[Feasibility of using esophageal balloon pressure-volume curve to calibrate esophageal pressure during assisted mechanical ventilation].

OBJECTIVE

To evaluate the feasibility of esophageal pressure (Pes) calibration by the esophageal balloon pressure-volume (P-V) curve during assisted mechanical ventilation.

METHODS

A prospective study was conducted. The postoperative patients admitted to intensive care unit of Beijing Tiantan Hospital Affiliated to Capital Medical University from June 2017 to January 2019 who needed pressure support ventilation by tracheal intubation and Pes monitoring with stable breath were enrolled. The Pes monitoring was performed by the esophageal balloon with a small geometric volume (2.8 mL). (1) Balloon volume tests of esophageal balloon were performed by inflating intermittently 0.5 mL increments up to 2.5 mL, the end-expiratory and end-inspiratory Pes were recorded to obtain end-expiratory and end-inspiratory P-V curves. The intermediate section in end-expiatory P-V curve that showed linear correlation was identified (as intermediate linear section), whose volume range was balloon working volume (V) and slope was esophageal wall elastance (Ees), the balloon volume with the largest difference between end-expiratory and end-inspiratory Pes was the best balloon volume (V), and the product of Ees and V was esophageal wall recoil pressure reacting to balloon filling. To minimize the effect of esophageal wall on Pes, the calibrated Pes was the difference of Pes and esophageal wall recoil pressure. The consistency of calibrated Pes obtained by balloon volume at V and other V were analyzed. (2) For the convenience of clinical application, a simplified method was introduced to calibrate Pes. Based on all V of patients located in 0.5-1.5 mL, the difference of end-expiratory Pes between balloon volume at 0.5 mL and 1.5 mL divided by 1.0 mL was used to estimate Ees, and the Pes among 0.5-1.5 mL was calibrated by Ees obtained by the simple method. The consistency of calibrated Pes obtained by the simple method and standard method were observed.

RESULTS

Totally 30 patients were enrolled, all end-expiratory and end-inspiratory P-V curves existed the intermediate linear section, the calibrated Pes at V did not increase with the balloon being inflated and had a good consistency with the calibrated Pes at V, mean difference and 95% confidence interval (95%CI) was -0.02 (-1.50-1.50) cmHO (1 cmHO = 0.098 kPa). The Ees and calibrated Pes estimated by the simple method had a good agreement with the standard method, mean difference and 95%CI was -0.2 (-1.0-0.6) cmHO/mL and 0.2 (-1.1-1.4) cmHO, respectively.

CONCLUSIONS

During assisted mechanical ventilation, the use of a small geometric volume esophageal balloon to monitor Pes and balloon P-V curve to calibrate Pes is feasible. The simple method can be used for simplifying clinical application, that's only by monitoring Pes at balloon volume at 0.5, 1.0 and 1.5 mL to evaluate the Ees and calibrate Pes.