Come misurare correttamente la pressione esofagea

Articolo

Autore: Dr. Jean-Michel Arnal, intensivista senior, Hôpital Sainte Musse, Tolone, Francia

Data: 19.10.2018

Last change: 09.09.2020

Formatting

Uno studio fisiologico recente ha dimostrato che la pressione esofagea rappresenta una stima della pressione pleurica nella zona centrale del torace a tutti i livelli di PEEP. Una misurazione assoluta della pressione esofagea è quindi utile per impostare la PEEP e monitorare la pressione transpolmonare.

Come misurare correttamente la pressione esofagea

Posizionamento iniziale e gonfiaggio

Come si misura correttamente la pressione esofagea?

È necessario posizionare e gonfiare correttamente il palloncino esofageo, quindi verificarne il posizionamento.

La posizione ottimale per il palloncino esofageo è nel terzo inferiore dell'esofago, a una distanza di 35-45 cm dalle narici. Con il paziente in posizione semi-supina, per prima cosa si inserisce il palloncino sgonfio nello stomaco, situato a circa 50-60 cm dalle narici. Si gonfia quindi il palloncino fino a un volume standard (1 ml per un catetere CooperSurgical e 4 ml per un catetere NutriVent). La pressione gastrica è caratterizzata da una deflessione positiva durante l'inspirazione sia nei pazienti passivi sia in quelli che respirano spontaneamente. Si verifica che il palloncino sia in posizione gastrica esercitando delicatamente una compressione epigastrica manuale che corrisponde a un aumento immediato della pressione (vedere la Figura 1).

Schermata che visualizza la curva in cui è visibile l'aumento della Pes — Figura 1

Arretramento del catetere con il palloncino gonfio

Occorre quindi tirare indietro delicatamente il catetere esofageo con il palloncino gonfio per posizionare il palloncino nel terzo inferiore dell'esofago. Quando si passa dalla pressione gastrica (vedere la Figura 2) a quella esofagea (vedere la Figura 3), la linea basale della curva di pressione cambia e compaiono le oscillazioni cardiache.

Curva che mostra la linea basale della pressione gastrica — Figura 2: pressione gastrica

Curva che mostra la linea basale della pressione esofagea — Figura 3: pressione esofagea

Deflessioni nella curva della pressione esofagea

Le deflessioni nella curva della pressione esofagea sono positive durante l'inspirazione nei pazienti passivi (vedere la Figura 4), mentre sono negative nei pazienti che respirano spontaneamente (vedere la Figura 5). Se le oscillazioni cardiache distorcono il segnale della pressione esofagea, è possibile tirare indietro il catetere ancora di 2-5 cm.

Curva che mostra le deflessioni della Pes in un paziente passivo — Figura 4: paziente passivo

Curva che mostra le deflessioni della Pes in un paziente che respira spontaneamente — Figura 5: paziente che respira spontaneamente

Gonfiaggio del palloncino

Il volume di aria necessario per un gonfiaggio adeguato del palloncino deve essere determinato su base individuale. È possibile fare questa operazione solo nei pazienti passivi. Secondo il metodo proposto da Mojoli et al. (2016), se si utilizza un catetere CooperSurgical il palloncino deve essere gonfiato da 0,5 a 3 ml con incrementi graduali da 0,5 ml, mentre se si utilizza un catetere NutriVent il palloncino deve essere gonfiato da 1 a 8 ml con incrementi graduali da 1 ml (vedere la Figura 6). Durante il progressivo gonfiaggio del palloncino, la linea basale della pressione esofagea sale e l'ampiezza della deflessione nella curva della pressione esofagea cambia. Il volume di gonfiaggio adeguato è quello associato alla deflessione più ampia nella curva della pressione esofagea. Se l'ampiezza della deflessione nella pressione esofagea è la stessa per due diversi volumi di gonfiaggio, è opportuno scegliere il volume di gonfiaggio più basso.

Verifica

Dopo aver posizionato il palloncino correttamente nell'esofago e dopo averlo gonfiato, occorre eseguire la verifica con un test di occlusione. L'idea di base è di chiudere le vie aeree al termine dell'espirazione per modificare la pressione delle vie aeree, quindi verificare che la pressione esofagea registri una variazione equivalente.

Nei pazienti passivi è possibile effettuare un'occlusione a fine espirazione. Quando la valvola espiratoria è chiusa, applicare una compressione manuale esterna su entrambi i lati della gabbia toracica: si osserva una deflessione positiva della pressione delle vie aeree e della pressione esofagea. L'entità dell'aumento deve essere la stessa nella pressione delle vie aeree e in quella esofagea. In altre parole, la pressione transpolmonare non deve subire variazioni (vedere la Figura 7).

Anche nei pazienti attivi il test di occlusione dinamica si basa su un'occlusione a fine espirazione. Non è necessario comprimere il torace manualmente, poiché il paziente compie uno sforzo inspiratorio spontaneo durante l'occlusione. Si crea così una deflessione negativa nelle curve della pressione delle vie aeree e della pressione esofagea. L'entità della diminuzione registrata nella pressione delle vie aeree e in quella esofagea deve essere la stessa, ovvero la pressione transpolmonare non deve subire variazioni (vedere la Figura 8).

Se si desidera monitorare in modo continuo la pressione esofagea, è importante rivalutare il corretto posizionamento e il volume di gonfiaggio.

Citazioni complete a fondo pagina: (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. Pubblicato l'11 aprile 2016. 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)

Curva che evidenzia l'aumento di Paw e Pes senza variazioni di Ptranspulm — Figura 7: test di occlusione in un paziente passivo

Curva che evidenzia la diminuzione di Paw e Pes senza variazioni di Ptranspulm — Figura 8: test di occlusione in un paziente attivo

Note

Bibliografia

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

Link to article

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

Link to article

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

Link to article

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

Link to article

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.