Use of bioimpedance for measuring cardiac output in the conscious dog

Cardiovascular profiling of developmental compounds by General Pharmacology/Safety Pharmacology is an integral part of the drug discovery process in support of registration of clinical candidates. Non-invasive screening tools which provide hemodynamic measurements can facilitate the drug development process. One such method, bioimpedance cardiography, is an indirect means of evaluating cardiac output. Changes in thoracic impedance in response to an applied current are related to changes in volume and velocity of blood flow in the thorax for the determination of stroke volume, which is coupled to heart rate for calculating cardiac output. Commercially available bioimpedance cardiography units have evolved considerably in recent years in step with advances in computing power. The use of these units, with modification, in the preclinical arena for determinations in anesthetized dogs and pigs has shown good correlation with other accepted methodologies for measuring cardiac output. Data presented here are the first to describe the application of this technology in conscious dogs. The utility and limitations of this method as a screening tool in the conscious dog are discussed. These cardiac output measurements combined with arterial pressure and electrocardiogram measurements, provide a simple means for more complete hemodynamic profiling of drug candidates.