Cardiovascular Diseases Poster Session



Materials & Methods


Discussion & Conclusion



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The PORTAPRES In The Non-invasive Assessment Of Dynamic Cardiovascular Function

Contact Person: Chris Hillier (C.Hillier@gcal.ac.uk)


The heart rate, mean arterial pressure and cardiac index all rose appropriately with exercise and the systemic vascular resistance dropped (data not shown).


Strong correlations between the Portapres and sphygmomanometer were seen for MAP and CI (table 1). In figure 1 a scatter diagram indicates the good correlation (r = 0.74) between MAP measured by the two techniques. However, sphygmomanometer readings were usually higher and lay to the right of the line of equality.

                             HR    MAP   CI    SVR
Absolute values (n = 75)    0.99  0.74  0.68  0.43
Percentage change (n = 50)  0.99  0.40  0.79  0.65

Table 1 Pearsons product-moment correlation coefficients for absolute data and percentage change from baseline. All correlates are significant at p < .01.

Figure 1 Scattergram showing 75 paired measurements of mean arterial pressure (MAP) made at rest and during the Bruce protocol by the sphygmomanometer and Portapres techniques. The line represents equality.


In Table 2 the mean difference and 95% limits of agreement for each of the parameters are recorded. On exercise, the percentage change from baseline was comparable for MAP 6.1 17% (mean difference SD) and CI 6.1 29%. However, the Portapres recorded absolute values of MAP and CI lower than ICG [MAP -7.8 10.1 (mmHg), CI -2.4 1.3 (l/min/m2)]. The comparison between measurements of absolute MAP and % change in CI are illustrated as Bland and Altman plots in Figures 2 & 3 for clarification.

The magnitude of mean differences in the absolute measurement of MAP and CI, and the width of the limits of agreement, were clinically significant.

                         HR        MAP       CI         SVR
Absolute values         (bpm)    (mmHg)  (l/min/m2)    (PRU)
Mean difference         -0.96      7.8       2.4       -0.45
d + 2s                   7.3      28.0       5.1        0.20
d - 2s                  -9.2     -12.4      -0.2       -1.1

Percentage change (%) (%) (%) (%) Mean difference 1.08 6.1 6.1 -2.2 d + 2s 17.7 40.2 64.8 38.3 d - 2s -15.6 -28.1 -52.6 -42.6

Table 2 Agreement between absolute and percentage change from baseline measurements of HR, MAP, CI and SVR obtained simultaneously by ICG and Portapres methods. Mean difference (d) and upper (+ 2s) and lower (- 2s) levels of agreement. Differences are reference - Portapres. Negative differences indicate higher readings for the Portapres and vice versa.

Figure 2 Bland and Altman plot of all MAP measurements by the two techniques. The difference between two paired readings is plotted against their mean in mmHg. The mean difference and upper and lower limits of agreement are indicated.

Figure 3 Bland and Altman plot of the percentage changes in CI from baseline during exercise. The difference between paired readings is plotted against their mean. The mean difference and upper and lower limits of agreement are indicated.


The within-subject coefficients of variation for baseline measurements of each parameter are displayed in Table 3.

                                HR      MAP    CI       SVR
Coefficient of variation (%)
Portapres                       5.0     6.3    8.5      13.9
ICG/Sphygmomanometer            3.7     4.7    6.3      6.9

Table 3 Reproducibility of the two techniques.

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Mills, NL; Spratt, PL; Padfield, DJ; Webb, DJ; (1998). The PORTAPRES In The Non-invasive Assessment Of Dynamic Cardiovascular Function. Presented at INABIS '98 - 5th Internet World Congress on Biomedical Sciences at McMaster University, Canada, Dec 7-16th. Available at URL http://www.mcmaster.ca/inabis98/cvdisease/mills0906/index.html
© 1998 Author(s) Hold Copyright