* adults \< 18 years. * indication for immediate orotracheal intubation. * pregnant woman / positive pregnancy test at the time of potential inclusion in the study. * chronic liver disease / liver cirrhosis child-pugh c. * confirmation of active bacterial or fungal infection. * uncontrolled hiv/aids disease (defined by presence of viral load \> 200 copies/ml). * previous history of copd gold c - d. * history of copd requiring hospitalization - hospitalization / icu in the last year. * known history of congestive heart failure nyha iii - iv. * left ventricular ejection fraction \< 45% previously known. * highly suspected or confirmed cardiogenic pulmonary edema. * hypercapnic respiratory failure (paco2 \> 55 mmhg). * central/peripheral demyelinating disorders due to medical history or high suspicion of these at the time of study eligibility. * patient who in the investigator's judgment suggests a progression to death is imminent and inevitable within the next 24 hours. * any serious medical condition or clinical laboratory test abnormality that, in the investigator's judgment, prevents safe patient participation and completion of the study. * participation in another clinical trial (except one related to sars-cov-2 - criteria to be discussed between group of researches).

* adults \< 18 years. * indication for immediate orotracheal intubation. * pregnant woman / positive pregnancy test at the time of potential inclusion in the study. * chronic liver disease / liver cirrhosis child-pugh c. * confirmation of active bacterial or fungal infection. * uncontrolled hiv/aids disease (defined by presence of viral load \> 200 copies/ml). * previous history of copd gold c - d. * history of copd requiring hospitalization - hospitalization / icu in the last year. * known history of congestive heart failure nyha iii - iv. * left ventricular ejection fraction \< 45% previously known. * highly suspected or confirmed cardiogenic pulmonary edema. * hypercapnic respiratory failure (paco2 \> 55 mmhg). * central/peripheral demyelinating disorders due to medical history or high suspicion of these at the time of study eligibility. * patient who in the investigator's judgment suggests a progression to death is imminent and inevitable within the next 24 hours. * any serious medical condition or clinical laboratory test abnormality that, in the investigator's judgment, prevents safe patient participation and completion of the study. * participation in another clinical trial (except one related to sars-cov-2 - criteria to be discussed between group of researches).

- adults < 18 years. - indication for immediate orotracheal intubation. - pregnant woman / positive pregnancy test at the time of potential inclusion in the study. - chronic liver disease / liver cirrhosis child-pugh c. - confirmation of active bacterial or fungal infection. - uncontrolled hiv/aids disease (defined by presence of viral load > 200 copies/ml). - previous history of copd gold c - d. - history of copd requiring hospitalization - hospitalization / icu in the last year. - known history of congestive heart failure nyha iii - iv. - left ventricular ejection fraction < 45% previously known. - highly suspected or confirmed cardiogenic pulmonary edema. - hypercapnic respiratory failure (paco2 > 55 mmhg). - central/peripheral demyelinating disorders due to medical history or high suspicion of these at the time of study eligibility. - patient who in the investigator's judgment suggests a progression to death is imminent and inevitable within the next 24 hours. - any serious medical condition or clinical laboratory test abnormality that, in the investigator's judgment, prevents safe patient participation and completion of the study. - participation in another clinical trial (except one related to sars-cov-2 - criteria to be discussed between group of researches).

- adults < 18 years. - indication for immediate orotracheal intubation. - pregnant woman / positive pregnancy test at the time of potential inclusion in the study. - chronic liver disease / liver cirrhosis child-pugh c. - confirmation of active bacterial or fungal infection. - uncontrolled hiv/aids disease (defined by presence of viral load > 200 copies/ml). - previous history of copd gold c - d. - history of copd requiring hospitalization - hospitalization / icu in the last year. - known history of congestive heart failure nyha iii - iv. - left ventricular ejection fraction < 45% previously known. - highly suspected or confirmed cardiogenic pulmonary edema. - hypercapnic respiratory failure (paco2 > 55 mmhg). - central/peripheral demyelinating disorders due to medical history or high suspicion of these at the time of study eligibility. - patient who in the investigator's judgment suggests a progression to death is imminent and inevitable within the next 24 hours. - any serious medical condition or clinical laboratory test abnormality that, in the investigator's judgment, prevents safe patient participation and completion of the study. - participation in another clinical trial (except one related to sars-cov-2 - criteria to be discussed between group of researches).