Clinical application of esophageal manometry: how I do it

Abstract

© The Author(s) 2021. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creat iveco mmons .org/licen ses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creat iveco mmons .org/publi cdoma in/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Our group uses esophageal manometry routinely to personalize mechanical ventilation in patients with acute respiratory distress syndrome (ARDS) [1, 2]. Esophageal pressures (Pes) allow for differentiation of chest wall, lung and respiratory system mechanics, and we use this for PEEP titration [1, 2], monitoring of parenchymal lung stress, limiting peak end-inspiratory transpulmonary pressures and monitoring for ventilator synchrony [3, 4]. We find that esophageal manometry is straightforward in the majority of patients although proper training and application are important. The initial step is to assure correct placement with insertion of stand-alone catheters or feeding tubes with integrated esophageal balloons which are similar to routine gastric tubes. Typical depth of insertion ranges from 33 to 40 cm, depending on body size and we assure proper placement through functional bedside assessment. First, we look for the presence of cardiac oscillations to assure correct position posterior to the heart. If absent, this suggests the balloon is too deep or shallow and we incrementally adjust while monitoring for these oscillations. Next we perform expiratory breath holds, with changes in Pes, airway (Pao) and transpulmonary pressure (PL = Pao − Pes) monitored during gentle chest pushes. Proper position is confirmed when Pes and Pao increase in equal measure, with no change in the calculated PL. If Pao increases more Pes, this suggests that position is too deep and the balloon is adjusted incrementally with repeat chest pushes. This may be confirmed with gentle abdominal pushes (with Pes increasing more than Pao). (Table 1). Using a balloon with a consistent working range of inflation volume is helpful for obtaining consistent and accurate measurements. While optimal inflation volume can be confirmed based upon the pressure–volume characteristics of the balloon itself [5], this is time-consuming and not required in practice when using a balloon with a known acceptable range. Overinflation results in inaccurately high measured pressures secondary to the compliance of the balloon, while underinflation causes dampening of waveform variation. Visualization and interpretation of data are facilitated by integrated pressure sensors within the ventilator or can be recorded using stand-alone devices as we used in the EPVent and EPVent2 studies [1, 2]. One of our primary applications of esophageal manometry is for titration of positive end-expiratory pressure (PEEP). Critically ill patients frequently exhibit increased chest wall weight and elevated basal end-expiratory pleural pressures secondary to edema, effusions, abdominal hypertension and other causes that may lead to derecruitment, increased lung elastance and hypoxemia. We measure Pes as a surrogate for pleural pressure [6] and if the pleural pressure is larger than the measured airway/ alveolar pressure (PL = Pao − Pes), these collapsing pressures can be countered with the application of PEEP. Our EPVent [2] and EPvent2 [1] studies investigated the use of esophageal manometry to titrate PEEP and while the latter study did not show clear benefit compared with empiric high-PEEP, further analysis suggested a benefit when end-expiratory PL were maintained in a tight physiological range of − 2 to + 2cmH2O with PEEP adjustment (publication under review) which is how we practice clinically. We aim for an end-expiratory PL of zero regardless of the FiO2 which is distinct from the original slidingscale protocols [1, 2] and is in part secondary to the slight Open Access