Objective: We prospectively studied the agreement
between transpulmonary aortic fiberoptic-based and pulse dye
densitometry (PDD) measurements of cardiac output and circulatory blood
Design: Prospective clinical study.
Setting: Operative ICU of a university hospital.
Patients: Sixteen critically ill, deeply sedated patients
receiving mechanical ventilation with ARDS (n = 8), sepsis/septic
shock (n = 6), subarachnoid hemorrhage (n = 1), and severe head
injury (n = 1).
Measurements and results: Each
patient received a 4F aortic catheter with an integrated fiberoptic and
thermistor that was connected to a computer system for automatic
calculation of the transpulmonary indicator dilution (TPID) technique
for the measurement of cardiac output (COtpid),
intrathoracic blood volume (ITBV), and total blood volume measured by
TPID technique (TBVtpid). In each patient, an indocyanine
green sensor was attached to one nasal wing and connected to an
analyzer for the PDD measurement of cardiac output (COpdd),
central blood volume (CBV), and TBV measured by PDD
(TBVpdd). For all first measurements, linear regression
analysis between COtpid and COpdd revealed that
COpdd = 0.63 × COtpid + 3.69 (L/min)[
r = 0.64, p = 0.008]. Mean bias between both
techniques was − 0.8 L/min (SD, 1.7 L/min). Correlations between
ITBV/CBV (r = 0.52) and
TBVtpid/TBVpdd were only moderate:
TBVpdd = 0.74 × TBVtpid + 2,362 (mL)[
r = 0.60, p = 0.015; mean bias, − 999 mL; SD,
1,353 mL]. Over all 55 measurements, TPID measurements were on average
11.5% (cardiac output) and 17.6% (TBV) higher than PDD measurements.
The differences between both measurements ranged from − 58 to 81%
(cardiac output) and from − 47 to 82% (TBV; 95% reference ranges).
The main source of variation were the intraindividual differences,
resulting in different peaks and trends in the patients’ time courses
depending on which measurement method was used.
Conclusion: PDD measurement of cardiac output and
circulatory blood volumes agrees moderately with transpulmonary
thermo-dye dilution technique in critically ill