An In-depth Review of NIHON KOHDEN Vismo PVM-2703 and PVM-4733, PVM-4753, PVM-4763 Bedside Monitors

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

NIHON KOHDEN Vismo Monitors

 

The Vismo PVM-2701 was a pilot move, designed in Japan but with the majority of parts sourced in China to lower the cost of production. This means some parts are still being sourced in Japan.

 

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 hard reality is, two fixed-purpose sockets

cannot be replaced by using only one flexible 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 Nihon Kohden is using one flexible socket for IBP or mainstream CO2. The manufacturer should know that although the multi-purpose socket is flexible, it is not capable of multitasking.

 

This monitor can only do six parameters at any one time, not seven; can this be called a seven-parameter monitor?

 

To start with, there is really nothing wrong with using one fixed-use socket for Invasive Blood pressure and a separate serial port for mainstream CO2 kit set, which is the norm in the industry, and a far superior way since the monitor can simultaneously do all 7 parameters with this arrangement. What need is the manufacturer targeting?

  

What the manufacturer had done is clearly questionable, since the use of a flexible socket to choose between IBP and CO2 is not a strength, but a shortcoming. Why would any one buy a disadvantaged monitor? This is the reason for the failure of PVM-2703 bedside monitor. There is no real demand for flexible sockets, it is just a demand imagined by the manufacturer.

 

 

The distinctive feature of the VISMO PVM-2703 bedside monitor is the inclusion of a flexible MULTI (short for multi-parameter) socket, and this socket is specially colored yellow for easy identification.

 

The yellow flexible MULTI socket on the PVM-2703 monitor is capable of doing either of two things.

1. Be connected to the internal IBP analog hardware for IBP monitoring

2. Send the digital serial data packet of a mainstream CO2 serial kit set straight to the digital processing stage. 

 

Whether the MULTI socket should be performing the role of (1) or (2) depends on the exact of code found in the special measurement cable to operate the MULTI socket. A flexible MULTI socket must by definition accept more than one type of measurement cable; the parameter code embedded in the plug of a special measurement cable is the method adopted to differentiate the cables, and inform the monitor what internal hardware or software are needed for support when a measurement cable is being plugged in. These measurement cables with codes embedded are known as Smart Cables.

 

There are therefore two types of Smart Cables that can operate the yellow flexible socket on the PVM-2703 bedside monitor, one with the code for IBP and another for using the MULTI socket as a serial port.

 

There is no free lunch, and the trade-off is flexibility vs. sufficiency. The consequence of using flexible sockets for general use actually translates to insufficient physical sockets for users, and the deprived users are not hesitating to demand back their missing sockets. How can there be any customer value from socket flexibility when its use creates a shortage of physical sockets for users?

 

What does this mean?

The manufacturer made the grave mistake of rationalizing the flexible MULTI sockets are exhibiting characteristics similar to what modular monitors offer, only to learn painfully from market rejections flexible sockets are actually poor man's sockets. It was unnecessary lessons, and to be expected if you truly understand the working principles. 

 

The wild assertion of a module in the cable needs a closer critical look.

 

 

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 public statements and the manufacturer has a duty to ensure its accuracy.

 

Where are the evidence of physical amplifiers in the Smart Cables?

Under US FDA 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. We have yet to find the stand-alone IBP measurement cable shown in the above brochure registered with US FDA as a medical device.

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.

 

 

This MULTI-PARAMETER UNIT (MPU) design from the 1990s

was a trade-off (Flexibility vs. Sufficiency)

 

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 the entire sales and marketing people employed in Japan Head Office have no engineering background, how could any one discuss anything of substance with the distributors or customers (except for prices and deliveries)? Mind you, the group comprises people who provide advice and product trainings to distributor frontline sales teams.

 

Why did the manufacturer forget that this flexible yellow socket was originally designed for frugal use should be the biggest challenge for sales. 

Here are the historical facts, and the company was looking for a solution to solve the problem of a new type of digital multi-parameter module with only a small front panel that did not have enough space to mount all the needed connection sockets.

 

The small panel space needing a solution

The problem was not unique to NIHON KOHDEN, and the solution from Marquette and SpaceLabs, for example, is to integrate more than one signal onto a socket and using an external splitter to get back the original individual signals. 

 

Example of getting back original P1 and P2 from an integrated signal

The thought-provoking solution from NIHON KOHDEN was, however, to share common sockets. So far, time sharing of connection sockets is only done by Nihon Kohden, and avoided by all other manufacturers of patient monitors.

 

That was in the 1990s, and the NIHON KOHDEN development team managed to identify five types of analog hardware (Temperature, IBP, Cardiac Output, Thermistor-method Respiration, FiO2) that could form a hardware group frugally sharing just two flexible sockets for common use. The two flexible sockets are known as MULTI (short for multi-parameter) sockets and are specially colored yellow for easy identification.

 

The hardware group and flexible sockets together made up the MULTI-PARAMETER UNIT (MPU), and was a peculiar design to reduce the number of physical sockets needed on a front panel with a limited space area.

 

The first MPU made by Nihon Kohden

To operate the yellow flexible MULTI socket, 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. Thus, the Smart Cables are mandatory to operate the yellow flexible MULTI sockets.

 

The MPU detects each type of measurement cable by reading the cable code

 

The original multi-parameter module (with networking capability) that made use of the MPU is known as the Saturn multi-parameter module, as shown below. The left side is the conventional section (ECG, SpO2 and NIBP) while the right side is the MPU with two flexible yellow MULTI sockets.

 

The MPU was a design to have flexibility over sufficiency, taking advantage of the space constraint for limited sockets

Each MULTI socket will 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 sharing pool comprising Temperature, Cardiac Output, Thermistor-method Respiration and FiO2 hardware. The hardware are configured, and placed in the MPU before leaving the factory, and as such limited, so it is not possible to exceed the maximum available hardware. The configured hardware for each MPU, therefore should be professionally specified by the manufacturer and not avoided to cause confusion.

The parameter code is a digital hexadecimal ID programmed into a non-volatile EEPROM (Electrically Erasable Programmable Read-only Memory) mounted on a small flexible PC board and wired to the plug of a Smart Cable at the factory.

 

The flexible PCB with an EEPROM chip

Users cannot change the code using settings on the monitor after production; the EEPROM is not expensive but the Smart Cables are, and only the common IBP cable can be sourced from China suppliers at a reasonable price. The hex code can be easily read by direct access to an exposed original cable.

 

A non-volatile code is embedded in the plug of a Smart Cable

Each yellow MULTI socket can only link to one channel of the internal hardware, except for Temperature which can accommodate up to two.

 

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

Given the large amount of hardware idling in the MPU, more physical sockets are needed to make good use of these valuable hardware; yet, only physical sockets in the form of MULTI sockets can access the MPU. The arrangement to add more physical sockets is thus achieved using external expansion boxes filled with two or more MULTI sockets (each with its own dedicated IBP amplifier hardware). It is important at this point to be clear the purpose is to add more physical sockets linking to the existing MPU, and not to add more monitoring parameters. The expansion boxes do not have new hardware, except for the IBP hardware that comes with each MULTI socket.

 

This is a process of adding more physical sockets, not more monitoring parameters

 

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

 

Shown below is a Saturn module 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

 

A bypass code send digital serial data packet

straight to the digital processing stage

 

Again, like a configured monitor, the MPU can accept use of serial kit sets for capability extension (supported by necessary software). This is done via a parameter code, whose execution means to bypass the internal analog hardware and go directly for digital processing; the MULTI socket is acting as a serial port using this code. As is common knowledge, the identity of a serial kit set is contained in the header of the data packet. By screening the header packet, the monitor can tell what type of serial kit set is being connected, and will not process the data if the system software does not support it.

 

The MULTI socket goes straight to the digital processing stage when the bypass code is detected

It was then a logical move, because the purpose of the MPU was to solve the problem of limited panel space area, and by using MULTI sockets as serial ports does help in furthering the reduction of one more physical socket on the front panel.

The digital network connecting the main unit to the module racks is known as the measurement network and is illustrated as follows. To add more module rack to the network, it was done using a cascading cable.

 

 

Unfortunately, the real-time measurement LAN network for data communication between 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.

 

Do not confuse the failed measurement LAN network with the clinical monitoring LAN network, which is for data exchanges between bedside monitors and central nurse stations.

 

The first two genuine modular monitors were failures

After the decision to stop development work on the measurement LAN network, a younger team of engineers with lesser experience took over key positions. The younger team proved risk-averse and decided to keep the MPU, using the expansion sockets to simulate scalability. This was unexpected, because they did it only to avoid the risk of working on a new measurement LAN; at the same time, they also knew they could get away with it in Japan given the low bargaining power of users in the domestic market. It means all current Life Scope monitors do not have a measurement network to address individual measurement device, which is what that makes a modular monitor different from a configured monitor.

 

The MPU was only a compromise to accommodate limited panel space area and should never be misrepresented as an innovation; the MPU is meaningless without the module rack, and there is no demand in the market for socket flexibility. In marketing, we first establish there must be a sizeable demand from market research before a product is actually created to meet the detected demand; this process was deliberately bypassed.

 

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.

 

 

The weak arguments for using the yellow flexible MULTI sockets

have begun to fall apart

In 2001, a popular Life Scope BSM-2301K (also known as Life Scope i) was launched and many customers bought it for standalone applications not restricted by system compatibility. It was popular because the Life Scope BSM-2300K series range of monitors were the first in the industry to adopt the new-generation type 8.4-inch high-resolution touchscreen introduced by the electronics industry. The new touchscreen display was a huge jump in touchscreen technology and made for highly-intuitive operation, hence its popularity. The company tried to attribute its popularity to the use of Smart Cables and a flexible MULTI socket. Let's see if this is true.

 

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

 

The Overlooked Flaw: You cannot use ONE flexible socket

to replace THREE dedicated sockets

 

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 bordering on frivolity.

 

It is obviously unwarranted stress and inconvenience for the users, 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?

 

This is compromised usage, like a poor man affording only one physical socket for three types of use

 

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 physical sockets for users. However, one of the parameter for the yellow MULTI socket is thermistor-method respiration, which is for use in the operating room to overcome electrical noise interference; this parameter is therefore not for use in the ward. The real shortage felt by users is only one missing physical socket, and they are not hesitating to demand it back. Imagine the initial wonder of a flexible socket turned into an outrage for being shortchanged!

 

Users do not want to be shortchanged with a poor man's socket

The manufacturer was pressured to respond with an updated model, Life Scope 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 manufacturer quietly conceded the MULTI socket of Life Scope BSM-2301

was indeed a poor man's socket

 

The MPU of the Life Scope BSM-2301K was not designed to take on expansion, and any additional MULTI socket will load (disturb) the operation of existing MPU, causing it to malfunction. An additional MULTI socket not linked to the MPU is just a standalone socket with its own dedicated IBP amplifier hardware. Such was the additional yellow socket offered for Life Scope BSM-2303K, noting there was a need to recognize and use the same IBP Smart Cable.

With a new socket for IBP, the existing MULTI socket can move away from doing IBP monitoring, and just focus on being a serial port for mainstream CO2 or being an amplifier for respiration monitoring using a thermistor transducer.

 

It was ironical, a solution relying on an extra dedicated socket for IBP; there are now two IBP amplifier hardware in the monitor, which was not the original intention. It was clear the complaints was the market rejection of sharing a flexible socket and the solution offered by Life Scope BSM-2303K was to return back the missing physical socket demanded by users. 

Market rejection forced the manufacturer to return back the missing socket demanded by users

 

More physical sockets had to be returned for later

Life Scope BSM-3000 series bedside monitors

 

Undeterred, NIHON KOHDEN again launched the Life Scope VS bedside monitors with the BSM-3500 series monitors (12.1-inch display) having two yellow MULTI flexible sockets while the BSM-3700 series monitors (15-inch display) come with three yellow flexible MULTI sockets. The value captured by users for both models are again negative.

 

The MPU of BSM-3500 series bedside monitors

 

The difference between the BSM-3500 series and the BSM-3700 series is the latter having one extra yellow MULTI flexible socket, and of course it also means an additional IBP amplifier hardware.

 

The MPU of BSM-3700 series bedside monitors

In below picture, the manufacturer cannot provide the left monitor (BSM-3500 series) more than two MULTI sockets because the IBP hardware channels intended for this model is only two, and therefore fixed at two flexible MULTI sockets. However, users require five physical sockets for simultaneous use, and that is only a 2/5 availability ratio using the two MULTI sockets. Noting all five parameters are freely available for carefree use via dedicated sockets, the use of Smart Cables/ MULTI sockets just makes things unnecessarily complicated, requiring deliberate operator attention and a conscious efforts to choose two among the five; this is unwarranted attention, stress and inconvenience.

 

What is wrong with using five dedicated sockets, which is a far superior norm since all parameters are available for connections at any time without hesitation. What user benefit is the manufacturer trying to provide?

  

Similarly, users of the right monitor (BSM-3700 series with 3 channels of IBP) requires six physical connection sockets for carefree use but the manufacturer insists three shared-use sockets are enough. This means the manufacturer only wants to place 3 channels of IBP hardware in the MPU of the BSM-3700 series monitors and ignore the user's pain; this kind of forceful approach can only happen in a protected Japanese market where bargaining power of users is low. It is another matter for the export markets, the manufacturer has to respond to such complaints as long as there is still interest to export their monitors.

 

How does such dire shortage of connector sockets benefit a user?

These monitors are in dire shortage of physical sockets, the values captured by users are negative

 

As expected, users soon found out the small number of MULTI sockets on Life Scope VS bedside monitors are not enough for use. The situation for Life Scope VS series bedside monitors is the same as Life Scope BSM-2301K bedside monitor, customers want their physical sockets back because they need it!

 

NIHON KOHDEN reluctantly had to offer two options for solution, the AA-372P Smart Expansion Unit returns two missing physical sockets while the AA-374P Smart Expansion Unit returns four missing physical sockets. The AA-374P expansion unit with four sockets is shown in below picture. 

Life Scope VS series bedside monitors were not designed for expansion, although we were not surprised to find expansion units from Life Scope TR belatedly being offered as solution to the demand from users for more physical sockets. There are modifications done to the original items since the model names (AA-372P, AA-374P) are different; the makeshift solution makes the bedside monitor look awkward, resembling a product prototypes still undergoing tests.

The manufacturer found a way to return back the missing physical sockets

If you look at the below picture, it is as good as going back to using dedicated sockets, but at a high cost. The rejection messages from the market are consistent and enough for the manufacturer to drop the flexible sockets for future products.

This picture tells us the manufacturer is returning back to users four missing physical sockets

 

The Life Scope VS monitors were originally not designed for socket expansion, there should be limitations and users may have to pay additional attention to correct socket selections as a result.

 

 

Returning the missing physical socket through

a new Vismo series bedside monitors

 

The patient monitoring hardware inside the VISMO PVM-2703 bedside monitor are divided into a conventional block and one isolated MULTI socket. The conventional block uses dedicated sockets and ordinary measurement cables while the MULTI socket makes use of Smart Cables embedded with parameter codes for different parameter.

 

CONVENTIONAL SECTION

- ECG

- SpO2

- NIBP

- 1-ch Temperature 

MPU SECTION (one flexible MULTI socket)

- 1-ch IBP

- [MULTI socket as serial port] mainstream CO2

 

PVM-2703 bedside monitor has one standalone MULTI socket in a bare MPU

The situation for VISMO PVM-2703 Bedside Monitor is the same as Life Scope BSM-2301K Bedside Monitor, and customers want their physical sockets back because they need it!

 

The missing physical socket in Vismo-2703 bedside monitor is solved by using new PVM-4000 series bedside monitors, which has two standalone MULTI sockets.

 

The PVM-4763 monitor has two standalone MULTI sockets in a bare MPU

There are six models in the Vismo 4000 series bedside monitors, three basic models do not make use of the yellow MULTI sockets.

1. PVM-4731 (Masimo SpO2) bedside monitor

2. PVM-4751 (Nellcor SpO2) bedside monitor

3. PVM-4761 (Nihon Kohden SpO2) bedside monitors

 

Another three with two standalone yellow MULTI sockets, using different SpO2 algorithm.

1. PVM-4763 bedside monitor (Nihon Kohden SpO2)

2. PVM-4753 bedside monitor (Nellcor SpO2)

3. PVM-4733 bedside monitor (Masimo SpO2)

 

The MPU of PVM-4763, PVM-4753 and PVM-4733 bedside monitor are similar to PVM-2703 bedside monitor, except this time there are two standalone yellow MULTI sockets.

 

CONVENTIONAL BLOCK

- ECG

- SpO2

- NIBP

- 2-ch Temperature 

MPU SECTION (two MULTI sockets)

- 2-ch IBP

- [MULTI socket as serial port] mainstream CO2

 

What you are really seeing is a PVM-2703 monitor with an additional MULTI socket, which is the same solution as what Life Scope BSM-2303 bedside monitor offered. Since this is a new design from scratch, Masimo and Nellcor SpO2 algorithm options are also offered, in addition to an extra dedicated socket for Temperature.

 

Again, the manufacturer is just avoiding the market rejection of using flexible sockets. The users did not ask for an additional channel of IBP hardware and there is no logical reason to continue use of Smart Cables/ MULTI sockets except to meet the manufacturer's own agenda in Japan, and they will want to keep doing it in the Japanese domestic market because the bargaining power of users is low in a protected market.

 

Adding an additional MULTI socket to PVM-4763, PVM-4753, PVM-4733 bedside monitors to do the same job PVM-2703 monitor could do using dedicated sockets

It is truly much ado about nothing

Manufacturers make their profits by providing product benefits to users but the yellow MULTI sockets is a burden to the users.

 

What benefit can it offer users when necessary physical sockets are missing?

 

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.

 

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 optimizes the use of expensive hardware, not the cheap sockets

 

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.

 

 

Beware the Lurking Dangers of

Reading Estimated CO2 Values presented as Actual CO2 Values

 

The adoption of semi-quantitative mainstream CO2 measurement by NIHON KOHDEN 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 of the adoption of semi-quantitative measurement; the method is not commonly seen and many are not aware of the risks of CO2 readings from the semi-quantitative CO2 kit sets. To make matter worse, the semi-quantitative measurements are also being used of to display a flawed continuous CO2 waveform on screen to the users.

 

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

 

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

Semi-quantitative CO2 measurements

are not a cheap alternative to quantitative measurements

 

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.

 

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 the actual CO2 level can be much higher.

 

In other words, it is an acknowledgement that:

 

1. The measured CO2 value is not the true CO2 level.

 

2. The true CO2 level = [measured CO2 value + x], where x is an unknown CO2 value carried forward from the inspiration phase. Only when x = zero will the measured CO2 value reflect the true CO2 level. 

 

It is unprofessional to specify a measurement tolerance

when there is an unknown in the equation

This is not professional specifications

As seen from the duty cycle, there is no measurement being made during the inspiration phase, how do the users verify the measured CO2 value is the true CO2 level?

 

The specified measurement tolerance is conditional on this assurance and the CO2 value shown to users is therefore wrong and misleading! Each semi-quantitative CO2 measurement is in fact only an estimation, because the users have no way to be sure the x value is indeed zero. It is only assumed to be zero by the manufacturer.

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 measurements are only

for selective uses with known risks

 

For example, semi-quantitative methodology can be used as an 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

It is a flawed continuous CO2 waveform when fed by a source

that does not have the 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

The dangerous assumption

that expiratory upstrokes always start from zero CO2 level

Quantitative measurements confirm 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

 

 

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