As dental professionals, our role in identifying and managing obstructive sleep apnea (OSA) has grown significantly with the widespread adoption of oral appliance therapy (OAT). We’ve moved well beyond just recognizing snoring as a nuisance and now play an essential part in a patient’s broader sleep health journey.
But as clinical tools and diagnostic pathways evolve, a new question arises, one that challenges how we define success in treatment:
Are we placing too much weight on the wrong metrics, and missing the full picture when it comes to patient outcomes?
Beyond AHI: The Search for Better Predictors
For decades, the Apnea-Hypopnea Index (AHI) has been the standard for diagnosing and classifying the severity of OSA. It’s familiar, widely used, and built into most diagnostic workflows.
But here’s the catch: AHI doesn’t always correlate with how patients feel or how well they respond to treatment.
Emerging research shows that AHI alone is a poor predictor of outcomes with oral appliance therapy. Two patients with identical AHI scores might have completely different responses to the same treatment. That’s because AHI measures the frequency of events, not the mechanism behind them.
This opens the door to a more physiologically meaningful marker: Pcrit (critical closing pressure).
What Is Pcrit, and Why Does It Matter?
A More Functional View of the Upper Airway
Pcrit quantifies the collapsibility of the upper airway during sleep. In simple terms, it measures the pressure at which a patient’s airway collapses. The more negative the Pcrit value, the less collapsible the airway and the better the patient is likely to respond to OAT.
Low Pcrit: Indicates a stable airway. These patients often respond well to oral appliances.
High Pcrit: Suggests a highly collapsible airway. These patients may require alternative or combination therapies such as CPAP, positional therapy, or surgery.
Passive vs. Active Pcrit: Why the Distinction Matters
Pcrit, or critical closing pressure, can be measured in two distinct ways—each offering unique insight into how the upper airway behaves during sleep.
Types of Pcrit
Passive Pcrit
This measures airway collapsibility without the influence of muscle activity. In this approach, the effect of pharyngeal muscle activation is intentionally eliminated during the measurement, providing a clear picture of the airway’s mechanical stability. Passive Pcrit reflects how easily the airway collapses under relaxed conditions, such as during non-REM sleep.
Active Pcrit
This measurement includes the contribution of the upper airway muscles, capturing the airway’s behavior with neuromuscular compensation engaged. Active Pcrit offers insight into how effectively a patient’s airway muscles respond to maintain patency, especially during more challenging breathing conditions like REM sleep or airway obstruction.
Although the techniques for measuring passive and active Pcrit differ slightly, both assessments can typically be performed using the same experimental or clinical setup.
The Case for Personalised Treatment in OSA
One Size Doesn’t Fit All
The challenge in treating OSA is that it’s not a one-disease-fits-all scenario. Beyond airway collapsibility, factors such as arousal threshold, loop gain, and muscle compensation also play a role in how and why OSA occurs in each patient. These traits vary widely between individuals.
By identifying patients’ underlying pathophysiology (such as high Pcrit), we can make more informed decisions about:
Whether to start with OAT or another therapy
How aggressively to titrate a device
Whether to combine treatments from the outset
This approach reduces trial and error, improves compliance, and enhances patient outcomes.
Where the Industry Could Go from Here
Imagine a clinical workflow where:
A home sleep test not only gives you an AHI but also estimates airway collapsibility.
You use this data to match patients to therapies with greater confidence.
You track long-term outcomes not just by device adherence, but by meaningful improvements in symptoms, function, and quality of life.
This isn’t science fiction anymore as it is already being explored through advanced sleep testing and data modeling. As this becomes more accessible, dental sleep professionals will need to evolve from device providers to sleep care partners.
How ResDent and the Good Sleep Test Support Personalised Care
At Good Sleep Co, we’re already helping practices embrace this future.
The Good Sleep Test, our at-home diagnostic tool, is integrated with the SleepCare App for patients and the ResDent platform for clinicians, creating a seamless, end-to-end pathway for sleep testing and follow-up care.
Through ResDent, clinicians can view sleep test results, order devices, and coordinate care, all in one place.
As science continues to support more nuanced patient assessment (including traits like airway collapsibility), our tools are evolving to support precision sleep care at the dental level.
The question is no longer “Do oral appliances work?”, we know they do.
The more valuable question is: “Can we predict who they’ll work for before we begin?”
By looking beyond AHI and embracing insights like Pcrit, we’re not just upgrading tools, we’re upgrading the way we think. That shift toward patient-specific care is where the future of dental sleep medicine is heading and we’re here to help you lead it.