Capnodynamic determination of cardiac output in hypoxia-induced pulmonary hypertension in pigs.

BACKGROUND: Effective pulmonary blood flow (COEPBF ) has recently been validated for its ability to measure cardiac output (CO) in children and animals. This study compared COEPBF with the Fick method (COFick ) and CO measurements using an invasive pulmonary artery flow probe (COTS ). The aim of the study was to validate COEPBF against these reference methods in a porcine model of hypoxia-induced selective pulmonary hypertension.

METHODS: Ten anaesthetised mechanically ventilated piglets (median weight 23.9 kg) were exposed to a hypoxic gas mixture inducing selective pulmonary hypertension. Pulmonary hypertension was subsequently reversed with inhaled nitric oxide. Simultaneous recordings of COEPBF , COFick , and COTS were performed throughout the protocol and examined for agreement and trending ability.

RESULTS: Overall bias (Bland-Altman) between COEPBF and COTS was 0.2 L min-1 (limits of agreement -0.5 and +0.9 L min-1 ) with a mean percentage error of 25%. Overall bias between COEPBF and COFick was -0.1 L min-1 (limits of agreement -0.9 and +0.6 L min-1 ) and a mean percentage error of 25%. The concordance rate was 86% for COEPBF when compared with COTS using a 10% exclusion zone.

CONCLUSIONS: Estimation of CO with COEPBF results in values very close to the gold standard reference methods COFick and COTS . COEPBF appears to be an accurate tool for monitoring absolute values and changes in CO during hypoxia-induced pulmonary hypertension and inhaled nitric oxide treatment.