Assessment of cardiac preload and extravascular lung water by single transpulmonary thermodilution

Abstract

Determinations of ITBV and EVLW by single thermodilution agreed closely with the corresponding values from the double-indicator technique. Since transpulmonary single thermodilution is simple to apply, less invasive and cheaper, all these features make it a promising technique for the bedside. Nevertheless, further validation studies are needed in the future.

Resolution of pulmonary edema with variable mechanical ventilation in a porcine model of acute lung injury

“…The significant decrease in global lung density further supports this conclusion. Scillia et al 20 revealed a significant correlation between CT derived density and EVLW by means of double indicator dilution in a canine OA model; this was confirmed later by Kuzkov et al 21 The single indicator thermodilution determination of EVLW has been validated clinically against the double indicator dilution method 16,22 and has been substantiated in animal studies against gravimetry. [23][24][25] As the PiCCO calculation of EVLW excludes both blood and tissue volumes, we anticipated lower PiCCO derived EVLW values compared with CT determined lung weights, but we expected EVLW to increase as CT lung weight increased with OA injury.…”

“…We used the default PiCCO settings with an adult patient population based constant = 1.25. 16 Correction of the EVLWI with constants of 1.52 or 1.72, as suggested by Rossi 23 or Neumann, 28 respectively, shifts the EVLWI to lower values at all time periods without changing the overall results. Systematic overestimation of EVLW at baseline and underestimation of EVLW post OA administration may render the single thermodilution method relatively insensitive in this small animal OA injury preparation, contributing to both the unexpectedly small measured increase in EVLW post OA and the discrepancy in results between CT weight/density and PiCCO derived EVLW.…”

“…Intrathoracic blood volume is calculated by the PiCCO system using an empirically established linear relationship between intrathoracic blood volume and GEDV (ITBV = 1.25 GEDV). 16 Intrathoracic blood volume is then subtracted from ITTV to determine EVLW. Measurements were performed in triplicate at control, following OA lung injury, and hourly for four hours.…”

Transpulmonary Thermodilution: Its Role in Assessment of Lung Water and Pulmonary Edema

“…The TPTD was found to have a systematic, yet, clinically acceptable overestimation of CO. This overestimation is widely thought to result from the loss of the indicator due to thermal transfer from the intravascular compartment between injection and detection sites 13,14 . This thermal transfer can be capitalized upon to measure intrathoracic volumes and most importantly extravascular lung water (EVLW).…”

“…Unlike dye techniques where the indicator is restricted to the vascular space, part of the thermal indicator escapes due to heat transfer to the vessel walls and the surrounding lung parenchyma. Thus the volume of distribution for a thermal indicator is significantly greater than the ITBV and is Unfortunately, the technique of 'double-indicator' TPTD is time consuming, cumbersome and expensive, and despite promise failed to become established in routine clinical practice 13,15,16 . Fortunately, a more clinically suitable alternative was developed utilizing a 'single' bolus thermal indicator that by a series of calculations and assumptions provided determination of EVLW.…”