Training tool
The blood vessel model for simulating filter insertion and retrieval mainly replicates the inferior vena cava, right and left renal veins, and right and left iliac veins. Three ringed thin protuberances were made in the part corresponding to the inferior vena cava below the renal vein so that the feet of the filters could be fixed easily to the wall of the model.
This life-size model was made using a three-dimensional computer-aided design system based on a drawing as shown in Figure 1a. The model is made of silicone resin coated internally with silicone oil (Figure 1b). The training tool, which is lightweight and easy to carry, has 3 end holes into which a 14-F sheath introducer can be inserted. Each hole can be covered when not used. Two end holes were used for training. These end holes correspond to entry to the cervical and right femoral veins. Movement of devices such as catheters and guide wires within the vessel is visible from outside of the training tool (Figure 1c). Furthermore, training under the guidance of a computer-controlled display camera that displays the tool and devices is possible.
Animal model
This study protocol was approved by the institutional Animal Experimental Committee. Three female pigs weighing 50.4–53.0 kg (mean weight 52.1 kg) were studied. All animals were carefully maintained and cared for before and during the experiment in accordance with the guiding principles on care and use of laboratory animals at Terumo Medical Pranex (Kanagawa, Japan). These guiding principles conformed to standards for care and management of experimental animals as established by the Japanese Prime Minister’s office and international guiding principles for biomedical research involving animals (The Japanese association for laboratory animal science (JALAS) 1987).
All procedures were performed with the swine under general anesthesia. Animals were placed in a supine position. Premedication was administered with an intramuscular injection of atropine sulfate (0.05 mg/kg; Tanabe-Mitsubisi-Seiyaku, Osaka, Japan), midazolam (5 mg/kg; Sando Inc., Tokyo, Japan), and xylazine (4 mg/kg; Bayen Health Care, Tokyo, Japan). Anesthesia was induced by thiamylal sodium (5-6.25 mg/kg (iv) Nichikou, Toyama, Japan). After anesthetic administration, an endotracheal tube was inserted, and anesthesia was maintained with sevoflurane (2-4%; Mylane, Osaka, Japan), nitrous oxide (3 l/min), and oxygen (3 l/min). Electrocardiography was used to monitor heart rate and rhythm. Oxygen saturation was monitored using a pulse oxymeter (OGS-2001; Nihon Kohden, Tokyo, Japan). A 7-F vascular sheath was inserted into the femoral artery to monitor real-time blood pressure using a pressure transducer (DTXTM PLUS DT-XX; Nihon Becton Dickinson, Inc., Fukushima, Japan) connected to a pressure polygraph (Cardiomaster RMC 3000; Nihon Kohden). For training with these animal models, a 14-F short sheath was placed into the jugular vein, through which devices for filter implantation and retrieval could be inserted repeatedly. Training procedures were performed using a single-plane fluoroscopy unit (Allura Xper FD20, Philips Electronics Japan, Tokyo, Japan).
Evaluation of training of beginners with the combination of a training tool and animal model
The effectiveness of training using a combination of a blood vessel model and animal model was evaluated in medical doctors who had little or just some experience as operators in filter insertion and retrieval. A Gunther tulip vena cava filter was used for the training (Cook, Bjaeverskov, Denmark).
Trainees were 30 young interventional radiologists (age: mean 33.4 y, median 33 y, range 28–42 y; years since passing the examination of the National Board of Medical Examiners in Japan, mean 8, median 7, range 3–17) who participated in the 10th academic seminar organized by the Japanese Society of Interventional Radiology at Terumo Medical Pranex held on July 28 and 29, 2012. Mean number of years since first performing interventional radiology was 4.1 (range 0.3 to 14; median 3). As to the number of filter implantations performed among participants as an operator, none had been performed by 11, 1-10 by 17, and more than 10 by 2. Eighteen participants had not performed retrieval while 12 performed 1 to 10 retrievals of an optional filter.
All 5 instructors were experienced in insertion and retrieval of optional filters and were board certified as interventional radiologists by the Japanese Society of Interventional Radiology. Mean number of years of experience as interventional radiologists was 14.2 (range 10 to 21; median 12).
After receiving classroom lectures from instructors on inferior vena cava filters, including those on procedures for implantation and retrieval of filters, trainees practiced with the training tool and animal model. Eleven trainees practiced with the animal model first, then with the blood vessel model while 19 trainees practiced with the blood vessel model first, followed by the animal model. Just after training with the animal model, the 19 trainees were asked to evaluate the usefulness of training with the tool prior to training with the animal model by selecting one of the following possible responses: 1, extremely; 2, quite; 3, moderately; 4, slightly; 5, no.
The trainees practiced using the training tool after one of the five instructors demonstrated implanting and removing the filter using the model. Trainees were allowed to ask advice from their instructor at any time. Instructors also used a hands-on approach as needed in assisting the trainees. This training was done in groups of 9 to 11 trainees. Allotted time for each group was approximately 60 minutes.
In training with the animal model, because the length between the jugular vein and renal vein is longer anatomically compared with the human, it was decided that the filter would be implanted in the inferior vena cava at the cephalad site of entry to the renal vein. After the instructor demonstrated implantation then retrieval of the filter, each trainee took a turn practicing the procedure. The trainees were allowed to ask advice from their instructor at any time. Instructors advised orally; however, they made an effort to let trainees do the procedure by themselves and to assist directly through hands-on instruction as little as possible. The trainee and instructors wore a protective lead apron and radio-protective glasses. An instructor evaluated the procedure on the monitor and timed the procedure. If the trainee could not either implant or retrieve a filter within 13 minutes, the instructor assisted with a hands-on demonstration and allowed the trainee to continue from that point or actually completed the procedure in place of the trainee from that point forward. Time required for implantation and retrieval of the filter, respectively, was measured. When a trainee could not successfully implant or retrieve the filter within 13 minutes, the procedure time was noted as 13 minutes.