This week I strung-up a 30m dipole in the attic and built an oscillator, keyer, and amplifier (all as separate modules). I finished the amplifier this morning and spotted the signal (the rectangular squiggle) on two grabbers. I was running 3 PPV into 50 Ohm so I think that's about 22 mW.
After 23 days living in the hospital I’m happy to report my bone marrow transplant is looking good, and I’m free to continue recovering at home! I’m not going to sugar coat it: this ordeal was rough. However, I planned and prepared well for it, had a lot of fantastic support along the way, and I feel great about how well everything went! It couldn’t feel more amazing to finally be home again. The air conditioning, my couch, my TV, my pillow, my high-speed internet! It’s great to be back.
For those of you finding this page for the first time, I just finished an autologous bone marrow transplant to treat a condition where I make abnormal cancer-causing white blood cells. To do this some stem cells were collected and frozen, then strong chemotherapy was used to kill all of my bone marrow (where blood cells are made) to the point my body could no longer make any blood. During this time my white blood cell count went to zero, and I required blood infusions to keep me alive (thanks all you blood donors out there!). I was then infused with stem cells that were able to start growing new bone marrow. I have a brand new immune system now (just like when I was a baby) and it will continue to grow over the next few months, but I have to keep it safe by wearing a mask and limiting my exposure with other people while it matures.
I made an infographic to show my bloodwork during transplant. What, you didn’t think I’d try to data mine stuff from my procedure? In the bone marrow transplant world, stem cell infusion (transplant day) is what everything is centered around. I was infused with strong chemotherapy multiple times a day from days -6 to -1 to kill all my blood-producing bone marrow. Day zero I was infused with previously-collected stem cells, and celebrated a new birthday for my immune system. Since the old bone marrow was dead and not producing any white blood cells, my circulating blood cells slowly dropped off until they reached zero. Note that healthy adults have a white blood cell count of 5-10 (thousand/µL). It was a scary feeling on day +5 knowing that I had a white blood cell count of zero! The bone marrow transplant floor is largely sealed and isolated, visitation was is highly restricted, and I was on multiple antibiotics, antifungals, and antiviral medicines to get me through it. On day +9 I got the first hint that the transplant was working, as my white blood cells were just barely detectable. This confirmed that stem cells had matured into white-blood-cell-producing bone marrow (engraftment), and as my levels climbed I felt better and better.
Now that the core of my bone marrow transplant procedure is over, I don’t plan to continue updating this web page regularly. The procedure isn’t a sure bet at curing my disease, but it’s the best shot I’ve got, so I’m just going to wait it out and take the best care of my body I can and hope for the best. There’s a chance I could need additional treatment some day (CAR-T immunotherapy, an allogeneic bone marrow transplant from another person as a donor, or additional chemotherapy) but for now I’m taking it easy, and if this page remains dormant that means I’m living a normal life!
Thanks to all the friends and family that supported me during my treatments both locally and from afar. This experience was challenging but doable, and I attribute a lot of my success to your support and encouragement. I hope I won’t need any more serious treatments from here, but even if I do I know I’m prepared! The whole team at the UF Health Bone Marrow Transplant Unit was amazing too, and I couldn’t be more grateful and impressed with the awesome treatment I got along the way.
Today I received the stem cells which will become my new immune system! The infusion itself was relatively uneventful (a gravity-fed bag of cells flowed into my PICC line for about an hour) but it represents a big day for me and a shot at one day having a healthy immune system. After the infusion the transplant team came in and sang happy birthday to celebrate!
While I spent the last week in the hospital focused on getting through chemotherapy to gear up for this transplant day, the next few weeks are focused more on preventing infections and managing symptoms related to the continuing drop in my immune function as my white blood cell count approaches zero. Realizing that I’m going to be feeling a lot worse before I start feeling better again, I don’t plan on updating this website until near the end of my hospital stay when my numbers begin to elevate again (which fingers-crossed is a couple of weeks from now). For now I’m happy to report that things are looking good and I’m eager to continue on this arduous but exciting journey!
I just finished my last bag of pre-transplant chemotherapy! As of this morning the doctors said they are pleased with my numbers, and things are looking good so far. Even though the chemotherapy infusions stopped today, my blood counts will continue to drop (to near zero) over the next couple weeks during which I’ll be feeling really lousy. For now though, I feel surprisingly good (my medications are doing a great job of controlling the pain and nausea) and while my blood counts are high enough I’m even allowed to take occasional little walks around the hospital with a mask.
Medical details: Over the last week I had a tri-lumen PICC line added through my left brachial vein to allow simultaneous infusion of drugs and blood products over the upcoming weeks (I’ll likely be requiring blood and platelet transfusions). While I still have an infusion port on my chest, accessing it is an infection risk so the transplant team has chosen not to use it during my stay. The chemotherapy drugs I’ve been on over the last week are: carmustine, cytarabine, etoposide, and melphalan. Tomorrow is transplant day, where I’ll receive my previously-collected stem cells through my PICC line.
Every few years I revisit the idea of building an ECG machine. This time I was very impressed with how easy it is to achieve using the AD8232, a single-lead ECG front-end on a chip. The AD8232 is small (LFCSP package) but breakout boards are easy to obtain online. Many vendors on eBay sell kits that come with electrode cables and pads for under $20. Sparkfun sells a breakout board but you have to buy the cable and electrodes separately. I highly recommend buying bags of electrodes inexpensively on eBay because having plenty will make life much easier as you experiment with this circuit. The signal that comes out of this ECG device (unlike other ECG machines I've built) is remarkably clean! It doesn't require any special spectral filtering (all that is accomplished on the chip), and it can be hooked right up to an oscilloscope or sampled with analog-to-digital converter.
The breakout board is easy to use: Just supply 3.3V, hook-up the chest leads, and a great looking ECG signal appears on the output pin. I prefer using a LD33V to drop arbitrary DC voltages to 3.3V. While using a 9V battery isn't the most power efficient option, it's certainly an easy one. Since the AD8232 claims to only draw 170 µA, inefficient use of a linear voltage regulator probably isn't too much of a concern for desktop experimenters. The low power consumption of this chip raises some interesting possibilities for wireless ECG analysis!
I like inspecting the output of this circuit using my computer sound card. Probing the output pin on an oscilloscope reveals a beautiful ECG signal, but not everybody has an oscilloscope. I've seen some project webpages out there which encourage people to use the ADC of a microcontroller (usually an Arduino) to perform continuous measurements of voltage and transmit them over the USART pins, which then get transferred to a PC via a USB-to-serial USART adapter (often built around a FTDI FT-232 breakout board or similar), only to get graphed using Java software. That sequence certainly works, and if you already have an Arduino, know its sketch language, and are happy writing software in Processing, that's a great solution for you! However I found the sound card option convenient because everyone has one, and with a click-to-run computer program you can visualize your ECG right away. Note that I added a potentiometer to drop the voltage of the ECG output to make it more suitable for my microphone jack. Ideally you'll find a resistance that uses a lot of your sound card's dynamic range without clipping.
The SoundCardECG project on GitHub is a click-to-run Windows program I wrote to display and analyze ECG signals coming into the computer sound card. The screenshot above shows my heart rate as I watched a promotional video for a documentary about free-climbing. You can see where my heart-rate elevated for a couple minutes in the middle as I watched a guy free-climb a cliff a thousand feet in the air without safety gear. This software is written in C# and fully open source. It certainly works, but has many avenues for improvement (such as enhanced QRS detection). Interactive graphing is provided by the ScottPlot library.
Most of the project details are in the video, so I won't type them all out here. However, this is an excellent first step for a variety of projects that could emerge from having an easy way to measure an ECG signal. Immediate ideas are (1) heart rate detection in circuitry (not using a PC), (2) data-logging ECG signals, and (3) adding wireless functionality. I may come back and revisit one or more of these ideas in the future, but if you're interested and inspired to make something yourself I'd love to see what you come up with! Send me an email with a link to your project page and I can share it here.
I built this AD8232 breakout board into a nice enclosure to make it easier to experiment with it in the future. The circuity isn't anything special: a linear voltage regulator with capacitive decoupling on the input and output, and an op-amp serving as a unity gain amplifier to buffer the output accessible through a SMA connector, and a current-limited output attached to a female 1/8" audio for easy connection to my computer sound card.
Personal update: My website posts (and YouTube videos) have slowed dramatically as I've been dealing with some complicated medical issues. I don't intend on posting medical updates on this web page, but anyone interested in following my medical treatments can do so at http://swharden.com/med/