Comparison of cardiac output and blood volumes in intrathoracic compartments measured by ultrasound dilution and transpulmonary thermodilution methods

To compare cardiac output (CO) and blood volumes measured by COstatus(A (R)) (Transonic Systems Inc., NY, USA) versus PiCCO (Philips IntelliVue MP40 with PiCCO-technology module M3012A#10, Netherlands) in adult ICU patients. This was a prospective single-center study. Each of the 30 patients studied received a 5-Fr Pulsiocath femoral arterial and a standard central venous catheter. Twenty ml of iced 5% dextrose solution was injected for PiCCO measurements. For COstatus measurements, an extracorporeal arteriovenous loop, with two sensors placed on it, was connected between the Pulsiocath femoral arterial and central venous catheters. Blood was circulated through this loop at 12 ml/min for 5-8 min using a pump. Twenty ml of warm saline was injected into the venous side for measurements. For each method, three injections were averaged for comparison. A good agreement for measured CO (range 3.65-16.3 l/min) with a percentage error of 20% was observed, with r = 0.95, bias = -0.037 l/min. PiCCO's global end-diastolic volume (GEDV) was 2.5 times larger than the analogous COstatus's total end-diastolic volume (TEDV) [TEDV = 0.28 x GEDV + 176 ml]. PiCCO's intrathoracic blood volume (ITBV) was larger than the analogous COstatus's central blood volume (CBV) [CBV = 0.73 x (ITBV) +78 ml]. CO measured by COstatus was found to be equivalent and hence interchangeable with PiCCO in this study population. COstatus blood volumes were found to be within the expected physiological range whilst PiCCO blood volumes were significantly higher, which was also observed in other studies. Future studies using 3D echo/MRI are required to validate these blood volumes.