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 thinking and illogical approach of the product series.

The First VISMO Monitors

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

 

 

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 art of exchanging two dedicated connector sockets for one flexible dual-use sockets

 

The 7-parameter Vismo PVM-2703 was released in February 2011 equipped with a yellow flexible MULTI-parameter socket for either Invasive Blood Pressure or mainstream etCO2 monitoring use. The prospective buyers should question the benefit of a flexible socket when there is shortage of one connector socket; do not focus on the flexible socket, but overall flexibility. In addition, the measurement cables for the dual-use sockets are special and of course priced at a premium.

 

The truth of the matter is, if the user could have one dedicated (i.e. non-flexible) 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 only from Shanghai, China.

The prominent feature of the VISMO PVM-2703 bedside monitor is the utilization of one common-use multi-parameter sockets that is colored yellow. The yellow common-use socket does not accept ordinary measurement cables but only cables that are embedded with digital codes defined by NIHON KOHDEN. The end result seen using a flexible Multi-parameter socket is the elimination of one usable connector socket on the monitor, which lead to serious usage inflexibility for users!

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

 

Veiled in secrecy, NIHON KOHDEN does not explain to the market how they could make sockets that are flexible for five types of internal hardware, as well as being able to accept a number of independent self-contained serial kit sets whose output are already-processed data in serial digital format. Almost all sales and marketing people employed in Japan Head Office have no engineering background, so there is no shortage of "company secrets" that must not be discussed with the distributors or customers.

Here are the relevant facts. Back in the 1990s,  NIHON KHODEN identified five types of analog hardware(Temperature, IBP, Cardiac Output, Thermistor Respiration, FiO2) that can be linked from the inside onto the yellow flexible common-use multi-parameter sockets and to make use of these internal hardware, an external measurement cable with a valid digital code on its plug needs to be inserted into one of the yellow common-use sockets. These measurement cables that comes with coded plugs are collectively cited as Smart Cables by the manufacturer and the embedded digital codes are also known as parameter-selection codes.

 

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

Note well the hardware mentioned here (Temperature, IBP, Cardiac Output, Thermistor Respiration and FiO2) are linked to the yellow flexible socket internally, and not from the outside

 

An external measurement cable with a valid digital code embedded in its plug can make use of corresponding internal hardware if available

The configured hardware using the Smart Cables are grouped into an electronic block known as MULTI-PARAMETER UNIT (MPU), complete with a small number of yellow common-use multi-parameter sockets. The number of yellow multi-parameter sockets in the MPU cannot be arbitrary, and must correspond to the number of internal IBP hardware channels specified.

It is the design rule that all yellow common-use multi-parameter sockets must be able to do IBP monitoring, and to adhere to this rule each yellow socket comes with its own exclusive IBP hardware. The term "exclusive" denotes the IBP hardware attached to each yellow socket is not intended for sharing by other yellow common-use multi-parameter sockets in the MPU block.

Principle of operation

During use, a multi-parameter socket makes use of its own associated IBP hardware when a measurement cable with an IBP code is plugged into it. For non-IBP monitoring, the socket can access a common pool of Temperature, Cardiac Output, Thermistor Respiration and FiO2 hardware in the Multi-Parameter Unit, which are designed for sharing by all yellow MULTI sockets.

 

Given the large amount of hardware in the MPU block, more yellow common-use sockets should be added whenever possible, so as to make good use of the hardware that would otherwise be idling; this is actually done by using an external expansion box filled with more yellow multi-parameter sockets (each with own associated IBP amplifier hardware).

The additional yellow common-use sockets are added using analog interface and limited to a maximum of four to avoid signal deterioration caused by voltage drop and noise.

 

Many are actually puzzled by the contents of the Multi-parameter Unit 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 common-use sockets for availability to users? The truth is because it was originally devised to solve the problem of limited panel space to mount many needed connector sockets! In situations when panel space is enough to accommodate all the necessary connector sockets, it is just a waste of money to adopt this design; clearly, its continued use regardless of need indicates there is more than meets the eye.

You can tell there is only one channel of internal IBP hardware in the PVM-2703 from the number of functional yellow MULTI sockets on the monitor

 

Knowing a functional yellow common-use multi-parameter socket always come with its own exclusive 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-parameter sockets. 

This being the hardware rule, and the key word is "functional" because a non-functional (fake) yellow common-use multi-parameter socket does not need to care about the capability to do IBP monitoring, such a socket can be found on the CardioLife TEC-5600 series defibrillators. The fake yellow multi-parameter socket on said TEC-5600 series defibrillators is just a serial port dressed as a common-use socket 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 out of five possible hardware types for use by Smart Cables. This being a simple monitor, the expansion box is not necessary.

Take note the parameters NIBP, SpO2, ECG and one channel of Temperature are not using Smart Cables, they are therefore not part of the Multi-parameter Unit.

The digital hexadecimal code is stored in a non-volatile EEPROM chip (Electrically Erasable Programmable Read-only Memory) mounted on a small flexible PC board electrically wired to the pins of the cable plug. It is not difficult to make the Smart Cables but they are being priced highly by the manufacturer; only the common IBP cable can be sourced from China suppliers at a reasonable price.

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

One MULTI-parameter socket can select two Temperature hardware channels.

Each MULTI-parameter socket can take two channels of Temperature measurements

The common-use yellow multi-parameter sockets are additionally diverted to serve as costly digital serial ports

As explained earlier, the design objective of Multi-Parameter Unit was to solve the problem of limited panel space, further reduction of sockets via use of multi-parameter sockets as serial ports will help towards this objective. This being an easy task since there is no need for additional internal analog hardware; the processed digital signals from the serial kit sets just bypass the analog stage and go straight to the digital processing stage of the monitor.

A mainstream CO2 serial kit set is linked to the VISMO PVM-2703 bedside monitor using a Smart Cable, treating the multi-parameter socket as a serial port.

The original label for the yellow MULTI socket indicated the five specific hardware and also serving as serial port for mainstream CO2 serial kits, the purpose was to minimize the number of sockets being used on a limited panel space.

 

The original label for the yellow MULTI-parameter sockets when they were first used

 

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

A yellow MULTI-parameter socket by itself does not automatically mean all the five types of mentioned parameters are available for measurements; it still depends on whether what hardware are actually being placed inside for selection by Smart Cables.

Additional parameter capability can be added using serial kit sets or via interfaces to external equipment.

When a model is not equipped with FiO2 hardware internally, no amount of yellow MULTI sockets is going to provide this measurement capability. The amount of configured hardware linked to each multi-parameter socket varies, so is the system support for serial kits and external interfaces.

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

Concluding, it is obvious 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 a connector socket that is of negligible hardware cost; it is just a magic show and illogical for practical use. We are therefore justified to look for the real motive behind its continued use.

The manufacturer has no clue the captured value from using Smart Cables is negative for users

Without sharing, both one channel of IBP and one channel of mainstream CO2 are freely available for use by plugging a non-coded measurement cable into their respective dedicated socket; it is poor logic to save the cost of a cheap connector socket at the expense of usage freedom!

The output of the CO2 kit sets are processed digital serial data that should go straight to the DPU

The mainstream CO2 parameter is supplied as a self-contained serial kit set with already-processed digital ready for direct-feeding to the digital processing stage of the monitor, using the multi-parameter socket only as a link. There is no need to compete for a yellow multi-parameter socket to connect.

Manufacturers make their profits by providing product benefits to users but the yellow MULTI-parameter sockets have no benefit. The first vehement complaint from users is always the yellow multi-parameter sockets on the monitor are not enough for use.

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

The only advantage is to save the cost of a cheap connector socket, but the monitor has been diminished to do only one of the parameter at a time; it is in reality inflexible and constrained monitoring.

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.

 

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

Are there monitoring hardware embedded in the NIHON KOHDEN Smart Cables?

 

So, do you really think there are monitoring hardware embedded in the NIHON KOHDEN Smart Cables? This is just a myth and we are going to show you beyond any doubt, there is absolutely no active electronics in the Smart Cables.

 

The marketing messages "New Modular Technology" and "The Module is in the cable!" are just the 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 assertion without offering any proof

 

Chip makers need huge demand to justify each of their products, so which chip manufacturer is supplying NIHON KOHDEN the variety of analog chips given the extremely low volume in demand? If we were to open up the plug of a Smart Cable, what do we see? A small PC board is seen attached 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 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.

Under US FDA rule, a cable is only a cable if it does not change the signal that passes through it. A Smart Cable with a 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 requires FDA registration. Can you find any stand-alone NIHON KOHDEN Smart Cable 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.

 

Irrefutable proof the IBP amplifier hardware is configured internally, an important fact withdrawn from later monitor manuals

The Life Scope BSM-2301 bedside monitor was launched before the Life Scope TR bedside monitors, 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, launched before the Life Scope TR bedside monitors.

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 MULTI-parameter 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-parameter socket doubles as a serial port without any need for internal monitoring hardware, only as a link to the monitor. In the block diagram below, the processed digital serial data from a CO2 kit set goes straight to the digital microcontroller APU (Analog-block Processing Unit) and is forwarded to the DPU.  For a parameter using the internal analog hardware, the analog signal needs to pass through an Analog-Digital converter before going to the APU for digital 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.

 

Life Scope BSM-2300K series bedside monitors case study

Preceding VISMO PVM-2703 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)

 

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

 

a. Invasive Blood Pressure

b. Thermistor Respiration

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

 

The MULTI-parameter socket does not, however, mean flexibility because you can only do one of the above parameter at any one time. It is so obvious using three dedicated sockets is a far superior proposal! Why must users endure pain of two missing sockets to gain use of one flexible socket with capability to make three types of parameter measurements? 

 

Life Scope-i does not have enough connector sockets

 

It is self-contradictory the monitor is using a dedicated socket to access the Temperature hardware instead of using the valuable MULTI-parameter socket. Why is this necessary if sharing a socket is preferred capability? This is a slap on the face for anyone proposing use of Smart Cables on a bedside monitor!

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

(ORDINARY BLOCK) The hardware using dedicated sockets and ordinary cables:

- 1-ch TEMP

- ECG

- SpO2

- NIBP

(MULTI-PARAMETER UNIT BLOCK with one MULTI-parameter sockets) The hardware only use Smart Cables for connections:

- 1-ch IBP

- Thermistor Respiration

Also using the MULTI-parameter socket are self-contained mainstream CO2 parameter kit sets utilizing the socket as serial ports

 

The reality is the shortage of two connector sockets, and users are all insisting the single MULTI-parameter connector socket on the BSM-2301K is not enough. The manufacturer was pressured to respond with an updated model (BSM-2303K) with an isolated MULTI-parameter socket added. The isolation was done so as not to disturb existing circuitry with an additional MULTI-parameter socket. It means the additional MULTI-parameter socket is a fake one and only could make use of the IBP amplifier hardware that comes with it.

The isolated fake MULTI-parameter socket was intended solely for IBP monitoring, effectively relieving existing functional MULTI-parameter socket to only measure either Thermistor Respiration or act as serial port for the mainstream CO2 kit set. It was not a solution, as a logical one would be to do away with the MULTI-parameter sockets. There is no need for socket sharing or the Smart Cables.

Alert salesmen knew there was no actual demand for additional IBP channel in the targeted segment, but the manufacturer claimed BSM-2303 bedside monitor was responding to market demand as an upgraded monitor with 2 channels of IBP.

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

Similar to Life Scope BSM-2301 Bedside Monitor, the VISMO PVM-2703 Bedside Monitor was another disappointment

Just like BSM-2301 bedside monitor, users were not impressed and want their missing socket back on the PVM-2703 bedside monitor so that they can do both IBP monitoring and mainstream CO2 measurement without any hesitation. In new PVM-4000 series bedside monitors, the VISMO PVM-4763, PVM-4753 and PVM-4733 are not exactly responding to what the user want. The new series offer users two MULTI-parameter sockets, but if you had not missed the details earlier, each MULTI-parameter socket comes with its own one-channel IBP amplifier hardware.

 

Thus, the VISMO PVM-4763 bedside monitor is adding one redundant IBP hardware channel just to do what the PVM-2703 monitor could already do if dedicated sockets were used instead. The user did not ask for an additional channel of IBP hardware, all this just to keep the archaic yellow MULTI-parameter socket!

There is just no reason to continue the use of Smart Cables except to meet the manufacturer's own agenda.

 

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 semi-quantitative CO2 measurements and ignorantly 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 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

 

How come the manufacturer is not aware Semi-quantitative CO2 measurements are only estimates?

 

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.

It is impossible for users to know if each measurement is reliable when the design is incapable of assuring them the CO2 level is indeed zero during the 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 assure measurement accuracy? The specified measurement tolerance is conditional and has no meaning for the users!

Each semi-quantitative CO2 measurement is therefore 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 but 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 is 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

 

 

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