Oesophageal and transdiaphragmatic pressure measurement: Implications for monitoring

A proper characterisation of respiratory mechanics, work of breathing and respiratory drive in patients with spontaneous breathing activity requires the knowledge of pleural pressure. Pleural pressure is difficult to be measured and requires highly invasive procedures. An alternative approach is estimating it starting from the less invasive and simpler measurement of esophageal pressure by the trans-nasal insertion in the esophagus of either an esophageal balloon or catheter provided by solid-state miniature pressure transducers. Even though these procedures are apparently simple, in order to obtain accurate estimation of pleural pressure special care must be devoted to a proper catheter positioning and calibration and the accuracy must be tested by applying validated procedures before use. Once available, the information provided by combining esophageal pressure with that at the airway opening and the respiratory flow allows to accurately monitor lung mechanics and patient-ventilator interaction, allowing a better tailoring of ventilatory parameters in patients receiving mechanical ventilation. However, the technical challenges as well as the expertise needed for interpreting the data are currently limiting the clinical application of esophageal pressure measures despite the useful information it provides. Such technical challenges are increased even more during NIV, where the dynamics of the upper airways may impact the transmission of the airway opening to the lung and where unavoidable leaks at the patients' interface may prevent accurate assessment of respiratory mechanics.