# Unraveling Functional Dysphagia: A Game-Changing Automated Machine-Learning Diagnostic Approach
## 1 Introduction  
In total, 16% of the US population experience dysphagia, only half of whom seek medical care. The remainder manage their symptoms by modifying their diet [1]. X-ray barium esophagogram and endoscopy with biopsy to exclude eosinophilic esophagitis are the initial tests for dysphagia diagnosis. If the above tests are normal, high-resolution esophageal manometry (HRM) is recommended to diagnose the primary and secondary esophageal motility disorder [2]. HRM is the gold standard for the diagnosis of esophageal motility disorders because it is not feasible to obtain muscle tissue (biopsy) for final confirmation. HRM records intraluminal pressures every 1 cm apart and displays these pressures as a heatmap or topographical plots over time, along the entire length of the esophagus and its two sphinters. Studies done before and after the advent of HRM show that primary esophageal motility disorders such as achalsia, diffuse esophageal spasm, and nutcracker esophagagus/jackhammer esophagus combined are seen in ~20% of patients. Another primary esophageal motility disorder, esophagaggastric junction outflow obstruction (EGJOO), i.e., impaired LES relaxation (integrate relaxation pressure (IRP) >15) in the presence of normal peristalsis, is seen in 5-24% of patients with dysphagia [3]. However, only in a minority it is likely the cause of dysphagia because uncontrolled studies show that therapeutic strategies to address EGJOO (Botox, dilation, and myotomy) do not relieve patients' symptoms. Therefore, in a significant number of patients, the cause of dysphagia remains obscure, and these patients are currently thought to have functional dysphagia, which implies sensory dysfunction of the esophagus [4; 5; 6; 7]. The current classification system (Chicago Classification 4.0, CC) [8] employs a hierarchical algorithm to assign the HRM diagnosis. The interpretation process involves two stages that utilize feature-based analysis algorithms. In the first stage, outcomes of each swallow are determined using landmark identification and predefined metrics, leading to swallow-level diagnoses, based on esophageal contraction amplitude, pressurization, and esophagaggastric junction (EGJ) pressure measurements. The second stage combines the swallow-level diagnoses and outcomes to generate the overall study diagnosis as per the Chicago Classification (CC) algorithm. There are two major problems with the CC approach of assessing esophageal motor function. The first hurdle is that the HRM interpretations are prone to inter-rater variability and inaccuracies due to the subjective nature of feature extraction, as evidenced by studies highlighting inconsistent landmark identification as a significant contributor to inter-rater disagreement [9]. This reliance on subjective experience poses challenges in medical training, as revealed by a recent survey showing a lack of confidence among GI fellows in interpreting esophageal manometry results [10]. A second and more significant issue arises from recent studies indicating that, in many patients, the abnormality lies in the distension rather than contraction phase of esophageal peristalsis [11; 12]. Since HRM records only the contraction phase of peristalsis, relying solely on pressure parameters would not be an effective predictor in classifying esophageal motility disorders. Functional dysphagia is a diagnosis of exclusion; it refers to difficulty in swallowing that is not caused by structural abnormalities or obviously identifiable physiological issues. Patients with functional dysphagia often exhibit symptoms such as difficult swallowing, a sensation of food sticking in the throat, or the regurgitation of food. The dysphagia score as determined by validated questionnaires in patients with functional dysphagia can be similar to patients with identifiable esophageal motility disorders such as achalasia esophagus, distal spasm, and esophagaggastric junction outflow obstruction [13; 14]. The esophagus has one simple function: to transfer swallowed contents to the stomach.