Quote from luv2shopp85
Thanks for your help. I really don't have money to be spending on a book though. I found a few websites that I've been reading and htey are helping a little bit.
I'm a lil confused though... isn't variability the same thing as accelerations when shown on a fetal heart rate strip? How do you tell the difference between the 2 on the strip ?
And also... with early decelerations... don't they occur right before a contractiion? Well in this picture it loooks like they are occuring at the same time or after the contraction. http://www.brooksidepress.org/Produc.../EFM/Early.jpg
Can someone elaborate on this please?
Does a contraction start as soon as the line leaves the baseline? And when it starts to get round .. is that the peak?
Ok...variablility. If you think of a ECG...and the QRS complex. The spike going upwards is the "R" wave. What a fetal monitor does is place a DOT on paper that represents the fetal R wave. It continues to record dots reflecting the R wave and then the monitor draws a line to connect them. This is variability. Beat to beat fluctuations. New NICHD terms have combined short term and long term variablity, so only LTV is documented now. Accelerations are ABRUPT increases from the baseline and can be associated with or without contractions. Reactive accels are 15X15 beats (meaning they go UP for 15 seconds and then last for 15 seconds). Variability is what you interpret in BASELINE. Decelerations and accelerations are not to be considered in baseline interpretation. So, to answer your question, accels and variablity are NOT the same.
Early decels are associated with head compression and are gradual (30>seconds) decreases in baseline. This is a vagal response to head compression and usually start with contraction and end with contraction. Same criteria with lates. They are gradual from onset and occur after the peak of the contraction. Lates are reflexive, meaning, that the placenta is reacting to lack of oxygen either from decreased blood flow or some sort of placental problem (IUGR or abruption). The late onset of this decel is because of a 'lag' in time in circulation of blood to the placenta to the receptors in the fetus (chemoreceptors). The baseline returns after the contraction has already ended. Over time, lates can certainly hack away at the fetus' ability to recover, and may lead to hypoxia. You want to fix those as quickly as possible.
Variables are cord problems. They are in direct response to cord vein or artery squish, sometimes both. When the cord is squished, the fetus notices changes in pressure (baroreceptor) and speeds up heart rate to compensate for loss of perfusion (this is vein squish) . If arteries become squished, then the fetus acknowledges this change thru baro and chemo receptors, and slows the HR down to conserve oxygen. When the contraction begins to subside, the HR speeds up as oxygen is restored and returns to baseline. You don't always have the pre-variable accel. Sometimes you have just complete cord squish right away. Variables are ABRUPT decels from baseline (<30 secs). Get in the habit of counting, NICHD definitions are pesky when it comes to this. Variables can be V shape, U shape and W shape.
This is also autonomic nervous system at work. Sympathethic and parasympathetic nervous systems need to be intact for this to work. If there are delays in maturity, or drugs on board, or fetal abnormality....all of these things can be affected.
It is a lot to absorb. I love the physiology of FHR. You can speak forever on it, and never get enough (at least for me). I hope this has helped you some.