Esophageal pH and pharyngeal pH monitoring - 48 Hour measures acid exposure in the upper and lower esophagus, helping to rule out other causes and is the most objective way to detect and assess the severity of reflux disease Pharyngeal pH monitoring detects acid in the pharynx, which is a good surrogate for aspiration events. This is particularly important in patients with laryngeal and respiratory disorders and may be a better predictor of successful surgical therapy than esophageal pH monitoring in some patients.