Evaluation of mean systemic filling pressure from pulse contour cardiac output and central venous pressure
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The volemic status of a patient can be determined by measuring mean systemic filling pressure (Pmsf). Pmsf is obtained from the venous return curve, i.e. the relationship between central venous pressure (Pcv) and blood flow. We evaluated the feasibility and precision of Pmsf measurement.
In ten piglets we constructed venous return curves using seven 12 s inspiratory holds transiently increasing Pcv to seven different steady state levels and monitored the resultant blood flow, by pulse contour (COpc) and by flow probes around the pulmonary artery (COr) and aorta (COl). Pmsf is obtained by extrapolation of the venous return curve to zero flow. Measurements were repeated to evaluate the precision of Pmsf.
During the inspiratory holds, 133 paired data points were obtained for COr, COl, COpc and Pcv. Bland–Altman analysis showed no difference between COr and COl, but a small significant difference was present between COl and COpc. All Pcv versus flow (COl or COpc) relationships were linear. Mean Pmsf was 10.78 with COl and 10.37 mmHg with COpc. Bland–Altman analysis for Pmsf with COl and with COpc, showed a bias of 0.40 ± 0.48 mmHg. The averaged coefficient of variation for repeated measurement of Pmsf with COl was 6.2% and with COpc 6.1%.
During an inspiratory hold pulmonary flow and aortic flow equilibrate. Cardiac output estimates by arterial pulse contour and by a flow probe around the aorta are interchangeable. Therefore, the venous return curve and Pmsf can be estimated accurately by pulse contour methods.
Keywordsvenous return mean systemic filling pressure cardiac output pulse contour
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