Novel method of transpulmonary pressure measurement with an air‑flled esophageal catheter

Background: There is a strong rationale for proposing transpulmonary pressureguided protective ventilation in acute respiratory distress syndrome. The reference
esophageal balloon catheter method requires complex in vivo calibration, expertise
and specifc material order. A simple, inexpensive, accurate and reproducible method
of measuring esophageal pressure would greatly facilitate the measure of transpulmonary pressure to individualize protective ventilation in the intensive care unit.
Results: We propose an air-flled esophageal catheter method without balloon, using
a disposable catheter that allows reproducible esophageal pressure measurements.
We use a 49-cm-long 10 Fr thin suction catheter, positioned in the lower-third of the
esophagus and connected to an air-flled disposable blood pressure transducer bound
to the monitor and pressurized by an air-flled infusion bag. Only simple calibration by
zeroing the transducer to atmospheric pressure and unit conversion from mmHg to
cmH2O are required. We compared our method with the reference balloon catheter
both ex vivo, using pressure chambers, and in vivo, in 15 consecutive mechanically
ventilated patients. Esophageal-to-airway pressure change ratios during the dynamic
occlusion test were close to one (1.03±0.19 and 1.00±0.16 in the controlled and
assisted modes, respectively), validating the proper esophageal positioning. The Bland–
Altman analysis revealed no bias of our method compared with the reference and
good precision for inspiratory, expiratory and delta esophageal pressure measurements
in both the controlled (largest bias −0.5 cmH2O [95% confdence interval: −0.9; −0.1]
cmH2O; largest limits of agreement −3.5 to 2.5 cmH2O) and assisted modes (largest
bias −0.3 [−2.6; 2.0] cmH2O). We observed a good repeatability (intra-observer, intraclass correlation coefcient, ICC: 0.89 [0.79; 0.96]) and reproducibility (inter-observer
ICC: 0.89 [0.76; 0.96]) of esophageal measurements. The direct comparison with pleural
pressure in two patients and spectral analysis by Fourier transform confrmed the reliability of the air-flled catheter-derived esophageal pressure as an accurate surrogate of
pleural pressure. A calculator for transpulmonary pressures is available online.
Conclusions: We propose a simple, minimally invasive, inexpensive and reproducible
method for esophageal pressure monitoring with an air-flled esophageal catheter
without balloon. It holds the promise of widespread bedside use of transpulmonary
pressure-guided protective ventilation in ICU patients.