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ADS1298R - Respiratory and EKG simultaneously

Eric Forkosh
Intellectual 275 points
Other Parts Discussed in Thread: ADS1298R

Good day,

Is it possible to obtain a respiratory signal and an EKG signal simultaneously? Would the respiratory measurement method ( injecting 32KHz) affect the EKG signal? 

What are some tips to achieving the best signal when reading respiratory + EKG at the same time?

Should Right Leg Drive of the EKG be used when obtaining respiratory and EKG signal simultaneously?

Thanks

  • 0
    TI__Guru 66906 points

    Hi Eric, 

    Yes - respiration and EKG can be measured at the same time using independent channels (RESP - CH1, EKG - CH2-8).

    The reality is that the 32kHz modulation signal injected onto the leads also will appear on the other EKG channels which use the same leads (i.e. if RA and LA are used for respiration on Channel 1 and EKG on Channel 2). It may even couple into other independent leads as well, but it's hard to say how much. In either case, the digital filter should significantly attenuate this signal, where the -3dB bandwidth is about 1/4 the Data Rate. The EKG signal content should not be affected much at all.

    That said, the recommendations for best EKG practices still hold true and RLD can still be used.

    The one caveat, however, is when you try to implement external hardware pace detection and respiration at the same time. In this case, the PGA output is brought out of the ADS1298R on the PACE_OUT1 and PACE_OUT2 pins, carrying both the EKG data and the 32 kHz modulation signal for respiration. A high-order low-pass filter is needed to remove the modulation signal while an external comparator circuit looks for the PACE signal presence.

     

    Best Regards,

  • 0 in reply to Ryan Andrews
    Intellectual 275 points

    Thanks for the reply.

    I'm just now working and fine tuning the system.

    Do you think RLD should be based off the Respiratory channel too? Or only my EKG channels? To me it seems like only EKG. should be read for RLD output.

    Sorry if this is asking too much.