{'fraction_non_alphanumeric': 0.017188459177409455, 'fraction_numerical': 0.009821976672805401, 'mean_word_length': 5.037037037037037, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Two incidents of complete failure of OAV 7750 ventilators

The Ohmeda OAV 7750 ventilator is designed to be used in conjunction with an Ohmeda Excel Anaesthesia System only, and consists of a control and a drive unit as a matched pair. Rebreathing or non-rebreathing patient system cassettes can be used, the bellows of which are then linked to the pneumatically operated, electronically controlled drive unit. In both instances an Excel 410 anaesthetic machine was in use with a rebreathing cassette and a circle system. Routine machine' and circuit checks had been completed satisfactorily. After connection of the anaesthetic circuit the ventilator delivered three breaths to the first patient before the chest ceased to move, despite the ventilator cycling normally. Manual ventilation similarly failed to generate any positive pressure within the circuit. After connection of the second patient, the ventilator was again observed to cycle normally but failed to move the chest. However, this patient's lungs could be ventilated by hand. The patient system manometer was noted to read zero and did not move with either attempted mechanical or manual ventilation. The rebreathing cassette features a pneumatic circuit let into the patient connection of the cassette for monitoring patient system pressure. Part of this circuit, underneath the cassette and hidden from view, consists of a moisture filter and a 11 cm length of neoprene hose (5 mm ID, 9 mm OD, Fig. 1). In the first incident this short hose had become disconnected, opening the ventilator circuit to atmosphere and rendering it impossible to ventilate the lungs