The novel vital signs alert built into the CRADLE for eclampsia and shock detection

 We've been working with the CRADLE device for the better part of the last decade.  There are few medical devices with as strong an evidence base as the CRADLE, developed by Dr. Andrew Shennan and his team.  It's imperative to think of this lithium ion battery run device as as a new type of device in maternal health, not solely a blood pressure cuff.  

Part of what's been challenging with the CRADLE VSA is that it looks like a regular blood pressure cuff, so it's hard to signal how different and how innovative it really is.  In our view it should be a neon green or a brilliant red to signal just how unique this device is.  And the 'vital signs alert' is a built in algorithm that simply doesn't advertise itself and its brilliance loudly enough.  

But for those 'in the know' the CRADLE Vital Signs Alert puts clinical horsepower in the hands of a community health worker.  Do you wish community health workers could better assess for eclampsia? They can with the CRADLE.  Do you want a way to assess whether a woman is in shock-- it's possible with the CRADLE VSA. 

The Vital Signs alert measures the patient’s blood pressure and heart rate, "calculating the shock index (heart rate divided by systolic blood pressure) and displays a traffic light early warning system based on shock index thresholds," according to a peer-reviewed study of the device.  In other words, the device takes blood pressure and heart rate and then calculates shock index, making the whole process semi-automatic (CRADLE 3 Trial, Giblin et al).

The thresholds are red (1.7) and amber (0.9).  Clinical trials have evaluated the shock index in low- and middle- income countries in women with postpartum haemorrhage and "have demonstrated predictive value with adverse outcomes (admission to high dependency units, blood transfusion over 4 units and maternal death)." This shock index compares favourably to conventional vital signs in consistently predicting risk of adverse clinical outcomes in women with post-partum haemorrhage.

The shock index thresholds are converted into 'traffic light signals' of green, amber and red (A green light is displayed if the woman is at low risk of shock or high blood pressure, amber if she needs careful monitoring, or red if she requires emergency treatment).  An arrow pointing up or down is also displayed alongside a red or amber light, to indicate whether the issue is related to high or low blood pressure, further guiding the user on appropriate clinical management. 

This ingenious device is being scaled up in countries like Sierra Leone, where a shortage of specialists means that triage and predictive value of diagnostic devices like the CRADLE VSA are the difference between life and death.  

In our next blog we will cover the implementation research on the CRADLE VSA.