RESPIRATORY CARE Paper in Press. Published on July 11, 2023, as DOI: 10.4187/respcare.11157
Esophageal Pressure Measurement: A Primer
Eduardo Mireles-Cabodevila, Michael Fischer, Samuel Wiles, and Robert L Chatburn
Introduction
Physiology
Pleural Pressure
Transmural Pressures
Partitioning Respiratory System Compliance
Patient Effort
Patient-Ventilator Synchrony
Technical Considerations
Supplies
Catheter Insertion and Position
Inflation Volume and Calibration
Validating Measurements
Recording Interface
Measurements and Calculations
Esophageal Pressure Measurements
End-Expiratory Esophageal Pressure
End-Inspiratory Esophageal Pressure (Elastance-Based)
Esophageal Pressure Swing
Static and Dynamic Transpulmonary Driving Pressure
Sources of Error
Clinical Applications
Partitioning the Respiratory System
Titration of PEEP
Evaluation of Patient-Ventilator Interactions
Summary
Over the last decade, the literature exploring clinical applications for esophageal manometry in
critically ill patients has increased. New mechanical ventilators and bedside monitors allow mea-
surement of esophageal pressures easily at the bedside. The bedside clinician can now evaluate
the magnitude and timing of esophageal pressure swings to evaluate respiratory muscle activity
and transpulmonary pressures. The respiratory therapist has all the tools to perform these meas-
urements to optimize mechanical ventilation delivery. However, as with any measurement, tech-
nique, fidelity, and accuracy are paramount. This primer highlights key knowledge necessary to
perform measurements and highlights areas of both uncertainty and ongoing development. Key
words: esophageal pressure measurement; mechanical ventilation; PEEP; lung-protective ventilation;
respiratory system driving pressure; transpulmonary driving pressure. [Respir Care 0;0(0):1–. © 2023
Daedalus Enterprises]
RESPIRATORY CARE
VOL NO 1
Copyright (C) 2023 Daedalus Enterprises ePub ahead of print papers have been peer-reviewed, accepted for publication, copy edited
and proofread. However, this version may differ from the final published version in the online and print editions of RESPIRATORY CARE
, RESPIRATORY CARE Paper in Press. Published on July 11, 2023, as DOI: 10.4187/respcare.11157
NEW HORIZONS SYMPOSIUM
Introduction space pressure measurement. Although it requires the place-
ment of an esophageal catheter, it is easier and safer than a
Since the 1960s, respiratory therapists (RTs) have adapted pleural tube. The validity and challenges of Pes as a surrogate
their role as caregivers while technology and practice evolved. of pleural pressure (Ppl) (Fig. 2) have been described in sev-
The evolution in ventilator technology provides tools previ- eral studies.4,7,8 We will discuss below what Pes reflects and
ously only available for research; one example is esophageal what it does not. The literature contains different terms and
pressure (Pes) monitoring. Although Pes measurement has symbols for respiratory system measurements and calcula-
been used for decades, it is only now that it is easily available tions. Unfortunately, this has led to confusion.9 Thus, we cre-
at the bedside. The availability is both a benefit and a curse. It ated Tables 1–3 following a standardized notation published
is a benefit because it is easily available and may provide use- in this Journal,10 which contains the terms and the calcula-
ful information and a curse because, as with any pressure tions distilled to the bedside level.
measurements, knowledge of both technique and physiology
is essential; when these are lacking, errors occur. Pleural Pressure
Pes measurement perfectly aligns with the RT skills. The
RT already possesses knowledge of the basic physiology Any particular Ppl measurement does not represent a ho-
related to transpulmonary pressures (PTP), patient-ventilator mogeneous pressure throughout the pleural space. Instead,
synchrony, and the work of breathing. However, with this Ppl measurements vary according to the gravitational gradi-
knowledge comes important responsibilities. Although evi- ent (ie, ventral vs dorsal if supine or apical and basal if
dence suggests some areas where Pes monitoring might be standing), lung weight, and regional lung inhomogene-
useful, we must be aware that currently there is no evidence ities.11 For example, the vertical pleural gradient has been
that it improves outcomes.1 This brings back memories of shown to increase by 1.8 times in the presence of lung
lessons learned with pulmonary artery catheters (PACs),2 injury due to an increase in lung weight.7 This is an impor-
where technology was available earlier than evidence and tant consideration because assuming Ppl measurements are
was applied indiscriminately and with poor technique. the same at different points on the pleural surface may lead
Thus, we are responsible for using Pes monitoring with a to errors in calculations, clinical interpretations of data, and
sound physiological understanding, clear indications, proto- therapy applications. See Figure 3 for Ppl gradients.
colized and standardized practices, and following quality-
assurance practices. Finally, we must continue to generate
Transmural Pressures
evidence to define for whom Pes measurement is needed
and beneficial.3 Although extensive reviews on this topic
A key concept in physiology is transmural pressure,
have been previously published,4-6 this primer aims to syn-
the pressure difference across a structure. The transmural
thesize the basic knowledge needed to perform Pes meas-
pressure is the stress the structure sees and, in the case of
urements in a single document.
the alveoli, a proposed determinant of lung injury.12,13
The transmural pressure is obtained by subtracting the
Physiology
pressure inside the structure minus the pressure outside
(a simple mnemonic is Pin minus Pout). Figure 2 demon-
The esophagus travels through the mediastinum and
strates the concept of transmural pressure. The simplistic
becomes adjacent to the pleural space (Fig. 1). The contigu-
interpretation is that if the pressure outside a flexible
ity of the esophagus with the pleura allows the measurement
structure is higher than inside the structure collapses, and
of the pressure inside the esophagus as a surrogate for pleural
if vice versa, the pressure inside is higher than outside
the structure distends. This explains alveolar collapse, as
The authors are affiliated with Respiratory Institute, Cleveland Clinic, well as vascular collapse.14,15
Cleveland, Ohio.
The topic of pressure gradients and what they are called
Dr Mireles-Cabodevila discloses a relationship with IngMar Medical. Mr are a common source of confusion in the literature10
Chatburn discloses relationships with IngMar Medical, Inovytec, Ventis, (Tables 1 and 2). For example, 2 commonly confused terms
AutoMedx, Vyaire, Aires, and Stimdia. The remaining authors have
are transalveolar pressure (PTA) and PTP. PTA is the differ-
disclosed no conflicts of interest.
ence between the alveolar pressure (PA) and Ppl. PTP is the
Supplementary material related to this paper is available at http://www. pressure difference across the larger structure of the air-
rcjournal.com. ways and lungs, calculated as the pressure at the airway
opening (PAO) minus Ppl. The legacy symbol for PTP has
Correspondence: Eduardo Mireles-Cabodevila MD, Cleveland Clinic, 9500
Euclid Avenue, M56, Cleveland, Ohio 44195. E-mail: .
been PL, but this obscures the fact that PTP is a difference in
pressure between 2 points in space, whereas PL seems to
DOI: 10.4187/respcare.11157 indicate the pressure at one point in space (ie, PA).
2 RESPIRATORY CARE
VOL NO
Copyright (C) 2023 Daedalus Enterprises ePub ahead of print papers have been peer-reviewed, accepted for publication, copy edited
and proofread. However, this version may differ from the final published version in the online and print editions of RESPIRATORY CARE
Esophageal Pressure Measurement: A Primer
Eduardo Mireles-Cabodevila, Michael Fischer, Samuel Wiles, and Robert L Chatburn
Introduction
Physiology
Pleural Pressure
Transmural Pressures
Partitioning Respiratory System Compliance
Patient Effort
Patient-Ventilator Synchrony
Technical Considerations
Supplies
Catheter Insertion and Position
Inflation Volume and Calibration
Validating Measurements
Recording Interface
Measurements and Calculations
Esophageal Pressure Measurements
End-Expiratory Esophageal Pressure
End-Inspiratory Esophageal Pressure (Elastance-Based)
Esophageal Pressure Swing
Static and Dynamic Transpulmonary Driving Pressure
Sources of Error
Clinical Applications
Partitioning the Respiratory System
Titration of PEEP
Evaluation of Patient-Ventilator Interactions
Summary
Over the last decade, the literature exploring clinical applications for esophageal manometry in
critically ill patients has increased. New mechanical ventilators and bedside monitors allow mea-
surement of esophageal pressures easily at the bedside. The bedside clinician can now evaluate
the magnitude and timing of esophageal pressure swings to evaluate respiratory muscle activity
and transpulmonary pressures. The respiratory therapist has all the tools to perform these meas-
urements to optimize mechanical ventilation delivery. However, as with any measurement, tech-
nique, fidelity, and accuracy are paramount. This primer highlights key knowledge necessary to
perform measurements and highlights areas of both uncertainty and ongoing development. Key
words: esophageal pressure measurement; mechanical ventilation; PEEP; lung-protective ventilation;
respiratory system driving pressure; transpulmonary driving pressure. [Respir Care 0;0(0):1–. © 2023
Daedalus Enterprises]
RESPIRATORY CARE
VOL NO 1
Copyright (C) 2023 Daedalus Enterprises ePub ahead of print papers have been peer-reviewed, accepted for publication, copy edited
and proofread. However, this version may differ from the final published version in the online and print editions of RESPIRATORY CARE
, RESPIRATORY CARE Paper in Press. Published on July 11, 2023, as DOI: 10.4187/respcare.11157
NEW HORIZONS SYMPOSIUM
Introduction space pressure measurement. Although it requires the place-
ment of an esophageal catheter, it is easier and safer than a
Since the 1960s, respiratory therapists (RTs) have adapted pleural tube. The validity and challenges of Pes as a surrogate
their role as caregivers while technology and practice evolved. of pleural pressure (Ppl) (Fig. 2) have been described in sev-
The evolution in ventilator technology provides tools previ- eral studies.4,7,8 We will discuss below what Pes reflects and
ously only available for research; one example is esophageal what it does not. The literature contains different terms and
pressure (Pes) monitoring. Although Pes measurement has symbols for respiratory system measurements and calcula-
been used for decades, it is only now that it is easily available tions. Unfortunately, this has led to confusion.9 Thus, we cre-
at the bedside. The availability is both a benefit and a curse. It ated Tables 1–3 following a standardized notation published
is a benefit because it is easily available and may provide use- in this Journal,10 which contains the terms and the calcula-
ful information and a curse because, as with any pressure tions distilled to the bedside level.
measurements, knowledge of both technique and physiology
is essential; when these are lacking, errors occur. Pleural Pressure
Pes measurement perfectly aligns with the RT skills. The
RT already possesses knowledge of the basic physiology Any particular Ppl measurement does not represent a ho-
related to transpulmonary pressures (PTP), patient-ventilator mogeneous pressure throughout the pleural space. Instead,
synchrony, and the work of breathing. However, with this Ppl measurements vary according to the gravitational gradi-
knowledge comes important responsibilities. Although evi- ent (ie, ventral vs dorsal if supine or apical and basal if
dence suggests some areas where Pes monitoring might be standing), lung weight, and regional lung inhomogene-
useful, we must be aware that currently there is no evidence ities.11 For example, the vertical pleural gradient has been
that it improves outcomes.1 This brings back memories of shown to increase by 1.8 times in the presence of lung
lessons learned with pulmonary artery catheters (PACs),2 injury due to an increase in lung weight.7 This is an impor-
where technology was available earlier than evidence and tant consideration because assuming Ppl measurements are
was applied indiscriminately and with poor technique. the same at different points on the pleural surface may lead
Thus, we are responsible for using Pes monitoring with a to errors in calculations, clinical interpretations of data, and
sound physiological understanding, clear indications, proto- therapy applications. See Figure 3 for Ppl gradients.
colized and standardized practices, and following quality-
assurance practices. Finally, we must continue to generate
Transmural Pressures
evidence to define for whom Pes measurement is needed
and beneficial.3 Although extensive reviews on this topic
A key concept in physiology is transmural pressure,
have been previously published,4-6 this primer aims to syn-
the pressure difference across a structure. The transmural
thesize the basic knowledge needed to perform Pes meas-
pressure is the stress the structure sees and, in the case of
urements in a single document.
the alveoli, a proposed determinant of lung injury.12,13
The transmural pressure is obtained by subtracting the
Physiology
pressure inside the structure minus the pressure outside
(a simple mnemonic is Pin minus Pout). Figure 2 demon-
The esophagus travels through the mediastinum and
strates the concept of transmural pressure. The simplistic
becomes adjacent to the pleural space (Fig. 1). The contigu-
interpretation is that if the pressure outside a flexible
ity of the esophagus with the pleura allows the measurement
structure is higher than inside the structure collapses, and
of the pressure inside the esophagus as a surrogate for pleural
if vice versa, the pressure inside is higher than outside
the structure distends. This explains alveolar collapse, as
The authors are affiliated with Respiratory Institute, Cleveland Clinic, well as vascular collapse.14,15
Cleveland, Ohio.
The topic of pressure gradients and what they are called
Dr Mireles-Cabodevila discloses a relationship with IngMar Medical. Mr are a common source of confusion in the literature10
Chatburn discloses relationships with IngMar Medical, Inovytec, Ventis, (Tables 1 and 2). For example, 2 commonly confused terms
AutoMedx, Vyaire, Aires, and Stimdia. The remaining authors have
are transalveolar pressure (PTA) and PTP. PTA is the differ-
disclosed no conflicts of interest.
ence between the alveolar pressure (PA) and Ppl. PTP is the
Supplementary material related to this paper is available at http://www. pressure difference across the larger structure of the air-
rcjournal.com. ways and lungs, calculated as the pressure at the airway
opening (PAO) minus Ppl. The legacy symbol for PTP has
Correspondence: Eduardo Mireles-Cabodevila MD, Cleveland Clinic, 9500
Euclid Avenue, M56, Cleveland, Ohio 44195. E-mail: .
been PL, but this obscures the fact that PTP is a difference in
pressure between 2 points in space, whereas PL seems to
DOI: 10.4187/respcare.11157 indicate the pressure at one point in space (ie, PA).
2 RESPIRATORY CARE
VOL NO
Copyright (C) 2023 Daedalus Enterprises ePub ahead of print papers have been peer-reviewed, accepted for publication, copy edited
and proofread. However, this version may differ from the final published version in the online and print editions of RESPIRATORY CARE
