Simultaneous Arterial and Venous Oximetry with a Novel Flexi-Frequency Cuff Actuator

The concurrent assessment of peripheral arterial oxygen saturation
$(SpaO_{2})$
and peripheral venous oxygen saturation
$(SpvO_{2})$
is imperative for understanding an individual's oxygen metabolism. However, unlike
$SpaO_{2}$
measurement, a universally accepted non-invasive method for measuring
$SpvO_{2}$
is lacking due to the absence of regular venous pulses. Some studies have proposed inducing finger pressure pulsations to create detectable venous modulations, measurable with photo-plethysmography (PPG). Yet, the influence of the modulation frequency on
$SpvO_{2}$
estimation remains understudied. Here, we introduce an innovative electro-pneumatic system capable of producing precise pressure pulses on a finger cuff across a broad frequency spectrum, from 0.2 Hz to above 6 Hz, without observable ripple effects. The system employs a 2-way high-pressure air pump, an overpressure and a safety valve, and a 3D-printed solution based on a switching valve and a stepper motor to switch between inflow and outflow in the finger cuff at high speed. Human trials during hypoxia testing revealed distinct modulation impacts on arterial and venous blood flow at varying frequencies using PPG. Furthermore, estimated
$SpaO_{2}$
and
$SpvO_{2}$
values aligned well with reference pulse oximetry values, particularly at 6 Hz modulation. Our findings highlight the potential of this system for accurately estimating
$SpaO_{2}$
and
$SpvO_{2}$
non-invasively, offering promising prospects for clinical diagnostics and treatment evaluation in conditions affecting tissue oxygen utilization.