Subira

Effect of Pressure Support vs T-Piece Ventilation Strategies During Spontaneous Breathing Trials on Successful Extubation Among Patients Receiving Mechanical Ventilation

Subira C et al. JAMA 2019;321(22):2175-2182. doi:10.1001/jama.2019.7234

Clinical Question

  • In patients weaning from mechanical ventilation, does a spontaneous breathing trial (SBT) with pressure support (PS) for 30 minutes vs a SBT with T-piece for 2 hours differ in the rate of successful liberation from mechanical ventilation (MV)?

Background

  • Weaning from MV accounts for up to 40% of time spent on MV and an SBT constitutes the gold standard diagnostic test to determine a patients’ readiness for extubation
  • Currently used SBT modalities include methods that provide ventilatory support, such as pressure support ventilation (5-8 cm H2O with or without PEEP), CPAP or automatic tube compensation; and methods without any ventilatory support, such as T-piece
  • Decades of research have been dedicated to finding the optimal protocolized SBT modality that best simulates physiologic conditions post-extubation, in order to infer a patients’ readiness to liberate from MV
  • Recent meta-analyses and guidance have been inconclusive or contradicting
  • Studies have shown that different SBT modalities and duration demonstrate no significant difference regarding success rate of extubation (PSV vs. T-piece for 2h, 30-minute vs. 2h PSV or 30-minute vs. 2h T-piece). The optimal SBT modality and duration to ascertain a patients’ readiness to be extubated remains unknown

Design

  • Multicenter prospective randomized control trial
  • Randomization was performed through a computerized random number tables and blinded blocks of 4 patients for each hospital
  • An estimated extubation success of 75%, with an increase in absolute success rate of 7%, an alpha error of 0.05 and a power of 80%, requires a sample size of 540 patients per group to detect a significant difference of successful extubation between groups
  • A prespecified interim analysis was performed when half of the sample was enrolled. There was a nonsignificant difference in successful extubation between groups
  • Analysis was performed using an intention-to-treat principle

Setting

  • 18 intensive care units in Spain
  • January 2016 to April 2017

Population

    • Inclusion: ≥ 18 years of age, met weaning criteria after at least 24 hours of mechanical ventilation
      • Suitable cough (Ability to raise secretions to the endotracheal tube) (or PiMax> -15 cmH2O)
      • Absence of excessive secretions (<3 aspirations in the last 8 hours)
      • Resolution or improvement of the pathology that led to intubation
      • Clinical stability (HR <140 bpm, SBP 90-160, without vasopressors or at minimum doses)
      • Adequate oxygenation (SatO2> 90% with FiO2 <0.4)
      • Adequate ventilatory mechanics (RR <35 rpm, MIP <-20 cmH2O, Vt> 5 ml / kg, VC> 10 ml/ kg, RR / VT <100 rpm/l)
      • Confident awareness level (Glasgow Coma Scale> 13)
    • Exclusion: Tracheostomy, do-not-reintubate orders, decision of the responsible physician (e.g., due to a preference for a particular weaning technique according to the underlying pathology), absence of informed consent, mental incapacity without legal representation
  • 2649 patients were assessed for eligibility, 1153 were randomized and included in primary analysis (575 for 30-min PS SBT and 578 for 2-h T-piece SBT)
  • Baseline characteristics: well-balanced for age, APACHE score on admission, reason for admission and days on MV before SBT. Most were medical ICU patients

Intervention

  • Low respiratory work strategy
    • Spontaneous Breathing Trial (SBT) with Pressure Support Ventilation (PSV)
    • PSV 8 cmH2O, PEEP 0 cmH2O for 30 minutes

Control

  • High respiratory work strategy
    • SBT with T-piece for 2 hours

Management common to both groups

  • FiO2: maintained the same as before the SBT
  • Postextubation non-invasive support: before SBT attending physician had to choose between providing ventilatory support with non-invasive ventilation or oxygenation support with high-flow nasal cannula or conventional low flow oxygen therapy
  • One-hour rest: patients could be rested for 1hr on mechanical ventilator prior to extubation
    • This was determined prior to randomization
  • Failure of SBT Criteria
    • Neurological causes: Agitation or anxiety. Low level of consciousness (Glasgow Coma Scale <13)
    • Increased respiratory work: use of accessory muscles, facial expression suggesting stress, severe dyspnea
    • Hypoxemia: PaO2 <60 mmHg or SatO2 <90% with FiO2 >0.5
    • Tachypnea: RR> 35 rpm
    • Hemodynamic instability: HR> 140 bpm or >20% from baseline; SBP >180 mmHg or >20% from baseline; SBT <90 mmHg; Cardiac arrhythmias

Outcome

  • Primary outcome: successful extubation, defined as remaining free of MV 72 h after the first SBT, was more frequent in the low respiratory work strategy group (SBT + PSV)
    • SBT+PSV: 82.3%
    • SBT+T-piece: 74%
    • Absolute Risk Reduction (ARR): 8.2% (95% CI 3.4-13%)
    • Kaplan-Meier curves show a higher successful extubation rate in SBT-PSV group
      • Hazard Ratio (HR) 1.54 (95% CI 1.19-1.97; P <0.001)
  • Secondary outcome: Comparing SBT+PSV vs SBT+T-piece
    • Successful extubation after first SBT: 92.5% vs 84.1%
      • Difference: 8.4 (95% CI 4. 7 to 12.1, P <0.001)
    • Reintubation within 72 h: 11.1% vs 11.9%
      • Difference: -0.8 (95% CI -4.8 to 3.1, P=0.63)
    • ICU length of stay: 9 days vs 10 days
      • Difference: -0.3 (95% CI -1.7 to 1.1, P=0.69)
    • Hospital length of stay: 24 days vs 24 days
      • Difference: 1.3 (95% CI -2.2 to 4.9, P=0.45)
    • Hospital mortality: 10.4% vs 14.9%
      • Difference: -4.4 (95% CI -8.3 to -0.6, P=0.02)
    • 90-Day mortality: 13.2% vs 17.3%
      • Difference: -4.1 (95% -8.2 to 0.01, P=0.04)
  • Exploratory outcome: comparing SBT+PSV vs SBT+T-piece
    • Time to reintubation: 23 hours vs 24.5 hours
    • Reason for reintubation: mostly due to excessive WOB, difficulty managing secretions and refractory hypoxemia
      • Well balanced between groups
    • Tracheostomy: 7.1% vs 8.7%
  • Post-hoc outcome:
    • ICU mortality: 5% vs 6.6%

Authors’ Conclusions

  • Among mechanically ventilated patients, an SBT consisting of 30 minutes of PSV, 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 SBTs

Strengths

  • Largest multi-center randomized controlled trial to asses an important clinical question
  • High adherence to specified protocol
  • Well-balanced baseline participant characteristics
  • Adequate methodology and sample size with sufficient power to test the trials’ hypothesis
  • Intention-to-treat analysis was performed
  • Fragility index of 21 for the primary outcome

Weaknesses

  • Investigators were not blinded to treatment randomization group
  • Post-extubation non-invasive support (HFNC or NIV) was not protocolized
    • The PSV 30-minute SBT received more post-extubation NIV or HFNC when compared to the T-piece 2-hour SBT (25% vs 19%; P=0.01) which could have skewed results favoring the PSV 30-minute SBT
  • One-hour rest prior to extubation was not standardized
  • Current practice favors 30-minute SBTs
    • Therefore, a comparison of 30-minute SBT PSV with 30-minute SBT T-piece more closely reflects current practice and generalizability
  • Protocol was only applied to a patients’ initial SBT
    • Therefore, the results cannot be applied to patients who failed their first SBT (a fairly common scenario)

The Bottom Line

  • A “less demanding” 30-minute SBT with PSV of 8 cmH2O is an efficient (more successful extubation rate) and safe (without increase in reintubation rate) initial screening SBT modality to ascertain a patients’ readiness to be liberated from MV
  • A “more demanding” 2-hour SBT with T-piece appears to be unnecessary and associated with fewer successful extubations
  • This trial does not inform whether a 30-minute SBT with either T-piece or PSV have similar outcomes
  • Based on this trial, I will continue to perform SBTs with 30-minutes of pressure augmentation support
  • Whether use of T-piece SBT over PSV in selected patients (with heart failure, severe COPD and neuromuscular weakness) where pressure support might obscure a patients’ ability to breathe remains unknown

External Links

Metadata

Summary author: Luisa Morales-Nebreda
Summary date: 03 Sept 2019
Peer-review editor: Duncan Chambler

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