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

OBJECTIVETo determine the utility of continuous noninvasive capnometry for monitoring pediatric patients with diabetic ketoacidosis as assessed by the agreement between end-tidal carbon dioxide (Petco2) and Pco2. DESIGNClinical, prospective, observational study. SETTINGUniversity affiliated children’s hospital. INTERVENTIONSPatients 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. Petco2values were correlated with respiratory rate, Pco2, and pH. MEASUREMENTS AND MAIN RESULTSOne hundred twenty-one patients were monitored for 5.9 ± 0.32 hrs. The average (mean ± sd) initial values for pH were 7.08 ± 0.18; respiratory rate, 35.1 ± 9.1 breaths/min; Petco2, 18.6 ± 10.8 torr; and venous Pco2, 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; Petco2, 35.3 ± 5.8 torr; and venous Pco2, 36.8 ± 5.3 torr. For all 592 observations, the correlations between Petco2 and venous Pco2 (r = .92, p = .0001), Petco2 and pH (r = .88, p = .0001), Petco2 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 Petco2. 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 Petco2 lower than venous Pco2 with 95% limits of agreement 0.8 ± 8.3 (2 sd) torr. CONCLUSIONSPetco2 monitoring of patients with diabetic ketoacidosis provides an accurate estimate of Pco2. Noninvasive Petco2 sampling may be useful in patients with diabetic ketoacidosis to allow for continuous monitoring of patients.