Pressure Support Ventilation in Neurosurgical Patients: Can We Safely Reduce Assistance? Evaluation of Neurosurgical Patients' Ventilation Distribution - The ENVISION Study

To compare cardiovascular and respiratory responses to different spontaneous breathing trials (SBT) in difficult-to-wean patients using T-piece and pressure support ventilation (PSV) with or without positive end-expiratory pressure (PEEP). Prospective physiological study. Fourteen patients who were monitored with a Swan-Ganz catheter and had failed a previous T-piece trial were studied. Three SBTs were performed in random order in all patients: PSV with PEEP (PSV-PEEP), PSV without PEEP (PSV-ZEEP), and T-piece. PSV level was 7 cmH(2)O, and PEEP was 5 cmH(2)O. Inspiratory muscle effort was calculated, and hemodynamic parameters were measured using standard methods. RESULTS [MEDIAN (AND INTERQUARTILE RANGE)]: Most patients succeeded in the PSV-PEEP (11/14) and PSV-ZEEP (8/14) trials, but all failed the T-piece trial. Patient effort was significantly higher during T-piece than during PSV with or without PEEP [esophageal pressure-time product was 292 (238-512), 128 (58-299), and 148 (100-465) cmH(2)O x s/min, respectively, p < 0.05]. Left ventricular heart failure was observed in 11 of the 14 patients during the T-piece trial. Pulmonary artery occlusion pressure and respiratory rate were significantly higher during T-piece than with PSV-PEEP [21 (18-24) mmHg versus 17 (14-22) mmHg, p < 0.05 and 27 (21-35) breaths/min versus 19 (16-29) breaths/min, p < 0.05 respectively]. Tidal volume was significantly lower during the T-piece trial. In this selected population of difficult-to-wean patients, PSV and PSV plus PEEP markedly modified the breathing pattern, inspiratory muscle effort, and cardiovascular response as compared to the T-piece. Caregivers should be aware of these differences in SBT as they may play an important role in weaning decision-making.

The influence of different spontaneous breathing trials on regional ventilation distribution in patients with prolonged mechanical ventilation

BackgroundRecent guidelines recommended conducting spontaneous breathing trial (SBT) with modest inspiratory pressure augmentation rather than T-piece or continuous positive airway pressure. However, it was based on few studies focused on the outcomes of extubation rather than the weaning process, despite the existence of various weaning situations in clinical practice. This study was designed to investigate the effects of SBT with pressure support ventilation (PSV) or T-piece on weaning outcomes.MethodsAll consecutive patients admitted to two medical intensive care units (ICUs) and those requiring mechanical ventilation (MV) for more than 24 h from November 1, 2017 to September 30, 2020 were prospectively registered. T-piece trial was used until March 2019, and then, pressure support of 8 cmH2O and 0 positive end-expiratory pressure were used for SBT since July 2019, after a 3-month transition period for the revised SBT protocol. The primary outcome of this study was successful weaning defined according to the WIND (Weaning according to a New Definition) definition and were compared between the T-piece group and PSV group. The association between the SBT method and weaning outcome was evaluated with logistic regression analysis.ResultsIn this study, 787 eligible patients were divided into the T-piece (n = 473) and PSV (n = 314) groups after excluding patients for a 3-month transition period. Successful weaning was not different between the two groups (85.0% vs. 86.3%; p = 0.607). However, the PSV group had a higher proportion of short weaning (70.1% vs. 59.0%; p = 0.002) and lower proportion of difficult weaning (13.1% vs. 24.1%; p < 0.001) than the T-piece group. The proportion of prolonged weaning was similar between the two groups (16.9% vs. 16.9%; p = 0.990). After excluding patients who underwent tracheostomy before the SBTs, similar results were found. Reintubation rates at 48 h, 72 h, and 7 days following the planned extubation were not different between the PSV and T-piece groups. Moreover, no significant differences in intensive care unit and hospital mortality and length of stay were observed.ConclusionsIn critically ill medical patients, SBT using PSV was not associated with a higher rate of successful weaning compared with SBT using T-piece. However, PSV could shorten the weaning process without increasing the risk of reintubation.

Daily spontaneous breathing trials (SBTs) are the best approach to determine whether patients are ready for disconnection from mechanical ventilation, but mode and duration of SBT remain controversial. To evaluate the effect of an SBT consisting of 30 minutes of pressure support ventilation (an approach that is less demanding for patients) vs an SBT consisting of 2 hours of T-piece ventilation (an approach that is more demanding for patients) on rates of successful extubation. Randomized clinical trial conducted from January 2016 to April 2017 among 1153 adults deemed ready for weaning after at least 24 hours of mechanical ventilation at 18 intensive care units in Spain. Follow-up ended in July 2017. Patients were randomized to undergo a 2-hour T-piece SBT (n = 578) or a 30-minute SBT with 8-cm H2O pressure support ventilation (n = 557). The primary outcome was successful extubation (remaining free of mechanical ventilation 72 hours after first SBT). Secondary outcomes were reintubation among patients extubated after SBT; intensive care unit and hospital lengths of stay; and hospital and 90-day mortality. Among 1153 patients who were randomized (mean age, 62.2 [SD, 15.7] years; 428 [37.1%] women), 1018 (88.3%) completed the trial. Successful extubation occurred in 473 patients (82.3%) in the pressure support ventilation group and 428 patients (74.0%) in the T-piece group (difference, 8.2%; 95% CI, 3.4%-13.0%; P = .001). Among secondary outcomes, for the pressure support ventilation group vs the T-piece group, respectively, reintubation was 11.1% vs 11.9% (difference, -0.8%; 95% CI, -4.8% to 3.1%; P = .63), median intensive care unit length of stay was 9 days vs 10 days (mean difference, -0.3 days; 95% CI, -1.7 to 1.1 days; P = .69), median hospital length of stay was 24 days vs 24 days (mean difference, 1.3 days; 95% CI, -2.2 to 4.9 days; P = .45), hospital mortality was 10.4% vs 14.9% (difference, -4.4%; 95% CI, -8.3% to -0.6%; P = .02), and 90-day mortality was 13.2% vs 17.3% (difference, -4.1% [95% CI, -8.2% to 0.01%; P = .04]; hazard ratio, 0.74 [95% CI, 0.55-0.99]). Among patients receiving mechanical ventilation, a spontaneous breathing trial consisting of 30 minutes of pressure support ventilation, compared with 2 hours of T-piece ventilation, led to significantly higher rates of successful extubation. These findings support the use of a shorter, less demanding ventilation strategy for spontaneous breathing trials. ClinicalTrials.gov Identifier: NCT02620358.

BackgroundNeurally Adjusted Ventilatory Assist (NAVA) is a proportional ventilatory mode that uses the electrical activity of the diaphragm (EAdi) to offer ventilatory assistance in proportion to patient effort. NAVA has been increasingly used for critically ill patients, but it has not been evaluated during spontaneous breathing trials (SBT). We designed a pilot trial to assess the feasibility of using NAVA during SBTs, and to compare the breathing pattern and patient-ventilator asynchrony of NAVA with Pressure Support (PSV) during SBTs.MethodsWe conducted a crossover trial in the ICU of a university hospital in Brazil and included mechanically ventilated patients considered ready to undergo an SBT on the day of the study. Patients underwent two SBTs in randomized order: 30 min in PSV of 5 cmH2O or NAVA titrated to generate equivalent peak airway pressure (Paw), with a positive end-expiratory pressure of 5 cmH2O. The ICU team, blinded to ventilatory mode, evaluated whether patients passed each SBT. We captured flow, Paw and electrical activity of the diaphragm (EAdi) from the ventilator and used it to calculate respiratory rate (RR), tidal volume (VT), and EAdi. Detection of asynchrony events used waveform analysis and we calculated the asynchrony index as the number of asynchrony events divided by the number of neural cycles.ResultsWe included 20 patients in the study. All patients passed the SBT in PSV, and three failed the SBT in NAVA. Five patients were reintubated and the extubation failure rate was 25% (95% CI 9–49%). Respiratory parameters were similar in the two modes: VT = 6.1 (5.5–6.5) mL/Kg in NAVA vs. 5.5 (4.8–6.1) mL/Kg in PSV (p = 0.076) and RR = 27 (17–30) rpm in NAVA vs. 26 (20–30) rpm in PSV, p = 0.55. NAVA reduced AI, with a median of 11.5% (4.2–19.7) compared to 24.3% (6.3–34.3) in PSV (p = 0.033).ConclusionsNAVA reduces patient-ventilator asynchrony index and generates a respiratory pattern similar to PSV during SBTs. Patients considered ready for mechanical ventilation liberation may be submitted to an SBT in NAVA using the same objective criteria used for SBTs in PSV.Trial registrationClinicalTrials.gov (NCT01337271), registered April 12, 2011.

BackgroundPredicting complete liberation from mechanical ventilation (MV) is still challenging. Electrical impedance tomography (EIT) offers a non-invasive measure of regional ventilation distribution and could bring additional information.Research question.Whether the display of regional ventilation distribution during a Spontaneous Breathing Trial (SBT) could help at predicting early and successful liberation from MV.Study design and methodsPatients were monitored with EIT during the SBT. The tidal image was divided into ventral and dorsal regions and displayed simultaneously. We explored the ventral-to-dorsal ventilation difference in percentage, and its association with clinical outcomes. Liberation success was defined pragmatically as passing SBT followed by extubation within 24 h without reintubation for 7 days. Failure included use of rescue therapy, reintubation within 7 days, tracheostomy, and not being extubated within 24 h after succesful SBT. A training cohort was used for discovery, followed by a validation cohort.ResultsAmong a total of 98 patients analyzed, 85 passed SBT (87%), but rapid liberation success occurred only in 40; 13.5% of extubated patients required reintubation. From the first minutes to the entire SBT duration, the absolute ventral-to-dorsal difference was consistently smaller in liberation success compared to all subgroups of failure (p < 0.0001). An absolute difference at 5 min of SBT > 20% was associated with failure of liberation, with sensitivity and specificity of 71% and 78% and positive predictive value 81% in a validation cohort.ConclusionDuring SBT, a large ventral-to-dorsal difference in ventilation indicated by EIT may help to rapidly identify patients at risk of liberation failure.

Introduction: Diaphragm weakness occurs after mechanical ventilation (MV), termed ventilator-induced diaphragmatic dysfunction. Weaning must balance diaphragmatic loading as well as prevention of overload after MV. The weaning methods pressure support ventilation (PSV) and spontaneous breathing trials (SBT) lead to gradual or intermittent reloading of an injured diaphragm. The trial investigated which weaning method allows more efficient restoration of diaphragm homeostasis. Methods: Rats (n=32) received 12h of MV followed by either 12h of pressure support ventilation (PSV) or intermittent spontaneous breathing trails (SBT) or rats were directly euthanized after 12h MV (CMV). Acutely euthanized rats served as controls (CON). Diaphragm force generation, activity of calpain-1, caspase-3 (proteolysis), oxidative modification in proteins (oxyblot) and lipids (4-HNE) (all Western blot) were detected. Normally distributed data were analyzed by 2-way or 1-way ANOVA. Results: MV resulted in a reduction of diaphragmatic force compared to CON (p=0.034). PSV and SBT further decreased contractility compared to CMV and CON (both p Discussion: MV resulted in a loss of diaphragmatic contractility, which was aggravated in SBT and PSV. This could indicate muscle overload during weaning. We could detect a reduction of oxidized proteins in SBT, while in PSV we found a reduction in caplain-1 and oxidized lipids and proteins. This might indicate a more efficient recovery by PSV compared to SBT.

A spontaneous breathing trial (SBT) is recommended to help patients to liberate themselves from mechanical ventilation as soon as possible in the ICU. The respiratory workload in SBT, which depends on being with or without respiratory support and a specific time, is more accurate to reflect how much support the weaning patients need compared with only considering SBT technologies. To compare and rank the effectiveness of different respiratory workloads during SBT via differing technologies (Pressure Support Ventilation and T-piece) and differing duration (30 and 120 min) in SBTs. A comprehensive literature search was performed in six English electronic databases to identify eligible randomized controlled trials (RCTs) published before September 2020. The pooled risk ratio (RR) with 95% confidence interval (CI) was calculated by Markov chain Monte Carlo methods. A Bayesian network meta-analysis was conducted using "gemtc" version 0.8.2 of R software. Each intervention's ranking possibilities were calculated using the surface under the cumulative ranking analysis (SUCRA). A total of nine RCTs including 3115 participants were eligible for this network meta-analysis involving four different commonly used SBT strategies and four outcomes. The only statistically significant difference was between Pressure Support Ventilation (PSV) 30 min and T-piece 120 min in the outcome of the rate of success in SBTs (RR=0.91; 95% CI, 0.84-0.98). The cumulative rank probability showed that the rate of success in SBT from best to worst was PSV 30 min, PSV 120 min, T-piece 30 min and T-piece 120 min. PSV 30 min and PSV 120 min are more likely to have a higher rate of extubation (SUCRA values of 82.5% for 30 min PSV, 70.7% for 120 min PSV, 36.4% for T-piece 30 min, 10.4% for T-piece 120). Meanwhile, T-piece 120 min (SUCRA, 62.9%) and PSV 120 min (SUCRA, 60.9%) may result in lower reintubation rates, followed by T-piece 30 min (SUCRA, 41.8%) and PSV 30 min (SUCRA, 34.4%). In comprehensive consideration of four outcomes, regarding SBT strategies, 30-min PSV was superior in simple-to-wean patients. Besides, 120-min T-piece and 120-min PSV are more likely to achieve a lower reintubation rate. Thus, the impact of duration is more significant among patients who have a high risk of reintubation. It is still unclear whether the SBTs affect the outcome of mortality; further studies may need to explore the underlying mechanism.

Comparing lung aeration and respiratory effort using two different spontaneous breathing trial: T-piece vs pressure support ventilation

Comparing lung aeration and respiratory effort using two different spontaneous breathing trial: T-piece vs pressure support ventilation

BackgroundPendelluft, the movement of gas within different lung regions, is present in animal models of assisted mechanical ventilation and associated with lung overstretching. Due to rebreathing of CO2 as compared to fresh gas, pendelluft might reduce ventilatory efficiency possibly exacerbating patient’s respiratory workload during weaning. Our aim was to measure pendelluft by electrical impedance tomography (EIT) in patients who failed a spontaneous breathing trial (SBT).MethodsThis is an observational study conducted in a general intensive care unit of a tertiary-level teaching hospital. EIT signal was recorded in 20 patients while pressure support (PS) ventilation was progressively reduced from clinical level (baseline) to 2 cmH2O, as in an SBT; four ventral-to-dorsal lung regions of interest were identified for pendelluft measurement. A regional gas movement (> 6 mL) occurring in a direction opposite to the global EIT signal was considered diagnostic for high pendelluft.ResultsEight patients out of 20 (40%) were classified as high-pendelluft; baseline clinical characteristics did not differ between high- and low-pendelluft patients. At PS reduction, pendelluft and EtCO2 increased more in the high-pendelluft group (p < .001 and .011, respectively). The volume of gas subject to pendelluft moved almost completely from the ventral towards the dorsal lung regions, while the opposite movement was minimal (16.3 [10:32.8] vs. 0 [0:1.8] mL, p = .001). In a subgroup of patients, increased pendelluft volumes positively correlated with markers of respiratory distress such as increased respiratory rate, p0.1, and EtCO2.ConclusionsOccult pendelluft can be measured by EIT, and is frequently present in patients failing an SBT. When present, pendelluft increases with the reduction of ventilator support and is associated with increased EtCO2, suggesting a reduction of the ability to eliminate CO2.

Additional work of breathing and breathing patterns in spontaneously breathing patients during pressure support ventilation, automatic tube compensation and amplified spontaneous pattern breathing

BackgroundThe aim of this study is to assess whether a strategy combining spontaneous breathing trial (SBT) with both pressure support (PS) and positive end-expiratory pressure (PEEP) and extended use of post-extubation non-invasive ventilation (NIV) (extensively-assisted weaning) would shorten the time until successful extubation as compared with SBT with T-piece (TP) and post-extubation NIV performed in selected patients as advocated by guidelines (standard weaning), in difficult-to-wean patients from mechanical ventilation.MethodsThe study is a single-center prospective open label, randomized controlled superiority trial with two parallel groups and balanced randomization with a 1:1 ratio. Eligible patients were intubated patients mechanically ventilated for more than 24 h who failed their first SBT using TP. In the extensively-assisted weaning group, SBT was performed with PS (7 cmH2O) and PEEP (5 cmH2O). In case of SBT success, an additional SBT with TP was performed. Failure of this SBT-TP was an additional criterion for post-extubation NIV in this group in addition to other recommended criteria. In the standard weaning group, SBT was performed with TP, and NIV was performed according to international guidelines. The primary outcome criterion was the time between inclusion and successful extubation evaluated with a Cox model with adjustment on randomization strata.ResultsFrom May 2019 to March 2023, 98 patients were included and randomized in the study (49 in each group). Four patients were excluded from the intention-to-treat population (2 in both groups); therefore, 47 patients were analyzed in each group. The extensively-assisted weaning group had a higher median age (68 [58–73] vs. 62 [55–71] yrs.) and similar sex ratio (62% male vs. 57%). Time until successful extubation was not significantly different between extensively-assisted and standard weaning groups (median, 172 [50–436] vs. 95 [47–232] hours, Cox hazard ratio for successful extubation, 0.88 [95% confidence interval: 0.55–1.42] using the standard weaning group as a reference; p = 0.60). All secondary outcomes were not significantly different between groups.ConclusionAn extensively-assisted weaning strategy did not lead to a shorter time to successful extubation than a standard weaning strategy.Trial registration The trial was registered on ClinicalTrials.gov (NCT03861117), on March 1, 2019, before the inclusion of the first patient. https://clinicaltrials.gov/study/NCT03861117.

Mechanical ventilation is important in caring for patients with criticalillness. Clinical complications, increased mortality, and high costs of health care are associated with prolonged ventilatory support or premature discontinuation of mechanical ventilation. Weaning refers to the process of gradually or abruptly withdrawing mechanical ventilation. The weaning process begins after partial or complete resolution of the underlying pathophysiology precipitating respiratory failure and ends with weaning success (successful extubation in intubated patients or permanent withdrawal of ventilatory support in tracheostomized patients). To evaluate the effectiveness and safety of two strategies, a T-tube and pressure support ventilation, for weaning adult patients with respiratory failure that required invasive mechanical ventilation for at least 24 hours, measuring weaning success and other clinically important outcomes. We searched the following electronic databases: Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2012, Issue 6); MEDLINE (via PubMed) (1966 to June 2012); EMBASE (January 1980 to June 2012); LILACS (1986 to June 2012); CINAHL (1982 to June 2012); SciELO (from 1997 to August 2012); thesis repository of CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) (http://capesdw.capes.gov.br/capesdw/) (August 2012); and Current Controlled Trials (August 2012).We reran the search in December 2013. We will deal with any studies of interest when we update the review. We included randomized controlled trials (RCTs) that compared a T-tube with pressure support (PS) for the conduct of spontaneous breathing trials and as methods of gradual weaning of adult patients with respiratory failure of various aetiologies who received invasive mechanical ventilation for at least 24 hours. Two authors extracted data and assessed the methodological quality of the included studies. Meta-analyses using the random-effects model were conducted for nine outcomes. Relative risk (RR) and mean difference (MD) or standardized mean difference (SMD) were used to estimate the treatment effect, with 95% confidence intervals (CI). We included nine RCTs with 1208 patients; 622 patients were randomizedto a PS spontaneous breathing trial (SBT) and 586to a T-tube SBT. The studies were classified into three categories of weaning: simple, difficult, and prolonged. Four studies placed patients in two categories of weaning. Pressure support ventilation (PSV) and a T-tube were used directly as SBTs in four studies (844 patients, 69.9% of the sample). In 186 patients (15.4%) both interventions were used along with gradual weaning from mechanical ventilation; the PS was gradually decreased, twice a day, until it was minimal and periods with a T-tube were gradually increased to two and eight hours for patients with difficult and prolonged weaning. In two studies (14.7% of patients) the PS was lowered to 2 to 4 cm H2O and 3 to 5 cm H2O based on ventilatory parameters until the minimal PS levels were reached. PS was then compared to the trial with the T-tube (TT).We identified 33 different reported outcomes in the included studies; we took 14 of them into consideration and performed meta-analyses on nine. With regard tothe sequence of allocation generation, allocation concealment, selective reporting and attrition bias, nostudy presented a high risk of bias. We found no clear evidence of a difference between PS and TT for weaning success (RR 1.07, 95% CI 0.97 to 1.17, 9 studies, low quality of evidence), intensive care unit (ICU) mortality (RR 0.81, 95% CI 0.53 to 1.23, 5 studies, low quality of evidence), reintubation (RR 0.92, 95% CI 0.66 to 1.26, 7 studies, low quality evidence), ICU and long-term weaning unit (LWU) length of stay (MD -7.08 days, 95% CI -16.26 to 2.1, 2 studies, low quality of evidence) and pneumonia (RR 0.67, 95% CI 0.08 to 5.85, 2 studies, low quality of evidence). PS was significantly superior to the TT for successful SBTs (RR 1.09, 95% CI 1.02 to 1.17, 4 studies, moderate quality of evidence). Four studies reported on weaning duration, however we were unable to combined the study data because of differences in how the studies presented their data. One study was at high risk of other bias and four studies were at high risk for detection bias. Three studies reported that the weaning duration was shorter with PS, and in one study the duration was shorter in patients with a TT. To date, we have found evidence of generally low quality from studies comparing pressure support ventilation (PSV) and with a T-tube. The effects on weaning success, ICU mortality, reintubation, ICU and LWU length of stay, and pneumonia were imprecise. However, PSV was more effective than a T-tube for successful spontaneous breathing trials (SBTs) among patients with simple weaning. Based on the findings of single trials, three studies presented a shorter weaning duration in the group undergoing PS SBT, however a fourth study found a shorter weaning duration with a T-tube.

BackgroundPreservation of spontaneous breathing (SB) is sometimes debated because it has potentially both negative and positive effects on lung injury in comparison with fully controlled mechanical ventilation (CMV). We wanted (1) to verify in mechanically ventilated patients if the change in transpulmonary pressure was similar between pressure support ventilation (PSV) and CMV for a similar tidal volume, (2) to estimate the influence of SB on alveolar pressure (Palv), and (3) to determine whether a reliable plateau pressure could be measured during pressure support ventilation (PSV).MethodsWe studied ten patients equipped with esophageal catheters undergoing three levels of PSV followed by a phase of CMV. For each condition, we calculated the maximal and mean transpulmonary (ΔPL) swings and Palv.ResultsOverall, ΔPL was similar between CMV and PSV, but only loosely correlated. The differences in ΔPL between CMV and PSV were explained largely by different inspiratory flows, indicating that the resistive pressure drop caused this difference. By contrast, the Palv profile was very different between CMV and SB; SB led to progressively more negative Palv during inspiration, and Palv became lower than the set positive end-expiratory pressure in nine of ten patients at low PSV. Finally, inspiratory occlusion holds performed during PSV led to plateau and Δ PL pressures comparable with those measured during CMV.ConclusionsUnder similar conditions of flow and volume, transpulmonary pressure change is similar between CMV and PSV. SB during mechanical ventilation can cause remarkably negative swings in Palv, a mechanism by which SB might potentially induce lung injury.Electronic supplementary materialThe online version of this article (doi:10.1186/s13054-016-1290-9) contains supplementary material, which is available to authorized users.