NIHON KOHDEN Vismo PVM-2703 patient monitor (Feb 2011)

Category: NIHON KOHDEN Vismo bedside monitors and networking. In this article we review both the PVM-2701, PVM-2703 and PVM-4763 Vismo patient monitors.

The First VISMO Monitors

NIHON KOHDEN had always wanted to have parts sourced in China to lower cost, and the Vismo PVM-2701 was a pilot move, designed in Japan but with many parts sourced in China.

 

The release of VISMO PVM-2701 bedside monitor was announced by Signal 718 dated November 2009. Vismo is short for Vital Signs Monitor. Notice this was the first model to do away with the suffix.

 

 

Initially, the PVM-2701 was assembled both in China and Japan, but that changed from February 2011. This coincided with the release of Vismo PVM-2703, and from its release, all production are only in China.

 

 

The monitor that is short of one physical connector socket

 

The Vismo PVM-2703 was released in February 2011, capable of monitoring ECG, Respiration, SpO2, NIBP, Temperature, IBP or CO2. This is not a true 7-parameter monitor because it is either IBP or mainstream CO2, but not both. Does that sound like a compromise? Yes, it is!

 

The differentiating feature of the VISMO PVM-2703 bedside monitor against the competitions is the utilization of a flexible MULTI (short for multi-parameter) socket that is for sharing use, and this socket is colored yellow. The yellow MULTI socket can be connected to internal analog hardware for IBP monitoring, or diverted to be a digital serial port for mainstream CO2 kit sets.

 

The shared-use MULTI socket, however, demands the use of costly proprietry measurement cables with valid NIHON KOHDEN digital hexadecimal parameter codes embedded in their connection plugs to work; this is a prerequisite because the socket is being shared for more than one parameter. The parameter code is needed to inform the monitor what internal hardware and software are needed to support a newly plugged-in measurement cable as more than one type of cable is expected.

 

Unfortunately, the market reaction to the use of the MULTI socket and coded measurement cables is not what the company wished for. Using the flexible MULTI socket in PVM-2703 monitor means one physical connector sockets is missing, which upsets users and they want the socket back. This means the manufacturer is looking at the wrong way to provide benefits of socket flexibility, more efforts and technology are needed in order to be of value to customers worldwide.

 

There is really nothing wrong with using one fixed-use socket for Invasive Blood pressure and a separate serial port for mainstream CO2, which is the norm in the industry, and a far superior way since the monitor can do all 7 parameters at once. What problem is the manufacturer trying to fix?

The archaic concept of a MULTI-PARAMETER UNIT (MPU) from the 1990s

 

Veiled in secrecy, NIHON KOHDEN does not explain to the market how they could make sockets that are flexible enough for a total five types of internal hardware, as well as being diverted for use as serial ports for self-contained kit sets. Almost all sales and marketing people employed in Japan Head Office have no engineering background, so there are plenty of "company secrets" that should not be discussed with the distributors or customers.

Here are the relevant facts, and it was a quest to find a solution for a small module with a front panel that did not have enough panel space area to mount all the needed connector sockets.

 

 

Back in the 1990s,  NIHON KHODEN identified five types of analog hardware (Temperature, IBP, Cardiac Output, Thermistor-method Respiration, FiO2) to form a hardware community that link to only two sockets meant for sharing use. These flexible communal sockets are known as MULTI (short for multi-parameter) sockets and colored yellow. The hardware community, known as a MULTI-PARAMETER UNIT (MPU), was actually a design to reduce the number of physical sockets on a front panel with limited space area, resulting in an MPU with the unusual characteristics of having more hardware than MULTI sockets. We need to view the MPU from the right perspective to understand that this is not a design to adopt when there is sufficient panel space to mount all the necessary sockets.

 

 

To access each type of hardware, an external measurement cable with a digital parameter code stored in its plug needs to be inserted into one of the two MULTI sockets. These measurement cables that come with yellow coded plugs are collectively cited as Smart Cables by the manufacturer and each embedded digital parameter code pinpoints the exact type of internal hardware and software needed by a particular measurement cable.

 

Each yellow MULTI socket selects only one channel of the internal hardware, except for Temperature allowing two channels of hardware to be selected.

As an exception, a MULTI socket can link up to two channels of Temperature hardware

  

Note the hardware mentioned here (Temperature, IBP, Cardiac Output, Thermistor-method Respiration and FiO2) are linked to the shared-use MULTI socket internally, and not from the outside

 

An external measurement cable with a valid digital code embedded in its plug selects the intended internal hardware (only if available)

Below image shows the MULTI-PARAMETER UNIT (MPU), complete with two yellow MULTI sockets for communal sharing. An external Smart Cable with a valid parameter code selects the needed hardware in the MPU using one of the MULTI sockets.

 

Based on the fact that all MULTI sockets must be capable of doing IBP monitoring, and the logic that IBP hardware should not be more than the number of MULTI sockets, the IBP hardware are therefore not placed in the MPU for sharing; instead, each MULTI socket comes with its own dedicated IBP hardware.

 

 

A MULTI socket can only access its own dedicated IBP hardware, and makes use of its when an IBP measurement cable is plugged into it. For non-IBP monitoring, both MULTI sockets can access the common hardware pool comprising Temperature, Cardiac Output, Thermistor-method Respiration and FiO2 hardware in the MPU.

 

The company observed with disappointment that the quantity of MULTI sockets in the MPU is not a number that can be decided at will, but corresponds exactly to the number of internal IBP hardware channels that are intended to be placed inside each MPU. This characteristics is highly undesirable for using the MULTI sockets in a practical way. 

 

Given the large amount of hardware in the MPU, more MULTI sockets are needed to make good use of the hardware that would otherwise be idling. As illustrated in the above image, this is achieved by using an external expansion box filled with more MULTI sockets (each with own dedicated IBP amplifier hardware).

 

This is a process of adding sockets, not monitoring parameters

The additional MULTI sockets are integrated using analog interface, and limited to a maximum of four sockets to avoid signal deterioration caused by voltage drop and noise.

The MULTI sockets are additionally diverted to be serial ports to save on one more physical socket

 

A MULTI socket can be diverted to be a serial port by bypassing the internal analog hardware

 

The design concept of MPU was to solve the problem of limited panel space area, and by using it as serial port does help in furthering the reduction of a physical socket on the front panel. The serial port in the original design was only for use by mainstream CO2 serial kit sets.

 

Original label on the MULTI sockets when they were first used

 

Shown above is the original label for the yellow MULTI sockets. It shows each socket can be utilized for monitoring of IBP, Temperature, Cardiac Output, FiO2 and Thermistor-method Respiration, as well as diverted to be a serial port for use by mainstream CO2 kit sets.

 

The term "MULTI PARAMETER UNIT" can be found in older service manuals

 

The small module mentioned earlier was named Saturn multi-parameter unit and the outcome of the MPU solution is as shown below. The Saturn module is housed in a 8-slot module rack, with two expansion boxes next to it; altogether there were six MULTI sockets (with six channels of IBP hardware) available for use in this arrangement. It is possible to use the Saturn module alone, but the two MULTI sockets would not be enough.

 

The MPU block without the module rack is meaningless

 

Unfortunately, the measurement-data communication platform between the module rack housing and monitor main unit was unstable with plenty of performance issues, and had to be finally given up for good. This means the first two modular monitors developed by the manufacturer were failures, and they were withdrawn before registration in the biggest US market.

 

  

After the decision to stop development work on the measurement-data networking platform, NIHON KOHDEN moved on to promote socket flexibility as a mean to achieve scalability. The initial concern was just to assure the protected Japanese domestic market, which was buying more than 90% of the factory production for monitors.

 

In reality, the MPU without the module rack is meaningless and most importantly, there was no demand for socket flexibility in the market outside of Japan.

 

Professionally, many are actually puzzled by the contents of the MPU but refrained from asking or faced with a wall of silence, why is this a design that has many internal hardware queuing up to share a limited number of low-cost sockets? The truth is because the design was actually a compromise to accommodate a limited panel space area not enough for all necessary connector sockets. In situations when we have ample panel space area, there is no need for such a compromise and the use of an MPU (with its Smart Cables and MULTI sockets) actually becomes a burden and waste of money. Its continued use regardless of need is the very reason for its eventual failure. 

Users must know there is one channel of IBP hardware inside the PVM-2703 monitor

 

Knowing a genuine MULTI socket always come with its own dedicated one-channel IBP hardware, a user can accurately tell the number of IBP monitoring hardware channels supplied with any monitor, just by counting the total number of available yellow MULTI sockets. 

The key word here is "genuine" because a non-functional (fake) yellow MULTI socket does not need to care about the capability to do IBP monitoring, such a socket can indeed be found on the CardioLife TEC-5600 series defibrillators. The fake yellow MULTI socket on said TEC-5600 series defibrillators is just a serial port that cannot be used for any other parameter except mainstream CO2 kit sets.

Variations to the basic theme

There are variations to the basic theme, such as

a. doing without use of external expansion box,

b. increasing the number of MULTI-parameter sockets in the MPU,

c. reducing the hardware configured in the MPU.

In the VISMO PVM-2703 bedside monitor, only one channel of IBP hardware is configured in the MPU, out of five possible hardware types for use by Smart Cables. This being a simple monitor, the expansion box is not necessary.

You can see the parameters NIBP, SpO2, ECG and one channel of Temperature on the Vismo PVM-2703 monitor are not using Smart Cables, they are therefore not part of the MPU.

The digital hexadecimal code is programmed into a non-volatile EEPROM chip (Electrically Erasable Programmable Read-only Memory) mounted on a small flexible PC board, and soldered to some pins of the yellow plug at the factory; users cannot change the parameter code using settings on the monitors. It is not difficult to make the Smart Cables but they are being priced highly by the manufacturer; only the IBP cable can be sourced at a reasonable price from China suppliers because it is a common cable with some demand.

A non-volatile digital parameter code is embedded in the plug of the measurement cable

It is simple-minded to think the use of Smart Cables can actually upgrade a configured monitor to be modular
 

A MULTI socket by itself does not automatically mean all the five types of mentioned parameters are available for measurements; it still depends on which hardware are decided for placement inside the MPU for selection by Smart Cables. The amount of hardware in an MPU is not standardized but customized for each case.

 

Additional monitoring parameter capability can be added to a configured monitor using serial kit sets or via interfaces to external equipment, but these are realized through the system software of the monitor and has nothing to do with the type of sockets or cables being used.

 

Putting things into perspective, most patient monitoring parameters cannot be added using self-contained serial kit sets. As shown, the AE-918P Neuro Unit or strip chart recorder are examples, and they are not linked using a MULTI socket, but as any external third-party device.

 

 

When an MPU is not equipped with FiO2 hardware internally, no amount of MULTI sockets is going to provide this measurement capability. The amount of configured hardware placed in each MPU varies, so is the system software support for serial kits and external devices.

Examples of configured hardware and serial kits using Smart Cables

 

 

It is the built-in hardware that determine the parameter capability; and in the case of serial kit sets, the system software. This of course, is the same description as a configured patient monitor

 

Actual internal hardware and system support for serial kits varies for each multi-parameter unit

Obviously, VISMO PVM-2703 bedside monitor making use of Smart Cables is still a configured monitor. The only advantage of using Smart Cables is to allow sharing of connector sockets (which are of negligible hardware cost), but the costs needed to make use of Smart Cables are far way higher. The customers are paying for the unnecessary higher costs, only to be led into having an unrealistic expectation of what the Smart Cables and MULTI sockets can actually deliver.

 

Regret there is no monitoring hardware embedded in the NIHON KOHDEN Smart Cables and this makes a big difference as to how you appraise a monitor that comes with MULTI sockets

 

Under US rule, a cable is only a cable if it does not change the signal that passes through it. A Smart Cable embedded with a non-volatile digital hexadecimal code is just a cable and does not change a signal passing through it, but if it has an amplifier it becomes a medical device and definitely requires FDA registration. Can you find any stand-alone NIHON KOHDEN Smart Cable registered with US FDA as a medical device? We do not.

Make no mistake, when the Smart Cables are used with serial kit sets, such as mainstream CO2 kit sets or the NMT AF-101P kit set, the registration is for the active serial kit set (just like any other manufacturers) and not the passive Smart Cable.

 

It is unsubstantiated marketing messages and the manufacturer should not have condoned it. We are going to show you beyond any doubt, there is absolutely no active electronics in the Smart Cables. Messages such as "New Modular Technology" and "The Module is in the cable!" are just the wild imaginations of people without the necessary electronics knowledge.

What do the manufacturer mean by this statement? 

It started with the Life Scope TR (BSM-6000) series monitors in the USA market and gradually adopted officially for International markets. These are precise statements.

The continued repetitions of an assertion without offering any proof does not make it the truth!

This is just wild assertion without offering any proof

 

Chip makers need huge demand to justify each of their products, there is unlikely any chip manufacturer that would want this low-volume business. If we were to open up the plug of a Smart Cable, a small PC board can be seen being soldered to some pins of the yellow plug.

 

A small PC Board is soldered to some pins of the yellow connection plug

 

The PC board confirms a cheap non-volatile digital EEPROM chip is being used to code the Smart Cable.

 

A cheap digital EEPROM chip was what we found inside the yellow Smart Cable plug

If we were to open up the plug of a compatible IBP cable from China suppliers, what do we see? It is the same thing, a plug with a digital code defined by NIHON KOHDEN.

 

Irrefutable proof the IBP amplifier hardware is configured internally, an important fact no longer shown on later monitor manuals

The Life Scope BSM-2301 bedside monitor was launched in 2001, and the Service Manual is clear on the design; manuals for later models stop providing such information. The major move to curb details in manuals started from Life Scope J (BSM-9101) Bedside Monitor, which was launched in June 2007. The Life Scope TR bedside monitors also do not provide details, as it was launched in April 2008 (after Life Scope J monitor).

 

In BSM-2301 service manual, you can see the IBP and thermistor respiration are internal hardware inside the Life Scope BSM-2301 monitor. These hardware are clearly shown being linked internally to the yellow MULTI socket, and to make use of either hardware, a Smart Cable with the correct code must be plugged into the MULTI socket.

 

Can you see the IBP amplifier and thermistor respiration hardware are internal components of the Life Scope BSM-2301 monitor?

The MULTI socket can be diverted to be a serial port by bypassing the internal analog hardware, going straight to the digital APU (Analog-block Processing Unit) and onward to the DPU.  For a parameter using the internal analog hardware, the analog signal needs to converted to digital before going to the APU for processing. 

Relevant page in the combined Service Manual for BSM-2301A, BSM-2301K, BSM-2303K, BSM-2304A

You should know by now the IBP amplifier hardware inside the monitor is the reason the VISMO PVM-2703 bedside monitor can do one channel of IBP monitoring, and that there is no IBP amplifier hardware embedded in the plug of the IBP Smart Cable.

 

The serious lack of physical sockets when using a MULTI socket (case study of Life Scope BSM-2300K series bedside monitors)

Preceding VISMO PVM-2703 bedside monitor was the Life Scope BSM-2300K series monitors, let's see how this sole yellow MULTI socket was actually being used in this series.

 

The portable 8.4-inch Life Scope i (BSM-2301K)

 

To insist the use of Smart Cables, the Life Scope BSM-2301K monitor has a yellow MULTI socket flexible enough for three types of measurements, namely:

 

a. Invasive Blood Pressure

b. Thermistor-method Respiration

c. Mainstream CO2 (using self-contained serial kit sets)

 

Without any use of Smart Cables, all three parameters (IBP, Thermistor Respiration and mainstream CO2 are freely available for carefree use via their respective dedicated sockets. The use of Smart Cables makes things unnecessarily complicated and requires deliberate operator attention and choice to choose one among three (IBP, Thermistor Respiration and mainstream CO2), but why introduced a need to choose?

 

This is obviously unwarranted stress and inconvenience, what is wrong with the conventional way of using three dedicated sockets for the job? If MULTI socket is such a superior proposal, why is the Temperature socket a dedicated one?

 

Life Scope-i does not have enough physical connector sockets

 

The patient monitoring hardware in the Life Scope BSM-2301 bedside monitor are divided into a conventional block and an MPU block. The conventional block uses dedicated sockets and ordinary measurement cables while the MPU block makes use of Smart Cables with different parameter code for different hardware.

CONVENTIONAL BLOCK

- 1-ch TEMP

- ECG

- SpO2

- NIBP

MPU BLOCK with one MULTI sockets

- 1-ch IBP

- Thermistor-method Respiration

- <MULTI socket as serial port> Mainstream CO2 kit sets

 

The reality is the shortage of two connector sockets, and an avalanche of complaints from users. The manufacturer was pressured to respond with an updated model, BSM-2303K. The solution from new model BSM-2303K is to add a new isolated yellow MULTI socket that can only do IBP monitoring.

 

The MPU of the Life Scope BSM-2301K was not designed to take on expansion, and any additional MULTI socket will load the operation of existing MPU, causing it to malfunction. The additional (fake) MULTI socket is not linked to the MPU, just an independent socket with its own dedicated IBP amplifier hardware.

The new socket's job was to relieve the existing functional MULTI socket. It was ironical, a solution relying on a dedicated socket for IBP; it was clear the complaints was the result of sharing a flexible socket.

 

Under pressure, the manufacturer returned to users a dedicated physical socket for IBP

Negative value captured by users of Smart Cables and MULTI socket in PVM-2703 bedside monitor

Without any use of Smart Cables, both one channel of IBP and one channel of mainstream CO2 are freely available for carefree use via their respective physical sockets. The use of Smart Cables just makes things unnecessarily complicated and requires deliberate operator attention and a conscious efforts to choose between IBP and mainstream CO2; this is unwarranted attention, stress and inconvenience. What is the benefit of having such a choice?

This is the norm in the industry; what is the manufacturer trying to fix?

The mainstream CO2 parameter is supplied as a self-contained serial kit set with processed digital output ready to go directly to the digital processing stage of the monitor; there is no need to compete for use of the MULTI socket with the IBP measurement cable.

Manufacturers make their profits by providing product benefits to users but the dual-purpose MULTI socket on PVM-2703 bedside monitor has no benefit. In fact, socket shortage is the unanticipated problem for users having to share a single MULTI socket for IBP and mainstream CO2.

What benefit can it offer users when necessary connector sockets go missing?

 

It does not make economic sense to save the cost of a cheap connector socket. Elaborate time-sharing are applied to things that are expensive (high in demand, an asset), and not worth the efforts for things that are cheap (high in supply, a commodity) like a connector socket or a switch! 

 

Productive efforts should be made to time-share a CPU, a car, a hotel room, a yacht, an airplane but not a calculator, a pencil or a pair of scissors.

 

Time-sharing of a car (an asset) creates value

The next picture shows Philips time-sharing one channel bio-amplifier hardware between IBP and Temperature measurements, and there was no sharing of connector socket; this is exactly the opposite of what Nihon Kohden is doing. The said manufacturer merely ensures physically it is not possible to make use of both the PRESS and the TEMP socket at the same time, and the purpose is to make it possible for the same hardware to be used for different purpose at different time.

 

This design shares the expensive hardware, not the cheap sockets

As expected, users soon found the single MULTI socket on VISMO PVM-2703 Bedside Monitor is not enough for use

The situation for VISMO PVM-2703 Bedside Monitor is the same as Life Scope BSM-2301K Bedside Monitor, the customers just want their physical sockets back! To that the manufacture responded with the new PVM-4000 series bedside monitors.

 

In new PVM-4000 series bedside monitors, the VISMO PVM-4763, PVM-4753 and PVM-4733 bedside monitors are again dodging the key issue. The new series now offer users two MULTI sockets, each MULTI socket comes with its own one-channel IBP amplifier hardware.

 

What you are really seeing is a VISMO PVM-4763 bedside monitor adding one redundant IBP hardware channel just to do what the PVM-2703 monitor could already do if the manufacturer had made use of dedicated sockets! The users certainly did not ask for an additional channel of IBP hardware and we are seeing the futility of using flexible sockets.

There is just no reason to continue the use of Smart Cables/ MULTI sockets except to meet the manufacturer's own agenda in Japan, and they can keep doing it in the Japanese domestic market because users have low bargaining power in a protected market.

Adding an additional MULTI socket to PVM-4763 bedside monitor to do the same job PVM-2703 monitor could do without using any MULTI socket

 

Beware the need for network isolation units to ensure electrical safety of monitored patients

For networking, the Vismo PVM-2701 and PVM-2703 need the QI-202P Interface option but the interface is not equipped with a isolated Ethernet LAN interface. When connecting to a real-time LAN network, it is important and mandatory for hospitals to observe patient electrical safety by using a network isolation unit.

 

When an isolated monitor with an non-isolated Ethernet port is connected to a hardwired network, it is no longer a medical device unless the above-shown network isolation transformer is introduced between the monitor and network. If the network isolation transformer is not installed, dangerous electric shocks can be delivered to a monitored patient through the wired Ethernet network. Such dangerous electric shocks are potentially lethal and no hospital should ignore this mandatory requirement.

WATCH OUT the dangerous use of estimated CO2 values and displaying a flawed CO2 waveform

Nihon Kohden lacks sidestream CO2 sampling expertise and buys OEM units to offer them as expensive standalone. The AG-400 CO2 unit as shown, for example, is technology from Oridion Medical. For monitoring such as post-surgery recovery, integration of the sidestream CO2 into the monitor is a mandatory requirement because an external unit requires additional power socket besides necessitating the use of a trolley.

 

For some unknown weakness, Nihon Kohden monitors have never been able to offer benefits of integrated sidestream CO2 measurement.

 

The inability to integrate the sidestream CO2 unit into the patient monitor main unit

The adoption of semi-quantitative mainstream CO2 measurement was to reduce cost and its simplicity also help in miniaturization of the transducers. The first solution offered by Nihon Kohden was the mainstream cap-ONE TG-920P CO2 sensor kit (order code P907) that can be used on non-intubated patients.

 

The cap-ONE TG-920P CO2 sensor kit (P907) has very small sensors because semi-quantitative measurement is adopted, the method is not commonly seen and many are not aware of the risks of obtained CO2 readings from the semi-quantitative CO2 kit sets, and to make matter worse, the semi-quantitative measurements are also being made used of to display a flawed continuous CO2 waveform.

 

Nihon Kohden cap-ONE P907 (TG-920P) mainstream CO2 sensor kit

How to remove a relatively big disposable adapter from the two tiny transducers after use?

 

When the sensors become smaller, it also means the disposable adapter becomes relatively much bigger as seen in this below picture. When trying to remove the disposable adapter from the transducers, it is difficult to separate the two because of the latching mechanism. A small size transducer means anything that latches onto it must be even smaller.

It is not easy to separate the disposable adapter from the Cap-ONE transducers after use

 

When removing disposable adapter from the mini sensors, users tend to just pull from the cables and this action quickly weakens the joint holding the sensors and cables. The action will cause stress to the two joints and quickly degenerate the performance of the transducers. This means the transducers are unlikely to last.

 

Users just doing the inevitable

 

Shown below is another TG-900P etCO2 kit set (order code P903) that makes semi-quantitative CO2 measurements on a traditional mainstream CO2 sensor. The TG-901T3 kit set (order code P906) is the same thing but using a non-coded connection plug. The medical devices from same manufacturer that make use of semi-quantitative CO2 kit sets for patient CO2 measurements and waveform include:

- Life Scope patient monitors

- Vismo patient monitors

- Cap-STAT OLG-2800

- CardioLife defibrillators

- Neurofax EEG machines etc.

 

Nihon Kohden semi-quantitative CO2 kit sets with traditional mainstream transducer

 

The manufacturer is not aware semi-quantitative CO2 measurements are only estimates and sell it as alternative to quantitative type

 

To save costs, the semi-quantitative kit sets do not make measurement during the inspiration phase. The important point is there is a measurement duty cycle and it is as shown; there is no way to know the actual CO2 measurements during the inspiration phase because CO2 measurements are not made.

Semi-quantitative means there is a duty cycle, and measurements are not continuous

 

Semi-quantitative measurement is also of low-accuracy type, performed using one IR detector instead of the usual two to save cost. This is reflected in the measurement tolerance.

 

Contrasting, quantitative measurement delivers high accuracy for critical care. To ensure the necessary high accuracy, quantitative measurement employed two IR detectors for simultaneous CO2 measurements at different wavelength for results comparison. CO2 measurements are also being made continuously.

 

Quantitative measurement employs two detectors to make continuous measurement at different wave-lengths to compare readings for high accuracy

NIHON KOHDEN specification for TG-901T CO2 sensor kit shows even the specified low accuracy of CO2 measurement using semi-quantitative method no longer holds true once CO2 is present during the inspiration phase.

This is because actual CO2 value will be more.

 

The manufacturer using a semi-quantitative design cannot assure the measurement tolerance specified because CO2 level is not measured during each inspiration phase!

 

Measurements are invalid when CO2 is present during inspiration, but the design does not measure CO2 level during this period!

 

As seen from the duty cycle, there is no measurement being made during the inspiration phase, how does the manufacturer know there is no interference from this phase? The specified measurement tolerance is conditional on this assurance and the CO2 value shown to users is therefore misleading!

Each semi-quantitative CO2 measurement is in fact, only an estimation.

In addition, since the users are not alerted on screen there is no CO2 measurement being made during the inspiration phase, they are unknowingly made to take on an unnecessary risk.

 

Semi-quantitative methodology means cost-effective estimations and the design cannot be used in a general way, only on a selective basis with known risks

 

For example, semi-quantitative methodology can be used as a simple estimation tool for obtaining the numerical value of End-tidal Carbon Dioxide level (etCO2).

 

Below picture shows the semi-quantitative method in the way it was intended for, estimating only the etCO2 numerical value for purpose of airway tube placement confirmation. It is not for continuous waveform display.

A hand-held semi-quantitative etCO2 estimation tool (with SpO2) for airway tube placement confirmation

The manufacturer ended up ignorantly displaying a flawed continuous CO2 waveform using semi-quantitative measurement kits that do not have ability to make continuous measurements

NIHON KOHDEN also allows data from semi-quantitative measurements to be displayed on screen with the non-measurement period reset to zero level. The insistence to display a continuous waveform using discontinuous measurement data from semi-quantitative mainstream CO2 estimation kits is unacceptable; the manufacturer is just subjecting the monitored patients and users to dangerous misinterpretation risks.

 

A zero CO2 reading on the waveform means zero measured value. No measurement can only mean a defective sensor, not by design!

Note the end tidal CO2 (etCO2) value shown is also not alerted as "estimated etCO2" only.

 

A flawed CO2 waveform with non-measurement intervals reflected as zero measured CO2 value

 

As seen from the two true CO2 traces below, expiratory upstrokes do not always start from zero CO2 level!

Quantitative measurements confirming expiratory upstrokes do not always start from zero CO2 level

  

Check the latest updated table to make sure you only use quantitative method for critical measurements and to display a true CO2 waveform on the screen.

 

Use only quantitative method for waveform display; the quantitative TG-950P (P905) shown here was already discontinued.

 

What you should know about fully-quantitative type miniaturized mainstream CO2 sensors

The TG-907P CO2 Sensor kit (order code P909) shown in above table is declared as using quantitative method. This sensor was designed for non-intubated adult CO2 monitoring, as well as neonatal CO2 monitoring. Nihon Kohden is thus offering an alternative to sidestream CO2 sampling methodology.

 

The miniaturized CO2 sensor is easily broken by the bigger and stronger adapter

 

In addition to the dead space problem, they had not foreseen miniaturized mainstream CO2 sensors could be easily broken by the disposable adapters. This happened because the disposable adapters are now relatively bigger and stronger!

These are common defects of a TG-970P CO2 sensor kit (P909). The design is impractical.

The fragile miniaturized CO2 sensor are clearly of poor design, and easily broken

The key point is, it does not last

 

 

---