Dead space ventilation in critically ill children with lung injury

Chest. 2003 Jun;123(6):2050-6. doi: 10.1378/chest.123.6.2050.


Study 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.

Design: A cross-sectional study.

Setting: Pediatric ICU of a university hospital.

Patients: A total of 45 mechanically intubated children (mean age, 5.5 years).

Interventions: 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.

Measurements and 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.

MeSH terms

  • Acute Disease
  • Adolescent
  • Calorimetry
  • Child
  • Child, Preschool
  • Critical Illness*
  • Female
  • Humans
  • Infant
  • Infant, Newborn
  • Male
  • Respiration, Artificial
  • Respiratory Dead Space / physiology*
  • Respiratory Distress Syndrome, Newborn / metabolism
  • Respiratory Distress Syndrome, Newborn / physiopathology*