title: Evaluation of the dead space to tidal volume ratio as a predictor of extubation failure.
abstract: OBJECTIVE
  The objective of this study was to evaluate the ratio of dead space to tidal volume (VD/VT) as a predictor of extubation failure of children from mechanical ventilation.
  
  
  METHODS
  From September 2001 to January 2003 we studied a cohort consisting of all children (1 day-15 years) submitted to mechanical ventilation at a pediatric intensive care unit who were extubated and for whom pre-extubation ventilometry data were available, including the VD/VT ratio. Extubation success was defined as no need for any type of ventilatory support, invasive or otherwise, within 48 hours. Patients who tolerated extubation, with or without noninvasive support, were defined as success-R and compared with those who were reintubated. Statistic analysis was based on a VD/VT cutoff point of 0.65.
  
  
  RESULTS
  During the study period 250 children received mechanical ventilation at the pediatric intensive care unit. Eighty-six of these children comprised the study sample. Twenty-one children (24.4%) met the criteria for extubation failure, with 11 (12.8%) of these requiring non-invasive support and 10 (11.6%) reintubation. Their mean age was 16.8 (+/-30.1) months (median = 5.5 months). The mean VD/VT ratio for all cases was 0.62 (+/-0.18). Mean VD/VT ratios for patients with successful and failed extubations were 0.62 (+/-0.17) and 0.65 (+/-0.21) (p = 0.472), respectively. Logistic regression failed to reveal any statistically significant correlation between VD/VT ratio and success or failure of extubation (p = 0.8458), even for patients who were reintubated (p = 0.5576).
  
  
  CONCLUSIONS
  In a pediatric population receiving mechanical ventilation due to a variety of etiologies, the VD/VT ratio was unable to predict the populations at risk of extubation failure or of reintubation.
authors.affiliation: Faculdade de Medicina, Universidade de São Paulo. abousso@terra.com.br
authors.forename: Albert
authors.initials: A
authors.lastname: Bousso
authors.forename: Bernardo
authors.initials: B
authors.lastname: Ejzenberg
authors.forename: Andréa Maria Cordeiro
authors.initials: AM
authors.lastname: Ventura
authors.forename: José Carlos
authors.initials: JC
authors.lastname: Fernandes
authors.forename: Iracema Cássia de Oliveira
authors.initials: IC
authors.lastname: Fernandes
authors.forename: Patrícia Freitas
authors.initials: PF
authors.lastname: Góes
authors.forename: Flávio Adolfo Costa
authors.initials: FA
authors.lastname: Vaz
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D015278:Intensive Care Units, Pediatric; D007442:Intubation, Intratracheal / Q000592:standards; D008297:Male; D012126:Respiratory Dead Space / Q000502:physiology*; D012131:Respiratory Insufficiency / Q000628:therapy*; D013990:Tidal Volume / Q000502:physiology*; D017211:Treatment Failure; D015300:Ventilator Weaning / Q000009:adverse effects / Q000592:standards*