NIHON KOHDEN Vismo PVM-2700 series patient monitors

Category: NIHON KOHDEN Vismo Scope patient bedside monitors and networking. In this article we review both the PVM-2701, PVM-2703 and PVM-4763 Vismo patient monitors, the thinking and illogical approach of the product series.

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The first Vismo monitor was the PVM-2701 model announced by Signal 718 dated November 2009. Notice this was the first model to do away with the suffix. Vismo came from Vital Signs Monitor.

 

 

In a pilot move, the new Vismo series was designed in Japan with as many parts sourced in China. Although initial shipment were assembled and shipped from Japan, this arrangement was changed from release of PVM-2703.

 

 

 

The Monitor that is short of one connector socket

 

The 7-parameter Vismo PVM-2703 was released in February 2011 equipped with a yellow shared-use MULTI socket for monitoring Invasive Blood Pressure or mainstream etCO2. There is shortage of one connector socket, if the user could have one dedicated socket for Invasive Blood pressure and another dedicated socket for mainstream etCO2, that would be a far superior design since the monitor can now do all 7 parameters at once.

 

From the release of PVM-2703, shipment for both PVM-2701 and PVM-2703 models started to be directly from Shanghai, China.

The manufacturer's insistence on Vismo PVM-2703 monitor having Invasive Pressure and mainstream CO2 serial kit sharing one yellow MULTI socket is a great puzzle, since dedicated sockets makes for flexible and unconstrained monitoring.

The yellow MULTI sockets are part of a legacy circuit known as a Multi-parameter Unit; sacrifices must be made to make use of them, but this is not explained to the market and easily leads customers into having an unrealistic expectation of what the yellow MULTI sockets can actually deliver. In addition, the MULTI sockets cannot be accessed using ordinary cables, but only by coded measurement cables cited as "Smart Cables".

 

The use of a Multi-parameter Unit in in a monitor, accessed only by coded Smart Cables, cannot be justified. Here are the details.

The legacy Multi-parameter Unit was originally devised only to solve a product issue

 

In the 1990s, when developing the first digital modular monitor, the development team encountered a problem of insufficient front panel space for connector sockets on the first digital multi-parameter module being made. A few sockets were specially adjusted for time-sharing use by a group of five types internal analog hardware to overcome the space limitation; to differentiate them, they were colored yellow and known as MULTI sockets.

 

At the time NIHON KOHDEN was responding to an important emerging trend of using a high-density digital multi-parameter module as basic building block for modular monitors

 

 

In analog modular monitors, only single parameter modules were produced by NIHON KOHDEN. When designing the first digital modular monitor, the company discovered the critical care market had already moved to using a digital multi-parameter module with higher density of electronic components as a basic building block for modular monitors.

 

Apart from the higher electronic density, the difference between a single parameter module and a multi-parameter module is the presence of a CPU processor in the latter; the output of a multi-parameter module is thus processed digital data. This new development of distributed processing made it possible for patient data to be stored and moved with the module. Digital modules can also be connected directly to a (proprietary) digital data-exchange network as a node.

 

NIHON KOHDEN wanted to follow the trend by offering the first digital multi-parameter module, and the first digital multi-parameter module made by the company was named the Saturn module.

Responding to new trend in the 1990s using a multi-parameter module with higher electronic density as a basic building block for modular monitor

Even occupying a 3-slot width of the module rack, the Saturn multi-parameter module (August 1998) was not big enough to hold all necessary connector sockets

 

Nihon Kohden intended a module rack integrated physically with the main unit to form a limited footprint just big enough to stack the display monitor on top of it (see below illustration). The physical size of the Saturn module was therefore constrained; in addition, the multi-parameter module must work in combination with other parameter modules like recorder, sidestream CO2, BIS, EEG, Flow/ PAW, SvO2 in the module rack.

The Saturn module was intended to be physically small in size

 

The elegant but expensive solution from NIHON KOHDEN for the physical size limitation of the Saturn module was to adjust two of the connector sockets for sharing use

 

Two yellow MULTI sockets had to be adjusted for time-sharing use because there was not enough free space on the Saturn module for more sockets

The solution from NIHON KOHDEN was to make use of coded measurement cables, promoted as "Smart Cables" to share connector sockets. There are two blocks of patient monitoring hardware in the Saturn module.

(Part A) The hardware using dedicated connector sockets and ordinary measurement cables:

- ECG

- SpO2

- NIBP

(Part B) The hardware sharing the two adapting MULTI sockets in a separate Multi-parameter Unit using coded "Smart Cables" for connections:

- 2 channels of IBP (2 MULTI sockets = 2-ch IBP)

- 4 channels of Temperature (2 MULTI sockets = 4-ch TEMP)

- Cardiac Output

- FiO2

- Thermistor Respiration

The adapting MULTI sockets were additionally allowed to be diverted to act as a costly digital serial ports so that mainstream CO2 digital serial kit sets can also use it; this being an easy task since no internal analog hardware is being involved.

The mainstream CO2 comes in the form of a self-contained serial kit set, utilizing the MULTI socket only as a serial port.

Remember this is for purpose of minimizing connector sockets on the Saturn multi-parameter module, as it does not make sense outside this context. In the next section, we will explain what is a Multi-parameter Unit in the Saturn module.

The label for the yellow MULTI socket indicated the five specific hardware plus mainstream CO2 using it as a serial port.

 

The label for the yellow MULTI sockets on the Saturn module

 

Time-sharing means only one type of the internal hardware sharing the connector sockets has exclusive use of it at any point of time

 

There are cheaper and more practical alternatives to solving the problem of insufficient space on the input panel, such as commonly integrating more than one signal onto a socket and using an external splitter to resolve the signals.

 

Example of resolving integrated signals to individual P1 and P2

 

So far, time-sharing of connector sockets is only done by NIHON KOHDEN and not repeated by any other leading manufacturers of patient monitors for obvious reasons.

It is foremost important to know the overall cost is very high to share connector sockets.

 

The connector sockets that were being time-shared are known as MULTI Sockets and colored yellow. The yellow MULTI sockets must be used in conjunction with coded measurement cables known as Smart Cables, and the plug of a Smart Cable has the same color as the MULTI sockets. The Smart Cables are each marked with a digital hexadecimal code to identify the purpose of the measurement cable (i.e. what parameter is being measured).

 

Overview

 

 

The digital code is stored in an EEPROM chip mounted on a small flexible PC board electrically wired to the pins of the cable plug. The hexadecimal code in the EEPROM is inserted at the factory and not allowed to change after production. It is not difficult to make the Smart Cables but they are priced highly by the manufacturer. However, if there is enough volume, suppliers from China are most willing to ship it to your doorstep.

A unique code is stored in the plug of the measurement cable to give switching instruction to an engaged MULTI socket

 

The code in the plug makes known what parameter a measurement cable is meant for and it is the instruction to the engaged MULTI socket to link internally to any of the five types of embedded parameter hardware, namely:

 

Temperature, Invasive Blood Pressure, Thermo-dilution Cardiac Output, Thermistor Respiration, and FiO2

 

Thus, a coded "Smart Cable" makes it possible for exclusive use of an engaged yellow MULTI socket via internal switching among five types of specific hardware.

 

The MULTI sockets are therefore adapter sockets with the ability to take unique switching instructions from the digital code stored in measurement cables known as Smart Cables

 

 

Principle of Operation

The Multi-parameter unit (MPU) in the Saturn module

 

In addition to coded Smart Cables, costly mechanism must be in place internally to select the correct active hardware corresponding to the unique code of the measurement cable being used.

The hardware sharing the two MULTI sockets are internal components of the Multi-parameter unit, together with the necessary mechanism to support the time-sharing. For example, when a measurement cable with a "Cardiac Output" code is plugged into a MULTI socket, the internal Cardiac Output hardware will have exclusive use of the engaged MULTI socket. If a hexadecimal code is not detected (such as a damaged Smart Cable plug), the MPU would not do anything and none of the internal hardware would be linked.

 

Sharing of connector sockets is made possible by coded measurement cables and an internal Multi-parameter Unit with necessary hardware

 

The MULTI PARAMETER UNIT is an official term found in the service manual

 

Extension is needed for the MULTI-PARAMETER UNIT

 

There are not enough connection sockets on the Saturn module, more sockets are needed. This is solved by having one or more satellite boxes containing two usable MULTI sockets each, placed next to the Saturn module. The image gives an impression of scalability without inquiring the details, but the necessary hardware are already embedded in the Saturn module except for additional IBP amplifiers which must only be tied to the number of MULTI sockets available.

What you are seeing is making use of space external to the Saturn module to put back the missing connector sockets.

The deficiency of connector sockets is addressed by making available additional usable MULTI connector sockets contained in external boxes

The Multi-parameter Unit of the Saturn module had only two yellow MULTI sockets, it is thus not possible to perform more than two channels of IBP monitoring; this means IBP hardware should correspond to the number of MULTI sockets available. For this reason, each MULTI socket is allocated their own one channel IBP hardware.

Each MULTI socket can take two channels of Temperature measurements, so the Temperature hardware is not an issue

The extension Smart module is therefore a 2-channel IBP box using two yellow shared-use MULTI sockets that can also access the Multi-parameter unit to make use of the Temperature, Cardiac Output, Thermistor Respiration and FiO2 hardware already embedded in the Saturn module.

The necessary hardware are already in the Saturn module except for additional IBP amplifiers tied to the number of MULTI sockets available

The necessary MULTI sockets hardware rule:

"Each functional yellow MULTI socket always come with one IBP amplifier hardware"

This of course, turns into a limitation when the MULTI sockets are being used out of context.

The Saturn module, together with two satellite boxes adding 4 channels of IBP to the Saturn module is shown below. The four MULTI sockets on the satellite boxes can also access the MPU of the Saturn module. Together, six IBP channels and six shared-use MULTI sockets are available to the users.

The sockets on the satellite boxes make up for those missing connector sockets on the Saturn module

A yellow shared-use MULTI socket is a high-cost serial port when it does not select any hardware

 

MULTI socket poorly utilized as a costly serial port

The initial arrangement was only for mainstream CO2 serial kit sets, but later extended enthusiastically to BIS kit set, 2nd-SpO2 kit set, APCO kit set, NMT kit set etc., whose motivation is highly questionable given this greatly increases the interface cost compared to a plain serial port.

The use of Smart Cables for serial communication, however, gives the false illusion of a mighty MULTI socket when the capabilities are in reality coming from the system software.

 

Make no mistake, the serial kit sets are self-contained and whether a particular kit set is supported depends on the system software, not on the type of connector sockets being used.

 

To reiterate, there is no difference if you connect digital serial data to the monitor using Smart Cables or ordinary serial cables

 

This is how you connect the BIS processor kit to a yellow MULTI socket

The modular monitor that made use of the Saturn module was a failure

The Saturn module was designed for the Life Scope S (BSS-9800) bedside station which was a modular monitor. The modular platform for the exchange of digital measurement data between the Saturn module and main unit was unfortunately, not reliable and resulting in product failure. Shown below is the Life Scope S bedside station with the Saturn module in a 8-slot module rack.

 

Life Scope S (BSS-9800) bedside station was a product failure

NIHON KOHDEN failed to justify use of the Multi-parameter Unit when out of context

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

 

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

 

In a puzzling move, the Life Scope BSM-2301K monitor makes use of a MULTI-parameter Unit with only one yellow MULTI socket for three types of measurements, namely:

 

a. Invasive Blood Pressure

b. Thermistor Respiration

c. Digital self-contained mainstream CO2 serial kit sets.

 

The MULTI socket does not mean flexibility because you can only do one of the above parameter at any one time. Using three dedicated sockets is a far superior proposal; why suffer pain of two missing sockets to gain use of one flexible socket?

 

Life Scope-i does not have enough connector sockets

 

The use of a MULTI socket is self-contradictory from the start. We have to ask why is the monitor avoiding the use of the MULTI socket to access the Temperature hardware if sharing is a preferred capability? This is a slap on the face for proposing use of MULTI sockets on bedside monitors.

The two blocks of patient monitoring hardware in the Life Scope BSM-2301 bedside monitor are:

(Part A) The hardware using dedicated connector sockets and ordinary cables:

- 1-ch TEMP

- ECG

- SpO2

- NIBP

(Part B) The hardware sharing the one adapting MULTI socket in the Multi-parameter Unit using Smart Cables for connections:

- 1-ch IBP

- Thermistor Respiration

The mainstream CO2 comes in the form of a self-contained serial kit set, utilizing the MULTI socket only as a serial port

The reality is the shortage of two connector sockets, and the flood of complaints from users insisting the single MULTI connector socket on the BSM-2301K was not enough. The manufacturer was pressured to respond with an updated model (BSM-2303K) with an isolated MULTI socket added. The isolation was done so as not to disturb existing Multi-parameter Unit with an additional MULTI socket. It means the additional MULTI socket is not a functional MULTI socket but it allows use of the Smart Cable for IBP measurement. 

Since the isolated MULTI socket is solely for IBP monitoring, it effectively relieves the MULTI socket of existing MPU to only measure either Thermistor Respiration or act as serial port for the mainstream CO2 kit set. The solution was only partial, and it reduced two missing sockets to one missing socket; a total solution would have been just using dedicated sockets as there is no need for socket sharing.

There was no actual demand for additional IBP channel, but the BSM-2303 bedside monitor was camouflaged as an upgraded monitor with 2 channels of IBP.

Under pressure, an additional isolated MULTI socket acting solely as an IBP amplifier had to be introduced

In the case of the PVM-2703, what is the benefit of removing one connector socket to gain use of a flexible socket?

Incorporating the Multi-parameter Unit in PVM-2703 Vismo patient monitor is illogical

The only type of hardware in the Multi-parameter Unit in Vismo PVM-2703 is just one IBP amplifier, and mainstream CO2 kit sets are supported by the system software. Without sharing, both one channel of IBP and one channel of mainstream CO2 are freely available for use by plugging into their respective dedicated socket; what is a good reason to restrict such freedom?

The digital serial data does not need to share the same connector socket with an IBP transducer

Similar to BSM-2301 bedside monitor, the Vismo PVM-2703 could not justify use of the MULTI socket

Just like BSM-2301 bedside monitor, users want their socket back on the PVM-2703 bedside monitor. The solution is provided by a new PVM-4000 series bedside monitors; in PVM-4763 bedside monitor (using NIHON KOHDEN SpO2 algorithm). From the MULTI sockets hardware rule, we can tell two IBP amplifiers are inside the PVM-4763 bedside monitor. However, the monitor is essentially doing the same parameter measurements.

Again, we have to ask why is the manufacturer avoiding use of the MULTI sockets for the two Temperature channels if sharing is a preferred capability?

The Multi-parameter Unit is configured

The yellow MULTI socket by itself does not automatically mean all the five types of mentioned parameters are available for measurements; it still depends on whether any of the five types of active hardware are actually being placed inside the Multi-parameter Unit. The amount of configured hardware inside each Multi-parameter Unit is always different; so is the system support for serial kits. If a model is not equipped with FiO2 hardware internally, no amount of yellow MULTI sockets can provide this measurement capability.

In other words, 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

This means Vismo bedside monitors making use of the Multi-parameter Unit are still configured monitors. The manufacturer has no reason to use a Multi-parameter Unit in a monitor at all; it is not flexibility, but dabbling with distortions and limitations.

Steer Clear! There is no customer value created by time-sharing cheap connector sockets

 

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! It only makes sense to see productive efforts being 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. The legitimate resources for a patient monitor to time-share are obviously the analog amplifier hardware and not the connector sockets or switches; this way there would not have any idling costly hardware leading to inefficient use of valuable resources!

 

Time-sharing of a car (an asset) creates value for the customers but time-sharing of a cheap connector socket does not

 

The next picture shows another manufacturer 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.

 

Only share the expensive hardware, not the cheap sockets

 

  

 

Hospitals should aware 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 semi-quantitative estimation data for uncertain measurements and concurrently 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 reason, Nihon Kohden monitors could not offer integrated sidestream CO2 unit.

 

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

Nihon Kohden solution was to offer miniaturized 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 (order code P907) has very small sensors because semi-quantitative measurement is adopted, the method is not commonly seen and many are not alerted to the risk of using data from semi-quantitative etCO2 kit sets for critical measurements and true CO2 waveform display.

 

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.

 

Users just doing the inevitable

 

Shown below is another TG-900P etCO2 kit set (order code P903) that makes semi-quantitative CO2 measurements; the TG-901T3 kit set (order code P906) is the same thing using a different connection plug. The medical devices from same manufacturer that uses semi-quantitative etCO2 kit sets for patient CO2 waveform monitoring have Life Scope patient monitors, Vismo patient monitors, Cap-STAT OLG-2800, CardioLife defibrillators and Neurofax EEG machines etc.

 

Nihon Kohden semi-quantitative etCO2 kit sets

 

An interesting question: Can users accept estimated measurements for patient monitoring?

    

To save costs, the semi-quantitative kit sets do not make measurement during the inspiration phase, the measurement duty cycle is as shown. This means semi-quantitative CO2 measurements are not made continuously.

Semi-quantitative means there is a duty cycle, and measurement is 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.

As seen from the duty cycle, there is no measurement being made during the inspiration phase; how do the users know specified measurement accuracy is valid?

  

Measurements are invalid when CO2 is present during inspiration, but CO2 is not measured during this period; can you have confidence in the measurements?

 

It should be clear each semi-quantitative CO2 measurement is only an estimation since its accuracy is rendered uncertain by the inability to confirm if CO2 is present during the inspiration phase. The specified measurement tolerance therefore has no meaning for the users!

 

The users are also not alerted on screen there is no CO2 measurement being made during the inspiration phase, and unknowingly made to take 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

 

 

How is it feasible to display a true continuous CO2 waveform when the semi-quantitative measurement kits do 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 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 true CO2 waveform display on screen.

 

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

 

 

How about fully-quantitative type miniaturized mainstream CO2 sensor?

   

The TG-907P CO2 Sensor kit (order code P909) shown in above table is using quantitative method as declared. This sensor was designed for non-intubated adult CO2 monitoring, as well as neonatal CO2 monitoring. In short, Nihon Kohden is trying not to rely on others for sidestream CO2 sampling expertise.

 

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.

 

 

Undeniable confirmation the fragile miniaturized CO2 sensor is of poor design, and easily broken

 

 

Key point is, it does not last