Validation of capnodynamic determination of cardiac output by measuring effective pulmonary blood flow: a study in anaesthetised children and piglets.

Abstract

Effective pulmonary blood flow (CO_EPBF) has recently been validated as a technique for determining cardiac output (CO) in animals of varying sizes. The primary aim of our study was to investigate this new technique in paediatric surgical patients, compared with suprasternal two-dimensional Doppler (CO_SSD). A total of 15 children undergoing cleft lip/palate surgery were investigated. Before the start of surgery, manoeuvres that were anticipated to reduce (increase in PEEP from 3 to 10 cm H₂O) and increase (atropine) CO were undertaken. A study in mechanically ventilated piglets was also undertaken under general anaesthesia, measuring CO_EPBF and pulmonary artery (CO_TS) flow by ultrasonic probe as the comparator. Bias (Bland-Altman plots) and limits of agreement were assessed for effective pulmonary blood flow and CO_SSD or CO_TS. In paediatric patients (median age 8.5 months), overall bias was -8.1 (limits of agreement -82 to +66) ml kg^-1 min^-1, with a mean percentage error of 48% and a concordance rate of 64%. In the piglet model, overall bias was -1 (-36 to +38) ml kg^-1 min^-1, with a mean percentage error of 31% and a concordance rate of 95%. Under controlled experimental conditions, CO_EPBF is associated with excellent agreement and good trending ability when compared with the gold standard CO_TS. In the paediatric clinical setting, CO_EPBF performs well; by contrast, CO_SSD, an operator- and anatomy-dependent technology, appears less reliable than CO_EPBF.