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

Abstract

We 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.