Lower Esophageal Sphincter Pressure Changes During Swallowing
At the initiation of swallowing, the pressure at the lower esophageal sphincter decreases and then increases (option b). This pattern of pressure change is essential for proper esophageal function during the swallowing process.
Physiological Mechanism of LES Pressure Changes During Swallowing
- During the initiation of swallowing, the lower esophageal sphincter (LES) must relax to allow passage of food from the esophagus into the stomach 1
- This relaxation is characterized by a decrease in LES pressure that occurs as part of the coordinated swallowing sequence 2
- After the bolus passes through the LES into the stomach, the sphincter pressure increases again to restore the antireflux barrier 2
- This pattern of pressure change (decrease followed by increase) is critical for allowing food passage while preventing gastroesophageal reflux 1
Measurement and Clinical Significance
- High-resolution manometry (HRM) can accurately measure these pressure changes at the LES during swallowing 1
- The integrated relaxation pressure (IRP) is calculated as the lowest mean deglutitive esophagogastric junction pressure during a 10-second window after swallowing onset 1
- Normal LES relaxation is essential for proper bolus transit; impaired relaxation can lead to symptoms such as dysphagia 1
- After swallowing, the restoration of LES pressure is important to prevent reflux of gastric contents 2
Pathological Conditions Affecting LES Pressure
- In achalasia, there is reduction or absence of inhibitory innervation to the LES, leading to impaired LES relaxation during swallowing 2
- In gastroesophageal reflux disease (GERD), transient lower esophageal sphincter relaxations (TLESRs) occur inappropriately and are the main mechanism of reflux 3
- TLESRs are not triggered by swallowing and last substantially longer (10-45 seconds) than swallow-induced LES relaxation (5-8 seconds) 3
- LES pressure is typically lower in patients with GERD (mean 6.4 ± 6.4 cm H₂O) compared to normal individuals (15.4 ± 5.0 cm H₂O) 4
Clinical Assessment of LES Function
- Videofluoromanometric studies can assess LES relaxation during swallowing 1
- During normal swallowing, the upper esophageal sphincter opens first, followed by LES relaxation to allow bolus passage 1
- After passage of the bolus, the LES closes to prevent swallowed material from reentering the larynx 1
- The pattern of LES pressure change (decrease then increase) is consistent across different body positions, though the absolute pressure values may differ 5