title: Dead space ventilation in critically ill children with lung injury.
abstract: OBJECTIVE
  In children with acute lung injury, there is an increase in minute ventilation (E) and inefficient gas exchange due to a high level of physiologic dead space ventilation (VD/VT). Mechanical ventilation with positive end-expiratory pressure, when used in critically ill patients to correct hypoxemia, may contribute to increased VD/VT. The purpose of this study was to measure metabolic parameters and VD/VT in critically ill children.
  
  
  METHODS
  A cross-sectional study.
  
  
  METHODS
  Pediatric ICU of a university hospital.
  
  
  METHODS
  A total of 45 mechanically intubated children (mean age, 5.5 years).
  
  
  METHODS
  Indirect calorimetry was used to measure metabolic parameters. VD/VT parameters were calculated using the modified Bohr-Enghoff equation. ARDS was defined based on criteria by The American-European Consensus Conference.
  
  
  RESULTS
  The group mean (+/- SD) ventilatory equivalent for oxygen (VeqO(2)) and ventilatory equivalent for carbon dioxide (VeqCO(2)) were 2.9 +/- 1 and 3.3 +/- 1 L per 100 mL, respectively. The group mean VD/VT was 0.48 +/- 0.2. When compared to non-ARDS patients (33 patients), the patients with ARDS (12 patients) had a significantly higher VeqO(2) (3.3 +/- 1 vs 2.8 +/- 1 L per 100 mL, respectively; p < 0.05), a significantly higher VeqCO(2) (3.7 +/- 1 L/100 vs 3.1 +/- 1 L per 100 mL, respectively; p < 0.05), and a significantly higher VD/VT (0.62 +/- 0.14 vs 0.43 +/- 0.15, respectively; p < 0.0005).
  
  
  CONCLUSIONS
  Critically ill children with ARDS have increased VD/VT. Increased VD/VT was the main cause of the excess of E demand in these patients. Increased metabolic demands, as shown by the VeqO(2), VeqCO(2), and ventilatory support, are the major determinants of E requirements in children with ARDS.
authors.affiliation: Section of Critical Care Medicine, Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA.
authors.forename: Jorge A
authors.initials: JA
authors.lastname: Coss-Bu
authors.forename: David L
authors.initials: DL
authors.lastname: Walding
authors.forename: Yadin B
authors.initials: YB
authors.lastname: David
authors.forename: Larry S
authors.initials: LS
authors.lastname: Jefferson
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D002151:Calorimetry; D002648:Child; D002675:Child, Preschool; D016638:Critical Illness; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D012121:Respiration, Artificial; D012126:Respiratory Dead Space / Q000502:physiology*; D012127:Respiratory Distress Syndrome, Newborn / Q000378:metabolism / Q000503:physiopathology*