I think you've made some interesting points there Alan.
I've seen the Nipset® - Paul brought some in for us to look at when they were first introduced and I was certainly interested in looking at them for our vital signs monitors that incorporate a
single-hose oscillometric NBP methodology. The Nipset® is a great idea and the connectors are really competitive, cost-wise, in comparison to the price of hose and cuff connectors from the OEMs. We have ongoing problems with operators breaking our traditional screw-type cuff and hose connectors since they're always swapping BP cuffs.
However since then we have begun to standardise on dual-hose devices again. My personal concern with Nipset® on dual-hose oscillometric NBP, in particular, is that the potential for
dampening of the cuff pulsations may be an issue if the hoses are physically connected together by the Nipset® manifold (hence the possibility of poorer sensitivity thus degradation in systolic/diastolic measurement capability for
low amplitude pulsations may be an issue).
This view is based on my understanding that one of the benefits of the dual-hose method of oscillometry is that cuff pulsations are measured by a transducer coupled to only one hose - that being the one that's connected directly to the transducer not the motor and any damping chamber that's connected to the other hose used to inflate the cuff.
This is a more complicated arrangement than single hose devices but this apparently stops dampening of the pulsations in the cuff, by the motor and inflation pneumatics, when cuff pulsations are being measured. That's what the clinical validation blurb from GE discusses anyhow.
If this is the case then, in theory, there's a potential for loss of accuracy due to failure to determine low-level pulsations in the cuff (noisy signal). If this were the case (I've no evidence for or against) then I'd want to know whether pulsations are damped or not before using something like Nipset® (from memory I think the dual-port Nipset manifold effectively connects both NBP hoses together to allow connection to a single hose cuff).
For strong pulsations there may not be an issue with BP determination using Nipset®, w.r.t accuracy or ability to make a determination with noise present, but since systolic and diastolic accuracy is not especially accurate using oscillometry anyhow (in comparison to IBP and manual sphygmomanometry) and depends upon the level of the pulsation wrt cuff "noise", i.e. SNR, then I'd be wary of using Nipset initially until someone comes up with some validation study.
Not that, personally speaking, I wouldn't evaluate Nipset® on dual-hose monitors - it's just that I'd prefer someone to have done a clincial trial or some meaningful research involving relative accuracy of Nipset® devices/Non-Nipset® on dual hoses including measurement repeatability or determination reliabilty versus pulse amplitude on dual-hose systems, i.e. using a NBP simulator to do this, at least.
I wouldn't want anything to unduly influence operators' in their attitudes to the new vital signs monitors being introduced into our NHS trust, for example, so I'd prefer not to suggest we try Nipset® at this time. Although we're having some difficulty with damaged screw-type connections on our new dual-hose monitors and they're relatively expensive in comparison to Nipset®. I think it's a really good idea but it'd be even better if there were a validation study carried out to give evidence that use of Nipset® does not degrade the performance of dual-hose NBP monitors.
Extract taken from a GE document: "THE DINAMAP DIFFERENCE ® A GUIDE TO OUR NIBP TECHNOLOGY"
ADVANTAGE: TWO-TUBE INFLATE/MONITOR SYSTEM
When a patient’s blood pressure is very low (e.g. Shock), the amplitude of the cuff pulsations become very small and difficult to measure. Under these conditions, it is essential that no dampening of the cuff pulsation signal occurs. Otherwise, the accuracy and length of the determination and thus, patient comfort, may be affected or the device may not make a determination at all. Competitive monitors utilize a single-tube inflate/monitor system, where the pump and pressure transducer are connected to the same pneumatic line. As a result, signal amplitude can be reduced by energy lost in pushing air back through the pump to the transducer. DINAMAP® Technology, on the other hand, employs a twotube inflate/monitor system where cuff inflation is achieved through one of the tubes and pulsation are sensed through the other. This system ensures that no dampening of the cuff pulsation signal occurs.
However much I like the idea of Nipset® I wouldn't want to "throw away" any advantages of the dual-hose method by modifying the connectors nor affect validation. This document seems to indicate that Dinamap technology meets AAMI/ANSI SP10 Standard 1992 thus I wouldn't want to inadvertently bugger-up the performance of a device that's actually been successfully validated. Apologies for rambling again - no criticism just observations and concerns.
I'd be interested in any information on NBP accuracy using Nipset if you have any Paul.
