Build your own ultrasound-guided thoracentesis simulator
By Ted Warren and Roger W. Bush, MD, FACP
The use of bedside, portable diagnostic ultrasound devices by nonradiologists is increasing, because of both maturing, more affordable technology and evidence supporting improved patient safety and process efficiency.
Hand-carried, battery-powered, high-quality ultrasound machines are now available at a small fraction of the costs of conventional technology. With minimal training, hospitalists, critical care clinicians, emergency physicians, and internal medicine residents have been shown to achieve competence in focused, brief, urgent and goal-directed sonographic applications such as:
Michael Westley, MD, ACP Member, of the Virginia Mason Medical Center in Seattle, practices using ultrasound guidance to identify and tap fluid on a do-it-yourself simulator made from pork ribs. Photos courtesy of Roger W. Bush, MD, FACP
- procedural guidance (arthrocentesis, paracentesis and thoracentesis),
- assessment of cardiac ventricular size and function in urgent and emergent settings,
- central venous pressure assessment and
- pneumothorax assessment.
Relying exclusively on physical examination and clinical assessment for these questions exposes patients to avoidable transfers, delays of care, inappropriate interventions and therapies and long wait times in diagnostic departments. Ultra-sound is superior to chest X-rays in determining the presence and location of pleural fluid, and ultrasound guidance is associated with a lower pneumothorax risk (<1% to 5%).
Training residents and physicians to use ultrasound for a procedure such as thoracentesis can be expensive from the standpoint of simulation technology. Many institutions now have portable ultrasound devices available to educators; however, lack of access to simulation models can present a stumbling block to training. Several very good simulation models include internal effusions for aspiration, but these can cost thousands of dollars for a single model.
Handheld ultrasound simulators can be reproduced in any training environment, practice group or at home as a very workable alternative to commercial models and for a small fraction of the cost. Both methods provide high-fidelity images and an authentic procedure experience. The do-it-yourself model does require more prep time in terms of setup and cleanup but much lower capital costs. Basically, it's the cost of a rack of pork ribs.
Supplies for the simulation:
- a utility knife,
- a magazine filing box or shallow cardboard book shipping box (Physicians' Desk Reference works well),
- 1-gallon sealable plastic bag,
- half-rack of pork spare ribs (preferably with parietal pleura attached) and
- twine or zip ties to attach ribs to box
Instructions for construction:
Step 1. Using a utility knife, cut a 10- to 15-cm square out of the flat/face side of box.
Step 2. Fill plastic bag with water so that it is relatively firm when sealed.
Step 3. Slip plastic bag into the cardboard box and tape up the box.
Step 4. Place ribs parietal pleura side down (against the fluid-filled bag) and secure them to cardboard box using twine or zip ties. Side of plastic bag should protrude slightly beyond the plane of the box wall.
The box with ribs attached should be elevated on some kind of semi-vertical stand if you intend to simulate the procedure on a seated patient. Conversely, the simulation model should be laid flat to simulate a supine patient.
Thoracentesis procedural checklist:
- Position patient as normal, seated upright vs. supine (ventilated).
- Determine whether there is fluid. (Scan dependently.)
- Map extent of fluid in two planes.
- Note proximity of lung, heart, liver, spleen, and diaphragm through respiratory cycle.
- Mark needle entry site (above rib to avoid neurovascular bundle).
- Prepare site with chlorhexidine or povidone-iodine.
- Anesthetize and aspirate.
Suggested teaching format
A typical ACP Clinical Skills workshop will consist of presenting introductory educational content, some faculty demonstration, and ample time for participants to practice the procedure or examination skill with feedback from the faculty.
The workshop should be scheduled to run at least a half-day and should be organized with an assumption of three to four participants practicing on a model and one instructor supervising/providing guidance for each small group.
A suggested format for a workshop would be as follows:
1. Begin with didactic presentation (ultrasound basics: image acquisition, probes and basic “knobology”).
2. Practice imaging anatomy of participants/volunteers. Nonphysician sonographers are often pleased to be involved.
3. Practice performing the procedure (with direct faculty observation, guidance and feedback).
4. Summarize the information provided and offer a chance for Q&A.
After the simulation is completed, cleanup involves disposal of the pork ribs. Here is a recipe for this process.
Resources at Internal Medicine 2012
Two resources at Internal Medicine 2012 will help internists learn more about using handheld ultrasound units. The first is a portable ultrasound presession course. Details are available online.
The second is the Herbert S. Waxman Clinical Skills Center, a collection of dynamic, hands-on educational workshops that allow attendees of ACP's Internal Medicine meeting to refine or learn new examination skills and procedures that can be used in the office setting. The Center has been an integral part of ACP's annual meeting for over 10 years and is free to all registered attendees. Details are available online.
Participants at the Herbert S. Waxman Clinical Skills Center work in small groups with expert faculty to learn the ins and outs of procedures, from the fine motor skills necessary to essential information about supplies and equipment, indications and contraindications, and background diagnostic information.
A number of the popular workshops offered at the Waxman Center over the years have been converted to packaged curricula that can be used by institutions to teach procedural, examination, and communication skills. Topics include arthrocentesis and joint injections, common skin biopsy techniques, efficiency through effective communication, screening and prevention of diabetic foot ulcers, counseling for behavior change, and more.
For questions about this series of teaching modules or the Waxman Clinical Skills Center, please contact the Education and Career Development Department at 215-351-2614 or by e-mail.
DeCara JM, Lang RM, Spencer KT. The hand-carried echocardiographic device as an aid to the physical examination. Echocardiography. 2003;20:477-85.
Kobal SL, Atar S, Siegel RJ. Hand-carried ultrasound improves the bedside cardiovascular examination. Chest. 2004;126:693-701.
Martin LD, Howell EE, Ziegelstein RC, et al. Hospitalist performance of cardiac hand-carried ultrasound after focused training. Am J Med. 2007;120:1000-4.
Step 1: Remove excess tissue
With a well-chosen rub and a few hours of slow-cooking in a kettle BBQ, the ribs used in the simulation can be repurposed for dinner. The mustard mop can serve both as simulated antiseptic preparation and as basting liquid applied every 30 minutes or so while barbecuing.
(We advise against repurposing if the ribs were used for more than one daily session, if chlorhexidine or povidone/iodine is used for antiseptic site preparation, or if procedure kits have been recycled from patient use. Goat, lamb, beef, or mutton ribs may be more acceptable to some learners and teachers but may be more difficult to obtain.)
Recipe for BBQ rub
Step 2: Apply dry rub to ribs
- 2 T smoked paprika
- 2 T kosher or pickling salt
- 3 T sugar
- 2 T brown sugar
- 1 T ground cumin
- 1 T chili powder
- 1 T ground black pepper
- ½ T cayenne pepper
- 1 T onion powder
- 1 T garlic powder
- 1 T celery salt
- 1 t oregano
Recipe for mustard mop
Step 3: Generously baste with mustard mop
- 2 cups cider vinegar
- ½ cup prepared yellow mustard
- 1 T salt
- 2 t fresh ground black pepper
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