title: Performance of noninvasive ventilation in acute respiratory failure in critically ill patients: a prospective, observational, cohort study.
abstract: BACKGROUND
  Noninvasive ventilation (NIV) is used in critically ill patients with acute respiratory failure (ARF) to avoid endotracheal intubation. However, the impact of NIV use on ARF patient's outcomes is still unclear. Our objectives were to evaluate the rate of NIV failure in hypoxemic patients with an arterial carbon dioxide partial pressure (PaCO2) < 45 mmHg or ≥ 45 mmHg at ICU admission, the predictors of NIV failure, ICU and hospital length of stay and 28-day mortality.
  
  
  METHODS
  Prospective single center cohort study. All consecutive patients admitted to a mixed ICU during a three-month period who received NIV, except for palliative care purposes, were included in this study. Demographic data, APACHE II score, cause of ARF, number of patients that received NIV, incidence of NIV failure, length of ICU, hospital stay and mortality rate were compared between NIV failure and success groups.
  
  
  RESULTS
  Eighty-five from 462 patients (18.4 %) received NIV and 26/85 (30.6 %) required invasive mechanical ventilation. NIV failure patients were comparatively younger (67 ± 21 vs. 77 ± 14 years; p = 0.031), had lower arterial bicarbonate (p = 0.005), lower PaCO2 levels (p = 0.032), higher arterial lactate levels (p = 0.046) and APACHE II score (p = 0.034) compared to NIV success patients. NIV failure occurred in 25.0 % of patients with PaCO2 ≥ 45 mmHg and in 33.3 % of patients with PaCO2 < 45 mmHg (p = 0.435). NIV failure was associated with an increased risk of in-hospital death (OR 4.64, 95 % CI 1.52 to 14.18; p = 0.007) and length [median (IQR)] of ICU [12 days (8-31) vs. 2 days (1-4); p < 0.001] and hospital [30 (19-42) vs. 15 (9-33) days; p = 0.010] stay. Predictors of NIV failure included age (OR 0.96, 95 % CI 0.93 to 0.99; p = 0.007) and APACHE II score (OR 1.13, 95 % CI 1.02 to 1.25; p = 0.018).
  
  
  CONCLUSIONS
  NIV failure was associated with an increased risk of in-hospital death, ICU and hospital stay and was not affected by baseline PaCO2 levels. Patients that failed were comparatively younger and had higher APACHE II score, suggesting the need for a careful selection of patients that might benefit from NIV. A well-designed study on the impact of a short monitored NIV trial on outcomes is needed.
authors.affiliation: Intensive Care Unit, Hospital Israelita Albert Einstein, Av. Albert Einstein, 627/701, 5° andar, São Paulo, CEP: 05651-901, Brazil. thiago.correa@einstein.br.
authors.forename: Thiago Domingos
authors.initials: TD
authors.lastname: Corrêa
authors.affiliation: Intensive Care Unit, Hospital Israelita Albert Einstein, Av. Albert Einstein, 627/701, 5° andar, São Paulo, CEP: 05651-901, Brazil. paula.sanches@einstein.br.
authors.forename: Paula Rodrigues
authors.initials: PR
authors.lastname: Sanches
authors.affiliation: Intensive Care Unit, Hospital Israelita Albert Einstein, Av. Albert Einstein, 627/701, 5° andar, São Paulo, CEP: 05651-901, Brazil. lubia.morais@einstein.br.
authors.forename: Lúbia Caus
authors.initials: LC
authors.lastname: de Morais
authors.affiliation: Intensive Care Unit, Hospital Israelita Albert Einstein, Av. Albert Einstein, 627/701, 5° andar, São Paulo, CEP: 05651-901, Brazil. farah.scarin@einstein.br.
authors.forename: Farah Christina
authors.initials: FC
authors.lastname: Scarin
authors.affiliation: Intensive Care Unit, Hospital Israelita Albert Einstein, Av. Albert Einstein, 627/701, 5° andar, São Paulo, CEP: 05651-901, Brazil. silva.eliezer@einstein.br.
authors.forename: Eliézer
authors.initials: E
authors.lastname: Silva
authors.affiliation: Intensive Care Unit, Hospital Israelita Albert Einstein, Av. Albert Einstein, 627/701, 5° andar, São Paulo, CEP: 05651-901, Brazil. carmen.barbas@gmail.com.|Pulmonary and Critical Care Division- INCOR, University of São Paulo, São Paulo, Brazil. carmen.barbas@gmail.com.
authors.forename: Carmen Sílvia Valente
authors.initials: CS
authors.lastname: Barbas
mesh_terms: D018806:APACHE; D000208:Acute Disease; D000368:Aged; D000369:Aged, 80 and over; D001784:Blood Gas Analysis; D001938:Brazil; D002245:Carbon Dioxide; D015331:Cohort Studies; D017714:Community-Acquired Infections / Q000150:complications / Q000628:therapy; D016638:Critical Illness / Q000401:mortality / Q000628:therapy*; D005260:Female; D017052:Hospital Mortality; D006801:Humans; D000860:Hypoxia / Q000097:blood / Q000209:etiology / Q000628:therapy*; D007362:Intensive Care Units; D007442:Intubation, Intratracheal / Q000706:statistics & numerical data*; D007902:Length of Stay; D008297:Male; D008875:Middle Aged; D009026:Mortality; D063087:Noninvasive Ventilation / Q000379:methods*; D010313:Partial Pressure; D011014:Pneumonia / Q000150:complications / Q000628:therapy; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications / Q000628:therapy; D011654:Pulmonary Edema / Q000150:complications / Q000628:therapy; D012121:Respiration, Artificial; D012128:Respiratory Distress Syndrome / Q000150:complications / Q000628:therapy; D012131:Respiratory Insufficiency / Q000097:blood / Q000209:etiology / Q000628:therapy*; D017211:Treatment Failure; D016896:Treatment Outcome
chemical_list: D002245:Carbon Dioxide