Determination of cardiac output during mechanical ventilation by electrical bioimpedance or thermodilution in patients with acute lung injury: Effects of positive end-expiratory pressure

Objective: To evaluate the usefulness of transthoracic electrical bioimpedance in sedated and paralyzed patients with acute lung injury during mechanical ventilation with and without early application of positive end expiratory pressure (PEEP). Design: Prospective, repeated measures study. Setting: University affiliated intensive care center, Patients: Ten patients with acute lung injury, Interventions: Simultaneous, three-paired cardiac output (CO) measurements by transthoracic electrical bioimpedance (TEB) and thermodilution (TD) were made at 0 and 15 cm H2O of PEEP. Measurements and Main Results: The average of the TD-CO measurements was 7.22 +/- 2.12 (SD) L/min during 0 cm H2O of positive end-expiratory pressure (ZEEP), and 6.91 +/- 1.72 L/min during PEEP (NS), The average of the TEE-CO measurements was 4.48 +/- 1.37 L/min during ZEEP, and 6.03 +/- 2.03 L/min during PEEP (p < .05). For each level of PEEP, bias and precision between methods were calculated, Bias calculations between TD CO and TEB-CO ranged from -1.54 +/- 7.02 L/min at ZEEP to -2.52 +/- 4.28 L/min at PEEP, and -2.47 +/- 6.09 L/min for mixed data at ZEEP and PEEP, There was no significant correlation between the percent change with PEEP in TEE-CO and TD-CO (r(2) = .05, NS). Conclusions: In patients with acute lung injury: a) the agreement between TEE-CO and TD-CO measurements is poor; b) agreement is not clinically improved by application of PEEP; and c) TEE cannot monitor trends in CO.