Rapid Shallow Breathing Index Research Articles

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Introduction: Successful liberation from mechanical ventilation remains a clinical dilemma when considering predictive factors. This involves evaluating quantitative parameters and qualitative experience of the patient. Spontaneous breathing trials (SBT), which measure aspects of pulmonary function such as respiratory rate and tidal volumes, have been demonstrated as an effective means for assessing weaning probability, albeit more a predictor of failure than success. The limitations of these evaluators may periodically at times be associated with the patient experience of agitation and anxiety while on ventilatory support. Traditional guidelines recommend cessation of all sedatives during weaning, which in turn may amplify the impact of these factors. This study aims to expose a category of patients who may benefit from concurrent sedation to levels that would lead to acceptable SBT demonstration of pulmonary function, affording reasonable opportunity for liberation from mechanical ventilation. Methods: A retrospective chart review was conducted on surgical intensive care unit (SICU) patients using the following inclusion criteria: mechanically ventilated patients at least 18 years old, who failed spontaneous breathing trial (SBT) per our institution protocol. Patients were otherwise hemodynamically stable and without identifiable active pathophysiologic processes contributing to prolonged ventilator dependence. Failure to wean was then attributed to excess anxiety and agitation and the patients underwent repeat SBT along with continuous sedation. Successful weaning was defined as extubation followed by at least 24 hours without reintubation. Results: Twenty-seven patients were identified. One male was excluded. Of the remaining, 22 (84.6%) were successfully weaned and extubated, 4 failed and ultimately required tracheostomy. Both groups were similar regarding hemodynamic status, arterial blood gas values, vent duration and APACHE II Score. Mean Rapid Shallow Breathing Index (RSBI) was 33.86 for all subjects. Glasgow Coma Scale (GCS) for success vs. failures was: 10.73T vs 10.0T (p=0.018). Confidence intervals did overlap between groups. Richmond Agitation and Sedation Scale (RASS) for successes vs. failures was: -0.27 vs. -1.5 (p=0.080). Conclusions: Reliably predicting successful extubation remains imperfect. Despite present guidelines to withdraw all sedation prior to SBT, there exists a potential subgroup of mechanically ventilated patients who could not be confidently liberated unless given a continuous level of mild sedation. This intervention would provide adequate means for patients to overcome the inherently noxious experience of ventilatory support and provide an opportunity to demonstrate their capacity for weaning success. Based on this feasibility study, further exploration of this cohort of immoderately agitated and anxious patients is warranted and may yield a unique exception to currently held precedent.

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Introduction: Respiratory failure (RF) following extubation is common after critical illness. Rapid shallow breathing patterns are ineffective and lead to increased work and RF. However, its conversion to a metric (rapid-shallow breathing index) failed to predict weaning failure. We used a continuous, piezoelectric, under-the-mattress sensor plate (EarlySense Inc) to record chest wall motion-generated complex waveforms in order to identify respiratory patterns characteristic or predictive of RF. Methods: Study design and patient population: Prospective, observational study recording waveforms 24/7 with a continuous, non-invasive piezoelectric sensor monitoring technology while the patients were intubated/mechanically ventilated with PSV and up to 24Hr after extubation. Adult critically ill surgical patients (37; or their surrogates) were consented for the study. Analysis: Two patient cohorts were studied: those who successfully extubated and those who failed (end-points of failure: reintubation, tracheostomy or death). The periods (6.5–24 hours) prior to extubation and (9–24 hours) following extubation were studied. The recordings were analyzed by an algorithm for abnormal patterns that correlate with respiratory outcomes and confirmed by visual examination of the raw signals. Results: Healthy respiratory pattern (normal frequency, minimally variable amplitude) is prevalent for those successfully extubated. Three forms of non-reassuring respiratory patterns were seen with those who failed extubation: 1. Generalized dys-organized respirations; 2.Frequent occurrences [every 30–120 sec] of a single high amplitude gasping breath; 3. Multiple periods of apnea >30sec. Positive patients had a cumulative duration of non-reassuring pattern at least twice as long as their periods with normal respiratory pattern during the entire recording period. After extubation, non-reassuring respiratory patterns will identify those patients likely to require ventilatory support (90% specificity, 50% sensitivity, PPV:60%, NPV:86%). Non-reassuring respiratory patterns prior to extubation show 91% specificity, 44% sensitivity, PPV:78%, NPV:71%). Conclusions: A pattern of unstable respirations (apparent in inconsistent chest wall motion amplitude) has been found to precede and correlate with respiratory failure. For ventilated patients this non-reassuring pattern (seen in PSV mode) may indicate that a patient is not ready for extubation. In the case of recently extubated patients, the pattern may indicate a need for interventions to prevent re-intubation. These conclusions will be tested in a prospective study to further validate their utility for clinical decision making.

Feasibility and Interest of Continuous Diaphragmatic Fatigue Monitoring Using Wavelet Denoising in ICU and Anesthesia

Measures of diaphragmatic electromyography (Edi), and respiratory mechanics, have demonstrated early changes before clinical complications. However, automatic Edi data collection is not adequate today due mainly to severe artefacts as well as to loss of signal. We thus intended to develop a new device with embedded artificial intelligence to optimize automatic Edi recordings independantly of artefacts and of probe displacement. We first chose the best mathematical tool to denoise Edi, using an established database, giving multiresolution wavelets as the best, resulting in the permanent availability of the H/L spectral index, a recognized representative of diaphragmatic fatigue. Fatigue was simultaneously measured using the classical mechanical f/Vt index (Rapid Shallow Breathing Index, RSBI), as well as the transdiaphragmatic pressure. We then performed a comparison of real-time H/L and RSBI in a group of seven healthy volunteers, before and during midazolam sedation infusion 0.1 mg.kg-1, with a parallel CPAP administration (2.5, 5.0, and 10 cm H2O) intended to compensate for airways resistance due to midazolam. Procedure was ended by delivering the antagonistic flumazenil 0.2 to 0.5 mg.kg-1. Progressive fatigue due to midazolam, the relief due to CPAP, as well as the answer to the anatgonist flumazenil, were shown earlier by the H/L index than by the RSBI change. Our new H/L monitoring device may greatly improve clinical follow-up of anesthetized patients as well as help to determine the optimal period for ventilatory weaning in ICU (Clinical Trials NCT00133939).

Prediction of Extubation Success in Myasthenic Crisis Using Bedside Functional Residual Capacity Measurement: A Prospective Feasibility Study

Address for Correspondence / Yaz›flma Adresi: Mehmet Akif Topcuoglu, MD, Department of Neurology, Faculty of Medicine, Hacettepe University, Ankara, Turkey Phone: +90 312 305 18 06 e.mail: mat@hacettepe.edu.tr doi:10.5152/dcbybd.2012.09 Aim: Extubation failure often complicates the recovery phase of a myasthenic crisis (MC). Bedside functional residual capacity (FRC) is a relatively new technique shown to be promising in the improvement of ventilation management in the intensive care unit (ICU), and may have a role in the estimation of extubation success. Since the prediction of extubation success is difficult due to the absence of formally evaluated disease-specific criteria, the appropriateness of any strategy described for non-neuromuscular conditions should be validated for specific neuromuscular diseases such as MC. In accordance, we designed a pilot study to determine the feasibility of bedside FRC measurement in the prediction of extubation success in MC and to determine its yield when added to the conventional parameters. Material and Methods: We prospectively studied the additive value of bedside FRC measurements to predict extubation outcome in 11 MC episodes. The area under the receiver operating characteristic curve (ROC AUC), sensitivity and specificity of all weaning and extubation indices that passed exploratory analysis were determined. Results: The frequency of extubation failure, defined as the need for reinstitution of ventilatory support within 72 hours of planned endotracheal tube removal, was 55% in this study population, in which all patients met the standard weaning indices indicating safety of extubation. The risk of extubation failure was connected to higher airway pressures (peak inspiratory and plato pressures; PIP and Pplato; ROC AUCs: 0.933 and 0.917), increased gradient of end-tidal CO2 to arterial CO2 (CO2 gradient; ROC AUC:0.900) and total airway care score (ACS; ROC AUC:0.983), but not to FRC, the simplified acute physiology score (SAPS-II) and the traditional weaning criteria such as the rapid shallow breathing index (RSBI) and mouth occlusion pressure (P0.1). Although perhaps useful when measurable, the utility of maximal inspiratory/expiratory mouth pressures (MIP and MEP) was also low due to the inability of MC patients to perform the maneuvers required to obtain these parameters. In contrast, FRC measurement was easily attainable at the bedside, with zero risk to the patient and correlated well to the aerated lung volume measured by chest CT (r=0.717). Conclusion: This preliminary study suggests that bedside FRC measurement is safe and feasible for long-term monitoring of intubated myasthenic patients. Its utility in determining weaning and extubation outcomes requires further studies with larger samples. Standard weaning parameters may not be accurate enough in the prediction of extubation outcome in MC, probably reflecting differences in the pathophysiology of failure of extubation and weaning. As a new semi-objective measurement of pulmonary secretion status, ACS can be helpful in the identification of the risk of extubation failure. (Yogun Bakim Derg 2012; 3: 36-42)

Comparison of Serial Rapid Shallow Breathing Index to Serial CROP Index in Prediction of Weaning Outcome in Critical Care Patients

Background :Recent data comparing several weaning parameters (RSBI,Cdyn,CStat,Pimax,CROP) concluded that CROP index has the highest predictive power for weaning outcome. It is the purpose of this study to compare serial RSBI with CROP in predicting weaning outcome. Methodology: This is a Prospective Cohort study done in the Philippine Heart Center Critical Care units done from December 2011-November 2012 . Patients aged >18yo on mechanical ventilator for >48hours and capable of being weaned.RSBI and serial CROP index was taken 30 minutes, 60minutes and 120minutes pre-extubation. ABG was taken at the of each cycle. Extubation is considered a success if patient is able to sustain spontaneous breathing for >48 hours. Results: There was a total of 56patients, in the study.It was observed that increasing trend of CROP predicted weaning success while increasing RSBI was related to weaning failure. There were 5patients who were bridged with NIV. These patients had low CROPscores. This maybe due to critical illness myopathy. Cut off value for both parameters were determined and revealed a sensitivity 72.1% and specificity 76.9% for CROP≥0.1. RSBI value≥ 53 had 67.4% sensitivity and 69.2% specificity. AUC yielded 0.6 for RSBI and 0.7 for CROP having a greater value is more predictive. Conclusion: Trends of weaning parameters can detect subtle changes in respiratory endurance. An increasing RSBI was noted in weaning failures. Conversely, an increasing CROP can predict weaning success. In this study, RSBI has 67.4% sensitivity and 69.2% specificity compared to CROP with sensitivity 72.1% and specificity 76.9%. CROP is a better predictor for weaning success.

The Effect of Flow Trigger on Rapid Shallow Breathing Index Measured Through the Ventilator

The rapid shallow breathing index (RSBI) has the best predictive value to assess readiness for weaning from mechanical ventilation. At many institutions, this index is conveniently measured without disconnecting the patient from the ventilator, but this method may be inaccurate. Because modern ventilators have a base flow in the flow trigger mode that may provide a substantial help to the patient, we hypothesized that the RSBI is significantly decreased when measured through the ventilator with flow trigger even without continuous positive airway pressure (CPAP) and pressure support (PS). The RSBI was calculated using the values of minute ventilation and respiratory rate obtained either through the digital display of the ventilator or from a digital ventilometer. The RSBI was measured using 3 different methods: method 1, CPAP and PS both 0 cm H2O with flow trigger; method 2, CPAP and PS both 0 cm H2O without flow trigger; and method 3, using digital ventilometer. A total of 165 measurements per method were obtained in 80 adult patients in the medical intensive care unit (MICU). The RSBI (breaths/min/L) values were 70.2 ± 26.5 with method 1, 85.4 ± 30.3 with method 2, and 80.1 ± 30.3 with method 3. The RSBI was significantly decreased using mechanical ventilation with flow trigger as compared with mechanical ventilation without flow trigger (P < .0001) or digital ventilometer (P < .0001). When method 1 was compared with methods 2 and 3, the RSBI decreased by 17% and 12%, respectively. The RSBI measurement is significantly decreased by the base flow delivered through modern ventilators in the flow trigger mode. If RSBI is measured through the ventilator in the flow trigger mode, the difference should be considered when using RSBI to assess readiness for weaning from mechanical ventilation.

The Use of Extubation Readiness Parameters: A Survey of Pediatric Critical Care Physicians

The pediatric literature addressing extubation readiness parameters and strategies to wean from mechanical ventilation is limited. We designed a survey to assess the use of extubation readiness parameters among pediatric critical care physicians at academic centers in the United States. The overall response rate was 44.1% (417/945). The majority of respondents check for air leak and the amount of tracheal secretions. Fewer respondents use sedation score, the rapid shallow breathing index, or the airway-occlusion pressure 0.1 s after the start of inspiratory flow prior to extubation. The majority perform a spontaneous breathing trial with pressure support. The majority consider 30 cm H2O as the upper limit of an air leak test, and the need for endotracheal suctioning once every 2-4 hours as acceptable for extubation. In preparation for termination of mechanical ventilation the majority daily wean the ventilator rate and/or the pressure support instead of conducting a spontaneous breathing trial. Most pediatric critical care physicians reported assessing extubation readiness by checking air leak and suctioning need, and less often consider or perform sedation score or the rapid shallow breathing index.

Predictors of Reintubation in Critically Ill Patients

Assessment of a patient's readiness for removal of the endotracheal tube in the ICU is based on respiratory, airway, and neurological measures. However, nearly 20% of patients require reintubation. We created a prediction model for the need for reintubation, which incorporates variables importantly contributing to extubation failure. This was a cohort study of 2,007 endotracheally intubated subjects who required ICU admission at a tertiary care center. Data collection included demographic, hemodynamic, respiratory, and neurological variables preceding extubation. Data were compared between subjects extubated successfully and those who required reintubation, using bivariate logistic regression models, with the binary outcome reintubation and the baseline characteristics as predictors. Multivariable logistic regression analysis with robust variance was used to build the prediction model. Of the 2,007 subjects analyzed, 376 (19%) required reintubation. In the bivariate analysis, admission Simplified Acute Physiology Score II, minute ventilation, breathing frequency, oxygenation, number of prior SBTs, rapid shallow breathing index, airway-secretions suctioning frequency and quantity, heart rate, and diastolic blood pressure differed significantly between the extubation success and failure groups. In the multivariable analysis, higher Simplified Acute Physiology Score II and suctioning frequency were associated with failed extubation. The area under the receiver operating characteristic curve was 0.68 for failure at any time, and 0.71 for failure within 24 hours. However, prior failed SBT, minute ventilation, and diastolic blood pressure were additional independent predictors of failure at any time, whereas oxygenation predicted extubation failure within 24 hours. A small number of independent variables explains a substantial portion of the variability of extubation failure, and can help identify patients at high risk of needing reintubation. These characteristics should be incorporated in the decision-making process of ICU extubation.

Inspiratory muscle training did not accelerate weaning from mechanical ventilation but did improve tidal volume and maximal respiratory pressures: a randomised trial

Does inspiratory muscle training accelerate weaning from mechanical ventilation? Does it improve respiratory muscle strength, tidal volume, and the rapid shallow breathing index? Randomised trial with concealed allocation and intention-to-treat analysis. 92 patients receiving pressure support ventilation were included in the study and followed up until extubation, tracheostomy, or death. The experimental group received usual care and inspiratory muscle training using a threshold device, with a load of 40% of their maximal inspiratory pressure with a regimen of 5 sets of 10 breaths, twice a day, 7 days a week. The control group received usual care only. The primary outcome was the duration of the weaning period. The secondary outcomes were the changes in respiratory muscle strength, tidal volume, and the rapid shallow breathing index. Although the weaning period was a mean of 8 hours shorter in the experimental group, this difference was not statistically significant (95% CI -16 to 32). Maximal inspiratory and expiratory pressures increased in the experimental group and decreased in the control group, with significant mean differences of 10cmH2O (95% CI 5 to 15) and 8cmH2O (95% CI 2 to 13), respectively. The tidal volume also increased in the experimental group and decreased in the control group (mean difference 72 ml, 95% CI 17 to 128). The rapid shallow breathing index did not differ significantly between the groups. Inspiratory muscle training did not shorten the weaning period significantly but it increased respiratory muscle strength and tidal volume.

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.

Association between the rapid shallow breathing index and extubation success in patients with traumatic brain injury

ObjectiveTo investigate the association between the rapid shallow breathing index and successful extubation in patients with traumatic brain injury. MethodsThis study was a prospective study conducted in patients with traumatic brain injury of both genders who underwent mechanical ventilation for at least two days and who passed a spontaneous breathing trial. The minute volume and respiratory rate were measured using a ventilometer, and the data were used to calculate the rapid shallow breathing index (respiratory rate/tidal volume). The dependent variable was the extubation outcome: reintubation after up to 48 hours (extubation failure) or not (extubation success). The independent variable was the rapid shallow breathing index measured after a successful spontaneous breathing trial. ResultsThe sample comprised 119 individuals, including 111 (93.3%) males. The average age of the sample was 35.0±12.9 years old. The average duration of mechanical ventilation was 8.1±3.6 days. A total of 104 (87.4%) participants achieved successful extubation. No association was found between the rapid shallow breathing index and extubation success. ConclusionThe rapid shallow breathing index was not associated with successful extubation in patients with traumatic brain injury.

Acupressure Improves the Weaning Indices of Tidal Volumes and Rapid Shallow Breathing Index in Stable Coma Patients Receiving Mechanical Ventilation: Randomized Controlled Trial

Background. Acupressure has been shown to improve respiratory parameters. We investigated the effects of acupressure on weaning indices in stable coma patients receiving mechanical ventilation. Methods. Patients were randomly allocated to one of three treatments: standard care with adjunctive acupressure on one (n = 32) or two days (n = 31) and standard care (n = 31). Acupressure in the form of 10 minutes of bilateral stimulation at five acupoints was administered per treatment session. Weaning indices were collected on two days before, right after, and at 0.5 hrs, 1 hr, 1.5 hrs, 2 hrs, 2.5 hrs, 3 hrs, 3.5 hrs, and 4 hrs after the start of treatment. Results. There were statistically significant improvements in tidal volumes and index of rapid shallow breathing in the one-day and two-day adjunctive acupressure study arms compared to the standard care arm immediately after acupressure and persisting until 0.5, 1 hr, and 2 hrs after adjustment for covariates. Conclusions. In the stable ventilated coma patient, adjunctive acupressure contributes to improvements in tidal volumes and the index of rapid shallow breathing, the two indices most critical for weaning patients from mechanical ventilation. These effects tend to be immediate and likely to be sustained for 1 to 2 hours.

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Introduction: Though multiple methods to predict successful extubation exist, minute ventilation has traditionally been disregarded in favor of rapid shallow breathing index (RSBI). This study was undertaken to determine if, amongst patients in a surgical intensive care unit, minute ventilation prior to extubation is higher in patients who required early reintubation. Hypothesis: We hypothesized that, amongst patients meeting standard criteria for extubation, high minute ventilation (MV) prior to extubation would be associated with increased risk for early failure. Methods: This retrospective cohort study assessed all patients admitted to the surgical intensive care unit at LAC/USC hospital who required mechanical ventilation and had at least one attempt at extubation over a 1-year period. Patients who died without attempted extubation, those with tracheostomies, and patients who self-extubated were excluded. Demographics, APACHE-II score, respiratory rate, and tidal volume were collected. MV was calculated from values recorded immediately prior to extubation. Failed extubation attempts were considered for this study if re-intubation occurred within 12 hours. Logistic regression, adjusted for age and APACHE II score was used to assess for the independent contribution of MV to failed extubation. Results: Over the study period, 161 patients met our inclusion criteria. The mean age of patients was 37 years (SD 17.3) and the mean APACHE score was 12 (SD 5). There were a total of 27 (17%) failed extuabtions. Patients who failed extubation had a significantly higher pre-extubation MV than those who were successful extubated (6643ml vs 5903ml, p=0.02). After adjusting for age and APACHE-II score, higher MV remained a significant predictor of failed extubation (p=0.01). Conclusions: Though RSBI is a useful indicator of successful extubation, it fails to consider the potential for fatigue that occurs with high minute ventilation requirements. For patients at the high end of adequate RSBI, high MV may identify patients who will tire, requiring early reintubation. This is the first study to assess high MV as predictor of failed extubation, and further prospective studies are warranted.

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

PurposeExtubation 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. MethodsEighty-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). ResultsFrom 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. ConclusionsPatients who successfully tolerate extubation have longer interbreath interval with greater complexity and variability of that series. Although the VT 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.

Cough strength, secretions and extubation outcome in burn patients who have passed a spontaneous breathing trial

The aim of this study was to develop a clinical prediction model to inform decisions about the timing of extubation in burn patients who have passed a spontaneous breathing trial (SBT). Rapid shallow breathing index, voluntary cough peak flow (CPF) and endotracheal secretions were measured after each patient had passed a SBT and just prior to extubation. We used multiple logistic regression analysis to identify variables that predict extubation outcome. Seventeen patients failed their first trials of extubation (14%). CPF and endotracheal secretions are strongly associated with extubation outcome (p<0.0001). Patients with CPF≤60L/min are 9 times as likely to fail extubation as those with CPF>60L/min (risk ratio=9.1). Patients with abundant endotracheal secretions are 8 times as likely to fail extubation compared to those with no, mild and moderate endotracheal secretions (risk ratio=8). Our clinical prediction model combining CPF and endotracheal secretions has strong predictive capacity for extubation outcome (area under receiver operating characteristic curve=0.96, 95% confidence interval 0.91–0.99) and therefore may be useful to predict which patients will succeed or fail extubation after passing a SBT.

The Weaning Index as Predictor of Weaning Success

The quest to obtain an accurate way to predict success when weaning a patient from mechanical ventilation continues. The established parameters such as tidal volume (Vt), respiratory rate (f), negative inspiratory force (NIF), vital capacity (VC), and minute ventilation (V) have not predicted weaning accurately. The frequency-to-tidal volume ratio (f/Vt), or rapid shallow breathing index (RSBI) is a good predictor of weaning success if the value is low, but not when the value approximates 105. Because of the aforementioned, we decided to add 2 corrective factors to the RSBI. The first one was elastance index (EI = peak pressure/NIF) and the second one, the ventilatory demand index (VDI = minute ventilation/10). The result of the product of the RSBI × EI × VDI was called the weaning index (WI). In order to assess the discriminatory power of WI, we obtained weaning parameters and calculated WI for 59 patients in our intensive care unit and extubated them if RSBI was ≤105. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and receiver-operating characteristics (ROC) curves were obtained. The results were compared with the previous studies involving the RSBI. The WI sensitivity was 98%, specificity was 89%, PPV was 95%, NPV was 94%, and area under the ROC curve was 95.9. The WI is a simple and reproducible parameter that integrates breathing pattern, compliance, inspiratory muscle strength, and ventilatory demand and is the most accurate predictor of weaning success.

Low pressure support changes the rapid shallow breathing index (RSBI) in critically ill patients on mechanical ventilation

The rapid shallow breathing index (RSBI) is the most widely used index within intensive care units as a predictor of the outcome of weaning, but differences in measurement techniques have generated doubts about its predictive value. To investigate the influence of low levels of pressure support (PS) on the RSBI value of ill patients. Prospective study including 30 patients on mechanical ventilation (MV) for 72 hours or more, ready for extubation. Prior to extubation, the RSBI was measured with the patient connected to the ventilator (DragerTM Evita XL) and receiving pressure support ventilation (PSV) and 5 cmH2O of positive end expiratory pressure or PEEP (RSBI_MIN) and then disconnected from the VM and connected to a Wright spirometer in which respiratory rate and exhaled tidal volume were recorded for 1 min (RSBI_ESP). Patients were divided into groups according to the outcome: successful extubation group (SG) and failed extubation group (FG). Of the 30 patients, 11 (37%) failed the extubation process. In the within-group comparison (RSBI_MIN versus RSBI_ESP), the values for RSBI_MIN were lower in both groups: SG (34.79±4.67 and 60.95±24.64) and FG (38.64±12.31 and 80.09±20.71; p<0.05). In the between-group comparison, there was no difference in RSBI_MIN (34.79±14.67 and 38.64±12.31), however RSBI_ESP was higher in patients with extubation failure: SG (60.95±24.64) and FG (80.09±20.71; p<0.05). In critically ill patients on MV for more than 72h, low levels of PS overestimate the RSBI, and the index needs to be measured with the patient breathing spontaneously without the aid of pressure support.

The Rapid Shallow Breathing Index as a Predictor of Failure of Noninvasive Ventilation for Patients With Acute Respiratory Failure

Noninvasive ventilation (NIV) may reduce the need for intubation in acute respiratory failure (ARF). However, there is no standard method to predict success or failure with NIV. The rapid shallow breathing index (RSBI) is a validated tool for predicting readiness for extubation. We evaluated the ability of the RSBI to predict failure of NIV and mortality in ARF. Prospective, observational trial of patients with ARF treated with NIV. NIV was initiated at the discretion of the clinicians, and an RSBI was recorded on the initial level of support (designated as assisted RSBI [aRSBI]). Patients were categorized by initial aRSBI value as either high (aRSBI > 105) or low (aRSBI ≤ 105). The primary end point was need for intubation, and the secondary end point was in-hospital mortality. Patients in the low and high aRSBI groups were compared using univariate analysis, followed by multivariable logistic regression to determine the association between aRSBI groups and outcome. A total of 101 patients were included. The majority of patients had an inspiratory pressure of 5-10 cm H(2)O in addition to an expiratory pressure of 5-8 cm H(2)O. Of 83 patients with an aRSBI ≤ 105, 26 (31%) required intubation, compared to 10/18 (55%) with an aRSBI > 105 (multivariate odds ratio 3.70, 95% CI 1.14-11.99, P = .03). When comparing mortality, 7/83 patients (8.4%) with an aRSBI ≤ 105 died, compared to 6/18 (33%) patients in the group with an aRSBI > 105 (multivariate odds ratio 4.51, 95% CI 1.19-17.11, P = .03). An aRSBI of > 105 is associated with need for intubation and increased in-hospital mortality. Whether patients with an elevated aRSBI could also have benefitted from an increase in NIV settings remains unclear. Validation of this concept in a larger patient population is warranted.

Diaphragm electromyographic activity as a predictor of weaning failure

To compare breathing pattern descriptors and diaphragm electromyographic activity (EAdi)-derived indices obtained from a neurally adjusted ventilatory assist catheter during a spontaneous breathing trial (SBT) in patients successfully and unsuccessfully separated from the ventilator and to assess their performance as a potential marker to discriminate these two categories of patients. Fifty-seven ready-to-wean patients were included in a prospective observational study. During a 30-min SBT (pressure support 7cmH(2)O, zero end expiratory pressure), tidal volume (V (T)) and respiratory rate (RR) were obtained from the flow signal at baseline and at 3, 10, 20 and 30min during the SBT. EAdi-derived indices were simultaneously computed: maximum of the EAdi (EAdi(max)), area under the inspiratory curve of EAdi (EAdi(AUC)), the difference between EAdi(max) and EAdi(min) (∆EAdi), EAdi(max)/V (T), EAdi(AUC)/V (T) and ∆EAdi/V (T). Patients, successfully (success group; n=35) and unsuccessfully (failure group; n=22) separated from the ventilator were compared. At baseline, the breathing pattern was similar in the two groups, whereas EAdi(max) and EAdi(AUC) were significantly lower in the success group (p<0.05). In the failure group, RR and RR/V (T) increased significantly during the trial, V (T) decreased, whereas EAdi(max) and EAdi(AUC) did not change. At 3min, the areas under the receiver operating characteristic-curve of RR/V (T) and the EAdi-derived indices to predict weaning outcome were 0.83 for the rapid shallow breathing index (RSBI), 0.84 for EAdi(max)/V (T) , 0.80 for EAdi(AUC)/V (T) (0.80) and 0.82 for ∆EAdi/V (T). The coefficient of variation for V (T) decreased in the failure group while that for EAdi(max) remained unchanged. EAdi-derived indices provide reliable and early predictors of weaning outcome. However, the performance of these indices is not better than the RR/V (T).

Acute Kidney Injury on Ventilator Initiation Day Independently Predicts Prolonged Mechanical Ventilation in Intensive Care Unit Patients

Purpose: The purpose of this study is to identify the predictors for prolonged mechanical ventilation (PMV) of more than 21 days among intensive care unit (ICU) patients. Material and Methods: A retrospective observational study was conducted in a respiratory ICU from December 2008 to November 2009. The outcome measurement was the occurrence of PMV. Acute kidney injury (AKI) was identified and defined as an increase in the serum creatinine level of 50% or greater from baseline. Results: Of154patientsenrolled,41patients(26.6%)hadPMV.PatientswithPMVshowedhigherAcute Physiology and Chronic Health Evaluation II scores, lower serum albumin levels, and more AKI on mechanicalventilation(MV)initiationdaycomparedwiththenon-PMVpatients.PatientswithPMVwere significantly associated with longer MV duration before the day of readiness for weaning (DRW) and a higher rapid shallow breathing index on DRW. In a multivariate regression analysis, the independent risk factors for PMV were AKI on MV initiation day (odds ratio [OR], 5.630; 95% confidence interval [CI], 1.378-22.994; P = .016), longer MV duration before DRW (OR, 1.289; 95% CI, 1.158-1.435; P b .001), and higher rapid shallow breathing index on DRW (OR, 1.012; 95% CI, 1.003-1.021; P = .010). Conclusions:AcutekidneyinjuryonMVinitiationdayisanindependentriskfactorforPMVofmorethan 21 days, which may be helpful for clinicians to refine their management of these ICU patients early.