In the world of sleep medicine, Pes is an abbreviation for pressure esophageal monitoring. Used in a handful of sleep laboratories, including Stanford University, it's a measurement that can aid in the diagnosis of sleep-disordered breathing. In particular, it may identify increased airway resistance and an effort of breathing that characterizes upper airway resistance syndrome (UARS) — a condition that may lie on the spectrum from snoring to obstructive sleep apnea.
Pes is measured by placing a flexible plastic tube in the nostril and down the back of the throat until it rests near the heart in the esophagus, the muscular tube that leads to the stomach. Once in place, a small balloon is inflated that can measure the pressure within the esophagus during sleep. With increased breathing effort against resistance, the pressure increases.
Pes may provide additional information beyond the other sensors that record breathing in a sleep study or polysomnogram, including respiratory belts and airflow monitors. If these measures fail to identify abnormal breathing in sleep, it may be captured by the use of Pes. As the placement may be uncomfortable, this measurement is not used in standard sleep studies at most centers, however.