Weaning from mechanical ventilation using pressure support or a T-tube for a spontaneous breathing trial

Patients with severe lung disease, such as acute respiratory failure, may require invasive mechanical ventilation through an endotracheal tube or tracheostomy until their underlying disease is either treated or stabilized. Both early suspension of or delay in withdrawing mechanical ventilation can however lead to complications that may delay the weaning of patients from mechanical ventilation and prolong their length of stay in the intensive care unit (ICU) and hospital. Previous studies and systematic reviews suggest that a weaning protocol should be implemented in order to make daily assessments of patients who may be ready for weaning from mechanical ventilation. The ability to breathe spontaneously can be assessed with a spontaneous breathing trial using a T-tube (T-piece) or by reducing the applied airway pressure to provide low levels of pressure support (PS) (5 to 10 cm H2O). After removal of the endotracheal tube (extubation) the patients are monitored for 48 hours. If over this period ventilatory support does not need to be reintroduced, this is taken to indicate successful weaning. For this Cochrane systematic review we searched the medical literature databases until June 2012 and included nine studies with 1208 adult patients who had been on invasive mechanical ventilation for at least 24 hours. The trials compared pressure support (PS) and the use of a T-tube (622 patients randomized to PS and 586 randomized to a T-tube). There was no clear evidence to confirm that PS was superior to a T-tube with regard to the success of weaning, need for reintubation, ICU mortality, and other factors including long-term weaning unit (LWU) length of stay, pneumonia and a rapid shallow breathing index. Among patients who received PS, a greater number of patients had a successful spontaneous breathing trial and the airway tube was removed. For respiratory rate and tidal volume outcomes PS was superior to using a T-tube in two trials. Three studies reported that the weaning duration was shorter during PS, and in one study in which patients submitted to a T-tube the weaning time was shorter. Because of limitations in the design of the studies and imprecision in the effect estimates we have rated the quality of the evidence to be low. We reran the search in December 2013. We will deal with any studies of interest when we update the review.

Authors' conclusions: 

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.

Read the full abstract...
Background: 

Mechanical ventilation is important in caring for patients with critical illness. 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).

Objectives: 

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.

Search strategy: 

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.

Selection criteria: 

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.

Data collection and analysis: 

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).

Main results: 

We included nine RCTs with 1208 patients; 622 patients were randomized to a PS spontaneous breathing trial (SBT) and 586 to 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 to the sequence of allocation generation, allocation concealment, selective reporting and attrition bias, no study 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.

Share/Save