Abstract
The oesophagus has been shown to be a reliable site for monitoring blood oxygen saturation (SpO2). However, the photoplethysmographic (PPG) signals from the lower oesophagus are frequently contaminated by a ventilator artefact making the estimation of SpO2 impossible. A 776th order finite impulse response (FIR) filter and a 695th order interpolated finite impulse response (IFIR) filter were implemented to suppress the artefact. Both filters attenuated the ventilator artefact satisfactorily without distorting the morphology of the PPG when processing recorded data from ten cardiopulmonary bypass patients. The IFIR filter was the better since it conformed more closely to the desired filter specifications and allowed real-time processing. The average improvements in signal-to-noise ratio (SNR) achieved by the FIR and IFIR filters for the fundamental component of the red PPG signals with respect to the fundamental component of the artefact were 57.96 and 60.60 dB, respectively. The corresponding average improvements achieved by the FIR and IFIR filters for the infrared PPG signals were 54.83 and 60.96 dB, respectively. Both filters were also compared with their equivalent tenth order Butterworth filters. The average SNR improvements for the FIR and IFIR filters were significantly higher than those for the Butterworth filters.
References
Freund PR, Overand PT, Cooper J, Jacobson L, Bosse S, Walker B, Posner KL, Cheney FW (1991) A prospective study of intraoperative pulse oximetry failure. J Clin Monit 7:253–258
Kelleher JF (1989) Pulse oximetry. J Clin Monit 5:37–62
Kyriacou PA, Powell S, Langford RM, Jones DP (2002) Investigation of oesophageal photoplethysmographic signals and blood oxygen saturation measurements in cardiothoracic surgery patients. Physiol Meas 23:533–545
Kyriacou PA, Powell S, Jones DP, Langford RM (2003) Evaluation of oesophageal pulse oximetry in patients undergoing cardiothoracic surgery. Anaesthesia 58:422–427
Pal SK, Kyriacou PA, Kumaran S, Fadheel S, Emamdee R, Langford RM, Jones DP (2005) Evaluation of oesophageal reflectance pulse oximetry in major burns patients. Burns 31:337–341
Palve H, Vuori A (1989) Pulse oximetry during low cardiac output and hypothermia states immediately after open heart surgery. Crit Care Med 17:66–69
Reich DL, Timcenko A, Bodian CA, Kraidin J, Hofman JB, Deperio M, Konstadt SN, Kurki T, Eisenkraft JB (1996) Predictors of pulse oximetry data failure. Anesthesiology 84:859–864
Saramäki T (1993) Handbook for digital signal processing. Wiley, New York, pp 155–279
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Shafqat, K., Jones, D.P., Langford, R.M. et al. Filtering techniques for the removal of ventilator artefact in oesophageal pulse oximetry . Med Bio Eng Comput 44, 729–737 (2006). https://doi.org/10.1007/s11517-006-0089-2
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11517-006-0089-2