Frequency response of the pleuro-esophageal tissue barrier and esophageal pressure waveform bandwidth in non-human primates

Dynamic intra-esophageal pressure (Pes) is used to estimate intra-pleural pressure (Ppl) for calculating lung compliance. We quantified the amplitude frequency response required of Pes catheter manometers to reproduce Pes waveforms faithfully, and determined the amplitude frequency response of the Ppl-Pes tissue barrier using simultaneous Ppl and Pes measurements in mechanically ventilated monkeys. Allowing for 3% Pes waveform reproduction error, Pes end-inspiratory to end-expiratory pressure (/spl Delta/Ppk) was not significantly affected by filtering Pes at low-pass cut-off frequencies>the Pes fourth harmonic frequency. The Ppl-Pes tissue barrier had a near-uniform amplitude frequency response over the band of current clinical interest, but at a low airway pressure offset significant resonance occurred in the 32-40 Hz band. We conclude that to reproduce dynamic Pes waveforms faithfully Pes catheter manometers require amplitude frequency responses with uniformity up to the Pes fourth harmonic frequency. Transmission of high frequency components across the Ppl-Pes tissue barrier is subject to amplification. These findings have implications for measurements of lung compliance at high respiratory frequencies and varied airway pressure offsets.