Elliott M W, Mulvey D A, Moxham J, Green M, Branthwaite M A
Department of Thoracic Medicine, Royal Brompton National Heart and Lung Hospitals (Chelsea), London, UK.
Anaesthesia. 1993 Jan;48(1):8-13.
Effective intermittent positive pressure ventilation can be achieved noninvasively using a nasal mask, but patient comfort may be compromised and respiratory effort increased unless the trigger threshold is low and the response time of the ventilator short. The effect of nasal ventilation upon inspiratory muscle effort and the functional characteristics of the trigger of a purpose-built ventilator were evaluated in five patients with chronic obstructive airways disease. A measure of inspiratory muscle effort, the average pressure time integral per minute, decreased by at least 80% in four patients and by 50% in one. Only two patients had significant numbers of triggered breaths (17% and 47% of total) during 1 h of ventilation with settings as used at home. Therefore trigger function was evaluated when the patients were made to trigger the ventilator by slowing the control rate. A high resting end-expiratory intrathoracic pressure decreased the effective trigger sensitivity so that a mean (SD) change in oesophageal pressure of 14.8 cmH2O was required to lower mask pressure by 2.4 (0.3) cmH2O and activate the trigger. Even under these conditions of lowest trigger sensitivity inspiratory muscle effort was not increased compared to spontaneous ventilation.
使用鼻罩可无创实现有效的间歇性正压通气，但除非触发阈值低且呼吸机响应时间短，否则患者舒适度可能会受到影响且呼吸功增加。对5例慢性阻塞性气道疾病患者评估了鼻通气对吸气肌做功的影响以及一台特制呼吸机触发装置的功能特性。吸气肌做功的一项指标，即每分钟平均压力时间积分，在4例患者中至少降低了80%，在1例患者中降低了50%。在家中使用的设置进行1小时通气期间，只有2例患者有大量触发呼吸（分别占总呼吸次数的17%和47%）。因此，当通过减慢控制频率使患者触发呼吸机时评估触发功能。较高的静息呼气末胸内压降低了有效触发灵敏度，以至于需要食管压力平均（标准差）变化14.8 cmH₂O才能使面罩压力降低2.4（0.3）cmH₂O并激活触发装置。即使在这些触发灵敏度最低的条件下，与自主通气相比吸气肌做功也没有增加。
