How to measure esophageal pressure correctly

Article

Author: Jean-Michel Arnal, Senior Intensivist, Hopital Sainte Musse, Toulon, France

Date of first publication: 19.10.2018

Last change: 09.09.2020

Formatting

A recent physiological study demonstrated that esophageal pressure estimates the pleural pressure at mid-thorax at all levels of PEEP. Therefore, an absolute measurement of esophageal pressure is useful for setting PEEP and monitoring transpulmonary pressure.

How to measure esophageal pressure correctly

Initial placement and inflation

So how do we measure esophageal pressure correctly?

The esophageal balloon has to be positioned and inflated correctly, and placement then verified.

The optimal position for the esophageal balloon is the lower third of the esophagus, at a distance of 35–45 cm from the nostrils. With a patient in semi-recumbent position, the empty balloon is first inserted into the stomach, which is situated around 50–60 cm from the nostrils. The balloon is inflated to a standard volume (1 ml for a Cooper Surgical catheter and 4 ml for a Nutrivent catheter). Gastric pressure displays a positive deflection during inspiration in both passive and spontaneously breathing patients. The gastric position is ascertained by gently applying manual epigastric compression, which shows an immediate increase in gastric pressure (see Figure 1).

Screenshot of waveform showing Pes increase — Figure 1

Withdrawal with balloon inflated

The esophageal catheter is then gently withdrawn while the balloon is still inflated, in order to position the balloon in the lower third of the esophagus. During the change from gastric (see Figure 2) to esophageal (see Figure 3) pressure, the baseline of the pressure waveform changes and cardiac oscillations appear.

Waveform showing baseline for gastric pressure — Figure 2: Gastic pressure

Waveform showing baseline for esophageal pressure — Figure 3: Esophageal pressure

Esophageal pressure deflections

Esophageal pressure deflections are positive during inspiration in passive patients (see Figure 4), but negative in spontaneously breathing patients (see Figure 5). If cardiac oscillations distort the esophageal pressure signal, you can withdraw the catheter by another 2–5 cm.

Waveform showing Pes deflections in passive patient — Figure 4: Passive patient

Waveform showing Pes deflections in spontaneous patient — Figure 5: Spontaneously breathing patient

Inflating the balloon

The volume of air for adequate inflation of the balloon should be individually titrated. This is only possible in passive patients. According to the method proposed by Mojoli et al (2016), the balloon is inflated from 0.5 to 3 ml in gradual steps of 0.5 ml for a Cooper Surgical catheter, and from 1 to 8 ml in steps of 1 ml for a Nutrivent catheter (see Figure 6). During progressive inflation of the balloon, the baseline of esophageal pressure increases and the magnitude of the esophageal pressure deflection changes. The adequate inflation volume is the one associated with the largest deflection of esophageal pressure. If two different inflation volumes show the same magnitude of esophageal pressure deflection, the lowest inflation volume is selected.

Waveform during balloon inflation — Figure 6: Balloon inflation performed with a Nutrivent catheter

Vertification

Once the balloon has been positioned correctly in the esophagus and inflated, verification is performed by means of an occlusion test. The principle is to close the airways at end expiration to change the airway pressure, and then to verify that esophageal pressure changes by the same amount.

In passive patients, you can perform an end-expiratory occlusion. When the expiratory valve is closed, apply an external manual compression of the rib cage on both sides of the chest in order to see a positive deflection of airway and esophageal pressures. The magnitude of the increase in airway and esophageal pressure should be the same. In other words, the transpulmonary pressure should not change (see Figure 7).

In active patients, the dynamic occlusion test also uses an end-expiratory occlusion. There is no need to press manually on the chest, as the patient will make a spontaneous inspiratory effort during the occlusion. The result is a negative deflection of airway and esophageal pressure. The magnitude of the decrease in airway and esophageal pressure should be the same, i.e., the transpulmonary pressure should not change (see Figure 8).

If you wish to monitor esophageal pressure continuously, it is important to reassess the correct position and inflation volume.

Full citations below: (Yoshida T, Amato MBP, Grieco DL, et al. Esophageal Manometry and Regional Transpulmonary Pressure in Lung Injury. Am J Respir Crit Care Med. 2018;197(8):1018-1026. doi:10.1164/rccm.201709-1806OC1, Mojoli F, Iotti GA, Torriglia F, et al. In vivo calibration of esophageal pressure in the mechanically ventilated patient makes measurements reliable. Crit Care. 2016;20:98. Published 2016 Apr 11. doi:10.1186/s13054-016-1278-52, Baydur A, Behrakis PK, Zin WA, Jaeger M, Milic-Emili J. A simple method for assessing the validity of the esophageal balloon technique. Am Rev Respir Dis. 1982;126(5):788-791. doi:10.1164/arrd.1982.126.5.7883, Akoumianaki E, Maggiore SM, Valenza F, et al. The application of esophageal pressure measurement in patients with respiratory failure. Am J Respir Crit Care Med. 2014;189(5):520-531. doi:10.1164/rccm.201312-2193CI4, Mauri T, Yoshida T, Bellani G, et al. Esophageal and transpulmonary pressure in the clinical setting: meaning, usefulness and perspectives. Intensive Care Med. 2016;42(9):1360-1373. doi:10.1007/s00134-016-4400-x5)

Waveform showing increase in Paw and Pes; no change in Ptranspulm — Figure 7: Occlusion test in passive patient

Waveform showing decrease in Paw and Pes; no change in Ptranspulm — Figure 8: Occlusion test in active patient

Footnotes

References

1. Yoshida T, Amato MBP, Grieco DL, et al. Esophageal Manometry and Regional Transpulmonary Pressure in Lung Injury. Am J Respir Crit Care Med. 2018;197(8):1018-1026. doi:10.1164/rccm.201709-1806OC
2. Mojoli F, Iotti GA, Torriglia F, et al. In vivo calibration of esophageal pressure in the mechanically ventilated patient makes measurements reliable. Crit Care. 2016;20:98. Published 2016 Apr 11. doi:10.1186/s13054-016-1278-5
3. Baydur A, Behrakis PK, Zin WA, Jaeger M, Milic-Emili J. A simple method for assessing the validity of the esophageal balloon technique. Am Rev Respir Dis. 1982;126(5):788-791. doi:10.1164/arrd.1982.126.5.788
4. Akoumianaki E, Maggiore SM, Valenza F, et al. The application of esophageal pressure measurement in patients with respiratory failure. Am J Respir Crit Care Med. 2014;189(5):520-531. doi:10.1164/rccm.201312-2193CI
5. Mauri T, Yoshida T, Bellani G, et al. Esophageal and transpulmonary pressure in the clinical setting: meaning, usefulness and perspectives. Intensive Care Med. 2016;42(9):1360-1373. doi:10.1007/s00134-016-4400-x

Esophageal Manometry and Regional Transpulmonary Pressure in Lung Injury.

Yoshida T, Amato MBP, Grieco DL, et al. Esophageal Manometry and Regional Transpulmonary Pressure in Lung Injury. Am J Respir Crit Care Med. 2018;197(8):1018-1026. doi:10.1164/rccm.201709-1806OC

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RATIONALE

Esophageal manometry is the clinically available method to estimate pleural pressure, thus enabling calculation of transpulmonary pressure (Pl). However, many concerns make it uncertain in which lung region esophageal manometry reflects local Pl.

OBJECTIVES

To determine the accuracy of esophageal pressure (Pes) and in which regions esophageal manometry reflects pleural pressure (Ppl) and Pl; to assess whether lung stress in nondependent regions can be estimated at end-inspiration from Pl.

METHODS

In lung-injured pigs (n = 6) and human cadavers (n = 3), Pes was measured across a range of positive end-expiratory pressure, together with directly measured Ppl in nondependent and dependent pleural regions. All measurements were obtained with minimal nonstressed volumes in the pleural sensors and esophageal balloons. Expiratory and inspiratory Pl was calculated by subtracting local Ppl or Pes from airway pressure; inspiratory Pl was also estimated by subtracting Ppl (calculated from chest wall and respiratory system elastance) from the airway plateau pressure.

MEASUREMENTS AND MAIN RESULTS

In pigs and human cadavers, expiratory and inspiratory Pl using Pes closely reflected values in dependent to middle lung (adjacent to the esophagus). Inspiratory Pl estimated from elastance ratio reflected the directly measured nondependent values.

CONCLUSIONS

These data support the use of esophageal manometry in acute respiratory distress syndrome. Assuming correct calibration, expiratory Pl derived from Pes reflects Pl in dependent to middle lung, where atelectasis usually predominates; inspiratory Pl estimated from elastance ratio may indicate the highest level of lung stress in nondependent "baby" lung, where it is vulnerable to ventilator-induced lung injury.

In vivo calibration of esophageal pressure in the mechanically ventilated patient makes measurements reliable.

Mojoli F, Iotti GA, Torriglia F, et al. In vivo calibration of esophageal pressure in the mechanically ventilated patient makes measurements reliable. Crit Care. 2016;20:98. Published 2016 Apr 11. doi:10.1186/s13054-016-1278-5

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In screening programmes it is important to assess a preliminary effectiveness of the screening method as soon as possible in order to forecast survival figures. In March 1981 a controlled single-view mammographic screening trial for breast cancer was started in the south of Stockholm. The population invited for screening mammography consisted of 40,000 women aged 40-64 years, and 20,000 women served as a well-defined control group. The main aim of the trial was to determine whether repeated mammographic screening could reduce the mortality in the study population (SP) compared to the control population (CP). The cumulative number of advanced mammary carcinomas in the screening and the control populations from the first five years of screening have shown a tendency towards more favourable stages in the screened population aged 40-64 years. A breakdown by age suggests an effect in age group 50-59 years, but not yet in age groups 40-49 and 60-64 years. When comparing the rates of stage II+ cancer, an increased number is found in the study group. As the total rate of breast cancer is higher in SP than in CP, there ought to be a concealed group of stage II+ cancers in the CP which makes the comparison biased. A new approach has been designed, where an estimation of the 'hidden' number of stage II+ cancers in CP is added to the clinically detected cases, and in this respect a comparison has shown a decrease in the cumulative number of advanced cancers in the SP in relation to the CP (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

A simple method for assessing the validity of the esophageal balloon technique.

Baydur A, Behrakis PK, Zin WA, Jaeger M, Milic-Emili J. A simple method for assessing the validity of the esophageal balloon technique. Am Rev Respir Dis. 1982;126(5):788-791. doi:10.1164/arrd.1982.126.5.788

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The validity of the conventional esophageal balloon technique as a measure of pleural pressure was tested in 10 subjects in sitting, supine, and lateral positions by occluding the airways at end-expiration and measuring the ratio of changes in esophageal (delta Pes) and mouth pressure (delta Pm) during the ensuing spontaneous occluded inspiratory efforts. Similar measurements were also made during static Mueller maneuvers. In both tests, delta Pes/delta Pm values were close to unity in sitting and lateral positions, whereas in the supine position, substantial deviations from unity were found in some instances. However, by repositioning the balloon to different levels in the esophagus, even in these instances a locus could be found where the delta Pes/delta Pm ratio was close to unity. No appreciable phase difference between delta Pes and delta Pm was found. We conclude that by positioning the balloon according to the "occlusion test" procedure, valid measurements of pleural pressure can be obtained in all the tested body positions.

The application of esophageal pressure measurement in patients with respiratory failure.

Akoumianaki E, Maggiore SM, Valenza F, et al. The application of esophageal pressure measurement in patients with respiratory failure. Am J Respir Crit Care Med. 2014;189(5):520-531. doi:10.1164/rccm.201312-2193CI

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This report summarizes current physiological and technical knowledge on esophageal pressure (Pes) measurements in patients receiving mechanical ventilation. The respiratory changes in Pes are representative of changes in pleural pressure. The difference between airway pressure (Paw) and Pes is a valid estimate of transpulmonary pressure. Pes helps determine what fraction of Paw is applied to overcome lung and chest wall elastance. Pes is usually measured via a catheter with an air-filled thin-walled latex balloon inserted nasally or orally. To validate Pes measurement, a dynamic occlusion test measures the ratio of change in Pes to change in Paw during inspiratory efforts against a closed airway. A ratio close to unity indicates that the system provides a valid measurement. Provided transpulmonary pressure is the lung-distending pressure, and that chest wall elastance may vary among individuals, a physiologically based ventilator strategy should take the transpulmonary pressure into account. For monitoring purposes, clinicians rely mostly on Paw and flow waveforms. However, these measurements may mask profound patient-ventilator asynchrony and do not allow respiratory muscle effort assessment. Pes also permits the measurement of transmural vascular pressures during both passive and active breathing. Pes measurements have enhanced our understanding of the pathophysiology of acute lung injury, patient-ventilator interaction, and weaning failure. The use of Pes for positive end-expiratory pressure titration may help improve oxygenation and compliance. Pes measurements make it feasible to individualize the level of muscle effort during mechanical ventilation and weaning. The time is now right to apply the knowledge obtained with Pes to improve the management of critically ill and ventilator-dependent patients.

Esophageal and transpulmonary pressure in the clinical setting: meaning, usefulness and perspectives.

Mauri T, Yoshida T, Bellani G, et al. Esophageal and transpulmonary pressure in the clinical setting: meaning, usefulness and perspectives. Intensive Care Med. 2016;42(9):1360-1373. doi:10.1007/s00134-016-4400-x

Link to article

PURPOSE

Esophageal pressure (Pes) is a minimally invasive advanced respiratory monitoring method with the potential to guide management of ventilation support and enhance specific diagnoses in acute respiratory failure patients. To date, the use of Pes in the clinical setting is limited, and it is often seen as a research tool only.

METHODS

This is a review of the relevant technical, physiological and clinical details that support the clinical utility of Pes.

RESULTS

After appropriately positioning of the esophageal balloon, Pes monitoring allows titration of controlled and assisted mechanical ventilation to achieve personalized protective settings and the desired level of patient effort from the acute phase through to weaning. Moreover, Pes monitoring permits accurate measurement of transmural vascular pressure and intrinsic positive end-expiratory pressure and facilitates detection of patient-ventilator asynchrony, thereby supporting specific diagnoses and interventions. Finally, some Pes-derived measures may also be obtained by monitoring electrical activity of the diaphragm.

CONCLUSIONS

Pes monitoring provides unique bedside measures for a better understanding of the pathophysiology of acute respiratory failure patients. Including Pes monitoring in the intensivist's clinical armamentarium may enhance treatment to improve clinical outcomes.