Deadspace to tidal volume ratio predicts successful extubation in infants and children

Objective: Using a modification of the Bohr equation, single-breath carbon dioxide capnography is a noninvasive technology for calculating physiologic dead space (VD/VT). The objective of this study was to identify a minimal VD/VT value for predicting successful extubation from mechanical ventilatio n in pediatric patients. Design: Prospective, blinded, clinical study. Setting: Medical and surgical pediatric intensive care unit of a university hospital. Patients: Intubated children ranging in age from 1 wk to 18 yrs. Interventions: None. Measurements and Main Results: Forty-five patients were identified by the p ediatric intensive care unit clinical team as meeting criteria for extubati on. Thirty minutes before the planned extubation, each patient was begun an pressure support ventilation set to deliver an exhaled tidal volume of 6 m L/kg. After 20 mins on pressure support ventilation, an arterial blood gas was obtained, VD/VT was calculated, and the patient was extubated. Over the next 48 hrs, the clinical team managed the patient without knowledge of th e preextubation VD/VT value. Of the 45 patients studied, 25 had VD/VT less than or equal to 0.50. Of the se patients, 24 of 25 (96%) were successfully extubated without needing add itional ventilatory support. In an intermediate group of patients with VD/V T between 0.50 and 0.65, six of ten patients (60%) successfully extubated f rom mechanical ventilation. However, only two of ten patients (20%) with a VD/VT greater than or equal to 0.65 were successfully extubated. Logistic r egression analysis revealed a significant association between lower VD/VT a nd successful extubation. Conclusions: A VD/VT less than or equal to 0.50 reliably predicts successfu l extubation, whereas a VD/VT >0.65 identifies patients at risk for respira tory failure following extubation, There appears to be an intermediate VD/V T range (0.51-0.65) that is less predictive of successful extubation. Routi ne VD/VT monitoring of pediatric patients may permit earlier extubation and reduce unexpected extubation failures.