I got a bit obsessed by this as a bloke a couple of weeks ahead of me couldn't have his HDR brachytherapy due to narrow urethra and them not being able to get the catheter in during the operation. I built myself a peak flow meter, which showed a flow of 25ml/s just after the start of external beam radiotherapy. (I think it had initially got faster when I started hormone therapy 5 months before - I'm guessing I might have been 15ml/s before diagnosis, but didn't measure it then.)
The first version was peeing into a jug on scales and videoing the weight. Then going through the video slowly to get the weight in grams every second, and the change is the flow rate in ml/s (assuming urine has a specific gravity of 1, which it near enough does unless it's very concentrated). Need to ensure the flow/force of urine stream doesn't subject the jug to extra force as that will give a too high reading. (Ideally pee against something like a spoon held inside the jug to deflect the urine horizontally, but that must not be supported by the jug or anything else on the scales. Having the jug half filled with water to start with improved the accuracy.)
Then I went on to build an electronic version which was a set of cheap kitchen scales bought for the purpose and the circuit inside replaced with a Raspberry Pi Zero computer which calculated and displayed the peak flow (and how long into the pee that was, typically about 5 seconds, and total volume).
It was interesting to see what happened. From memory, I started of with a respectable 25ml/s. Immediately after each external beam radiotherapy it reduced, but recovered later in the day, although there was a slight downward trend during the treatment. From memory, I was around 18ml/sec at the end of the course of radiotherapy, just before my HDR Brachytherapy. After the brachytherapy, it was about 8ml/s, but recovered over the following weeks to about 15ml/s and stayed there. (This was all without Tamsulosin.) I assumed this was my new normal. However, about 5 months later, it started improving further and got back to about 20ml/s. I haven't measured it for a couple of years now, but I don't think it's changed much since then.
Edited by member 11 Dec 2022 at 10:55
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