Is the ResMed AutoSet Algorithm Really the “Gold Standard” of APAP Therapy?

For many patients and even healthcare professionals in North America, the ResMed AutoSet algorithm has become almost synonymous with premium APAP therapy.

It is frequently described—formally or informally—as the “gold standard” against which other automatic CPAP algorithms are compared.

There is good reason for some of that reputation.

ResMed has been one of the dominant manufacturers in sleep medicine for decades, its AutoSet algorithm has been extensively studied, and the company has invested heavily in research, physician education, remote monitoring, patient software and brand recognition.

First: What Does an APAP Algorithm Actually Do?

An APAP machine does much more than simply increase pressure when an apnea occurs.

The machine continuously analyzes signals such as:

• inspiratory flow limitation
• snoring
• obstructive apnea
• hypopnea
• breathing stability
• leak
• and, depending upon the device, other characteristics of the respiratory flow signal

The manufacturer's proprietary algorithm then decides:

Those decisions differ substantially between manufacturers.

Published bench testing has demonstrated exactly that. When several commercially available APAP machines were exposed to the same simulated obstructive breathing patterns, their responses varied considerably. Maximum pressures, average pressures and even the time required to reach maximum pressure differed significantly between devices.

In one published comparison of seven APAP platforms, maximum pressures ranged from approximately 10.4 to 17.9 cmH₂O, while the time required to reach maximum pressure varied dramatically—from approximately 4.4 minutes to 96 minutes.

Perhaps even more interestingly, the AirSense 10 itself was tested using two different response settings. The standard response reached a higher maximum pressure and increased pressure more rapidly than its alternate response.

That distinction is important.

The study did not demonstrate that every slower algorithm was equally effective—several machines failed to completely eliminate the simulated obstruction. What it demonstrated very clearly is that APAP algorithms can behave dramatically differently, and a more aggressive pressure response is not the only possible route to effective airway stabilization.

The researchers' overall conclusion was straightforward:

That does not automatically make one machine right and another wrong. It means their treatment philosophies are different.

The ResMed AutoSet Philosophy

ResMed's AutoSet algorithm monitors breathing on a breath-by-breath basis and responds to inspiratory flow limitation, snoring and obstructive apnea.

The philosophy is proactive.

When signs of upper-airway obstruction appear, the machine can increase pressure in an attempt to prevent further deterioration of the airway.

This responsiveness is one of the major reasons AutoSet developed such a strong reputation. For some patients, it works exceptionally well.

A patient who rapidly develops significant airway obstruction may benefit greatly from a machine that recognizes the progression quickly and responds accordingly.

But pressure responsiveness has another side.

The objective of PAP therapy is generally to use enough pressure to maintain the airway while preserving comfort, sleep continuity and adherence.

Depending upon the individual patient, unnecessary or rapid pressure increases may contribute to:

• mask leakage
• mouth leakage
• aerophagia or abdominal bloating
• difficulty exhaling
• pressure intolerance
• awakenings
• discomfort
• treatment-emergent central events in susceptible individuals

This is precisely why comfort settings, expiratory relief, pressure-response options and careful clinical titration exist.

Then ResMed Introduced AutoSet for Her

ResMed introduced the AirSense 10 AutoSet for Her in 2014.

It wasn't simply an AutoSet machine with different colours.

It contained a modified APAP algorithm.

According to ResMed, AutoSet for Her incorporated several important differences from the standard AutoSet algorithm, including:

• a reduced rate of pressure increase
• slower pressure decreases
• greater sensitivity to flow limitation
• smaller incremental pressure adjustments
• a treatment strategy driven more heavily by flow limitation and snoring
• modified apnea response above approximately 12 cmH₂O

One of ResMed's stated objectives was particularly important:

Think about that statement for a moment.

For years, one of AutoSet's major perceived advantages had been its ability to respond assertively to developing obstruction.

Yet ResMed subsequently developed another clinically validated treatment mode that deliberately made pressure changes more subtle because rapid pressure changes themselves could potentially disturb sleep.

That does not mean AutoSet was a bad algorithm.

Nor does it mean AutoSet for Her was inherently superior.

The Ontario “For Her” Era

Those of us working in Ontario sleep medicine during the latter part of the 2010s may remember another interesting phenomenon.

At SleepEZ, we encountered a period approximately between 2017 and 2021 in which device-specific prescriptions for the AirSense 10 AutoSet for Her appeared with remarkable frequency.

In some cases, the prescription wasn't simply:

This is an observation from our experience working within the Ontario sleep-therapy market; we are not suggesting that every Ontario physician or sleep laboratory followed this practice or that there was a provincially mandated program.

And an even more interesting question follows.

“Gentler” Does Not Mean Less Effective

A gentler APAP response does not necessarily mean an ineffective APAP response.

AutoSet for Her actually illustrates this perfectly.

Its algorithm can be more sensitive to flow limitation while simultaneously making smaller pressure adjustments.

Those are two separate characteristics.

An algorithm can recognize airway deterioration very early without responding with a large or rapid pressure increase.

ResMed Eventually Added a “Soft” AutoSet Response Too

The evolution becomes even more interesting when looking at later ResMed AutoSet systems.

ResMed also incorporated an AutoSet Response setting allowing clinicians to choose between standard and softer pressure responses when pressures exceeded 10cmH20.

ResMed describes the Soft setting as providing gentler pressure increases for patients who are sensitive to faster pressure changes.

Even within one manufacturer's ecosystem there are multiple ways to deliver automatic therapy. That is exactly how personalized respiratory therapy should work.

Before ResMed Dominated the Conversation

It is worth remembering what the CPAP industry looked like before today's market consolidation.

During the earlier part of the 2010s, the North American PAP market was dominated primarily by ResMed and Philips Respironics, with Fisher & Paykel Healthcare holding a smaller but meaningful position.

Interestingly, Fisher & Paykel was also one of our personal favourite APAP machines during this period.

Patients frequently commented positively on its compact design, sound level, humidification performance, portability and overall build quality.

Yet excellent engineering does not necessarily guarantee market dominance.

In a publicly funded system such as Ontario's ADP program, providers must also work within established reimbursement structures. Equipment with a substantially higher provider acquisition cost can become commercially difficult to offer—even when clinicians and patients genuinely like the product.

Historical market estimates vary depending upon the dataset and whether masks, PAP devices or the broader sleep market are included, but contemporary market documents consistently showed ResMed and Philips Respironics dominating the category.

One 2015 market disclosure estimated approximately:

And patients did quite well on more than one of them.

Philips Respironics Took a Different Approach

Historically, Respironics Auto-CPAP systems were often perceived clinically as taking a more gradual approach to pressure adjustment than ResMed AutoSet.

That didn't automatically make Respironics inferior.

It represented another approach to balancing event suppression against pressure stability and patient comfort.

In clinical practice, some patients responded beautifully to the ResMed pressure behaviour. Others preferred Respironics.

We even saw practical advantages that had little to do with algorithms.

Certain Respironics humidifier designs incorporated safeguards intended to reduce the likelihood of water travelling back toward the blower. That could be particularly valuable for patients who frequently transported their equipment.

Commercial drivers were a good example. Someone finishing a night in a sleeper cab might pack the machine quickly and forget that water remained in the chamber.

Small engineering decisions involving water management and blower protection can become surprisingly important in real-world use.

Others preferred Fisher & Paykel.

Fisher & Paykel Took Yet Another Approach

Fisher & Paykel's SleepStyle platform has long placed considerable emphasis on the entire breathing environment rather than concentrating solely on pressure response.

A machine can produce a beautiful residual AHI while the patient still sleeps poorly.

Sleep therapy should ultimately improve sleep, not simply produce an attractive number on a compliance report.

What Happened to Fisher & Paykel?

Fisher & Paykel never stopped being an engineering-driven respiratory company.

SleepStyle remains a premium PAP platform.

Fisher & Paykel Healthcare is headquartered in Auckland, New Zealand, and the company continues to emphasize its New Zealand engineering heritage and sophisticated humidification technology.

Its relative visibility in the North American CPAP-machine market, however, has historically been much lower than ResMed's.

The loudest company in a market is not automatically the manufacturer producing the best machine for every patient.

Even “Premium” Can Have Leaks

There is another piece of CPAP history that tends to disappear as products gain legendary reputations.

During the AirSense 10 generation, users also reported leaking humidifier chambers—with some waking to find water across the table or nightstand supporting their CPAP machine.

One CPAPTalk discussion dates all the way back to August 2015, when an AirSense 10 AutoSet user reported waking to find that the machine's water chamber had been leaking throughout the night and that the table underneath it was flooded.

According to the user, when the chamber was subsequently removed and placed on a plate, it continued leaking from the bottom.

There are additional AirSense 10 humidifier discussions throughout the CPAP community as the platform aged, including users reporting leaking chambers and abnormal water consumption.

These reports should be understood for what they are: individual user experiences, not evidence establishing the incidence of a manufacturing defect across the entire AirSense 10 population.

None of this means the AirSense 10 was a poor CPAP machine.

Quite the opposite.

The AirSense 10 became one of the most successful and recognizable PAP platforms ever produced.

Every manufacturer makes engineering compromises.

Every manufacturer eventually encounters component failures.

And every manufacturer learns from previous generations.

A premium brand does not become immune to:

• leaking water chambers
• failing seals
• turbine failures
• electronic failures
• noisy bearings
• cracked plastics
• connectivity issues
• design revisions

These are realities of medical-equipment manufacturing.

The European Perspective: Löwenstein prisma

One of the best examples of how different North American and European CPAP markets can be is Löwenstein Medical's prisma platform.

The prisma series is manufactured in Germany.

Löwenstein offers multiple APAP pressure-response dynamics within its own platform, reinforcing the same principle discussed throughout this article:

The prisma platform is particularly interesting from an engineering perspective because Löwenstein has continued to invest heavily in physical device construction, acoustic performance and humidification.

Its prismaAQUA humidifier, for example, uses a heater rod rather than the conventional heating-plate arrangement commonly seen beneath many CPAP water chambers.

The removable chamber can be dismantled into its components, including the heater rod, for maintenance and cleaning.

It is a very different engineering approach.

For patients concerned about long-term durability, serviceability and humidification performance, those details matter.

Humidification Is More Important Than Many CPAP Comparisons Admit

CPAP comparisons frequently become obsessed with algorithms.

But there are multiple systems operating simultaneously inside a CPAP machine.

A patient's experience is influenced by:

Poor humidification can contribute to nasal dryness, congestion, oral dryness, rainout, discomfort and ultimately therapy abandonment.

This is an area where companies such as Fisher & Paykel and Löwenstein have historically invested considerable engineering attention.

Resvent Has Taken Yet Another Interesting Approach

Resvent's iBreeze platform provides another example of engineering choices that rarely enter the “best CPAP algorithm” conversation.

The iBreeze humidification system incorporates water-level detection.

When the water level falls below the threshold required for safe heating, the system can stop humidifier heating and provide a low-water notification.

That is a small feature—but from an equipment-design perspective, it is an intelligent one.

Allowing a heating element to continue heating an empty water chamber provides no therapeutic benefit.

Resvent also provides automatic humidification control, multiple humidity levels and heated-tubing capabilities while using its own adaptive APAP pressure algorithm.

So Which APAP Algorithm Is Best?

This is where we disagree with much of the traditional CPAP conversation.

There probably isn't one.

There are excellent APAP algorithms.

There are excellent CPAP machines.

But there is no machine that automatically becomes ideal for every patient simply because one manufacturer's algorithm reacts faster than another.

That is precisely why respiratory clinicians exist.

The Problem With Calling Anything the “Gold Standard”

Calling one manufacturer's APAP algorithm the gold standard can unintentionally transform a clinical tool into a marketing hierarchy.

It creates a very simple story:

But the actual engineering landscape is considerably more complicated.

• Published research demonstrates substantial differences between APAP algorithms.
• ResMed itself offers different pressure-response strategies.
• Löwenstein offers different APAP dynamics.
• Fisher & Paykel incorporates pressure reduction in response to wakefulness.
• Resvent combines adaptive pressure control with its own comfort and humidification technologies.

These aren't necessarily deficiencies.

They are different solutions to the same difficult engineering problem.

There Is Also a Business Side to Sleep Medicine

We also shouldn't pretend CPAP exists independently of healthcare economics.

ResMed has built an extraordinarily successful ecosystem around PAP therapy.

The AirSense 10 generation combined:

• PAP hardware
• integrated wireless connectivity
• AirView clinician monitoring
• remote troubleshooting
• compliance reporting
• patient-facing software
• masks
• accessories
• cloud-connected therapy management

That was smart engineering.

It was also smart business.

Healthcare providers became familiar with AirView. Clinicians became familiar with ResMed reports. Patients became familiar with myAir. Sleep laboratories became familiar with ResMed terminology. Physicians saw ResMed prescriptions repeatedly. HMEs stocked ResMed accessories.

This phenomenon exists throughout medicine and technology.

It doesn't mean the product is bad.

It means brand dominance and clinical superiority are not the same measurement.

The Prescription Should Define the Therapy — Not the Marketing Ecosystem

There are certainly situations where a physician has a legitimate clinical reason to specify a particular machine, mode or capability.

A prescription may require:

• CPAP
• APAP
• BiLevel
• ST
• ASV
• specific pressure support
• backup respiratory rate
• specialized ventilation capabilities

Those are clinical decisions.

But for uncomplicated CPAP/APAP therapy, there is an important discussion to be had about unnecessarily restricting patients to a particular manufacturer's ecosystem.

Our Position at SleepEZ

We carry and support equipment from multiple manufacturers because different patients value different things.

We don't believe a CPAP machine should win solely because of its logo.

We look at:

ResMed makes premium PAP equipment.

So does Löwenstein.

Fisher & Paykel has built some of the most sophisticated humidification technology in respiratory care.

Resvent has introduced genuinely intelligent equipment-protection and humidification features.

Yuwell has become a serious global respiratory manufacturer with increasingly sophisticated PAP platforms.

There is room for all of them.

Maybe “Gold Standard” Is the Wrong Question

Instead of asking:

We should probably ask:

That is a much more clinically useful question.

Because the history of AutoSet itself provides perhaps the best lesson.

Standard AutoSet offered one response. AutoSet for Her introduced another. Soft Response introduced another variation.

Each was intended to solve a slightly different patient problem.

And that tells us something important: