Precision of Measure of Resistive Index
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08/04/18
Impact of Mild Hypoxemia on Renal Function and Renal Resistive Index during
Mechanical Ventilation
Electronic supplementary material
Michael DARMON MD, Frédérique SCHORTGEN MD, Rusel LEON MD, Stéphane
MOUTEREAU MD PhD, Julien MAYAUX MD, Fabiano DI MARCO MD, Jérôme
DEVAQUET MD, Christian BRUN-BUISSON MD, Laurent BROCHARD MD PhD
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Precision of measure of resistive index:
Precision of the RI measurements was evaluated by computing the Spearman correlation coefficient between the results showing the greatest difference across oxygenation conditions, and these differences were also compared with Bland and Altman plots to evaluate the mean difference±2 SDs between two measures (Y axis) relative to the average of the measurements
(X axis) [28].
RI was obtained in every of the patients and each reported RI is the mean of three consecutive measures. The two most different values among the three RI values measured under each oxygenation condition were strongly correlated (=0.98; P<0.0001) (Figure E1).
When comparing these values, bias, as illustrated by the mean difference in the Bland and
Altman analysis, was negligible (-0.009). The differences between these values corresponding to the ±95% confidence interval in the Bland-Altman graphs were +0.045 and –0.054 (Figure
E2 in the online supplement).
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Figure E1: Graph of the relationship between the results showing the largest differences across oxygenation conditions. Correlations were evaluated using Spearman’s correlation coefficient. Measures a and b were the RI values that showed the largest difference across the three oxygenation conditions.
Figure E2: Bland and Altman plot of the mean resistive index, compared with the largest difference between values across oxygenation conditions in each patient.
Figure E3: Relationship between baseline resistive index and age. Correlations were assessed using Spearman’s correlation coefficient.
Figure E4: Relationship between baseline resistive index and mean arterial pressure at baseline. Correlations were assessed using Spearman’s correlation coefficient.
Figure E5: Effect of mild hypoxemia on resistive index values in patients with and without norepinephrine (NE) infusion. Wilcoxon’s nonparametric test was used for comparisons of low oxygenation with high oxygenation period.
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Figure E1
RI n°1 0.9
0.8
0.7
0.6
0.5 R² = 0.963
0.5 0.5 0.6 0.6 0.7 0.7 0.8 0.8 0.9 0.9
RI RI n°2 n°2
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Figure E2
0.10
0.05
0.00
-0.05
-0.10
0.4 0.5 0.6 0.7 0.8 0.9 Mean RI
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Figure E3.
1.0
0.9
0.8
0.7
0.6
0.5 R² = 0.783 P=0.0001 0.4 R Sq Linear = 0.783
Age (years)
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Figure E4.
1.0 R R²=0.396 Sq Linear = 0.396 P=0.003 P=0.03 0.9
0.8
0.7
0.6
0.5
0.4
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Figure E5.
Renal resistive index With Norepinephrine 0.9 P = 0.03 Without Norepinephrine
0.8
0.7
0.6
P = 0.03 0.5
Low oxygenation High oxygenation
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