Residual Sleep-Disordered Breathing

Man suffering from side effects from sleep apnea

According to the American Academy of Sleep Medicine, about 25 million people in the United States have obstructive sleep apnea (OSA). The gold standard in treatment for most people with OSA is continuous positive airway pressure (CPAP).

But in some cases, OSA symptoms can continue even for patients maintaining good CPAP compliance. When residual sleep-disordered breathing is still present, the adverse effects of sleep apnea may still occur. That is why it is critical to re-evaluate the effectiveness of your CPAP therapy and make adjustments to treatment if your symptoms return.

Signs CPAP may not be effective

In some cases, someone that uses CPAP may feel that treatment is not sufficient. For instance, symptoms may be present that led to the initial treatment. Symptoms of ineffective CPAP and continued residual sleep-disordered breathing may include:

  • Persistent or worsening daytime sleepiness
  • Worsening or poor self-reported sleep quality
  • Worsening comorbidities, such as arrhythmia, high blood pressure, or diabetes
  • Significant weight gain (greater than 10 pounds)

In other cases, an individual may not know that treatment is ineffective unless they have their apnea-hypopnea index measured (AHI).

The AHI is used during a sleep study to access OSA at baseline. But it is also helpful to determine the effectiveness of treatment with CPAP. AHI is the number of times in an hour that a person’s upper airway completely or partially collapses, which leads to a decrease in oxygen level or awakening or arousal from sleep.

Newer CPAP machines measure AHI by identifying the number of apnea-hypopnea events and dividing it by the number of hours a person slept.

Assessing CPAP effectiveness using WPAT

But is CPAP always the best way to measure AHI? A study in the Journal of Clinical Sleep Medicine investigated the use of the Watch PAT 200 (WPAT), a home sleep apnea test, in measuring apnea-hypopnea index (AHI) while simultaneously measuring AHI using continuous positive airway pressure (CPAP).

The study included 100 adults that had OSA ranging from mild to severe and were being treated with CPAP. The participants were suspected of having residual sleep-disordered breathing based on symptoms, such as poor sleep quality, daytime sleepiness, and worsening comorbidities.

AHI was measured through CPAP at the user’s prescribed settings. It was also measured simultaneously using WPAT.  Participants wore WPAT only when they were also using CPAP simultaneously.

Data collected included the following:

Usage time Recording time
Pressure settings Total sleep time
Degree of air leak Sleep efficiency
Mask type Sleep staging
Rapid eye movement (REM)-related AHI
Respiratory disturbance index
Oxygen desaturation index


The results indicated that WPAT AHI was higher than CPAP AHI in about half of the participants suspected of having residual sleep-disordered breathing. WPAT also identified other respiratory events, such as hypoxemia and respiratory effort arousals that CPAP did not detect. The study suggests that WPAT provided a more accurate measurement of AHI than CPAP.

Why an accurate AHI measurement is essential

CPAP is often an effective treatment for OSA. It can improve sleep quality and daily functioning, along with decreasing the risk of serious health problems. But residual sleep-disordered breathing may occur in some cases even with good compliance with CPAP use.

Continued residual sleep-disordered breathing may have significant consequences. Without an optimal reduction in apnea, the full benefits of CPAP treatment may not be met. Accurate measurement of AHI is essential to get the most effective treatment.

If it goes undetected, residual sleep-disordered breathing may have several consequences, including the following:

Increased risk of cardiovascular disease: If OSA is not effectively treated, periods of apnea and hypoxia may continue, which puts a person at an increased risk of a heart attack or stroke.

Ongoing symptoms: Ineffective treatment may mean continued symptoms of OSA, such as daytime sleepiness and fatigue, which adversely impact quality of life.

Decreased CPAP compliance: If symptoms continue, an individual may decide CPAP is not helping and stop using it as prescribed.

What should I do?

By getting an accurate AHI measurement, your healthcare provider can adjust CPAP settings or discuss additional treatment options. For patients using CPAP that are suspected of having residual sleep-disordered breathing, a home sleep apnea test may be a good option.

Click here to locate a WPAT provider.



Epstein, M., Musa, T., Chiu, S., Costanzo, J., Dunne, C., Cerrone, F., & Capone, R. (2020). Use of the WatchPAT to Detect Occult Residual Sleep-Disordered Breathing in Patients on CPAP for Obstructive Sleep Apnea. Journal of Clinical Sleep Medicine, jcsm-8406.

Rising prevalence of sleep apnea in the U.S. threatens public health. (2014).

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