Thermal Angel Blood and IV Fluid Warmer Innovative Technology

Other fluid warmers require the use of a separate medical instrument that only accepts a proprietary disposable fluid path, either a custom tubing set or a custom cassette. The Thermal Angel is the only smart disposable that combines the required features of a sterile fluid path with the intelligence of an advanced technology medical instrument, thus requiring no custom delivery sets. Inside each Thermal Angel is a calibrated microprocessor that directly controls all heating of the integrated fluid path. This design advantage eliminates clinical setup errors.

The Thermal Angel mechanical design consists of a heat exchanger and integral heater control board, contained within a flame resistant plastic housing. The fluid path of the heat exchanger is manufactured from passivated 316L medical grade stainless steel tubing, shaped into a serpentine coil within the housing. To complete the heat exchanger, a lightweight heater flex circuit is tightly bonded to the fluid path by a sonic welding process. This design provides a total fluid volume of approximately 8 ml. Standard luer fittings at each end of the tubing allow the Thermal Angel to be matched with all standard IV administration sets and IV extension sets. Two highly accurate temperature sensors are installed into the fluid stream for direct fluid temperature measurement and control, increasing clinical confidence in patient outcomes.

Other fluid warmers heat either plastic tubing sets or plastic cassettes using circulating water baths or warming plates, respectively. Any heat intended for the infused fluid must first be propagated through the walls of these plastic fluid paths. After this delay, the heat can then begin warming the infusate. Unfortunately, medical device plastics have an extremely low ability to transmit heat as defined by their respective thermal conductivity (between 0.12 and 0.42 W/m ^oK). [1] Other fluid warmers must overheat to compensate for the low thermal conductivity of their plastic fluid paths.

Significantly different, the Thermal Angel fluid path is made from medical grade stainless steel with a much higher thermal conductivity (9.42 W/m ^oK). [2] This design advantage means the Thermal Angel is able to transmit heat to the infusate over 20 times better than the closest competitor. Better heat transfer means faster initial warming and faster response to changing flow conditions. Notably safer in a clinical regard, the Thermal Angel does not overheat to obtain normothermic infusate.

Low Mass Heater:

The Thermal Angel was designed to have fluid path heaters with little mass, to minimize the temperature impact in a stop flow condition. In other fluid warming products, the heater mass consists of either large area hot warming plates or large volume hot circulating water. If the infusate is stopped, any residual heat contained in the heater mass continues to be transferred to the infusate. This residual heat transfer may cause a spike in the infusate temperature. On the other hand, the Thermal Angel heater mass is extremely small (0.25 oz). In a stop flow condition, the Thermal Angel heater mass does not contribute to infusate temperature since there is insignificant thermal energy stored in such a small mass. The lightweight flex heater circuits used exclusively in the Thermal Angel are able to attain normothermic infusate because the stainless steel fluid path has such a high thermal conductivity. This design choice ensures clinical safety by avoiding any source of stored excess residual heat.

Temperature Regulation in the Fluid Path:

The Thermal Angel electrical design consists of a microprocessor-based temperature controller circuit and an independent analog temperature failsafe circuit, located on the heater control board. In turn, the heater control board is mated to the heater flex circuit bonded to the fluid path. The first primary function of the processor is to sample the fluid temperature, via two high accuracy temperature sensors that are directly embedded into the stainless steel fluid path. The second primary function of the processor is to adjust the heater power to maintain an output temperature of 38°C, via calibrated control software capable of responding to all clinical conditions. The microprocessor is an 8-bit device running at 8 MHz, to enable fast sampling of temperatures and efficient execution of Thermal Angel system control software. In addition to the control function, the microprocessor also performs continuous integrity tests of the temperature sensors and the heater flex circuits. The green status LED is included to provide the user with a simple indication of operational status. The analog failsafe circuit is completely independent from the microprocessor based control circuitry, adding another level of clinical safety.

With one sensor located in the fluid path near the output luer, the Thermal Angel directly measures the temperature of the fluid delivered to the patient. Based on this actual temperature, the control software then modifies the output of the heater flex circuit nearly 5000 times per second to attain normothermic temperature. Other products indirectly measure the infusate temperature through plastic, water, or warming plates. Uniquely, the fast Thermal Angel direct temperature measurement allows quick and automatic reactions to clinical conditions such as stopped flow, flow rate change, bolus delivery, and change out of IV or blood bag.

The proprietary sets used with other fluid warmers require the instrument to be placed anywhere from several feet up to 8 feet from the patient. As a smart disposable, the Thermal Angel distance to the patient is limited only by the length of the standard extension set chosen by the user. Using the 9 inch IV Extension Set (TA-9EXT or TA-9EXTNF) sold as an accessory, the Thermal Angel can be placed at least three times closer to the infusion site than any other fluid warming device. This design choice allows for the least amount of ambient cooling of normothermic fluids among all fluid warmers.

The Thermal Angel was designed to be compatible with any standard IV or blood administration/extension set. For customer convenience, a 9 Inch IV Extension Set (TA-9EXT or TA-9EXTNF) is sold as an accessory to the Thermal Angel. However, standard luer connections at the proximal and distal ends allow universal use of the Thermal Angel in any clinical setting. Unlike other fluid warmers, the Thermal Angel requires neither proprietary tubing sets nor proprietary cassettes. In addition, the Thermal Angel was designed to be compatible with any clinical infusion pump, up to the maximum flow rate specification of 150 ml/min.

Due to their size and AC power requirement, other fluid warming devices are clearly not intended as portable fluid warming solutions.

Uniquely, the Thermal Angel allows for a continuum of care with no interruption of the infusion of warm blood or intravenous fluids. The Thermal Angel can be used at first contact with the patient, whether at a trauma scene, in transport to a healthcare facility, or inside a hospital, clinic or surgery center.

Unlike other fluid warmers, the Thermal Angel does not require a different disposable for different flow rates. The smart disposable design makes the Thermal Angel the simplest logistical solution to fluid warming requirements, as only one disposable product needs to be inventoried and tracked within the facility. A wide range of patients, from neonatal to trauma to geriatric to pediatric to surgical, all use the same smart disposable Thermal Angel.

Historically, there has never been a competing fluid warmer that is capable of working in field environments such as EMS, Flight Service or Military. Because all competing fluid warmers require AC power and a stationary environment, they are useless in the early echelons of care, and thus incapable of helping to proactively preventing hypothermia in the field before evacuation.

As the US Military has discovered, warming fluids in the most forward echelons of care has profound effects on the health of the patients during transport and recovery. Due to its diminutive size and weight, the Thermal Angel can be used at first contact with the patient, either outside of the hospital, or inside. The Thermal Angel can also travel with the patient between vehicles or departments. We find that many hospitals coordinate with the EMS providers to accept patients already receiving the benefit of a Thermal Angel that had been administered at the scene. The hospital simply unhooks the Battery, hooks up their own Battery, and provides a new Thermal Angel unit to the EMS provider in exchange. The patient never stops receiving warm fluids.

Competing fluid warming products require extensive training by a qualified instructor. Issues include proper set up procedures, calibration procedures, choice of proper disposables for each particular application, an understanding of flow rate limitations, and sterilization. Their complex nature requires cumbersome training to use them effectively.

Because the logistics of training users is so difficult, especially in an austere environment, the Thermal Angel was designed to require minimal training. The 5 Steps are printed on the Thermal Angel label, bag, and instruction insert. Furthermore, there is an instructional video available on the Thermal Angel website which can be viewed in less than 3 minutes. By providing multiple avenues for training, the end user chooses the approach most appropriate for them and their time schedule. Most hospitals and EMS facilities train themselves on the Thermal Angel and do not require an in-house training session.

Studies have shown that competing fluid warmers take critical minutes to set up. Issues include ensuring sterilization of key components, selection of proper disposables given the infusion situation, configuration and setting of switches and knobs, and power up procedures to start the warming process.

Because the Thermal Angel is elegantly simple, there are no knobs, settings or switches. An experienced user can set up the Thermal Angel in a matter of seconds. The U.S. Army Ranger Medics are trained to set up and use the Thermal Angel in complete darkness in less than one minute in battlefield conditions. No other fluid warmer in the world can meet these stringent military specifications.

A competing fluid warmer requires 6 to 8 minutes to warm up to proper fluid delivery temperature. Because of this delay, compounded by the long set up time, the bulky AC powered machine often goes unused due to time constraints.

In comparison, the Thermal Angel is warming within 45 seconds, more than 6 times faster.

Historically, hospitals only purchase a few fluid warming machines to service specific areas of the hospital. If the hospital is constrained in their capital budget and has one or two expensive fluid warmers, the hospital is limited in its ability to concurrently provide warm fluids to multiple patients.

The Thermal Angel was designed to be small, disposable and inexpensive, so that dozens of patients can be receiving warm fluids concurrently at any point in the day. For the same price as a Bair Hugger Ranger fluid warmer that would serve one patient at a time, the hospital could instead buy enough Thermal Angel Battery Sets ($330 each for full set) to service a dozen patients concurrently. This paradigm shift allows the hospital to enhance protocols and serve patients like never before, opening up the possibility of warming fluids anywhere inside or outside the walls of the hospital.

Other fluid warming devices have an initial expense for the warming unit and more charges for the disposables. Extreme scenarios may even add the cost of a clinician to monitor the equipment. When a patient is to receive warm fluids, the hospital must account for the cost of the warming unit and the disposables. If the patient requires continuous warming and is moved between departments, the hospital must also be willing to move the large AC-powered equipment to another room, leaving the disposables attached to the patient and machinery. This causes logistical issues with equipment that has been removed from its primary location. Instead, if the hospital has the budget to purchase multiple warming stations in various departments, they will then be forced to open another disposable after the move, and accept the time constraints of starting up another piece of warming equipment. In either situation, the hospital must incur substantial costs.

Since the Thermal Angel is a portable, battery-powered single patient device, there are no additional costs due to movement. The Thermal Angel stays with the patient throughout the continuum of care to virtually any department the patient visits, untethered by the requirements of AC power. There are no new disposable costs from OR, to Recovery, to ICU, and finally, to the patient room.

Other fluid warmers may require volume commitments by the hospitals in order to offset the expensive capital equipment costs. As has been shown, many of those competing fluid warmers go unused for various reasons, leading to wasted capital tied up in both hardware and disposables.

The Thermal Angel was designed to require a minimal capital expenditure with no commitments from the hospital in order to encourage warming for all patients, not just a select few cases. As a comparison, the Hotline sells for $1,500 per unit, serving one concurrent user. The Thermal Angel Battery Set, also serving one concurrent user, sells for $330 per unit. This illustrates the dramatic reduction in capital costs for hospitals using the Thermal Angel.

Some competing fluid warmers such as the Hotline require a labor intensive sterilization procedure. The Hotline uses a water bath for heat transfer, and this bath must be maintained and sterilized. Failure to follow the proper sterilization procedures may have detrimental effects. This is a time consuming task that must be managed and documented, often dissuading the caregiver from using the Hotline fluid warmer.

The Thermal Angel is sterilized by Ethylene Oxide according to ANSI/AAMI/ISO, 11135 and EN 550 Medical Devices—Validation and Routine Control of Ethylene Oxide Sterilization. Additionally, a Limulus Amebocyte Lysate Endotoxin test is performed per USP and FDA Standards. After sterilization, the Thermal Angel is delivered to the end user in a sterile package ready for use. Because the Thermal Angel is a disposable, single patient fluid warmer, it is discarded after use. There are no sterilization procedures required by the user.

Competing fluid warmers are based on a reusable hardware component that provides the warming technology and temperature management. Because the reusable component is so active, the end user must be concerned with changes in the equipment over time which may necessitate recalibration to remain within specification. This creates an extra cost to use the equipment represented by downtime and labor.

In order to assure that the Thermal Angel performs within the design specifications, each production unit undergoes calibration and performance testing as part of the manufacturing process. The calibration process consists of operating the Thermal Angel while connected to a fluid delivery system. The fluid delivery system is set to deliver water at a flow rate of 50 ml/min and input temperature of 20°C. The temperature of the fluid exiting the unit is measured after a stabilization time of 3 minutes. Adjustments to the output temperature are made electronically by placing the Thermal Angel into a special test mode. After each adjustment, the output temperature is rechecked. The stable output temperature must be 38.0°C ± 0.5°C in order to pass calibration. After calibration, 3 individual performance tests are executed. As with the calibration process, the performance tests also consist of operating the Thermal Angel while connected to the water based fluid delivery system. For the first test, the fluid flow rate is set to 50 ml/min. For the second test, the fluid flow rate is set to 100 ml/min. For the third test, the fluid flow rate is set to 20 ml/min. For all of the tests, the fluid input temperature is set to 20°C. In order to pass each test, the Thermal Angel must maintain an output temperature of 38.0°C ± 1.5°C after a 3 minute stabilization period.

Because of the extensive calibration of every Thermal Angel produced and its disposable nature, the end user will never have to recalibrate the Thermal Angel. It is simply discarded and replaced for the next patient.

Our research has shown that while hospitals may carry some competing fluid warmers, they often go unused because of a repair situation that has never been remedied due to time constraints or capital equipment expenditure issues. One hospital spoke of a $20,000 capital equipment machine that has gone unused, even though they have a contract for disposables, because they cannot afford to repair the machine. Beyond the actual cost of the repairs, the hospital must also consider the loss of time due to coordination of repairs by hospital technicians. Ultimately, the patients are losing the benefit of warm fluids.

The Thermal Angel was designed as a disposable product to help avoid downtime due to service calls.
If by chance a Thermal Angel is damaged, another inexpensive Thermal Angel is used in its place. There is nothing to repair, no time lost waiting for a service call, and no single point of failure that cannot be replaced within a minute. This feature is extremely beneficial, especially in a fast-paced environment such as an ER, EMS setting or battlefield.

[1] ASM Engineered Materials Handbook, Desk Edition, 2002.

[2] ASM Engineering Properties of Steel, 1982.