Friday, June 15, 2018

Guatemala, Day 26

Its over! We did our final hospital visit today and the students did really well. The program's first month has come to a close. In a couple hours, I'll be heading to the bus station to catch my 4 hour ride back to Guatemala City and then to the airport. The students head to their new assignments on Sunday afternoon and they all seem capable and ready to go. Its been a fun month, and even though I missed my family something wicked, I learned a lot, which is really all I could have hoped for.

So today we visited a dental school and clinic. The facility is associated with a local university and I believe is set up to train dental hygienists and dentists, as well as treat patients. The facility was a big open space which it appeared was owned by the Lions Club. The main hall was the size of a basketball court and filled with maybe 35 dental chairs, some desks, and an x-ray lab in the back.

We were asked to take a look at some of the dental chairs that were having various issues. A couple of them had problems with the control unit that you use to make the chair go up and down and a couple more had lighting issues. Given the chairs were a good 20 years old, it was no surprise that everything we looked at had been messed around with by some other engineers at some point, and some of that work was, regrettably, a bit sloppy. We got to work.

The control pedals were pretty interesting. It turns out that the four-way controller (up, down, recline, sit up) is just a knob that forces one of four switches to close. When the switch is closed, the appropriate motor wire is connected to power, and the motor turns causing the chair to move.
Inside the chair's control unit - just four switches!

One of the two units we looked at was just a bit loose and we got it working by tightening up the cover. The other one was a hot mess of short circuits and amateur soldering. I had the students take it all apart and resolder all the connections, testing them one by one as they went, and they did a great job fixing it.

We also looked at some lighting problems. One light had a loose connection and flickered on and off quite a lot. That turned out to be an easy (but very time consuming) fix. It just needed a few loose wires re-connected and soldered, but the wires were very hard to access and it took a long time just to get them sufficiently free to work with.

What should have been an easy fix wound up being very time consuming!

It didn't help at all that the Portugal-Spain World Cup match was on and people kept running to the TV when things got interesting!

While the students were working, I decided to teach myself exactly how a dental chair works. I got down on all fours (and then flat on my stomach) to see what mysteries lurked beneath. Turns out it's pretty straightforward. There are two motors, one for the up-down action, and the other for the recline action. Each motor is only connected to power when the user pushes the control switch. There were two especially cool parts. First: the up-down motor was connected to two massive start capacitors. Most AC motors need some sort of a start cap in order to get spinning. In this case, there were two 147uF caps connected - real monsters!
As capacitors go, this one is pretty big!

The second cool thing was the mechanism the chair uses to know when to stop going up and down. I found two little switches under the chair that get depressed when the chair gets too high or too low. Once the switch is depressed, it cuts off power to the motor and the chair stops.

Overall, it's a pretty simple design but elegantly done.

That was pretty much it. After work, we went back to our classroom so the students could reorganize their tools and supplies for their Sunday departure. Afterwards, there was a funny ceremony of sorts where I was presented with a plastic trophy cup that says "#1" on it, along with a photo of our group.  It was a wonderful gesture and also very goofy and we all laughed pretty hard.

Me and our outstanding TA, Paul.
I was really proud of our group: smart, resourceful, and diligent, all of them. It was really fun to work with them and they made the effort of teaching very much worthwhile. They're all going to make excellent engineers.

And that was that! Another successful EWH trip is in the books. All that's left to do is get home safely ... and start planning for the next adventure.

Monday, June 11, 2018

Guatemala, Day 22

Well its Day 22 and I'm almost done here. I miss my family very much and I'm counting the hours till I can go home. Today I booked my transportation back to the airport (4:30am bus, anyone?) and if everything goes according to plan, I should sleep in my own bed on Saturday night.

Our program is wrapping up. The afternoon labs are pretty much finished and now we're just focused on drilling the students on the all-important "soft skills" they'll need. For example, they need to know how to write effective instructions (including diagrams) for equipment usage, as well as detailed summaries on how equipment was repaired. We're also training them to do staff interviews (as a means of needs assessment) and equipment inventories. The equipment inventories are helpful, as they get tracked from year to year so we can see what equipment falls into disrepair at a given hospital. Engineering students often complain about having to learn soft skills, but I can guarantee that its even harder when doing so in a foreign language!

Typical Guatemalan dress (not my photo: shamelessly
stolen off some website)
The Guatemalan people are really something. There are many women around town who dress in colorful traditional clothes and carry their babies in cloth swaddles on their backs. I've been wanting to take some photos but its pretty hard to do so without looking like a jerk tourist. One nutty thing we've all observed is how unfiltered some of the locals are when they interact with us. Last week at the clinic we visited, some random woman on the street stopped in her tracks to tell our Indian American student that he was the most exotic looking young man she'd seen in forever. Que guapo!!! In my own experience, people have said some daffy stuff to me when I've told them I'm "├írabe". At one hospital, the technicians started miming machine guns and and giggling, and last week the clinic director decided I had to be filthy rich with petroleum money!  The comments aren't malicious (and I wasn't really offended) but still its nutty to see people say stuff out loud that wouldn't fly in the States.

Last Friday we visited the local health clinic in town. From what I could tell, it seemed like a place for regular checkups and somewhat-urgent care, especially for mothers and children. It was pretty small but quite packed. There was tons of equipment for us to look at - some infant scales to weigh newborn babies that needed calibrating and cleaning, some blood pressure cuffs with leaks, and a wonky handheld ultrasound device. A good chunk of the day was devoted to cleaning and de-scaling the autoclaves.

Super old school autoclave

The autoclaves at this place were super minimal - basically just industrial sized pressure cookers. Without any fancy electronics, it falls on the user to manually monitor the pressure gauges and use a stopwatch to time the whole process. One model went right on the stove to get heated, whereas the rest were electric. The electric ones have a heating coil like you would see in an electric kettle or  coffee maker. The problem with these things is that if you don't use distilled water, then over time the minerals in the water will come out of solution and stick to the heating coils, which in turn become insulated and lose their ability to heat the water. Those minerals are super hard to get off - you can't chip them or scrub the coils with anything abrasive, because you'll ruin the metal coating on the heating element.

Severe scaling means subpar heating.

The best course of action is to soak the coils in an acidic solution and hope that dissolves the minerals. In your home coffee pot, you might use vinegar and let it soak over night. In this case, we didn't have all night and we had a lot of scaling to clean up so we did what any reasonable person would do: we bought a liter of hydrochloric acid for about a dollar and got to work.

Muriatic (hydrochloric) acid
The plan was to dilute the acid down to a 4:1 ratio and let it soak for about three hours. We were about to get started when we decided maybe we should wear some protective equipment. We ran to the hardware store to get some safety glasses, but came up short looking for rubber gloves. Every hardware store we went to told us to try at the pharmacy. Every pharmacy we tried said to check at a hardware store. Even the local supermarket was a bust. Finally, after an hour of searching, we wound up at a high end supermarket and eventually found some garden variety dishwashing gloves. Finally! Time to soak the autoclaves!

Enjoying sweet victory after an epic goose chase

While they were soaking, we realized that we had a new problem: how to dispose of a the dangerous hydrochloric acid. We certainly couldn't dump it in the sewer or down the drain. After some debate and Googling, we decided to try to neutralize it with baking soda. To my surprise, the very first tienda I went to had some in stock, although I was amused to see that it was sold in pre-packaged plastic baggies that made me look like I was carrying around a few grams of blow.

Hey man, you know were I can score some baking soda?

Eventually someone found a more normal sized container of baking soda and we started mixing it into the acid. It took an entire pound of baking soda before the acid finally stopped bubbling and we were able to pour the mess down the drain with a clean conscience. The process definitely worked to some extent, although it had been so long since the autoclaves were cleaned that they definitely need another round, possibly with a less diluted acid soak.

Scrubbing autoclaves right on the sidewalk

Pretty thankless job

Acid plus baking soda equals lots of bubbles

Oops! Too much baking soda too quickly and it overflowed...

Oh, one last thing I loved about this clinic. At the entrance, there were these three ladies selling all sorts of snacks. Two of them had babies with them, which they had carried to the clinics in swaddles on their backs while they carried big cardboard boxes with the snacks. Once they arrived, they set up the snacks on a blanket on the ground and then put their babies to sleep in the now-empty cardboard boxes! Seeing "babies in boxes" was definitely a first for me, but I guess as long as the cardboard stays dry, its a pretty good bassinet in a pinch!

One last hospital visit to go this coming Friday, and then I'll be heading home the next morning. Hopefully there'll be time for one last post before I head home!

Thursday, June 7, 2018

Guatemala, Day 18

Well the volcano eruption turned out to be pretty serious, but it seems that the devastation is contained to the villages directly in the line of ash flow. I'm well over 50 miles from the volcano so there's nothing to see here. The locals are all hustling to take relief supplies to the affected areas. People are donating cash and goods, and pickup trucks are being loaded with supplies and driven down. Its a pretty impressive mobilization effort. These are good, good people.

Lab has continued to be a lot of fun. Earlier this week the students finished building their variable power supplies. The supplies convert wall AC into a DC source that can go from 1-29V and source up to 2 amps. We use a full wave rectifier, some big smoothing capacitors, a linear voltage regulator, and a 2A fuse, just to be safe.
The finished product! A variable DC power supply.
The lab took forever, because getting all the connections soldered correctly and safely is a time consuming process. It was getting really late and I was getting really hungry, and so it was a blessing when there was a city-wide power outage and we were forced to pack up in the dark and go home.
Engineering in the dark.
We used our power supplies to recharge some NiCad batteries yesterday. Students had to work out a series of equations in order to satisfy the following requirements:

  1. Battery has to charge at a reasonable speed
  2. In order to charge the battery at that speed, you need voltage and current. Both those elements have to be in the range that can be delivered by our homemade power supplies
  3. There needs to be a current limiting resistor. You can't dissipate more power in the resistor than its max rating, or else it'll burn up
  4. You can reduce power in the resistor by reducing the current flow, but then your battery will take longer to charge
Eventually each group settled on a series of parameters and we connected up their batteries and waited for them to charge. No one started any electrical fires in the process, which was certainly appreciated.

We hold our classes in a community work space, where anyone can rent out space. One of our space-mates is a woman who works with a Michigan-based non-profit that builds and places water purifiers around the world. She showed us an example of one of their water systems. It was super interesting! The group is called Clean Water for the World (follow that link to read about what they do and maybe even donate a few bucks). The system is pretty simple (by design) - a thick paper filter followed by a UV light tank that kills all the biologicals in the water. It can do up to five gallons per minute and can be installed in a school or other community center. The specific one you see in the picture below will be installed at the volcano rescue and relief center this weekend. They have 270 of these suckers in use around the world!

The system has a built in counter that lets the locals know when its time to change the UV lightbulb. Units get delivered with enough filters and bulbs to last for two years, after which time the local communities must start buying their own.

Another fun experiment we did was testing to see what percentage of the air we breath is oxygen. This is a useful skill because a common piece of medical equipment in the developing world is the oxygen concentrator. These gizmos pump pressurized atmospheric air into special "zeolite" tubes that sequester nitrogen and allow mostly pure oxygen to pass through. How do you know if your concentrator is working? Well you have to test the percent oxygen that gets produced. We didn't have an oxygen concentrator to work with so we just tested atmospheric air. Here's how the test went:
  1. Fill a glass with the gas you intend to test (regular air in our case)
  2. Stick a candle to the bottom of a tub, and then fill the tub with some water. Light the candle
  3. Flip the glass over the lit candle, and submerge the lip of the glass.
  4. As the candle burns the oxygen in the glass, it will suck water up into the upside-down glass.
  5. The more water gets sucked up, the more oxygen there was in the glass that had to be displaced as it burned.
  6. If you measure the percentage of the glass that fills up, that tells you the percentage of the air that is oxygen
Insanely, this nonsense actually worked, and we found that our glass sucked up 20% of its volume with water, which is roughly the percent of oxygen in the air we breath. We tried doing a follow-up test where we filled the glass with only exhaled air (which is a little lower in oxygen than atmospheric air) but alas our system wasn't sensitive enough to notice the difference.

If you look closely, you can see that there is some water that's been sucked up in to the glass

That's pretty much all the fun news to share. Here are a few other tidbits you might enjoy. Today we were testing whether an IV infusion pump was properly working and we needed something to function as an IV bag for the test. My students came up with a pretty cool solution:
Yes, that's a rubber glove filled with water and tied to the tubing using a hair band.
Next tidbit - I took apart a potentiometer to show the students how the magic inside works. Turns out, its just a strip of resistive material...
This is the guts of a potentiometer. There is a wiper (which I pulled out) that connects a point on the outer ring to the smaller inner ring that's connected to the middle contact.

Tidbit 3: here's the teaching staff. Me, Paul, and Luis. Paul teaches computer science at the University of Kansas and is on his third trip with EWH. Luis is our logistics coordinator, which works out nicely since he's a native Spanish speaker.

Finally, here's a shot of most of our group on our first hospital visit two weeks ago.

We're going to a community health center tomorrow - should be an interesting site visit. Stay tuned for more pictures and stories.

Sunday, June 3, 2018

Guatemala, Day 14

A relative of someone I know took this photo
of Volcan de Fuego today.
Today's big news is that a volcano near Antigua erupted pretty dramatically today. Several people died and hundreds were injured. Luckily its nowhere near where I am but it may impact my family's arrival on Saturday, as well as some of our vacation plans. Pretty nuts.

Our program is going well. We had lectures about suction pumps, ventilators, anesthesia machines, and medical gasses, and we started working on building our power supplies. We'll be spending lab this week making them into variable DC power supplies suitable for actual use! On Friday I took a group of five students back to the public Occidental hospital to work on more equipment. Apparently I had come away with an unrealistically rosy picture of the hospital last week. My host family assured me that despite some newer equipment, the hospital is poor and underequipped. Families of inpatients are often given prescriptions and told to go buy the meds at a pharmacy because they aren't available in the
hospital. Anyone who can afford it goes to the private hospitals. I haven't been to any but I'm told they're pretty nice. With that said, villagers sometimes travel for hours on end to visit the public hospital and their families even camp out front if they have nowhere else to stay.

Laundry air-drying at the hospital.
We spent a good chunk of the day back in the odontology office. We were trying to fix two things - a small autoclave which was on the fritz and the suction system which wasn't quite working right. They have three dental chairs but the suction mechanism (for sucking up saliva and blood from the mouth) on one of them hadn't worked for four years! We started by looking at the compressors to make sure they were working properly. They have two compressors tied together without the use of any check valves or anything, which seemed a bit fishy to me. I wasn't sure if that was causing any problems so I spent a good hour plus messing around with them. Eventually I determined that the suction problem in the clinic still existed if I only used a single compressor. Furthermore, I decided that I could probably tie them together if I set the tank pressures as close together as possible. If you don't do this, then one compressor tries to fill up the other one and it gets messy. All of this was made massively more complicated by the fact that none of the plastic tubing they had was the right size to fit any of the nozzles, so moving and testing different configurations took a lot of doing just to get things airtight. We resorted to using a lighter to melt the tubing a little so it would wiggle down on the various nozzles. After that we started debugging why there was no suction at the one chair. It didn't help things whatsoever that neither me nor any of my students know how the suction and water on a dental chair are connected.
Lots of tubing to sort out.

The yellow line holds pressurized air (from the compressor) and the green line is the suction. High speed air blows past the suction tube and into the drain (at left). As the air draws across the port to the suction tube, it creates negative pressure.

But as engineers are wont to do, we worked to isolate the problem - tracing the air lines to see how far the pressurized air was getting. We had to take some of the dental chair apart to do this but in the end we discovered a pretty elegant mechanism. The pressurized air is forced through a very narrow channel. On the side of that channel there is an outlet port that connects to the suction tube. As the pressurized air flows past that port at high speeds, it creates negative pressure, which is the source of suction. All the liquids that are sucked up by the suction get pulled through that port and whooshed into a drain in the floor. Everything seemed to be mostly in order so we tried to clean all the tubing and valves as best we could, suspecting a small clog was to blame. Eventually we got it all back together and lo and behold: suction! The dentist was besides himself and was very grateful. I had a lot of fun because I got to take something apart and learn how it works. And the students had fun watching and learning too. Good times. The only downside was that I got really dirty. There is some unspeakable funk lurking inside tubes and valves that don't get cleaned very often. Needless to say I took an aggressive shower when I got home.

Earlier today I went to a barbecue fundraiser for an Australian lady who lives in town. She shelters dogs and has a monthly cookout to raise money for their care. I had an incredibly delicious plate of ribs and beans. I also got to taste an unusual drink. I don't remember what its called but its basically a Bloody Mary with beer instead of vodka. I enjoyed it - very refreshing and just perfect to wash down the ribs.
This very adorable creature wanted to share my ribs.

A very satisfying lunch!

Wednesday, May 30, 2018

Guatemala, Day 10

Greetings again from Quetzaltenango. I spent my first weekend down here trying to get some work done as well as exploring the town a bit. I found a laundromat that charged Q20 (about $3USD) to do my laundry (washed and folded!), and I got invited to a family gathering by my host family. We drove out to Tio Tito's house to celebrate his birthday. The family was highly amused by my weak Spanish skills and so we laughed alot and bonded over a tipple or two. Families are fun.

More relevant to this blog, we've been busy working with our students to strengthen their basic engineering and fix-it skills. On Monday I gave a lecture on the fundamentals of motors - just about everything we'll be tackling in a hospital will have a motor of some sort in it. And yesterday (Tuesday) the lecture was about ventilators and oxygen concentrators. We talked about way of testing whether a ventilator is pushing out the correct volume an pressure. To measure volume, you can use the ventilator to inflate a balloon, and then put the balloon in a bucket of water to see how many inches the water level goes up. From there you can calculate the volume of displaced water, which is more or less the volume of air. To measure air pressure you can connect the ventilator to a clear tube with a u-bend that's filled with water. The more pressure, the more the column of water will be displaced.

The transformer and light bulb.
Our labs have been fun, too. On Monday we had the students solder a cable into a transformer that we're going to be using to build a power supply later this week. The transformers are supposed to convert 115V input to 24V output, but we measured outputs closer to 27V. After some research, we decided that this difference was because we were running the transformers without loads. Loads draw current, which will tend to lower the output voltage a bit. To test this hypothesis, we endeavored to try loading our transformers. The transformers are rated for 2.5A, so we needed a lot of load. We found some ceramic-encased high-power resistors in our toolkits and tried putting two of them in parallel. That drew a measly 200mA and barely affected the output voltage. Then we had the idea to take a light bulb out from the ceiling fixture and try putting that in the circuit as well. The bulb drew an additional 300mA and we succeeded in getting the output down to about 26V. I'm guessing we'd need to draw something closer to the full 2.5A rating to get the actual 24V output. We had fun though - the students got a kick out of seeing the lightbulb used as a tool.

Battery pack, switch (red), and LED (clear, at left)
Yesterday we had the students wire up a flashlight using a very simple circuit of batteries, a switch, and an LED. The point of the lab is to get some more experience soldering and trying to think through basic issues such as how should I glue this all together to make it feel like a useful tool. We also had the students determine whether a current limiting resistor was needed. The two AA batteries gave 3V total, and the forward voltage rating for our LED was about 3.6V. Because we're operating below the diode "on" voltage, we knew there was a good chance that we could use the diode resistance to limit current. We tested this by wiring up the circuit with a potentiometer in series and then slowly decreasing the resistance while simultaneously measuring the current. Sure enough, even when the resistor went to zero, the diode wasn't drawing more that its max recommended current of 20mA, and that sucker was *bright*.

We also spent some time learning about fuses. Every lab group took a 1A fuse and shorted it across a pair of AA batteries. That created more than enough current to get the fuse to blow - we looked at the fuses before and after and you can see the little fuse wire inside gets physically burned away. Blown fuses are a constant source of headache when repairing medical equipment!

Friday, May 25, 2018

Guatemala, Day 5

We've spent the past few days getting our students up to speed on the basics of medical electronics. So far we've mostly covered electrical safety and power supplies (and batteries). Experience has shown that most of the problems we will tend to encounter are due to either power supply problems or user error. The lectures were supplemented with a series of labs designed to underscore basic electrical skills. We started by having the students make an extension cord - we give them the cable, the plug, and the outlet receptacle, and they have to connect it all together. Its not super complicated but it does require attention to detail. We also practiced soldering: resistors onto perfboard and spliced wires. The soldering irons we got this year seem to work pretty well but they came with massive chisel tips which aren't exactly ideal for fine pitch soldering.

Wiring together our extension cords

Wrangling the soldering iron
Today we had our first hospital visit, at the "Hospital Regional de Occidente". My first impression was that the hospital was in decent shape all things considered. The building infrastructure seems solid enough and we saw lots of equipment that looked relatively new and well maintained. Our hosts took us around the hospital to see different services with equipment that might need to be repaired. Our goal with these day trips is mostly to learn what we can, although if we can fix things along the way that's nice too. Sometimes it can be helpful just to take things apart and observe how they're supposed to work.
Hospital main entrance

Waiting to be allowed on-site
Our first stop was the sterilization facility, where all manner of surgical instruments are autoclaved. They had five or six fairly large steam autoclaves. One of them had a burned out heating element and they didn't have a replacement handy, so we just learned to follow the flow of the pipes to gauge how it worked. We also inspected a water purifier that just boils water and then collects the condensate.

One of the bigger autoclaves
Next we visited the lab, where there was a fume hood which occasionally made a rattling noise. We took of the front cover and it was pretty icky back back where the fan unit runs - lots of dust and debris that "naturally" builds up over time. We cleaned it as much as we could. We tried to get the HEPA filter out to see if there was something loose close by it but couldn't work out how to get it out. We'll research that and try again next week.

Does anyone know how to change the air filter on a fume hood?
Then it was off to the oral care clinic. They have a pair of air compressors, which apparently are responsible for all the magic one sees in a dentists chair: the compressed air can be used to make suction, and it apparently pressurizes the water pik. Anyways, they were complaining about no pressure at the chairs, so we spent some time trying to debug what was going on. The compressors seem to be working ok but something might be amiss with one of the flow valves that sends the compressed air out where it's needed. We ran out of time but we'll have another whack next week.
The air compressors that weren't quite doing their job
After lunch (tacos, duh), we toured the surgery suite. They seem to be having a problem with bulbs burning out prematurely in their surgical lights. We made a note to look into it next week. I'm worried it might be poorly regulated AC service to that part of the hospital which is burning out the bulbs - if so that isn't something we can do much about. It may be time for them to call an electrician.
Surgical lights with burned out bulbs

An operating room

So that was our trip. I learned a lot because I got to see a few odds and ends I haven't seen before, which makes me happy. The students seem to be pretty sharp and are learning quickly.
Taco lunch: $3

Tuesday, May 22, 2018

Guatemala, Day 2

Minerva Temple
I woke up a bit early this morning and went for an hour's walk before breakfast. I wandered over to what turned out to be a somewhat drabber neighborhood. There were lots of kids running to school and people heading to work. I wound up near a structure called the Minerva Temple, which is one of a number of similar structures built around the country in the early 1900's. They symbolized wisdom, I believe. There was an outdoor market next to the temple with produce and meat but I didn't have time to get a good look. I also learned that right around the corner from there is a Walmart, of all things. I am definitely going back to check out the Walmart sometime. I am curious whether the "people of Walmart" phenomenon exists in Central America or whether its just a US thing.

At work today I went through the basics of working with hospital equipment in the developing world - why equipment fails to work and what we can and can't expect to do about it during our short time here. We also had an interesting discussion about the complex dynamics surrounding equipment donations and repairs. For example, apparently a lot of countries in the developing world have programs to educate people on repairing and maintaining hospital equipment, but once trained, those people can make a lot more money in other sectors than healthcare. Our TA was telling us that in Tanzania, where he worked last year, they get so many donations that they often don't bother to repair broken equipment. They know that some do-gooder hospital in the west will be sending them new equipment sooner or later. There was also an interesting discussion around the topics of "what metrics distinguish a country as a 'developing' nation" and "why are some countries poor". Just for good measure, I also threw in a mini-lecture covering what is essentially the first two years of a typical electrical engineering undergrad curriculum, condensed down to about 30 slides.

Nachos for dinner!

Fried banana goodness
Food-wise, we had another pretty good day. We had nachos for dinner and for dessert we had these amazing bananas that were floured, fried, and then garnished with milk, cinnamon, and sugar. Our host mom was telling us about all the different kids of bananas they get in Central America. The ones we had for desert were "bananos de manzana" but there are a ton of others, each with their own flavor. I have made a mental note to taste as many as possible.

Below are a few photos I snapped of the town today. Enjoy!

I want to guess these are walnuts but I'm not sure.

The courtyard at our school

The coffee shop where I drink tasty espresso drinks