Accuracy and precision of non-invasive cardiac output monitoring by electrical cardiometry: a systematic review and meta-analysis

Abstract

Cardiac output monitoring is used in critically ill and high-risk surgical patients. Intermittent pulmonary artery thermodilution and transpulmonary thermodilution, considered the gold standard, are invasive and linked to complications. Therefore, many non-invasive cardiac output devices have been developed and studied. One of those is electrical cardiometry. The results of validation studies are conflicting, which emphasize the need for definitive validation of accuracy and precision. We performed a database search of PubMed, Embase, Web of Science and the Cochrane Library of Clinical Trials to identify studies comparing cardiac output measurement by electrical cardiometry and a reference method. Pooled bias, limits of agreement (LoA) and mean percentage error (MPE) were calculated using a random-effects model. A pooled MPE of less than 30% was considered clinically acceptable. A total of 13 studies in adults (620 patients) and 11 studies in pediatrics (603 patients) were included. For adults, pooled bias was 0.03 L min^-1 [95% CI - 0.23; 0.29], LoA - 2.78 to 2.84 L min^-1 and MPE 48.0%. For pediatrics, pooled bias was - 0.02 L min^-1 [95% CI - 0.09; 0.05], LoA - 1.22 to 1.18 L min^-1 and MPE 42.0%. Inter-study heterogeneity was high for both adults (I² = 93%, p < 0.0001) and pediatrics (I² = 86%, p < 0.0001). Despite the low bias for both adults and pediatrics, the MPE was not clinically acceptable. Electrical cardiometry cannot replace thermodilution and transthoracic echocardiography for the measurement of absolute cardiac output values. Future research should explore it's clinical use and indications.

Keywords: Bioimpedance; Cardiac output; Electrical cardiometry; Electrical velocimetry; Hemodynamic monitoring; Meta-analysis; Non-invasive; Systematic review.

Fig. 1

a Placement of electrodes on the left base of the neck and on the left inferior side of the thorax at the level of the xiphoid process. b Arrangement and orientation of erythrocytes during diastole (left) and systole (right) explaining the difference in thoracic impedance. Figure reproduced from Osypka Medical GmbH, an introduction to Electrical Cardiometry [19]

Fig. 2

Flow diagram of the study selection process. CI cardiac index, MPE mean percentage error, SV stroke volume

Fig. 3

Forest plot showing the bias, LoA and MPE for the studies in adults. The random effects pooled bias was 0.03 L min⁻¹, LoA − 2.78 to 2.84 L min⁻¹ and MPE 48.0%. Significant heterogeneity was detected (I² = 93%, p < 0.0001). ^aOR, ^bICU, ^cat rest, ^dduring exercise, ^eduring NO inhalation, ^fintermittent PAC as reference method, ^gTPTD as reference method, LoA limits of agreement, MPE mean percentage error, N number of patients

Fig. 4

Forest plot showing the bias, LoA and MPE for the studies in pediatrics. The random effects pooled bias was − 0.02 L min⁻¹, LoA − 1.22 to 1.18 L min⁻¹ and MPE 42.0%. Significant heterogeneity was detected (I² = 86%, p < 0.0001). ^anormal weight, ^boverweight and obese, LoA limits of agreement, MPE mean percentage error, N number of patients

Fig. 5

Funnel plot for detection of publication bias across included studies in adults. Egger’s regression test showed no significant p-value (p = 0.4147). The funnel plot shows asymmetry

Fig. 6

Funnel plot for detection of publication bias across included studies in pediatrics. Egger’s regression test showed no significant p-value (p = 0.6572). The funnel plot shows asymmetry

Fig. 7

Forest plot showing the results of subgroup analysis for reference method in adults. The subgroup intermittent TD showed a random effects pooled bias of 0.04 L min⁻¹ [95% CI − 0.28; 0.37], LoA − 3.14 to 3.22 L min⁻¹ and MPE 53.5%. Heterogeneity was high (I² = 80%, p < 0.0001). The subgroup continuous TD showed a pooled bias of − 0.56 L min⁻¹ [95% CI − 1.70; 0.57], LoA − 2.90 to 1.78 L min⁻¹ and MPE 31.1%. Heterogeneity was high (I² = 82%, p = 0.02). The subgroup other reference showed a pooled bias of 0.16 L min⁻¹ [95% CI − 0.57; 0.90], LoA − 2.34 to 2.66 L min⁻¹ and MPE 48.5%. Heterogeneity was high (I² = 97%, p < 0.0001). There was no statistically significant difference in subgroup effects (p = 0.55). ^aOR, ^bICU, ^cat rest, ^dduring exercise, ^eduring NO inhalation, ^fintermittent PAC as reference method, ^gTPTD as reference method. LoA limits of agreement, MPE mean percentage error, N number of patients, TD thermodilution

Fig. 8

Forest plot showing the results of subgroup analysis for clinical setting in adults. The subgroup cardiac surgery showed a random effects pooled bias of 0.01 L min⁻¹, LoA − 1.34; 1.36 L min⁻¹ and MPE 33.3%. Heterogeneity was high (I² = 73%, p < 0.01). The subgroup OR showed a pooled bias of 1.00 L min¯¹, LoA − 4.05; 6.05 L min⁻¹ and MPE 67.7%. Heterogeneity was high (I² = 97%, p < 0.0001). The subgroup ICU showed a pooled bias of 0.04 L min⁻¹, LoA − 2.37; 2.45 L min⁻¹ and MPE 42.9%. Heterogeneity was moderate (I² = 38%, p = 0.17). The subgroup other clinical setting showed a pooled bias of − 0.35 L min⁻¹, LoA − 3.17; 2.47 L min⁻¹ and MPE 53.5%. Heterogeneity was high (I² = 96%, p < 0.0001). There was no statistically significant difference in subgroup effects (p = 0.82). ^aOR, ^bICU, ^cat rest, ^dduring exercise, ^eduring NO inhalation, ^fintermittent PAC as reference method, ^gTPTD as reference method, ^hbefore cardiac surgery, ⁱimmediately post cardiac surgery, ^jICU. ICU intensive care unit, LoA limits of agreement, MPE mean percentage error, N number of patients, OR operation room

Fig. 9

Forest plot showing the results of subgroup analysis for reference method in pediatrics. The subgroup TTE in children showed a random effects pooled bias of − 0.10 L min⁻¹, LoA − 1.61 to 1.41 L min⁻¹ and MPE 43.9%. Heterogeneity was high (I² = 75%, p < 0.001). The subgroup TTE in neonates showed a pooled bias of 0.01 L min¯¹, LoA − 0.14 to 0.16 L min⁻¹ and MPE 35.1%. No heterogeneity was detected (I² = 0%, p = 0.94).The subgroup other reference method in children showed a pooled bias of 0.15 L min⁻¹, LoA − 0.73 to 1.03 L min⁻¹ and MPE 41.6%. Heterogeneity was high (I² = 96%, p < 0.0001). There was no statistically significant difference in subgroup effects (p = 0.21). ^anormal weight, ^boverweight and obese. LoA limits of agreement, MPE mean percentage error, N number of patients, TTE transthoracic echocardiography