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Measuring fetal heart rates accurately and safely--without ultrasound

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Edmond Zahedi
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re: Measuring fetal heart rates accurately and safely--without ultrasound
Edmond Zahedi   10/17/2010 9:08:13 AM
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Using with AED's or other electrical apparatus applying shocks: good idea! The optical sensor could be integrated with the defib's head (external). If the objective is to detect the pulse (heart rate), this is also feasible by using conventional pulse-oximeter probes. As here the idea was to use the system for pregnant ladies, not sure if AED is applicable.

DrFPGA
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re: Measuring fetal heart rates accurately and safely--without ultrasound
DrFPGA   10/5/2010 11:24:25 PM
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Can this technique be extended to AED applications? It might be nice to have a non-electrical sensor that won't conflict with the electrical signal shocking the patient...

p_g
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re: Measuring fetal heart rates accurately and safely--without ultrasound
p_g   10/1/2010 1:31:41 AM
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Nice idea. As already few concerns been raised but I accept that no technology is free from side effects. Bob, As you asked does anyone like to see light coming straight to eyes, I guess same applies to sound, do you want sound coming straight to your ears?

KB Gan
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re: Measuring fetal heart rates accurately and safely--without ultrasound
KB Gan   9/23/2010 8:55:16 AM
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Thank you! Since this was our pilot study, all fetuses in this study were singleton with gestation weeks from 30 weeks to 40 weeks. Subjects with twin pregnancies, anterior placed placenta, obesity (BMI less than 30), gestational diabetes mellitus (GDM) and hypertension were excluded from this study. It is of course more complex to target twin pregnancies as signals will be even more mixed. However, we think that extended DSP concepts may help (such as blind source identification). The position of the fetus definitely affects the recording, and some details were provided in the paper with this respect. It will certainly be interesting to study other effects you mentioned (age, obesity, …) in future works. You are right, there is a need for an automatic placement of the sensors. We are currently working towards designing detector arrays which will allow the automatic selection of the optimum sensor channel with the highest SNR. This will allow getting around having to manually position the belt around the mother’s abdomen – especially that the optimum position depends on the fetus position.

KB Gan
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re: Measuring fetal heart rates accurately and safely--without ultrasound
KB Gan   9/23/2010 8:53:49 AM
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It is true that so far, there has been no evidence demonstrating unwanted bioeffects (including cavitational effects) in the fetus at routinely used intensity levels. As the main indicator of potential mechanical effect is the “mechanical index” (MI), the FDA recommends a value of the MI less than 1.9 (except for ophthalmic usage). Given the sufficient sensitivity of current technology, the respect of such limits is warranted therefore it can be safely concluded that cavitation does not occur. However, the use of Doppler ultrasound in the first trimester is generally not recommended as a routine as it may increase the occurrence of intrauterine growth restriction. Moreover, due to the complexity of the Doppler signal and the effects of fetal and maternal breathing, FHR measurements using Doppler ultrasound are not always reliable. This technique could be an alternative to conventional ultrasound. It should be emphasized that the final aim is the non-invasive measurement of fetal oxygen saturation (fSpO2) via the mother abdomen, something that ultrasound is and will be unable to deliver. It is thought that a dual-purpose device (heart-rate as well as fSpO2) will be less cost-sensitive. A small correction is due here: the fetal eye is not exposed directly to the IR source! The limits mentioned in the paper are judged safe by applying the ICNIRP exposure limit for incoherent radiation and the recommendation by CIE TC 6-38 (Lamp Safety) for realistic viewing condition. Furthermore, NIR light sources will be judged safe as long as they comply with the skin exposure limit specified by the ICNIRP. Direct viewing is not advised and is not/shall not be the objective. Given these conditions, the maximum allowable optical power shone to the skin should be less than 48.3 mW for a continuous light source and less than 87 mW for a 50% duty cycle pulsed light source.

_hm
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re: Measuring fetal heart rates accurately and safely--without ultrasound
_hm   9/2/2010 5:10:50 PM
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Our kudos to you for researching this novel concept, conducting experiment and tabulating results. In your experiment did you encountered twin pregnancy? Where you able to differentiate fetal heart rate in both? How were your results affected with weight, age of person or position of baby? Did you provide tuning mechanism to get optimum result?

Bob Lacovara
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re: Measuring fetal heart rates accurately and safely--without ultrasound
Bob Lacovara   9/1/2010 5:50:03 PM
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This article provides an interesting example of a measurement system facilitated by NI's LabVIEW. However, the article states that "the safety of long-term fetal exposure to ultrasound waves has yet to be established." I think a more accurate statement would be that at the acoustic levels used in medical diagnostic ultrasound, no damage mechanism has yet to be described. These levels are well below those needed to even raise the temperature of tissue measurably. My point is that ultrasonic diagnostic systems are about as safe and non-intrusive as can be expected. That said, I am willing to take the author at his word that his optical technique may be easier to use or possibly more accurate, but both optical and ultrasonic techniques will benefit from the competition. This technique will not translate into a certified medical instrument cheaply: the cost relative to a Doppler ultrasound unit will be interesting to see. Lastly, what damage may result from 68 mW of IR energy? Would you place an IR LED a 10 mm from your eye and turn it on? My interest isn't entirely disinterested: readers should know that I use LabVIEW to design non-destructive ultrasonic inspection systems.

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