Are you concerned that your AHI keeps showing as two, three or four despite doing everything possible to ensure your CPAP is working right?

It’s a fair question: Why don’t CPAP machines deliver an AHI of zero?

“Thinking logically about this issue, it’s clear that there are two general explanatory paths,” says Joseph Krainin, MD, board certified in sleep medicine and neurology and founder of the online sleep apnea clinic Singular Sleep.

“One, your machine is not set correctly for you, or you have a problem with the delivery of the pressure to your upper airway, i.e., elevated leak.

“Two, the machine-calculated AHI is not perfect and can be spurious.

“I like to counsel patients that it’s a good ‘spitball’ estimate. If you are awake with your mask on and hold your breath for a few seconds, the machine will register that as an abnormal breathing event.”

There’s no data on just how many people in any demographic consistently have an AHI of zero, without any CPAP therapy.

However, sleep medicine doctors deem an AHI of under five to be in the normal range, not qualifying for a diagnosis of disordered breathing during sleep.

There probably are people out there who naturally have an AHI of zero, night after night. Maybe they’re the ones who always sleep straight through the night, and when they get up in the morning, they don’t even have to urinate. Maybe they have big jaws and chins and a big roomy airway. Who knows?

But an AHI of two, three or four is perfectly fine, under the radar for sleep-disordered breathing. Thus, you should not fret if your CPAP machine can’t get your AHI to zero.

Nevertheless, a good question is why wouldn’t a CPAP machine keep the AHI at zero, being that it’s forcing air pressure down the throat?

Dr. Krainin explains, “Centrals [central apneas] can register in the machine’s calculated AHI, but also, being under-pressurized can lead to residual events. If auto-titrating machines are not adjusted properly, that can cause residual obstructive events as well.” cpap