Capnometry for noninvasive continuous monitoring of metabolic status in pediatric diabetic ketoacidosis

Objective. To determine the utility of continuous noninvasive capnometry for monitoring pediatric patients with diabetic ketoacidosis as assessed by the agreement between end-tidal carbon dioxide (Petco(2)) and Pco(2). Design: Clinical, prospective, observational study. Setting. University affiliated children's hospital. Interventions. Patients with diabetic ketoacidosis were monitored with an oral/nasal carbon dioxide (CO2) sampling cannula while in the emergency department. Laboratory studies were ordered per protocol. Petco(2) values were correlated with respiratory rate, Pco(2), and pH. Measurements and Main Results., One hundred twenty-one patents were monitored for 5.9 +/- 0.32 hrs. The average (mean +/- so) initial values for pH were 7.08 +/- 0.18; respiratory rate, 35.1 +/- 9.1 breaths/min; Petco(2), 18.6 +/- 10.8 torr, and venous Pco(2), 20.2 +/- 10.6 torr. At the conclusion of the observation period, averages were pH, 7.29 +/- 0.05; respiratory rate, 22.4 +/- 3.7 breaths/min; Petco(2) 35.3 +/- 5.8 torr; and venous Pco(2), 36.8 +/- 5.3 torr. For all 592 observations, the correlations between Petco(2) and venous Pco(2) (r = .92, p = .0001), Petco(2) and pH (r = .88, p = .0001), Petco(2) and respiratory rate (r = -.79, p = .0001), and respiratory rate and pH (r = -.80, p = .0001) were statistically significant and the correlations with respiratory rate were inversely related to pH and Petco(2). The difference scores were not related to the average scores for initial readings (r = -.073, p = .43), final readings (r = -.124, p = .18), and overall readings (r = .057, p = .17). Limits of agreement between the two methods were established with Petco(2) lower than venous Pco(2) with 95% limits of agreement 0.8 +/- 8.3 (2 SD) torr. Conclusions: Petco(2) monitoring of patients with diabetic ketoacidosis provides an accurate estimate of Pco(2). Noninvasive Petco(2) sampling may be useful in patients with diabetic ketoacidosis to allow for continuous monitoring of patients.