In some circumstances, we may use our hearing instruments’ accessories such as telecoil (T-switch) or direct audio input (patch cord.) Or even stream wirelessly using FM or Bluetooth.
Hearing aids usually have a poor low frequency response. Cochlear implants vary, some extending to lower frequencies than others. I haven’t been able to find out about BAHAs. If you have a pure conductive loss, your cochlear can still respond to low frequencies. But whether the setup works will depend on whether the BAHA processor has a good low frequency response too. I’m trying to find out more. Please get in touch if you can help. Thanks.
So connecting a stethoscope to hearing aid or implant must be done cautiously. You may need a programme on the aids or processors specifically for stethoscope use. Cardionics advises “increasing the gain of low frequency improves heart sounds … [and you] will need to disable automatic noise reduction.” But this still won’t address hearing aids’ and implants’ limitations due to poor low-frequency response. Heart and lung sounds might be distorted or may not be transmitted at all.
You should test your setup carefully to make sure you can recognise and diagnose normal and abnormal heart and lung sounds. You can practice with a simulator and make a point of seeking out patients known to have abnormal heart and lung sounds to make sure you can detect these with your stethoscope set-up. You may be able to sit in on some adult and child respiratory and cardiac clinics, especially useful if you have local valve disease and paediatric cardiology clinics.
If your hearing aids have telecoils (a T-switch), you can use a “silhouette” similar to the “T-link” you may already use with a mobile phone. Hook it over your ear(s) and switch your hearing aids to T setting. Cardionics still supply single and dual silhouettes though they no longer recommend them, describing both silhouettes and direct audio input as a “last resort.” HATIS also makes silhouttes and have told me their Epic has been used with electronic stethoscopes. This was before Cardionics raised their concerns.
Silhouettes can be used with cochlear implants with BTE processors, depending on the implant’s low frequency response.
I’m not sure whether BAHAs can be used with a telecoil accessory as a silhouette may not be close enough to the telecoil stick. Neck loops don’t usually give a strong enough signal to transmit from stethoscope clearly.
Direct Audio Input
If the stethoscope has a suitable output socket you can connect it directly to your processor by a patch cord or to BTEs via “shoes.” This may work with the Cardionics and Thinklabs stethoscopes but the Littmann socket isn’t suitable. See the Connevans Beginners Guide to Direct Input if you haven’t come across DAI before.
Wireless – FM and Bluetooth equipment
If you haven’t come across FM assisted listening devices (ALD) before, this leaflet from Phonak illustrates what they can do. (There are other makes as well.) Tiny FM receivers can be plugged into some hearing aids and implants. Or a separate receiver links to your hearing aids by telecoil or DAI. Other ALDs connect to hearing aids and implants with Bluetooth.
You can make a wired connection from the Cardionics or Thinklabs stethoscopes to an FM ALD or Bluetooth streamer. If your hearing aids or implants have FM or Bluetooth capability, this transmits wirelessly to your hearing aids/implants. If not, you link the ALD to your hearing aids by telecoil or direct audio input. It seems to work for some of us and not others and you may have to experiment with different configurations, programmes and stethoscopes to set it up. If you are using an ALD or streamer a lot of the time anyway, this setup may be little trouble as you simply switch from one source to another. Otherwise, there’s a risk of finding yourself juggling equipment from the midst of a cat’s cradle of cables! You may want to reconsider using adapted eartips or moulds or headphones (link link).
- Have you read the essential safety information: “limitations of hearing aids and implants?”
- Consider funding
- Arrange a trial period
- And see how your audiogram matches up to heart and lung sounds to find out whether you need amplification or not.
Which stethoscope? Comparison chart.