Detection of strong inspiratory efforts from the analysis of central venous pressure swings: a preliminary clinical study

BACKGROUND: Swings of central venous pressure (Delta CVP) may reflect those of pleural and esophageal (Delta PES) pressure and, therefore, the strength of inspiration. Strong inspiratory efforts can produce some harm. Herein we preliminarily assessed the diagnostic accuracy of Delta CVP for strong inspiratory efforts in critically-ill subjects breathing spontaneously.METHODS: We measured Delta CVP and Delta PES in 48 critically-ill subjects breathing spontaneously with zero end-expiratory pressure (ZEEP) or 10 cmH(2)O of continuous positive airway pressure (CPAP). The overall diagnostic accuracy of Delta CVP for strong inspiratory efforts (arbitrarily defined as Delta PES >8 mmHg) was described as the area under the receiver operating characteristic (ROC) curve, with 0.50 indicating random guess. The agreement between Delta CVP and Delta PES was assessed with the Bland-Altman analysis.RESULTS: Delta CVP recognized strong inspiratory efforts with an area under the ROC curve of 0.95 (95% confidence intervals, 0.85-0.99) with ZEEP and 0.89 (0.76-0.96) with CPAP, both significantly larger than 0.50 (P<0.001). With the best cut-off value around 8 mmHg, the diagnostic accuracy of Delta CVP was 0.92 (0.80-0.98) with ZEEP and 0.94 (0.83-0.99) with CPAP. With ZEEP, the median difference between Delta CVP and Delta PES (bias) was -0.2 mmHg, and the 95% limits of agreement (LoA) were -3.9 and +5.5 mmHg. With CPAP, bias was -0.1 mmHg, and 95%-LoA were -5.8 and +4.5 mmHg. In both cases, Delta CVP correlated with Delta PES (r(s) 0.81 and 0.67; P<0.001 for both).CONCLUSIONS: In critically-ill subjects breathing spontaneously, Delta CVP recognized strong inspiratory efforts with acceptable accuracy. Even so, it sometimes largely differed from Delta PES.