The aim of the study is to determine the incidence of failure of extubation in high-risk patients using High Flow Nasal Cannula (HFNC) to prevent such failure in the Intensive Care Unit. A prospective cohort study was performed. To all adult patients receiving invasive mechanical ventilation ≥ 48 hours and ready for scheduled extubation according to tolerance of spontaneous breathing trial, with at least one of the criteria for high-risk for extubation failure (age greater than 65 years, hypoxemic acute respiratory failure as a cause of invasive mechanical ventilation, > 1 spontaneous ventilation test failed consecutive, history of chronic heart failure, history of chronic obstructive pulmonary disease or PaCO2> 45 mmHg, body mass index >30 kg/m2, post-operative solid organ transplantation), HFNC is applied for 24 hours. Demographic variables and clinical and gasometric parameters at the end of the spontaneous breathing trial, at 60 minutes, at 6 and 24 hours after the start of HFNC are recorded.

At the end of the successful spontaneous breathing trial, clinical and gasometric parameters will be recorded and extubation will be performed. HFNC is placed with a flow of 50 l / m (only the flow is reduced before intolerance, at 5 l / min but only up to 40 l / min). Inspiratory oxygen fraction (FiO2) initially at 1 and progressively decreases until pulse oximeter saturation (SpO2) ≥ 92% is achieved. Said configuration is maintained for 60 minutes. After this time, arterial blood samples are taken and clinical and gasometric parameters are recorded in the follow-up chart. Based on them, behavior to be followed is defined. If "Fault criteria" are presented, a higher ventilatory support will be initiated. If not, continue with HFNC for the next 23 hours without exception. In this period the initial flow is maintained (40 to 50 l / min) and the FiO2 is programmed according to the SpO2 objective (≥ 92%). At 6 o'clock a new clinical and gasometric evaluation and data loading is carried out. 24 hours after the start of HFNC, a blood gas sample is taken and clinical and gasometric parameters are recorded. Treatment with HFNC is only suspended if the "Failure criteria" or the "Interruption criteria" are met. In the presence of the "Failure Criteria" and prior to delivering a greater ventilatory support, the clinical and gasometric parameters are recorded in the spreadsheet.

The data of categorical variables will be presented as frequency and percentage, while in quantitative variables, after testing normality by Shapiro-Wilks test, they will be presented as mean and standard deviation or median and interquartile range depending on their distribution. For comparisons between groups, chi-square or Fisher tests will be used, depending on the frequency expected in discrete and categorical variables, and in the continuous T or Mann-Whitney tests, depending on the type of distribution and variance. To determine the factors of risk of failure to extubation, a logistic regression study will be carried out with a system of selection of variables by forward steps. The odds ratio and its 95% confidence intervals will be calculated. Variables that are significant in the univariate study (p value <0.2) will be included in the multiple logistic regression study.

Inclusion criteria:

- All adult patients receiving invasive mechanical ventilation ≥48 hours and ready for scheduled extubation according to tolerance of spontaneous breathing trial, with at least one of the following criteria for high-risk for extubation failure:

• Age greater than 65 years.
• Hypoxemic acute respiratory failure as a cause of invasive mechanical ventilation.
• >1 spontaneous ventilation test failed consecutive.
• History of chronic heart failure.
• History of chronic obstructive pulmonary disease or PaCO2 >45 mmHg.
• Body mass index >30 kg/m2.
• Post-operative solid organ transplantation.

Exclusion criteria:

• Need for orotracheal intubation and invasive mechanical ventilation (IOT / AVMI) according to the decision of the attending physician.
• Deterioration of the state of consciousness determined by Kelly Matthay's Scale >3.
• Hemodynamic instability: systolic blood pressure (TAS) <90 mmHg or TAM <65 mmHg despite receiving fluids and/ or vasopressors.
• Neuromuscular disease
• Neurocritical pathology.
• Epistaxis
• Skull base fracture, or inability to fix the HFNC.
• History of obstructive sleep apnea-hypopnea syndrome with indication and use of nocturnal continuous positive pressure.
• Participation in another research protocol of HFNC.

Elimination criteria

. Directives before or after the onset of a disease that limits the therapeutic effort and indicates not to intubate or perform cardiopulmonary resuscitation.

All adult patients receiving invasive mechanical ventilation ≥48 hours and ready for scheduled extubation according to tolerance of spontaneous breathing trial.