Что такое diaphragm fitting rings в представленном перечислении?

Examples of medical devices that may be cleaned, disinfected and/or sterilized in accordance with the embodiments described in the present disclosure include but are not limited to: surgical instruments, irrigation systems for sterile instruments in sterile tissues, endoscopes and endoscopic biopsy accessories, duodenoscopes, endotracheal tubes, bronchosopes, laryngosopes blades and other respiratory equipment, esophageal manometry probes, diaphragm fitting rings and gastrointestinal endoscopes, infusion pumps, ventilators, and continuous positive airway pressure devices (CPAP), prone to bacterial build-up because of humidified air and contact with a patients mouth.

Ага. особенно с "contact with a patients mouth"