Esophageal and transdiaphragmatic pressure swings as indices of inspiratory effort

Abstract

Aim: To describe the correlation between the inspiratory esophageal and transdiaphragmatic pressure swings (ΔPes and ΔPdi), easily measured indices of inspiratory effort, with the gold-standard, the transdiaphragmatic pressure time product (PTP_Pdi/min), and assess the accuracy of swing pressures in predicting very high or low effort.

Method: Retrospective analysis of data from patients enrolled in four previous studies. ROC curves of ΔPes and ΔPdi values for specific PTP_Pdi/min thresholds (50, 150, 200 cmH₂O × sec/min) were constructed, and the diagnostic accuracy of different thresholds of swing values were computed.

Results: A threshold of inspiratory ΔP<7cmH₂O can be used to identify most patients with low effort, as lower ΔP thresholds have low sensitivity. Thresholds of inspiratory ΔP>14-18cmH₂O can be used to identify patients with very high inspiratory effort (PTP_Pdi/min> 200 cmH₂O × sec/min).

Conclusions: The results of this study can help clinicians better select and interpret thresholds of ΔP to evaluate inspiratory effort.

Keywords: Diaphragm; Pressure-time product; Protective ventilation.