Validation of the mean systemic filling pressure assessment with preserved arterial blood flow by comparing two methods of calculation

AbstractWe developed a method for measuring in vivo venular volumes and the mean systemic filling pressure in the limbs using near-infrared spectroscopy (NIRS). We aimed to validate the NIRS methodology by comparing two independent methods of calculation based on different physiological approaches. Pressure–volumes (P–V) curves were recorded following graded venous occlusion on the forearm. Values from a P–V curves analysis model (method 1) were compared with data derived from a resistor-capacitance calculation model (method 2) based on arterial pressure and venous compliance. We tested these methods on 10 healthy participants at rest and during exercise and on 6 severely ill patients. Results from method 1 were comparable with those calculated by method 2. Venular volumes calculated using method 1 correlated linearly with those calculated using method 2 both in participants (R2 = 0.98) and in patients (R2 = 0.94). A good agreement between methods was shown with few values out of the range of ± 1.96 standard deviation. Our findings added mathematical consistency for the NIRS methodology validation in the venular P–V assessment with no flow interruption. Further research will be required to confirm the relevance of the methodology in the clinical setting.

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Systemic filling pressure in intact circulation determined on basis of aortic vs. central venous pressure relationships

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1994.267.6.h2255 ◽

1994 ◽

Vol 267 (6) ◽

pp. H2255-H2258 ◽

Cited By ~ 4

Author(s):

E. A. Den Hartog ◽

A. Versprille ◽

J. R. Jansen

Keyword(s):

Central Venous Pressure ◽

Flow Resistance ◽

Venous Pressure ◽

Aortic Pressure ◽

Filling Pressure ◽

Central Venous ◽

Mean Systemic Filling Pressure ◽

Systemic Filling ◽

The Mean ◽

Systemic Filling Pressure

In the intact circulation, mean systemic filling pressure (Psf) is determined by applying a series of inspiratory pause procedures (IPPs) and using Guyton's equation of venous return (Qv) and central venous pressure (Pcv): Qv = a - b x Pcv. During an IPP series, different tidal volumes are applied to set Pcv at different values. From the linear regression between Qv and Pcv, Psf can be calculated as Psf = a/b. Guyton's equation can also be written as Qv = (Psf - Pcv)/Rsd, where Rsd is the flow resistance downstream of the places where blood pressure is equal to Psf. During an IPP, a steady state is observed. Therefore, we can also formulate the following equation for flow: Qs = (Pao - Psf)/Rsu, where Qs is systemic flow, Rsu is the systemic flow resistance upstream to Psf, and Pao is aortic pressure. Because both flows (Qs and Qv) are equal, it follows that Pao = Psf(1 + Rsu/Rsd) - Rsu/Rsd x Pcv. This equation implies a method to determine mean systemic filling pressure on the basis of Pao measurements instead of flow determinations. Using 22 IPPs in 10 piglets, we determined the mean systemic filling pressure, and we compared the values obtained from the flow curves with those obtained from the aortic pressure curves. The mean difference between the two methods was 0.03 +/- 1.16 mmHg. With the use of Pao measurements, the Psf can be estimated as accurately as in using flow determinations. The advantage of the new method is that estimation of cardiac output is not required.

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Validation of the mean systemic filling pressure assessment with preserved arterial blood flow by comparing two methods of calculation

10.21203/rs.3.rs-241999/v1 ◽

2021 ◽

Author(s):

Roberto Alberto De Blasi ◽

Stefano Finazzi

Keyword(s):

Near Infrared ◽

Venous Occlusion ◽

Calculation Model ◽

Arterial Blood Flow ◽

Venous Compliance ◽

Model Method ◽

Arterial Blood ◽

Methods Of Calculation ◽

Multi Phase

Abstract Significance: We developed a method for measuring in vivo venular volumes and pressures in the limbs using near-infrared spectroscopy (NIRS).Aim: 36 We aimed to validate the NIRS methodology by comparing two independent methods of calculation based on different physiological approaches.Approach: Pressure-volumes curves were recorded following graded venous occlusion on the forearm. Values from a multi-phase model (method 1) were compared with data derived from a resistor-capacitance calculation model (method 2) based on arterial pressure and venous compliance. We tested these methods on 10 healthy participants at rest and during exercise and on 6 severely ill patients.Results: Pressure-volume curves measured by method 1 were comparable with those calculated by method 2. Venular volumes calculated using method 1 correlated linearly with those calculated using method 2 both in participants (R2 = 0.98, p < 0.001) and in patients (R2 = 0.94, p < 0.001). The Bland-Altman test showed a good agreement between methods with few values out of the range of ± 1.96 SD.Conclusions: Our findings showed that the NIRS methodology may be valid for the assessment of venular bed with no flow interruption. Further research will be required to confirm the relevance of methodology in the clinical setting.

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