Blood draw

Medical “Vampire” Robot Seeks Human Vein, Inserts Needle, Sucks Blood

July 30, 2020
This nearly autonomous medical robotic system uses ultrasonic imaging to locate a suitable forearm vein, then inserts a needle at the critical angle and distance, and finally draws a sample of blood.

This article appeared in Electronic Design and has been published here with permission.

Inserting a needle into the vein in someone’s arm and drawing a blood sample, or inserting an intravenous line, is a common medical procedure and often an essential first step in patient care. The challenge of obtaining successful venous access ranges from easy to very difficult depending on the subject’s veins and physiology as well as the skill of the medical technician. Oftentimes, it ends in a frustrating unsuccessful outcome that requires retries, delays and even additional help.

This clinical procedure is performed more than 1.4 billion times yearly in the United States. However, according to clinical studies, it fails in 27% of patients without visible veins, 40% of patients without palpable veins and 60% of emaciated patients. Instrumentation with ultrasound imaging is available to assist clinicians in locating the vein, but manual needle insertion under ultrasound guidance requires careful hand-eye coordination for steady placement and control of both the probe and needle. Near-infrared (NIR) imaging systems are also used, but they have a penetration depth of only about 3 mm and tend to be ineffective with obese patients.

Venipuncture Device

Now, a team based at Rutgers University has developed and is field-testing a nearly autonomous robotic system that locates a likely suitable vein, inserts the needle and even draws the blood sample. This venipuncture device is designed to safely perform blood draws on peripheral forearm veins. The system combines ultrasound imaging and miniaturized robotics to identify suitable vessels for cannulation and robotically guide an attached needle toward what’s called the lumen center.

A clinician does the setup of general positioning of the machine with respect to the subject’s arm, sterilizing/wiping the target zone, applying ultrasound hydrogel and selecting the target vein’s center as displayed on a monitor. These coordinates are then used by the device to determine the necessary kinematics to ensure that the needle tip intersected the ultrasound imaging plane at the vessel center.

Once aligned and steady, the operator then initiates the insertion procedure, and the injection-axis carriage drives the attached needle tip forward at a 25-degree angle relative to the participant’s forearm to the target of the vein center, inserts the needle and draws a 5-ml blood sample.

System Setup

The system consists of two major mechanical assemblies: a two-dimensional ultrasound probe on a linear motion carriage and the single-dimension needle thrust, both linked by a microcontroller for coordinated control (Fig. 1).

Guidance and task execution employs a combination of force-vs.-displacement feedback profiling along with ultrasonic imaging (Fig. 2). Real-time analysis of that profile data indicates the likely success of the procedure, including the desirable sudden “breakthrough” that occurs as force suddenly drops over a short distance when the vein wall is pierced.

If the force/distance profile indicates the attempt will be unsuccessful (veins aren’t rigid, of course, and can move or roll during the process) or if no blood flows, the needle withdraws and the operator guides the machine to a new possible site. A graphical user interface shows the ultrasound image, force sensor, injection motor velocity and position profiles for both Z-axis and injection motors (Fig. 3).

Efficacy

The results thus far on a limited number of test subjects are favorable and comparable to or better than those of clinical standards. The overall success rate was 87% on all 31 participants and 97% on the 25 participants who had easy-access veins, with an average procedure time of 93 ± 30 seconds.

The researchers note that future versions of this system device could be extended to other areas of vascular access, such as IV catheterization, central venous access, dialysis and arterial line placement. Further, the system could be combined with an integral blood-assessment subsystem for an “all-in-one” blood-draw and test-result arrangement.

Details of the project are in the team’s paper “First-in-human evaluation of a hand-held automated venipuncture device for rapid venous blood draws” published in Technology (World Scientific). It focuses primarily on sensor data, profiles, algorithms and results and with less discussion of the machine’s actual construction. While that paper is behind a paywall, it’s also available here as an HTML page with a link to a downloadable PDF file.

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