Medical Device Troubleshooting Checklist: From ResMed Machines to Lab Incubators

Who This Checklist Is For

If you manage or maintain any of these devices — ResMed sleep apnea machines, histology equipment, defibrillators (AEDs), or laboratory incubators — this list is for you. I've personally killed a $3,200 order because I missed a heating system error on a ResMed AirSense 11. That was September 2022. The unit went back to the manufacturer, the patient lost a week of therapy, and my credibility took a hit.

Since then, I've built a pre-check routine that's caught 70+ potential issues across four equipment categories. Here are the seven steps I run through every time. They work whether you're dealing with a CPAP machine or a CO2 incubator.

Step 1: Check Power and Environmental Conditions First

Most people jump straight to error codes. Don't. Start with the basics: Is the device plugged into a functioning outlet? Is the voltage correct? I once spent an hour chasing a ResMed "heating system error" — turns out the outlet was on a dimmer switch that couldn't supply enough current. (Honestly, that was embarrassing.)

For laboratory incubators and certain histology equipment, ambient temperature matters. A ResMed machine will complain in a cold room; an incubator will fail to hold setpoint. Check ambient temp against the manufacturer's spec. Simple. But I've missed it twice.

Step 2: Verify Airflow and Filter Condition

ResMed machines — especially the AirSense 10 and 11 — have sensitive airflow sensors. A clogged filter triggers all sorts of alarms. I'd say 40% of the "error" calls I've handled were just dirty filters. Replace them on a schedule, not when they look dirty (which, by the way, is too late).

Same logic applies to incubators: if the HEPA filter is old, CO2 levels drift. And for defibrillators? Most AEDs run a self-check, but if the pads are expired or the battery is low, it'll yell at you. Check those monthly.

Step 3: Decode the Error Message — Don't Guess

The question everyone asks is: "What does error code X mean?" The question they should ask is: "What sequence of events led to this code?" ResMed's heating system error (often E:0 or E:1) isn't always the heater. It can be a humidity sensor failure, a disconnected hose, or even a software glitch.

Use the official troubleshooting guide (ResMed clinican's manual is gold). For defibrillators, the AED manufacturer's self-test log tells you everything. For lab incubators, look at the temperature chart over the last 24 hours — a gradual drift is different from a sudden spike. (I learned this the hard way: misdiagnosed a gradual drift as sensor failure and replaced a perfectly good incubator controller. $1,800 mistake.)

Step 4: Check Consumables and Accessories

Most buyers focus on the main device and completely forget about the parts that actually do the work. ResMed machines need clean water chambers, proper tubing, and compatible masks. A full face mask with a wrong-size cushion won't seal — you'll get an "air leak high" alert. I once ordered 50 masks for a sleep center and every single one had the wrong cushion size. (That was a $2,300 reorder plus a two-week delay.)

For defibrillators, check electrode pad expiration dates. They dry out. For histology equipment, think about reagents and slides. For incubators, verify CO2 gas tank pressure and humidity pan water level. These are the things that make the difference between a working system and a service call.

Step 5: Run a Full Self-Test Cycle

After you've resolved the immediate issue, run the device's built-in self-test. ResMed has a "mask fit" check and a "device test" in the clinical menu. Defibrillators have automated self-tests — but many techs skip them because they think "it just passed yesterday." (It didn't — I ignored an AED's low-battery warning for three days and then had to rush-ship a replacement battery at 2× cost.)

For laboratory incubators, do a 24-hour stability test after any repair. Set the target CO2 and temperature, and log data every hour. If it holds, great. If not, you caught it before your cell cultures died. Save yourself the heartache.

Step 6: Document Everything with Specifics

I used to write vague notes like "fixed error." Not helpful. Now I record: the exact error code, the ambient conditions, the filter status, what I did, and the self-test result. This is what creates institutional knowledge. When the same ResMed heating error pops up on a different machine three months later, I know exactly what to check first. (And I can show the new tech the checklist instead of repeating my mistakes.)

According to FDA's Medical Device Reporting system (fda.gov), proper documentation is also required for any serious incident. Even if yours isn't reportable, good records protect you. Plus, if a vendor asks for troubleshooting history, you have it.

Step 7: Set a Follow-Up Reminder

This is the step everyone forgets. I schedule a one-week and a one-month follow-up check. Why? Because some issues are intermittent. A ResMed machine with a borderline heater element might pass the initial test but fail after three nights. A defibrillator with a weak battery might hold for a week, then drop below threshold. An incubator with a slightly high CO2 might drift back within spec after calibration — until the next gas cylinder change.

I use a simple spreadsheet that emails me. You can use a calendar. Doesn't matter how, just do it. I've caught 15 latent problems using this approach in the last 18 months. That's 15 expensive breakdowns avoided.

Common Mistakes I Still See

Ignoring the manual. The ResMed clinical guide is online and free. The AED manufacturer's service manual is often included in the box. Read it.

Using third-party parts without verification. Generic filters for incubators may not have the same efficiency. ResMed's heated tubing is calibrated to the device; aftermarket ones might not communicate properly.

Thinking one error code has one cause. The same "E:2" on an AirSense 10 can be a failed pressure sensor, a blocked vent, or a firmware issue. Always check the logs.

Skipping the self-test. Just because the device powers on doesn't mean it works. I've seen an AED boot up and pass its first self-check but fail the second test five minutes later because the battery pack was loose.

Prices and procedures as of May 2025. Always verify current manufacturer guidelines and local regulations.