Dead space to total ventilation (Vd/Vt) ratio predicts successful extubation in infants and children


Journal Article

Introduction: Determining the optimal time for extubation in infants and children is challenging. Prior studies suggest that no single measurement or test adequately predicts extubation success. We hypothesized that the Vd/Vt ratio would provide a single, clinically relevant measurement for predicting extubation success or failure. Methods: We prospectively evaluated children one week to eighteen years of age (n=44) who were considered ready for extubation by the clinical care team. Patients with known cardiac mixing lesions, neuromuscular disease, upper airway obstruction, absent airway reflexes, and EGA < 37 weeks were excluded. The clinical team determined extubation readiness using "traditional clinical practice." After the extubation decision was made, a study investigator changed the patient's venulatory mode to pressure support ventilation set to deliver an exhaled tidal volume of 6 mL per kilogram. Tidal volumes were measured at the endotracheal tube using the CO2SMO PLUS (Novametrix Medical Systems). Ventilator settings included an IMV = 0. PEEP = 5-7 cmH2O and H2O, and FiO2≤ 0.40. After twenty minutes, an arterial blood gas was obtained. Vd/Vt computed with the CO2SMO PLUS, and the patient extubated. Over the next 48 hours, the patient was followed for evidence of respiratory failure requiring reintubation or noninvasive support (e.g. CPAP. BIPAP. or Hayek negative pressure ventilation). Clinical team members remained blinded to the Vd/Vt value throughout the post-extubation period. Results: Logistic regression indicated a linear relationship between the Vd/Vt ratio and the probability of extubation failure (chi-square=10.7, p-value= 0.001). Vd/Vt Success Failure Type 0.10-0.50 24/25 (96%) Noninvarive Support (1) 0.51-0.64 6/9 (67%) Noninvasive Support (3) 0.65-0.95 2/10 (20%) Noninvasive Support (6), Reintubation (2) Conclusions: A Vd/Vt ratio less than 0.50 reliably predicts successful extubation whereas a Vd/Vt ratio greater than 0.65 correlates with extubation failure. There is an intermediate Vd/Vt range (0.51-0.64) which is less predictive Routine monitoring of Vd/Vt ratios in pediatric patients may permit earlier extubation and may also reduce unexpected extubation failures.

Duke Authors

Cited Authors

  • Hubble, CL; Gentile, MA; Tripp, DS; Craig, DM; Meliones, JN; Cheifetz, IM

Published Date

  • December 1, 1999

Published In

Volume / Issue

  • 27 / 1 SUPPL.

International Standard Serial Number (ISSN)

  • 0090-3493

Citation Source

  • Scopus