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A new model-free index of dynamic cerebral blood flow autoregulation.

Chacón M, Jara JL, Panerai RB - PLoS ONE (2014)

Bottom Line: Although this index is often used in clinical research and is also included in some commercial equipment, it exhibits considerable intra-subject variability, and has the tendency to produce false positive results in clinical applications.This new index uses two parameters that are obtained directly from the response signal of the cerebral blood flow velocity to a transient decrease in arterial blood pressure provoked by the sudden release of bilateral thigh cuffs, and a third parameter measuring the difference in slope of this response and the change in arterial blood pressure achieved.In 16 healthy subjects who underwent repeated thigh-cuff manoeuvres, the model-free approach exhibited significantly lower intra-subject variability, as measured by the unbiased coefficient of variation, than the classic autoregulatory index (p = 0.032) and the Rate of Return (p<0.001), another measure of cerebral autoregulation used for this type of systemic pressure stimulus, from 39.23%±41.91% and 55.31%±31.27%, respectively, to 15.98%±7.75%.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Ingeniería Informática, Universidad de Santiago de Chile, Santiago, Chile.

ABSTRACT
The classic dynamic autoregulatory index (ARI), proposed by Aaslid and Tiecks, is one of the most widely used methods to assess the efficiency of dynamic cerebral autoregulation. Although this index is often used in clinical research and is also included in some commercial equipment, it exhibits considerable intra-subject variability, and has the tendency to produce false positive results in clinical applications. An alternative index of dynamic cerebral autoregulation is proposed, which overcomes most of the limitations of the classic method and also has the advantage of being model-free. This new index uses two parameters that are obtained directly from the response signal of the cerebral blood flow velocity to a transient decrease in arterial blood pressure provoked by the sudden release of bilateral thigh cuffs, and a third parameter measuring the difference in slope of this response and the change in arterial blood pressure achieved. With the values of these parameters, a corresponding classic autoregulatory index value could be calculated by using a linear regression model built from theoretical curves generated with the Aaslid-Tiecks model. In 16 healthy subjects who underwent repeated thigh-cuff manoeuvres, the model-free approach exhibited significantly lower intra-subject variability, as measured by the unbiased coefficient of variation, than the classic autoregulatory index (p = 0.032) and the Rate of Return (p<0.001), another measure of cerebral autoregulation used for this type of systemic pressure stimulus, from 39.23%±41.91% and 55.31%±31.27%, respectively, to 15.98%±7.75%.

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Comparison of the cumulative distributions of both indices.Percentage cumulative probability distribution of mfARI values (filled circles, solid line) compared to the corresponding distribution for classic ARI values (open squares, dotted line).
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pone-0108281-g004: Comparison of the cumulative distributions of both indices.Percentage cumulative probability distribution of mfARI values (filled circles, solid line) compared to the corresponding distribution for classic ARI values (open squares, dotted line).

Mentions: mfARI values for manoeuvres showed no evidence of deviation from normality (A = 0.588, p = 0.122), as did classic ARI values (A = 0.687, p = 0.071). Fig. 4 presents the cumulative distributions of both indices, in which it can be seen that the classic method assigned very low ARI values (≤2.0) to several thigh-cuff manoeuvres, whereas the lowest mfARI value assigned was 2.7 (for the sixth manoeuvre of subject 6, which obtained a classic ARI value of 0.0).


A new model-free index of dynamic cerebral blood flow autoregulation.

Chacón M, Jara JL, Panerai RB - PLoS ONE (2014)

Comparison of the cumulative distributions of both indices.Percentage cumulative probability distribution of mfARI values (filled circles, solid line) compared to the corresponding distribution for classic ARI values (open squares, dotted line).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4196773&req=5

pone-0108281-g004: Comparison of the cumulative distributions of both indices.Percentage cumulative probability distribution of mfARI values (filled circles, solid line) compared to the corresponding distribution for classic ARI values (open squares, dotted line).
Mentions: mfARI values for manoeuvres showed no evidence of deviation from normality (A = 0.588, p = 0.122), as did classic ARI values (A = 0.687, p = 0.071). Fig. 4 presents the cumulative distributions of both indices, in which it can be seen that the classic method assigned very low ARI values (≤2.0) to several thigh-cuff manoeuvres, whereas the lowest mfARI value assigned was 2.7 (for the sixth manoeuvre of subject 6, which obtained a classic ARI value of 0.0).

Bottom Line: Although this index is often used in clinical research and is also included in some commercial equipment, it exhibits considerable intra-subject variability, and has the tendency to produce false positive results in clinical applications.This new index uses two parameters that are obtained directly from the response signal of the cerebral blood flow velocity to a transient decrease in arterial blood pressure provoked by the sudden release of bilateral thigh cuffs, and a third parameter measuring the difference in slope of this response and the change in arterial blood pressure achieved.In 16 healthy subjects who underwent repeated thigh-cuff manoeuvres, the model-free approach exhibited significantly lower intra-subject variability, as measured by the unbiased coefficient of variation, than the classic autoregulatory index (p = 0.032) and the Rate of Return (p<0.001), another measure of cerebral autoregulation used for this type of systemic pressure stimulus, from 39.23%±41.91% and 55.31%±31.27%, respectively, to 15.98%±7.75%.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Ingeniería Informática, Universidad de Santiago de Chile, Santiago, Chile.

ABSTRACT
The classic dynamic autoregulatory index (ARI), proposed by Aaslid and Tiecks, is one of the most widely used methods to assess the efficiency of dynamic cerebral autoregulation. Although this index is often used in clinical research and is also included in some commercial equipment, it exhibits considerable intra-subject variability, and has the tendency to produce false positive results in clinical applications. An alternative index of dynamic cerebral autoregulation is proposed, which overcomes most of the limitations of the classic method and also has the advantage of being model-free. This new index uses two parameters that are obtained directly from the response signal of the cerebral blood flow velocity to a transient decrease in arterial blood pressure provoked by the sudden release of bilateral thigh cuffs, and a third parameter measuring the difference in slope of this response and the change in arterial blood pressure achieved. With the values of these parameters, a corresponding classic autoregulatory index value could be calculated by using a linear regression model built from theoretical curves generated with the Aaslid-Tiecks model. In 16 healthy subjects who underwent repeated thigh-cuff manoeuvres, the model-free approach exhibited significantly lower intra-subject variability, as measured by the unbiased coefficient of variation, than the classic autoregulatory index (p = 0.032) and the Rate of Return (p<0.001), another measure of cerebral autoregulation used for this type of systemic pressure stimulus, from 39.23%±41.91% and 55.31%±31.27%, respectively, to 15.98%±7.75%.

Show MeSH
Related in: MedlinePlus