No abstract

Non‐contact coded hemodynamic imaging (CHI) is a novel wide‐field near‐infrared spectroscopy system which monitors blood volume by quantifying attenuation of light passing through the underlying vessels. This study tested the hypothesis that CHI‐based jugular venous attenuation (JVA) would be larger in men, and change in JVA would be greater in men compared to women during two fluid shift challenges. The association of JVA with ultrasound‐based cross‐sectional area (CSA) was also tested. Ten men and 10 women completed three levels of head‐down tilt (HDT) and four levels of lower body negative pressure (LBNP). Both JVA and CSA were increased by HDT and reduced by LBNP (all p < 0.001). Main effects of sex indicated that JVA was higher in men than women during both HDT ( p = 0.003) and LBNP ( p = 0.011). Interaction effects of sex and condition were observed for JVA during HDT ( p = 0.005) and LBNP ( p < 0.001). We observed moderate repeated‐measures correlations ( r rm ) between JVA and CSA in women during HDT ( r rm = 0.57, p = 0.011) and in both men ( r r m = 0.74, p < 0.001) and women ( r rm = 0.66, p < 0.001) during LBNP. While median within‐person correlation coefficients indicated an even stronger association between JVA and CSA, this association became unreliable for small changes in CSA. As hypothesized, JVA was greater and changed more in men compared to women during both HDT and LBNP. CHI provides a non‐contact method of tracking large changes in internal jugular vein blood volume that occur with acute fluid shifts, but data should be interpreted in a sex‐dependent manner.

An optical imaging system is proposed for quantitatively assessing jugular venous response to altered central venous pressure. Methods: The proposed system assesses sub-surface optical absorption changes from jugular venous waveforms with a spatial calibration procedure to normalize incident tissue illumination. Widefield frames of the right lateral neck were captured and calibrated using a novel flexible surface calibration method. Jugular venous optical attenuation (JVA) signals were computed using an optical model for quantifying hemodynamic changes, and a jugular venous pulsatility map was computed using a time-synchronized arterial waveform. JVA was assessed in three cardiovascular protocols that altered central venous pressure by inducing acute central hypovolemia (lower body negative pressure), venous congestion (head-down tilt), and impaired cardiac filling (Valsalva maneuver). Results: JVA waveforms exhibited biphasic properties and sub-wave timing consistent with jugular venous pulse dynamics with timesynchronized electrocardiogram waves. JVA correlated strongly (median, interquartile range) with invasive central venous pressure during graded central hypovolemia (r=0.85, [0.72, 0.95]), graded venous congestion (r=0.94, [0.84, 0.99]), and impaired cardiac filling (r=0.94, [0.85, 0.99]). Reduced JVA during graded acute hypovolemia was strongly correlated with reductions in stroke volume (SV) (r=0.85, [0.76, 0.92]) from baseline (SV: 79 ± 15 mL, JVA: 0.56 ± 0.10 a.u.) to −40 mmHg suction (SV: 59 ± 18 mL, JVA: 0.47 ± 0.05 a.u.; p<0.01). Conclusion:The proposed non-contact optical imaging system demonstrated jugular venous dynamics consistent with invasive central venous monitoring during three protocols that altered central venous pressure. Significance: This system provides non-invasive monitoring of pressure-induced jugular venous dynamics in clinically relevant conditions where catheterization is traditionally required, enabling monitoring in non-surgical environments.