If you're on CPAP therapy and your AHI (Apnea-Hypopnea Index) looks great, but you still feel exhausted, you're not alone. It's frustrating when the numbers look good, but the reality is different. Let's break down why this might be happening and how you can validate your CPAP therapy results for better sleep quality.

The Truth Behind the AHI

AHI is the most common number used to gauge CPAP therapy effectiveness—it's the number of respiratory events you have per hour during sleep. In Joe's case, his AHI was 6.32, which seems pretty mild and even "acceptable" at first glance. The goal is to get this number under 5, but 6.32 isn’t alarming, right?

Well, here’s the issue: The AHI number given by your CPAP machine is not always accurate. CPAP machines, like the ResMed system in Joe's case, often fail to flag many hypopneas—partial blockages in the airway that can still disrupt your sleep.

The Power of Detailed Data

Unlike apps like MyAir or DreamMap, SleepHQ provides a high-definition, detailed breakdown of each breath you take throughout the night. This is where the true value lies. By zooming in on Joe's airflow data, we see regular, consistent breathing initially, but then something changes—his breathing pattern becomes irregular, with shallow breaths followed by deep breaths. This is where hypopneas (partial blockages) occur, but you may not see them flagged by the CPAP machine.

What the CPAP Machine Misses

The CPAP machine in Joe’s case flagged 51 events, resulting in an AHI of 6.32. However, after a manual review by five sleep techs, including 14 years of experience, the lowest count was 115 events, giving an AHI of 14.3. This is a huge difference—almost double the AHI the CPAP machine provided. So, what’s going wrong?

The problem lies in how CPAP machines classify hypopneas. The machines have a very high threshold for flagging these events—only those with more than a 50% reduction in airflow for 10 seconds or more are flagged. This means many milder events are going unrecognized, and your machine is missing a lot of what's actually happening to your airflow.

Why This Matters

Even if your CPAP machine shows a low AHI, if it’s missing many of the subtle issues like hypopneas, your sleep quality could still be affected. CPAP machines aren't perfect—they’re just computer algorithms, and they can’t capture the nuances of your breathing. The result? You might think your therapy is working, but your sleep quality and overall health could be suffering due to unflagged events.

What Can You Do?

You don’t need to be a sleep tech to identify when your breathing isn’t normal. The first step is to understand what your regular breathing looks like—you can do this by reviewing the beginning of your night’s data before sleep sets in. Once you know what regular, stable breathing looks like, it’s easier to spot irregularities throughout the night.

For Joe, periods of shallow breathing followed by deep breaths were clearly visible. While some of these events were flagged, many were missed. By reviewing your data, you can start to spot these irregularities yourself.

Taking Control of Your Therapy

While you can’t fix everything with your CPAP machine alone, monitoring your oxygen levels is a great way to validate your therapy. Devices like O2 rings can help you see if your blood oxygen levels are dropping—this will often correlate with poor airflow and unflagged hypopneas.

Final Thoughts

The bottom line: Don't just trust the numbers provided by your CPAP machine. The AHI number isn't always accurate, and the real truth lies in what the machine misses. By manually reviewing your data, looking at your flow rate, and using tools like SleepHQ or open-source software like Oscar, you can get a clearer picture of how well your therapy is really working. If you find that your AHI number doesn't reflect your true sleep quality, it might be time to adjust your therapy for better results.

Remember, the key to successful CPAP therapy is understanding your breathing, trusting your data, and validating those results.