Pes: Unlocking the Hidden Patterns of Breathing
Sometimes the key to a life-changing diagnosis is the subtle inhale. Enter Pes, your VIP pass to the inner workings of breathing effort during sleep.
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What Is Pes?
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Pes stands for Pressure in the Esophagus, which is a technique for measuring the effort of breathing during sleep. A thin catheter, placed in the lower esophagus, detects the vacuum created as the lungs draw breath—providing a direct, reliable measure of respiratory effort.
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How Does Pes Work?
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Pes relies on a fluid- or air-filled catheter placed in the esophagus during polysomnography (PSG). It records the intrathoracic pressure changes associated with each breath. Although more invasive than modern alternatives, it remains the gold standard for measuring respiratory effort—especially valuable in nuanced cases PMC.
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Solar power might be trending, but when it comes to breathing diagnostics, Pes remains the MVP of precision.
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Benefits of Pes in Sleep Disorder Diagnosis
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Sensitive Detection of Respiratory Effort: Pescan catch subtle abnormalities—like respiratory effort–related arousals (RERAs)—that standard airflow sensors may miss.
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Reference Standard: It remains the benchmark method for assessing respiratory effort during PSG.
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Minimal Impact on Sleep: A large study confirmed Pes led to only minor—and likely clinically insignificant—changes in sleep architecture, such as slightly reduced REM and total sleep time.
In the world of sleep diagnostics, it's like using a microscope instead of a magnifying glass. Pes catches what others gloss over.
How Dr. Jerald H. Simmons Impacted Sleep Medicine
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Dr. Jerald H. Simmons, MD, is a true pioneer in sleep medicine—with deep roots at Stanford. Under the mentorship of William Dement ("father of sleep") and Christian Guilleminault, Dr. Simmons helped coin the term and protocol now known as Esophageal Pressure Monitoring (Pes) back in the early 1990s at Stanford, around 1992–93.
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He developed this technique to better diagnose upper airway resistance and obstructive sleep apnea, particularly in cases with excessive daytime sleepiness that might otherwise be missed. The Pes method provides a more detailed, quantitative measure of respiratory effort than other diagnostic tools.
Since then, he has lectured extensively—over 30 years—to the healthcare community about connections among clenching, sleep bruxism/TMJ disorders, ADHD, and sleep disturbances—all underpinned by insights derived from Pes.
How Pes Enhances Diagnosis of UARS and OSA
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Upper Airway Resistance Syndrome (UARS): Patients with UARS may not meet the apnea/hypopnea criteria but still experience chronic daytime symptoms. PES can reveal increased respiratory effort and arousals that otherwise fly under the diagnostic radar.
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OSA & Pediatric Impact: Even in children, Pes has helped identify subtle breathing disruptions tied to behavioral and neurocognitive impairments—long before the appearance of clear apneas or desaturations.
Thanks to Pes, clinicians can pinpoint the elusive breathing disruptions that often disrupt quality of life.
How Pes Helps Uncover UARS
Upper Airway Resistance Syndrome (UARS) can be difficult to identify because patients may continue breathing throughout the night without experiencing the obvious apneas, oxygen drops, or loud snoring commonly associated with obstructive sleep apnea. Their airway narrows, however, forcing the body to work progressively harder to draw in each breath.
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During an overnight sleep study, the Pes catheter measures pressure changes inside the esophagus as an indicator of the effort required to breathe. When the upper airway becomes restricted, the chest must generate stronger suction to move air into the lungs. On the Pes recording, this appears as increasingly negative pressure with successive breaths—a pattern known as a Pes crescendo.
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The increased effort may eventually cause a brief arousal that allows the airway to reopen and breathing effort to return toward normal. This sudden change is called Pes reversal. The patient usually does not remember waking, but repeated arousals can fragment sleep and interfere with the deep, restorative rest the body needs.
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By reviewing these pressure patterns alongside airflow, brain activity, oxygen levels, and the other measurements collected during polysomnography, CSMA’s sleep specialists can identify:
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Increasing breathing effort caused by upper-airway resistance
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Flow-limited breaths that may not qualify as apneas or hypopneas
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Respiratory effort-related arousals, also called RERAs
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Repeated disruptions that help explain fatigue, brain fog, headaches, mood changes, and unrefreshing sleep
This added information can be especially valuable when a conventional sleep study appears “normal,” yet the patient continues to experience symptoms of disrupted sleep. Pes gives the clinical team a closer look at what the body is doing to maintain airflow—and may reveal breathing resistance that less-sensitive measurements do not fully capture.
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Pes at CSMA
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At CSMA, we’re proud to feature Pes within our advanced diagnostic repertoire.
Our FAQs state:
“The Pes is a method of measuring the effort of breathing… This is the most reliable method… Disorders such as Upper Airway Resistance Syndrome … can only be accurately diagnosed with the Pes.”
Dr. Simmons continues to lead in sleep diagnostics, ensuring that CSMA remains at the forefront of patient-centered, precise evaluation for complex sleep-breathing disorders.
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Why Pes Still Matters (Even in 2026)
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