Comparing two adaptive methods for removing cardiac beat artifact in esophageal pressure measurement: MANC and AFIR

The measurement of esophageal pressure (Pes) is a simple technique that can be used to calculate the lung mechanical parameters. In clinical practice the traditional strategy for cardiac beat artifact minimization in Pes measurement is to adjust either the position of esophageal balloon or the posture of the body under test. The authors propose a new scheme combining a modified adaptive noise cancellation (MANC) method and an adaptive FIR (AFIR) filter to eliminate the cardiac beat artifact from Pes measurement. In experiments, the authors also find that the harmonic effect interferes with the measurement of Pes. In using the MANC the authors do not have to carefully adjust the position of the esophageal balloon to avoid the results being affected by body posture, and it is independent of frequency variations of cardiac beat and respiration. In using the AFIR it is found to be suitable for most cases that the frequency of the cardiac beat is different from the respiration frequency but not suitable for the frequencies or harmonics that overlap slightly