机械通气的基本原理

Basic Mechanical Ventilation

机械通气是危重病人重要的支持手段,其重要目的是改善低氧血症、支持肺泡通气、降低呼吸功,并维持或增加肺容积。目前有多种呼吸模式,可根据患者情况选择。机械通气时,应认真评估气道压力、吸呼比、呼气末正压和吸入氧浓度对病人的影响。吸入氧浓度和平均气道压是决定氧合的关键因素,而肺泡通气量主要决定二氧化碳的排除。为防止呼吸机相关性的肺损伤,应将气道平台压维持在30cmHO以下。

Mechanical ventilation is a important therapeutic approach for critically ill patients. The primary goals of mechanical ventilation are support of the ventilatory and oxygenation functions of the lung and reduction in work of breathing, while assuring or increasing lung volume. Various types of breaths and modes are available to facilitate synchrony between the patient and ventilator. The complex interactions of inspiratory pressure, I：E ratio, PEEP, and FiO2 must be appreciated to evaluate the beneficial and harmful effects in each patient. The primary determinants of oxygenation are FiO2 and mean airway pressure, whereas minute alveolar ventilation primarily affects CO2 exchange. Ideally, the inspiratory plateau pressure should be less than 30 cmH2O for prevention of ventilator associated lung injury.