Boom

After a week of government red-tape delays, our technical instructor finally arrived today (lectures were given instead by substitutes in his absence). A resident of the Philippines, Ric Fontanilla has been working for years in the developing world as a biomedical technician after receiving training in Japan. Since he frequently encounters the same challenges we will face at our host hospitals in Nicaragua and Honduras, he is an ideal instructor for our summer program. The difficulty in getting him from the Philippines to Costa Rica in time for the first week of lecture was a U.S. government policy that prohibited him from even catching a transfer flight at an international airport on U.S. soil. EWH eventually got him a flight, however, from the Philippines to Japan to Mexico.

Today’s lecture was about pulse oximeters, the familiar machines that measure heart rate and blood oxygenation with a clip-on finger probe. Since the redness of blood is directly proportional to the blood’s concentration of oxygen-saturated hemoglobin, pulse oximeters simply sense the intensity of near-red light shined through the patient’s flesh. This signal is calibrated in real time by a second light which is unaffected by changes in blood oxygen level, providing an accurate and reliable measure of the patient’s actual SpO2. “We usually repair this kind of probe because it’s very, very expensive. If you can repair three or four like this, you already save the hospital a lot of money,” Ric said.

Ric then reiterated the importance of safety testing before returning any repaired device to the floor for medical use (or before allowing an electrical outlet to be used). “NEVER neglect an electrical plug or the leakage current,” he said, “if a patient dies because of an electrical problem, you’ll be sued.” He then reassured us of the general success that we are capable of achieving, “No matter what the manufacturer, make, model, or age of a machine, the principle is only one. Remember that. If you understand what a machine does, you’ll be able to understand how it works and what might be wrong with it.” Separate from our training in troubleshooting and repairing skills, we’ll be receiving dedicated safety training to avoid allowing any unsafe device that is entrusted to us to be put into clinical use.

Gladys, the Spanish teacher and owner of the academy, had another announcement for us today during lunch. “Normally I wait for a week or two before deciding whether or not I’m going to do this—I first need to see how a group behaves. But with this group I know already in less than a week from having seen you together in classes, lectures, and breaks. You’re a very well behaved group. So, I’d like to invite you all over to my house for dinner next week.”

Today’s lab was the introduction to power supplies. Using perfboard, solder, a capacitor, and four diodes, my partner and I created a diode bridge that functions as a full-wave rectifier, converting 30 volt, 1 Watt AC power into 40 volt, 1.5 Watt DC power. If it seems impossible to you for us to obtain 1.5 Watts of power out of 1 Watt of power, as we did, continue reading my blog and I’ll provide an explanation sometime when I’m running out of more interesting things to say. For example, many other groups made a mistake in wiring their diode bridge circuit, and as a result, their capacitors blew-up when they tried to test them. My only mistake today was to accidentally bump the soldering iron towards me. It burned a small hole through my pants.