Limits...
Aortic pressure wave reconstruction during exercise is improved by adaptive filtering: a pilot study.

Stok WJ, Westerhof BE, Guelen I, Karemaker JM - Med Biol Eng Comput (2011)

Bottom Line: The optimal resonance frequency was predicted from regression formulas using variables derived from the individual's peripheral pressure pulse, including a pulse contour estimation of cardiac output (pcCO).Using a genTF and without calibration, the error in estimated aortic pulse pressure was -7.5 ± 6.4 mmHg, which was reduced to 0.2 ± 5.7 mmHg with the indTFs using pcCO for prediction.Calibration resulted in less scatter at the cost of a small bias (2.7 mmHg).

View Article: PubMed Central - PubMed

Affiliation: Heart Failure Research Centre, Academic Medical Center, University of Amsterdam, Room M01-215, Meibergdreef 9, NL-1105 AZ, Amsterdam, The Netherlands. w.stok@amc.uva.nl

ABSTRACT
Reconstruction of central aortic pressure from a peripheral measurement by a generalized transfer function (genTF) works well at rest and mild exercise at lower heart rates, but becomes less accurate during heavy exercise. Particularly, systolic and pulse pressure estimations deteriorate, thereby underestimating central pressure. We tested individualization of the TF (indTF) by adapting its resonance frequency at the various levels of exercise. In seven males (age 44-57) with coronary artery disease, central and peripheral pressures were measured simultaneously. The optimal resonance frequency was predicted from regression formulas using variables derived from the individual's peripheral pressure pulse, including a pulse contour estimation of cardiac output (pcCO). In addition, reconstructed pressures were calibrated to central mean and diastolic pressure at each exercise level. Using a genTF and without calibration, the error in estimated aortic pulse pressure was -7.5 ± 6.4 mmHg, which was reduced to 0.2 ± 5.7 mmHg with the indTFs using pcCO for prediction. Calibration resulted in less scatter at the cost of a small bias (2.7 mmHg). In exercise, the indTFs predict systolic and pulse pressure better than the genTF. This pilot study shows that it is possible to individualize the peripheral to aortic pressure transfer function, thereby improving accuracy in central blood pressure assessment during exercise.

Show MeSH

Related in: MedlinePlus

Bland–Altman plots (average ± 2 SD) plot of measured aorta pressure and reconstructed pulse pressure with the genTF (genAorPP, top) and the individual TFs (indAorPP, bottom). Results without (a, c) and with (b, d) additional calibration. Points are results from all measured workloads in seven subjects
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3139898&req=5

Fig3: Bland–Altman plots (average ± 2 SD) plot of measured aorta pressure and reconstructed pulse pressure with the genTF (genAorPP, top) and the individual TFs (indAorPP, bottom). Results without (a, c) and with (b, d) additional calibration. Points are results from all measured workloads in seven subjects

Mentions: Differences between measured and reconstructed AorPP were reduced with the indTFs using any of the three regression formulas for prediction of the resonance peak. Formula 1 performed best with respect to precision although Formulas 2 and 3 were only marginally inferior. The incorporation of the AorP-to-FinAP pulse wave time delay in the regression, in addition to BP and HR, did not improve reconstruction. Table 2 gives the differences for rest and exercise combined using the genTF and the indTFs both without and with additional calibration. With a calibration for each level of exercise, precision improved using the indTFs, but a small bias was introduced. As can be observed in the corresponding Bland–Altman plots (Fig. 3a–d), the negative bias at the higher pulse pressures was reduced (for aorta pulse pressures above 70 mmHg, from −10.4 to −0.8 mmHg for the uncalibrated data).Fig. 3


Aortic pressure wave reconstruction during exercise is improved by adaptive filtering: a pilot study.

Stok WJ, Westerhof BE, Guelen I, Karemaker JM - Med Biol Eng Comput (2011)

Bland–Altman plots (average ± 2 SD) plot of measured aorta pressure and reconstructed pulse pressure with the genTF (genAorPP, top) and the individual TFs (indAorPP, bottom). Results without (a, c) and with (b, d) additional calibration. Points are results from all measured workloads in seven subjects
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3139898&req=5

Fig3: Bland–Altman plots (average ± 2 SD) plot of measured aorta pressure and reconstructed pulse pressure with the genTF (genAorPP, top) and the individual TFs (indAorPP, bottom). Results without (a, c) and with (b, d) additional calibration. Points are results from all measured workloads in seven subjects
Mentions: Differences between measured and reconstructed AorPP were reduced with the indTFs using any of the three regression formulas for prediction of the resonance peak. Formula 1 performed best with respect to precision although Formulas 2 and 3 were only marginally inferior. The incorporation of the AorP-to-FinAP pulse wave time delay in the regression, in addition to BP and HR, did not improve reconstruction. Table 2 gives the differences for rest and exercise combined using the genTF and the indTFs both without and with additional calibration. With a calibration for each level of exercise, precision improved using the indTFs, but a small bias was introduced. As can be observed in the corresponding Bland–Altman plots (Fig. 3a–d), the negative bias at the higher pulse pressures was reduced (for aorta pulse pressures above 70 mmHg, from −10.4 to −0.8 mmHg for the uncalibrated data).Fig. 3

Bottom Line: The optimal resonance frequency was predicted from regression formulas using variables derived from the individual's peripheral pressure pulse, including a pulse contour estimation of cardiac output (pcCO).Using a genTF and without calibration, the error in estimated aortic pulse pressure was -7.5 ± 6.4 mmHg, which was reduced to 0.2 ± 5.7 mmHg with the indTFs using pcCO for prediction.Calibration resulted in less scatter at the cost of a small bias (2.7 mmHg).

View Article: PubMed Central - PubMed

Affiliation: Heart Failure Research Centre, Academic Medical Center, University of Amsterdam, Room M01-215, Meibergdreef 9, NL-1105 AZ, Amsterdam, The Netherlands. w.stok@amc.uva.nl

ABSTRACT
Reconstruction of central aortic pressure from a peripheral measurement by a generalized transfer function (genTF) works well at rest and mild exercise at lower heart rates, but becomes less accurate during heavy exercise. Particularly, systolic and pulse pressure estimations deteriorate, thereby underestimating central pressure. We tested individualization of the TF (indTF) by adapting its resonance frequency at the various levels of exercise. In seven males (age 44-57) with coronary artery disease, central and peripheral pressures were measured simultaneously. The optimal resonance frequency was predicted from regression formulas using variables derived from the individual's peripheral pressure pulse, including a pulse contour estimation of cardiac output (pcCO). In addition, reconstructed pressures were calibrated to central mean and diastolic pressure at each exercise level. Using a genTF and without calibration, the error in estimated aortic pulse pressure was -7.5 ± 6.4 mmHg, which was reduced to 0.2 ± 5.7 mmHg with the indTFs using pcCO for prediction. Calibration resulted in less scatter at the cost of a small bias (2.7 mmHg). In exercise, the indTFs predict systolic and pulse pressure better than the genTF. This pilot study shows that it is possible to individualize the peripheral to aortic pressure transfer function, thereby improving accuracy in central blood pressure assessment during exercise.

Show MeSH
Related in: MedlinePlus