). During SBT, heart rate (HR) and mean artery pressure (MAP) were monitored continuously and minute volume (VE), respiratory rate (RR), tidal volume of spontaneous breath (VT), rapid shallow breathing index (RSBI), change and rate of change (ΔRSBI60_1 and ΔRSBI60_1/RSBI1, etc.) were recorded or calculated at the first, 30(th) and 60(th) minute of SBT. Patients tolerating the trial were extubated immediately. Clinical data and respiratory indices during SBT were compared between patients in extubation success group and those in extubation failure group. Predictive accuracy of extubation success was assessed by area under the receiver operating characteristic (ROC) curve (AUC) for each index. The duration of mechanical ventilation was longer in patients of extubation failure group than that of extubation success group (10.75 ± 2.73: 7.47 ± 5.11, P = 0.035) and extubation failure rate was 17.14%. During SBT, RSBI increased initially and then decreased in patients of extubation success group, but increased continuously in patients of extubation failure group. There were significant difference of ΔRSBI60_1 and ΔRSBI60_1/RSBI1 in patients between extubation success and failure groups (-11.5 ± 16.6: 12.1 ± 38.9, P = 0.001 and -17 ± 26: 13 ± 39, P = 0.028). AUCs of RSBI60, ΔRSBI60_1 and ΔRSBI60_1/RSBI1 were 0.75, 0.73 and 0.72 and the sensitivity, specificity and diagnostic accuracy 81.0%, 66.7% and 78.5% respectively. It is important to observe change of various respiratory indices dynamically during SBT in patients ventilated in ATC pattern. ΔRSBI60_1 and ΔRSBI60_1/RSBI1 have greater predictive value for extubation success. Stable or decreased RSBI60 means higher extubation success rate.

Increases in B-type natriuretic peptide for detecting weaning-induced heart failure: reply to Liu et al.

Dear Editor, We thank Liu et al. [1] for their comments on our study published in your journal [2] and would like to clarify the points raised. First, it is important to keep in mind that our study aimed to predict and diagnose the onset of heart failure (HF) during a spontaneous breathing trial (SBT). HF was predicted by determining BNP before the SBT (baseline BNP[263 ng/l, accuracy 68%), while HF was diagnosed during the SBT based on the changes in BNP (DBNP [48 ng/l, accuracy 88.9%). Second, the use of non-invasive ventilation (NIV) certainly reduces the need for reintubation by 16% [3], but only in a selected group of patients at risk of postextubation respiratory failure. In our study ten patients were reintubated, but only five could be considered ‘‘at risk’’ [3]. This means that less than one patient would have benefited from the prophylactic use of NIV. We do not therefore consider that this bias alters the interpretation of our results. Third, we agree that our SBT failure rate (32%), albeit within the range described in other studies [4], may seem high, especially compared with that of Segal et al. [5] (19%). This discrepancy, however, could be due to differences in populations. In our study the mean days of mechanical ventilation (MV) prior to SBT in patients who failed was 10 days, whereas in Segal’s study it was 6 days. This suggests that a greater proportion of patients in our study had weaning defined as difficult according to the international consensus conference [6]. In reply to the next point, we did not study mortality in our study. However, we observed that patients who failed their first SBT due to HF had a longer duration of MV and ICU stay. Predicting (baseline BNP) the onset of HF caused by the SBT allows for prompt treatment, possibly reducing the days of MV. A DBNP [48 ng/l during SBT is a non-invasive diagnostic indicator of HF, available 24 h a day. To answer Liu et al.’s question, we would like to point out that we did not analyze the following SBTs, so we do not possess any data that allow us to elucidate to what extent the patients may have benefited from diuretic and vasodilator treatment. Lastly, regarding their suggestion to combine analysis of HF at the end of the SBT with that appearing in the next 48 h after extubation, we consider such an approach would be erroneous for the following reasons. First, the two groups were not homogenous as the timing between blood tests was shorter in the patients failing the SBT than in the patients requiring reintubation within 48 h. Second, after succeeding in the SBT trial and until reintubation was necessary, patients requiring reintubation were on therapies that could alter natriuretic peptide concentrations. Third, the disease under study is HF during SBT. Therefore, even extubated patients that were reintubated because of HF should be considered ‘‘disease absent’’ (D-). Analysis of these patients would require a specific study design. Acknowledgments Reagents for natriuretic peptide analyses were kindly supplied by Biosite and Roche Diagnostics.

B-type natriuretic peptides for prediction and diagnosis of weaning failure from cardiac origin

To evaluate and compare BNP and NT-proBNP concentrations to predict weaning failure from mechanical ventilation (MV) due to heart failure (HF) before a spontaneous breathing trial (SBT) and to identify HF as the cause of failure. Prospective, observational study in a university hospital. The sample included 100 patients on MV for over 48 h who underwent an SBT. Echocardiography and sampling for natriuretic peptides were performed immediately before and at the end of SBT. HF was diagnosed by pulmonary artery occlusion pressure >18 mm Hg or signs of elevated filling pressures in echocardiography. Thirty-two patients failed the SBT, 12 due to HF and 20 due to respiratory failure (RF). Before SBT, BNP and NT-proBNP were higher in patients failing due to HF than RF or in successfully weaned patients. Cut-off values using ROC curve analyses to predict HF were 263 ng/L for BNP (p < 0.001) and 1,343 ng/L for NT-proBNP (p = 0.08). BNP and NT-proBNP increased significantly during SBT in patients failing due to HF. Increases in BNP and NT-proBNP of 48 and 21 ng/L, respectively, showed a diagnostic accuracy for HF of 88.9 and 83.3% (p < 0.001). BNP performed better than NT-proBNP for HF prediction (p = 0.01) and diagnosis (p = 0.009). B-type natriuretic peptides, particularly BNP, can predict weaning failure due to HF before an SBT; increases in natriuretic peptides during SBT are diagnostic of HF as the cause of weaning failure. BNP performs better than NT-proBNP in prediction and diagnosis of HF.

Reduced breathing variability as a predictor of unsuccessful patient separation from mechanical ventilation*

To compare descriptors of the breath-to-breath respiratory variability during a 60-min spontaneous breathing trial in patients successfully and unsuccessfully separated from the ventilator and the endotracheal tube and to assess the usefulness of these predictors in discriminating these two categories of patients. Prospective observational study. Four general intensive care units in university hospitals. A total of 51 consecutive patients mechanically ventilated for >24 hrs. None. Tidal volume, respiratory period, inspiratory time, expiratory time, mean inspiratory flow (tidal volume/inspiratory time), and duty cycle (inspiratory time/respiratory period) were obtained from the flow signal. Breath-by-breath variability was expressed in terms of their coefficients of variation (CV), the number of breaths among which a significant correlation was found (lag), and the autocorrelation coefficient between one breath and the following one. Five patients were excluded because of nonstationarity of the data, leaving 46 cases for analysis. Between-group comparison was conducted with the Mann-Whitney test, and a nonparametric classification and regression tree was used to identify variables discriminating "success" (n = 32) and "failure" patients (n = 14). All coefficients of variation were significantly higher in success patients, who also exhibited significantly less respiratory autocorrelation (shorter "short memory"). The classification and regression tree analysis allocated all success patients to a group defined by a coefficient of variation of tidal volume/inspiratory time of > or =19% and a coefficient of variation of inspiratory time/respiratory period of > or =10% that did not contain any failure patient. All failure patients belonged to a group with coefficient of variation of tidal volume/inspiratory time of <19%, a lag tidal volume of > or =11, and that contained no success patient. In intensive care unit patients undergoing a spontaneous breathing trial, breathing variability is greater in patients successfully separated from the ventilator and the endotracheal tube. Variability indices are sufficient to separate success from failure cases.