By Kathryn Radigan, MD, MSc

Attending Physician, Division of Pulmonary and Critical Care, Stroger Hospital of Cook County, Chicago

SYNOPSIS: Post-hoc analysis of a multicenter, randomized clinical trial among adults receiving at least 24 hours of mechanical ventilation who were ready for ventilator weaning revealed that the use of pressure support significantly increased the proportion of patients successfully extubated compared to T-piece.

SOURCE: Thille AW, Coudroy R, Nay MA, et al. Pressure-support ventilation vs T-piece during spontaneous breathing trials before extubation among patients at high risk of extubation failure: A post-hoc analysis of a clinical trial. Chest 2020;158:1446-1455.

Although T-piece still is the most frequently performed trial prior to extubation, guidelines suggest that an initial spontaneous breathing trial (SBT) should be conducted using pressure support ventilation (PSV) rather than a T-piece trial. This guideline was based on a large randomized controlled trial (RCT) that showed the proportion of patients who were extubated successfully 72 hours after an initial SBT was higher with PSV than with T-piece. Since this trial was thought to include mostly patients at low risk for extubation failure, Thille and colleagues performed a post-hoc analysis of a multicenter RCT from April 2017 to January 2018 among 641 adults who were intubated more than 24 hours, were ready for extubation after successful SBT, and deemed high risk for extubation failure in 30 intensive care units (ICUs) in France. The initial SBT was performed using PSV or T-piece according to either the physician’s or center’s decision. The primary outcome was the proportion of patients who were extubated successfully 72 hours after the initial SBT and not reintubated. High-risk patients were identified as patients older than 65 years of age or with underlying cardiac or respiratory disease. The underlying chronic cardiac diseases included left ventricular dysfunction (defined by left ventricular ejection fraction less than or equal to 45%), a history of cardiogenic pulmonary edema, documented ischemic heart disease, or permanent atrial fibrillation. The underlying chronic lung diseases included chronic obstructive pulmonary disease (COPD), obesity-hypoventilation syndrome, or restrictive pulmonary disease. The exclusion criteria were long-term treatment with noninvasive ventilation (NIV) at home, contraindication to NIV, underlying neuromuscular disease, traumatic brain injury leading to intubation, patients with unplanned extubation (accidental or self-extubation), or patients with a do-not-reintubate order at the time of extubation.

The initial SBT was accomplished with PSV (7 cm H2O in median without positive end-expiratory pressure [PEEP]) in 243 patients (38%) and with a T-piece in 398 patients (62%). The amount of patients who were extubated after the first attempt at SBT was 77% (186/283) in the PSV group and 63% (249/398) in the T-piece group (P = 0.0002). Sixty-seven percent (162/243) of patients in the PSV group remained successfully extubated 72 hours after initial SBT, compared to 56% (223/398) of patients in the T-piece group (absolute difference 10.6%; 95% confidence interval [CI], 2.8 to 28.1; P = 0.0076). Reintubation rates within the subsequent 72 hours did not differ significantly between the PSV and T-piece groups (13% vs. 10%, respectively, P = 0.4259). First attempt SBT with PSV was independently associated with successful extubation (adjusted odds ratio (OR), 1.60; 95% CI, 1.30 to 2.18; P = 0.0061).

COMMENTARY

Approximately 10% to 15% of all mechanically ventilated patients who are extubated will fail, and higher numbers are expected for those at particularly increased risk.1 SBT may be performed using T-piece (no inspiratory pressure augmentation) or using PSV (generally limited to 5 cm H2O to 8 cm H2O or automatic tube compensation). There has been controversy regarding which method is optimal.

Many argue that patients who demonstrate an ability to breathe while receiving no inspiratory pressure augmentation convincingly prove readiness to wean. Those who disagree stress that patients who otherwise may be extubated safely will fail an SBT without pressure augmentation but will pass with pressure support. In a systematic review and meta-analysis of 31 trials, it has been shown that patients undergoing SBTs using PSV vs. T-piece appear to be 6% (95% CI, 2% to 10%) more likely to be extubated successfully.2 The most recent international practice guidelines published in 2017 made a conditional recommendation (moderate quality of evidence) that the initial SBT be conducted with inspiratory pressure augmentation (5 cm H2O to 8 cm H2O) rather than without (T-piece or continuous positive airway pressure [CPAP]) for patients who are acutely hospitalized and ventilated for more than 24 hours.3 Shortly after these recommendations, Subirà and colleagues conducted a randomized clinical trial among 1,153 adults deemed ready for weaning after at least 24 hours of mechanical ventilation in 18 ICUs.4 They found that significantly higher rates of successful extubation occurred using an SBT consisting of 30 minutes of PSV than with two hours of T-piece ventilation. Unfortunately, there was concern that this trial included a majority of patients who were low risk for extubation failure. The current study, therefore, focused on high-risk patients.

It is important to point out that this study was a post-hoc analysis of a multicenter trial. Patient characteristics were similar between the two groups, except that the PSV group had a lower body mass index (BMI). The PSV trials were conducted using a pressure-support level of 7.0 cm H2O, a PEEP level of 0 cm H2O, and an FiO2 of 30%. The T-piece trials were conducted using an additional oxygen flow of 4 L/min. In addition, the PSV trials were longer than the T-piece trials (60 minutes vs. 50 minutes). This is in contrast to the Subirà article, in which PSV trials were substantially shorter than the T-piece trials.4 Among the 30 participating centers, six centers always performed SBT using PSV (114 patients, 18%), 11 centers always performed SBT using T-piece (229 patients, 36%), and 13 centers used PSV or T-piece (298 patients, 46%). Even though the physician had the opportunity to choose the type of SBT, the proportion of patients successfully extubated 72 hours after initial SBT was lower in the 11 centers that always performed T-piece trials compared to the six centers that always performed SBTs using PSV and the 13 centers that could also use PSV for SBTs (P = 0.0014). Since the proportion of patients who remained extubated 72 hours after the initial SBT was significantly higher in centers that only performed PSV trials compared to centers that only performed T-piece trials, the potential effect of bias is diminished to some extent.

The previously mentioned study by Subirà and colleagues had attending physicians decide on the extubation strategy (e.g., whether to reconnect the patient to the ventilator for one hour before extubation, or whether to administer NIV or high-flow nasal cannula after extubation).4 The physicians were not blinded, and more patients were provided with prophylactic high-flow nasal oxygen or NIV in the PSV SBT group (24.7% vs. 18.7%), which may have affected the results. It is an added benefit to the literature that the postextubation plan of care was randomized in this trial. Although the original study showed that NIV immediately after extubation decreased reintubation rates significantly in patients who were at high risk of extubation failure, the proportion of patients who received NIV after extubation was identical in the two groups.

Although it also is important to note that Thille’s data further support SBT with PSV, the question remains whether all patients will benefit from the same strategy. Interestingly, Thille and his group had equally distributed the patients with underlying chronic cardiac disease or lung disease between the PSV and T-piece groups. Unfortunately, it is not clear how many patients were known to have COPD and the severity of that COPD. One would consider that a patient with more severe emphysematous changes, a quite compliant state, may not respond to a PSV of 8 cm H2O the same as a patient with mild COPD without emphysematous changes. Although a trial published by Pellegrini and colleagues did not particularly address patients with emphysema, it revealed that T-piece almost doubled the time to liberation in the difficult/prolonged-weaning COPD subgroup, although it did not influence the overall or 48-hour reintubation rates.5 Even though underlying chronic cardiac disease also was distributed equally, the details regarding heart failure were not known. Small amounts of pressure support and PEEP may have significant hemodynamic effects and may reduce the work of breathing.6 Removal of this support after extubation may result in rapid deterioration of left ventricular function leading to pulmonary edema. Although trials overall are pointing to PSV as an ideal weaning mode, T-piece trials still may be considered in patients with impaired cardiac function or severe emphysematous COPD since it is possible that this mode may unmask the need for further optimization prior to extubation.

This study supports the practice of SBT using PSV since it may hasten extubation without the increased risk of reintubation, especially in patients who are at high risk of extubation failure. Prior to applying this strategy to all patients in the ICU, a larger prospective RCT may be warranted to confirm these findings since this trial was a post-hoc analysis. Interestingly, Thille and colleagues are conducting an investigator-initiated, multicenter RCT comparing T-piece to PSV for SBTs in critically ill patients at high risk of reintubation.7 This trial promises to give further clarity to this controversy.

REFERENCES

  1. Thille AW, Richard JC, Brochard L. The decision to extubate in the intensive care unit. Am J Respir Crit Care Med 2013;187:1294-1302.
  2. Burns KEA, Soliman I, Adhikari NKJ, et al. Trials directly comparing alternative spontaneous breathing trial techniques: A systematic review and meta-analysis. Crit Care 2017;21:127.
  3. Schmidt GA, Girard TD, Kress JP, et al. Official Executive Summary of an American Thoracic Society/American College of Chest Physicians Clinical Practice Guideline: Liberation from mechanical ventilation in critically ill adults. Am J Respir Crit Care Med 2017;195:115-119.
  4. Subira C, Hernandez G, Vazquez A, et al. Effect of pressure support vs T-piece ventilation strategies during spontaneous breathing trials on successful extubation among patients receiving mechanical ventilation: A randomized clinical trial. JAMA 2019;321:2175-2182.
  5. Santos Pellegrini JA, Boniatti MM, Boniatti VC, et al. Pressure-support ventilation or T-piece spontaneous breathing trials for patients with chronic obstructive pulmonary disease - A randomized controlled trial. PLoS One 2018;13:e0202404.
  6. Kuhn BT, Bradley LA, Dempsey TM, et al. Management of mechanical ventilation in decompensated heart failure. J Cardiovasc Dev Dis 2016;3.
  7. Thille AW, Coudroy R, Gacouin A, et al. 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). BMJ Open 2020;10:e042619.