Connections! They’re everywhere! From the cable that plugs into your monitor and that oddly specific charging cable that charges your phone, getting connected can be frustrating! The major issue with incompatibilities are due to manufacturer specific proprietary technology and regulations that haven’t or won’t catch up to consumer requirements of peace of mind. Fear not, though, for with a few simple principals, you can identify what you’ve got and/or what you need! This guide will cover a few different applications in the medical field from the common to the bizarre. This is the first of a number of posts that help demystify connection types in biomedical technology. For starters, some basic principals need to be kept in mind.
Dimensions are how we numerically describe physical qualities of shape and geometry. Length, width, height, diameter, radius, area and volume may be important to know in order to properly communicate specifications of an accessory. Some accessories are standardized and can be referred to by a common name or a part number. Dimensions can be measured using tools such as rulers, calipers, tape measure, or approximation. Accompanying pictures or drawings allow us to communicate what we mean about specific dimensions if the name is not clear or easily understood by the recipient.
Type may refer to common variations within a part. This may be described using numbers, letters, or alphanumeric combinations like part numbers. Types are very important because there may be similarity between types in terms of dimension, and may be compatible between each other, but can cause problems if used if not specified that way. An example of this are different DC power supplies which are usually circular connectors of differing diameter. Plugging the wrong types together may result in equipment malfunction, connection unreliability or shock.
Composition is what an item is physically made up of. Metal, plastic, rubber, silicone, or other proprietary material names are all possible ways to describe a material composition. Within the composition may be sub composition such as stainless steel being a type of metal or PVC being a type of plastic. Composition will determine how it can respond to fluid, how flexible it is, heat tolerance, how quickly it will break down over time, or even how it is suggested to be used.
Blood Pressure Connectors
One large area of confusion for a lot of healthcare professionals, especially ones that work with a wide array of manufacturer’s products, is the proper use of standardized blood pressure unit connectors. This may be present on the input to your device, to the hose attachment, or on the cuff itself. Improper connections not only affect the accuracy of your measurement, but also are frustrating when working between different types of units. TRH Services technicians are skilled at identifying, troubleshooting problems, and if necessary, repairing problems related to blood pressure accessories. If a technician is not on site, it is very helpful to understand the means of describing what you need. Pictures are a plus too.
Broken down, blood pressure machines are pretty basic. Manual machines, battery powered drug store ones, and high quality professional ones all operate using the same principals, with differing reliability and accuracy. The way a blood pressure machine works is by applying a pressure to the cuff, and sensing the resistance from the oscillations of the vasculature depending how far above or below systolic and diastolic pressure you are, through the air inside the tube. If there is any issue with air leakage in any part of this circuit, you have inaccuracy emerging. For more information about blood pressure units, please refer to the “Blood Pressure Units” post from June 2017.1
Gauge: A dial that displays the pressure in the system. Usually in mmHg. These are typically very durable, but may either be out of calibration and can be calibrated, or will be broken with no chance to repair. Inflating the gauge too much without a volume attached may damage it. This is realized by an electronic sensor for the electronic blood pressure units.
Inflation bulb: The squeezable device you hold in your hand to add air to the system. There is a valve that can be opened to release air. As this device ages, cracking in the rubber or weakening of the valve will let air out undesirably. This is done automatically with electronic units; pressurizing and releasing pressure as the programming sees fit with a safety valve.
Hose: The tubing that connects from your gauge to your cuff and cuff to bulb.
Cuff: The protective sheath around the inflation bladder of varying size.
Inflation bladder: The sealed rubber tubing that inflates when you apply pressure to the system and is located inside the cuff (or is a part of the cuff as one piece).
Connectors: Detachable ports that allow the swapping out of various components of the blood pressure unit.
The connectors themselves are pretty standard, but highly numerous. Over the hundred plus years the technology has been around, there have been an incredible amount of variations of the same thing. Historically, before modern manufacturing practices that allowed for easy production of gauges and sensors, mercury was used to give a reading. Like this unsettling, and potentially dangerous practice, many low quality connectors have gone the way of the dinosaurs.
Before exploring types of connectors, some attention needs to be paid to language when describing and communicating effectively. There are a number of miscellaneous brands, styles, configurations and other considerations to keep in mind and this explanation is in no way exhaustive. Due to the quantity of types, discussion is limited to description of general terms and explanation of a few common brands.
The most basic connection in the blood pressure measurement system is a ‘hose to barb’ connection, which takes the straight hose and is held in place by a series of increasing diameter ‘barb’ to hold the tube in place.
Luer refers to a shape and style that often has a a few threads and quickly slips in with a lot of room to start, and gets snug when fully inserted. This is realized in both blood pressure measurements as well as IV lines. There is a gradual move away from this type of system because in a a number of near miss situations in major hospitals, a blood pressure, gas, or tourniquet system has been mistakenly hooked up to an IV line causing serious injury and death. This occurs with some leur connectors which happen to be the same size as an IV line, while other sizes will not fully fit, and others don’t attach at all.
Thread refers to the type that the two connectors screw together like a bolt and nut. The advantages of this type are that it is cheap to produce, quick to change, and cleaning-friendly. The disadvantage is that the connectors themselves are fragile and the threads can be damaged if used too much or incorrectly, regardless of material. You can specify ‘threads per inch’ when specifying this type, along with diameter and composition.
Bayonet is also a pointed shape as the name implies. It is recognizable below for Mind Ray, Criticare, Spacelabs, Edan, or Philips. All these brand names happen to use the same specifications so some of their accessories are interchangable; at least for cuffs. The general principal here is that a long section with a groove snaps in for a tight seal which may or may not involve small gaskets or o-rings. The disadvantage of the bayonet is that the female end can get stuck if not replaced or maintained yearly, since it snaps in a spring like fashion and gets gummed up from cleaning agents. Bayonets typically are standardized nowadays but length may differ. This will likely end up to be the best, standardized connector for all blood pressure technology for the near future.
Locking refers to the means by which the connector fits with its counterpart which usually clicks or snaps in place. A slip type connector is held in by pressure, sometimes with a twist, whereas a locking fitting has threading or partial threading to hold it in place when pressure is exerted on the system or not. Depending on the quality of connector and the pressure applied over the volume, some slip types are more susceptible to coming loose, especially if they’re metal and the metal rusts over time. Locking or slip connections exist in a number of brands/varieties.
Metal vs plastic (PVC) is an increasingly important consideration due to the fact that historically, the metal type connectors are not infectious-control friendly and get stuck often. They are also significantly more expensive. Almost every type of connector has a plastic or metal version of it.
Dimensions (for pneumatics) as above, are the ways we describe the physical geometry of the fitting beyond its common name and type. There are differing diameters, length and interior width that, while look like other ones, will not fit, or may appear to fit, but will leak. For instance: many off-brand bayonet connectors will have a slightly longer length, and the snapping feature of the female end doesn’t work. If the indent on the bayonet is slightly thinner, there may be an imperceptible leak that will cause inaccuracy of your measuring device. If your unit has a clearly identifiable model, the dimensions are set and standardized to that unit, with a few exceptions. It’s not always necessary to be able to read part numbers or SKUs of the package it came in, but it may help save research time.
The barb is the most common type of connection you will see in manual blood pressure measurements as well as on the other side of all the connectors. The disadvantage of this connector is that every time it is removed, the hose end may be enlarged, and would need to be cut back. It is advised not to remove this connection very often. A lot of manual gauges use this connector type, and, while on site, TRH Services technicians will likely remove and cut the tubing back to eliminate leaks. They will also do this if there is noticeable cracking that forms at the edges of cut or expanded rubber. If the hose is too short, it would be recommended to replace the hose as well. Cracking is usually a sign that the extension hose and the hose attached to the cuff should be replaced, as you will get random leakage during measurement.
Following this, in terms of popularity are the new FlexiPort + UNF screw-type technology. The FlexiPort is identifiable by the quick disconnect tabs and circular fitting, by Welch Allyn. This fits into the all-in-one cuff that forgoes the need for a separate inflation bladder. This attaches into a highly compliant (stretchy!) hose, which connects to the male fitting (white/black), which will connect to your female (black), go to your tube, then directly to a metal barb on the unit in question. The advantage of this is easy and fast swapping of blood pressure cuff sizes without unscrewing anything and is most useful in areas of high patient turnover. For this reason, most newer units are increasingly using this type of connector; for more information, see the blog post titled “Patient Monitor Maintenance” from December 20162 and ask if your units might benefit from an upgrade.
The second most popular recognizable brand is the bayonet type. Bayonet refers to the shape in which the male connector looks like. Mind Ray, Criticare, Philips, Siemens, and a few other brands use this technology due to its quick connection and ‘snap’. Like the FlexiPort, it will terminate into the hose using a barb. This type of connection will rarely need to be replaced because of the hose, since both ends are solid connectors that will plug in directly to the unit in question, but needs to be maintained yearly. Philips, for instance, use their own proprietary monitor connector and both connectors are fitted tightly on the connector and do not move unless through extreme force. ZOLL, similarly, yet differently, uses bayonet female and bayonet male, with both ends snugly attached.
The third category of connectors you will encounter are variants of: locking or slip which comes in the leur or thread types. GE, newer Welch Allyn, and ZOLL, for instance, use two opposite gendered locking connectors because they have ‘dual lumen’ hose technology which allows for quicker readings and thicker hoses. All three of these product lines will have patient monitor connectors specific to the brand, as more and more companies are trying to make their accessories standardized. The newer models are typically known for what type of connector they use. These machine-connectors also have different standards they need to abide by if they are hooking into a critical patient monitor or an anaesthetic gas machine and the proprietary connector is sometimes used for quality standards and liability sake. Should these proprietary cables be modified in any way, your warranty or liability coverage may be void and this is usually avoided by the means by which the connector is sealed by the hose.
The fourth variety of connectors you may encounter are types of interconnects between cuff and hose to give extension or extra accuracy and are mostly historical. What this means is that it is very important that you have the correct model number, and if possible, a picture to describe what sort of accessories you need for the older models. It is possible to upgrade what connector you have to a newer type for standardization and ease of use. Older and odd styles also are prone to inaccuracy and breakage because that product line may have been discontinued.
For quick reference, there is a graphic prepared for easily identified connectors that you may encounter in the medical / hospital environment. Many of these are manufacturer specific, and the newer your device, the likelihood of only using one standard type increases. Companies have merged over the years and the partent company will end up taking responsibility of making the accessories compatible; for example, General Electric acquired Datex-Ohmeda, so you may find interchangeable descriptions between these two companies.
Below is a limited list of some major connector types:
While the servicing of your equipment may only be yearly and you may make do with that, it is worth considering the extent by which you can standardize your accessories for blood pressure measurement devices. Some hospitals or offices have 3-4 different types of connectors, which results in needing to stock and understand which cuff goes with what unit, but this doesn’t need to be the case!
If you’re finding that your cuffs are confusing, a TRH Services technician can work with you to find which accessories work best for you at the most affordable cost. We can identify which cuff works best for you in terms of replacement interval, along with the sizes available depending on your patient demographic. After the cuff is chosen, we can provide direction on how to realize your selection with the given units you have. Through our partnerships and knowledge, we’re able to arrange a blood pressure cuff plan that is not only cost-effective, but headache free. The more standardized your practice is, the easier it is to just ship what we know you’ll need, instead of going on a scavenger hunt, matching cuff to hose. The advantage here on our side, as well as yours, when it comes to preventative maintenance, is that testing takes much less time.
While the complexities of blood pressure connectors may be confusing, know that regardless of what type of unit you have, TRH Services is capable and more than willing to sort out any confusion. Feel free to give us a call or ask your questions by email to see if we can help you source out the proper accessories or give your equipment a once-over. Knowing your unit’s model number and the manufacturer, along with any pictures, will always be beneficial to both of us to get you what you need.