Predictors of Airway Extubation/Weaning Failure

Airway management in intensive care unit (ICU) patients is challenging. Benefit risk ratio of extubation has to be daily assessed in intubated patients. If the patient stay intubated too long, complications of prolonged mechanical ventilation may appear. If the patient is extubated too early, reintubation is associated with higher morbidity and mortality. "Airway failure", defined as the inability to breathe without endotracheal tube, differs from "weaning failure", defined as the inability to breathe spontaneously without invasive mechanical ventilation. "Mixed failure" occurs when extubation failure is caused by both airway and weaning failure. However, most of the studies assessing criteria of success of extubation did not separate airway from weaning success.

Study design and population A prospective, observational, multicenter study will be conducted in ICUs to develop a predictive model for airway failure following extubation. All adult patients consecutively intubated in ICU will be included. Exclusion criteria are pregnancy, refusal to participate after information was provided or age under 18 years old.

Ethics and consent Because of the observational, non invasive design of this study, the need for written consent is waived. The local ethics committee "Comité de Protection des personnes Sud-Mediterranée III" approved the study design (code UF: 9242, register: 2013-A01402-43).

Data collection Clinical parameters will be prospectively assessed before, during and after extubation procedure. In summary, the following data will be assessed before extubation : demographic data, body mass index (BMI), severity scores (Simplified Acute Physiologic Score (SAPS) II at admission, Sequential Organ Failure Assessment (SOFA) score on the day of the procedure), type of admission (medical vs surgical), co morbidities such as ethylism, smoking, cirrhosis, chronic obstructive pulmonary disease (COPD), cause of admission, cause and location of initial intubation, hypotension episode during the stay, difficulty of intubation, material used for intubation, Mallampati score, Cormack score, date and hour of extubation, a previous intubation in the last two weeks. Will be also assessed before extubation the type of spontaneous breathing trial (SBT), the use of a weaning mode before extubation, standard analysis, physiotherapy measurements, the assessment of agitation and answer to simple orders, the strength of cough, the perception of the extubation by the patient, a leak test before extubation, the blood results at the end of the SBTs, the succion rate and secretions aspect, the use of systemic corticotherapy before extubation.

Just before and during the extubation, sequential organ failure assessment (SOFA) score will be assessed, as the information of the patient, the nature and number of the operators, preoxygenation before extubation, precautions used in case of extubation failure.

Just after extubation, will be assessed physiotherapy after extubation, aerosols of corticoids or adrenalins post extubation, and the occurrence in the hour after extubation of complications. At 48 hours post extubation, the occurrence of reintubation will be evaluated, and its relation with airway failure, weaning failure, or both (mixed failure). In case of reintubation, the delay between extubation and reintubation will be informed, and the cause of reintubation. Finally, at ICU discharge, the mortality will be analyzed, the occurrence of late reintubation (>48h), the use and the length of mechanical or non invasive ventilation, the need for vasopressors or dialysis after extubation, the occurrence of a nosocomial pneumonia, a catheter infection, a bacteremia, a urinary infection. At the exit of the hospital, the mortality at day 28 following extubation will be assessed.

Definition of extubation failure, airway failure, weaning failure, mixed failure and complications Extubation failure is defined as the need to reintubate less than 48 hours after extubation. The need to reintubate was left to the physician appreciation in this observational study. Airway failure is defined as an extubation failure because of the inability to breathe without a tracheal tube. Weaning failure is defined as an extubation failure because of the inability to breathe without an invasive mechanical ventilation. Mixed failure is a combination of airway and weaning failure. Severe life-threatening complications are defined as death, cardiac arrest, severe cardiovascular collapse, defined as systolic blood pressure<65 mmHg recorded at least one time and/or <90 mmHg that lasted 30min despite 500-1,000 ml of fluid loading (crystalloids/or colloids solutions) and/or requiring introduction of vasoactive support, or severe hypoxemia (decrease in SpO2 below 80% during attempts), occurring during the first hour following intubation.

Outcomes The primary outcome are the risk factors for airway failure following extubation. The secondary outcomes are the risk factors of extubation failure, weaning failure and mixed failure, the incidence of extubation failure, airway failure, weaning failure and mixed failure, the severe life-threatening complications related to extubation in ICU, the moderate complications related to extubation in ICU, the rate of difficult intubation in case of extubation failure.

Statistical analysis Quantitative variables will be expressed as means (standard deviation) or medians (interquartiles 25%-75%) and compared using the student t test or the Wilcoxon test as appropriate (Gaussian or non Gaussian variables). Qualitative variables will be compared using the chi 2 test or the Fisher test as appropriate.

A logistic regression will be used to identify risk factors of airway failure. A multivariate model will be established.

A p-value of < and = 0.05 will be considered statistically significant. The statistical analysis will be performed by the medical statistical department of the Montpellier University Hospital with the help of statistical software (SAS, version 9.3; SAS Institute; Cary, NC and R, version 2.14.1).