A 65-year-old woman with history of COPD, congestive heart failure with ejection fraction of 35%, Hepatitis C cirrhosis without ascites, and body mass index of 35 is intubated for hypoxemic respiratory failure after an aspiration event and transferred to the ICU for further management. A chest radiograph demonstrates bilateral patchy infiltrates, and initial PaO2 is 145 on FiO2 100%. The patient remains hypoxemic on standard ventilation with tidal volumes 6 mL/kg and PEEP titrated to 12 cm H2O on FiO2 100%.
Which clinical factor suggests this patient may benefit from esophageal pressure measurements to titrate ventilation parameters?
A. COPDCorrect Answer: D
The pressure in the lower third of the esophagus closely parallels the pressure in the adjoining pleura. The measurement is accurate when taken in the upright lung, without the pressure of the mediastinum compressing the esophagus. The esophageal pressure balloon can therefore be used to estimate the transpulmonary pressure (Ptranspulmonary = Pairway opening − Ppleura ). Referring to the transpulmonary pressure equation, elevated pleural pressure can result in negative end-expiratory transpulmonary pressure, which is clinically manifested as alveolar collapse. Esophageal pressure measurement as a proxy for pleural pressure allows for titration of PEEP to maintain positive transpulmonary pressure at end expiration, maintaining functional residual capacity and preventing airway collapse. Patients ventilated to achieve transpulmonary pressure 0 to 10 cm H2O had significantly improved oxygenation and lung compliance.
Esophageal pressure is most likely to be useful in patients with elevated pleural pressure due to a decrease in extrapulmonary compliance. Direct pulmonary causes of ARDS, such as aspiration or pneumonia, are associated with decreased lung compliance but often have normal chest wall compliance. They are characterized by alveolar consolidation, which is not typically responsive to changes in PEEP. By contrast, extrapulmonary decreases in compliance, caused by factors such as obesity, ascites, bowel edema, pancreatitis, peritonitis, or other intra-abdominal pathologies, manifest as atelectasis and have a greater potential for alveolar recruitment. COPD, congestive heart failure, and cirrhosis without ascites do not particularly decrease extrapulmonary compliance and thus are not likely to specifically benefit from esophageal pressure measurements.
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