Respiratory effort monitoring is a crucial aspect of Nocturnal polysomnography (NPSG) testing. This is usually carried out by strain gage belts which measure chest or abdominal wall expansion. This approach is recognized to be less accurate and less sensitive than intrathoracic pressure measurements monitored from within the esophagus (Pes - Pressure within the esophagus). Most consider current methods of Pes monitoring too cumbersome and impractical for routine NPSG testing. Our proposal is to develop a small electronically based catheter for practical routine Pes monitoring in patients undergoing NPSG testing. This catheter utilizes new MEMS (Micro Electro Mechanical Systems) pressure transducers allowing for an approximate 1 mm diameter size, minimizing patient discomfort. This catheter satisfies a recognized need of enhanced sensitivity and specificity of respiratory monitoring during the testing process and could clearly become the standard method of measuring respiratory effort during Nocturnal polysomnography (NPSG) studies. Additionally, with multiple transducers, it can provide insight into the anatomic region(s) of obstruction within the upper airway and thus assist in the surgical management of patients suffering from obstructive sleep apnea. Recent advances in transducer technologies and methods packaging have paved the way for the development of our Micro Esophageal Respiratory Catheter (MERC).