CAS Medical System's 740 monitor.

Question: What is about the size of a hardback novel, provides lots of information and does so at a reasonable cost? Answer: The neatly packaged CAS 740 monitor, which provides quick and easily obtained information on the status of a patient's vital signs. We here at the University of Kansas recently analyzed the performance of this device in our lab in conjunction with its optional infrared printer. Here are our findings:

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Physical characteristics -- The CAS 740 monitor is small and lightweight hence very portable. Its footprint is 6.75" (17 cm) X 8.5" (21.8 cm) X 3.0" (7.5 cm) and the unit weighs in at just about 3 lb (1.4 kg). It is constructed of a lightweight yet rugged plastic and incorporates two slide proof safety strips on the bottom--(some small details that particularly impressed us). There is a molded carry handle on the top of the monitor and there is a sizable LED screen is found on the front of the CAS 740 which allows continual review of the data displayed. Additionally, on the front panel of the monitor are simple direct control buttons some of which allow multiple levels of settings and review.

Manual -- The operating manual is well laid out, is clear, logically sequenced and provides all the information needed to assemble the peripheral equipment and start gathering data. There are clear and concise directions to achieve safe and effective data gathering. The manual also contains ample white space for notes.

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Power Requirements -- The CAS 740 can operate almost anywhere, on emergency vehicle power (12V), direct AC or battery. Power requirements are line power 100-250 VAC, user removable NiMH battery, or direct 12 VDC source for EMS applications. The fully charged NiMH battery will take 100 NIBP readings at 5-minute intervals and recharge in about 4 hours. An optional "Smart Battery" is also available which includes a built in LED battery capacity indicator that is useful when grabbing a spare battery from the drawer.

Parameters and Modes -- The CAS 740 offers a good range of vital sign monitoring capability. The following parameters were available in the top of the line unit we tested.

Automatic Non-Invasive Blood Pressure (NIBP) -- using motion artifact extraction (MAXNIBP[TM]) oscillometric technology. Neonatal/Adult ranges were Systolic 3-135/30-255mmHg +/- 5 mmHg, Diastolic 15-110/15-220 +/- 5 mmHg, MAP 20-125/20-235 mmHg +/- 5 mmHg. NIBP Pulse rate--40-240/ 30-240 +/- 2 BPM.

Pulse Oximetry -- Three brands of pulse oximetry are currently available with the 740. These are Masimo SET[R], Nonin[R], and Nellcor[R] OxiMax[TM]--all listed a measurable range of 70-100% with +/- 3 digit accuracy for neonatal probes and +/- 2 digit accuracy for adult applications. Pulse reading accuracy of the oximeters was listed as +/- 3 BPM over a range of pulse rates from 25-240 (Masimo), 20-240 (Nellcor), and 18-240 (Nonin). Sensor wavelengths were listed as IR/R Masimo 905/660, Nellcor 890/660, Nonin 910/660.

Temperature -- An on-board electronic thermometer (Welch Allyn SureTemp[TM]) and an attached rack for probe cover storage makes acquisition of temperature data convenient and easy. The predictive thermometry technology (another nifty feature), can measure oral temperatures in only four seconds. The thermometer reads from 28.9 to 42.2 C* or 84.0 to 108.0 F* at the operator's choice. Accuracy is listed as +/- 0.1 C* - 0.2 F*.

Modes -- NIBP is available in adult or neonatal ranges. SpO2 use is optional or continuous at the user's choice. Temperature is continuous or on a "spot check" basis.

History -- the trending and history capability of this device is truly impressive--480 trends or events over a 24-hour period can be held in memory for display, printing or downloading.

Operational Characteristics -- Assembly was under 1.5 minutes from shipping container to activation ready for use. The 740 self-tests on every startup. The learning curve for skilled use of this device was under 5 minutes. All connections were foolproof--no part fits where it should not be.

Accessories -- The optional accessory list includes the infrared printer, a roll stand with accessory basket, a hard mount with swivel capability and a protective soft carrying case.

Analysis

Automatic Non-Invasive Blood Pressure -- The CAS 740 tested well for non-invasive blood pressure measurement. The oscillometric technology accurately determined blood pressures over a wide range of systolic and diastolic measurements. Besides monitoring our own blood pressures, we attached it to an ABG practice arm and applied a series of measured blood pressures. The monitor took a little more time than normal with this method since our manual pumping action, while measurable, was difficult to maintain an even blood pressure. The displayed value came within only a few mmHg of our average over several simulated pulses. Normal and hypertensive values consistently followed this pattern. The only hesitation occurred when simulating severely hypotensive conditions. Nevertheless, pressures as low as 18 mmHg diastolic were displayed. We must point out though, that on live subjects there were no hesitations in determining blood pressure values, and readings displayed as we expected them to.

Pulse Oximetry -- The 740 monitor we tested was equipped with Masimo SET[R] pulse oximeter technology. We tested the oximeter in resting conditions and during exercise activity. The pulse oximeter was subjected to motion artifact produced from running motion. After some minor sensor adjustments, extraneous pulsations were filtered out, and the plethysmograph LED bar display resumed the baseline pulsations. During exercise there were no unexpected drops in saturation. The 740's performance was very stable and we considered it reliable under motion conditions.

Printer -- The infrared printer is a handy device that allows for printing out a serial history of the patient monitored. We were supplied with the CAS 740 portable external printer, which can operate on AC power or from its lithium ion battery. The printer itself has a very small footprint approximately 4" X 3" X 5" in size with a weight under 1 pound. The thermal printing strip is about 2.5 inches wide, but easily readable. The printer is not dedicated to a given monitor but can be used to download data from many monitors, a thoughtful feature on CAS' part. The printer can also be connected directly to the RS-232 port on the back of the unit. The RS-232 port is also used to interface to a nurse call system.

Two disadvantages to using this printer are in relation to permanent records. The small size of the printed strip requires taping the record onto a larger sheet for placement into a chart or record. Also, thermal printing tends to fade over time. To prevent these problems from occurring the record must be transcribed, or photocopied. The printer however, is a convenient small size and durable. We also found that loading the thermal paper roll was extremely easy with no complex feeding through mazes of wheels required. An interesting feature was the presence of two small "d"--ring like devices built into the printer. It appears that these could be attached to a lanyard, which would allow it to be easily carried for mobile printing applications.

Use of an infrared data transmission requires careful positioning of the monitor so that wireless transmission can occur. A clear visual path between monitor send unit and printer receiving port must be established and maintained--all very do-able.

Thermometer -- The integrated thermometer system, utilizes a probe for temperature measurement. It is capable of monitoring axillary, oral, or rectal temperature continuously, or intermittently on demand. Rectal measurements use a different probe than the oral or axillary probe. We did not test the rectal measurement mode. Continuous monitoring with these non-invasive methods is difficult, as the probe must maintain contact with the measuring surfaces. However, the predictive thermometry technology is designed primarily for "spot check" applications. While difficult to simulate a febrile state, appropriate changes in temperature were noted following drinking hot coffee or ice water. The probe, covers, and thermometer system operate in a manner similar to standalone electronic thermometers commonly available on most nursing units. This aids with ease of use, since most people are already familiar with this technology.

We have some suggestions related to this monitor. Functional excellence is evident but placement of the IR sending unit's access port would improve ease and versatility of use. Addition of a Lead II ECG recording would also increase the monitor's capability with probably just a small increase in technology investment.

Recommendations -- This device would be excellent for monitoring patients during procedural sedation, intra-hospital transport, in ambulances, fixed and rotary wing aircraft, in pulmonary labs, step down units and in large first aid facilities such as those found in sports venues or theme parks. The CAS 740 would be an excellent companion for the AEDs being purchased as first aid/CPR adjuncts, as well.

We found this device to be well thought out, easy to use, accurate and extremely portable. In fact we hesitated to send it back to CAS after the test period as we wanted one for our own lab. The CAS 740 is favorably priced when compared to similar hospital based technology. CAS Medical seems to have bridged the gap by offering low end pricing while still providing leading edge technology i.e. Nonin pulse oximetry and Welch Allyn SureTemp thermometry, for example. We believe the CAS 740 is worth a look. You can arrange for that look as well as other information by contacting CAS Medical Systems at 800-227-4414 or by visiting their website at www.casmed.com.

Michael Czervinske BSRT, RRT & Paul Mathews PhD, RRT