影响肺顺应性和气道阻力的因素(薛张纲).ppt

Factors Affecting Pulmonary Compliance Airway Resistance Xue Zhanggang, M.D. Shanghai Medical University Tissue Elasticity Compliance Elasticity（弹性）是指组织在外力作用下发生变形，外力消失后恢复其原有形状的能力。符合Hooke’s Low Compliance（顺应性）肺和胸廓的顺应性定义为单位压力变化所导致的相应的容量变化 计算公式 静态顺应性（Static）和动态顺应性（Dynamic） Lung Thoracic Cage Compliance Relationships Mechanics - movement of gas into the lung Lung Mechanics Chest Wall Mechanics Respiratory System Mechanics Recall... Lung Mechanics Transpulmonary Press Ptp = Palv - Ppl Lung Elastic Recoil “Balloon-like” “deflates” Model of lung compliance Model of lung compliance under artificial ventilation Pressure – volume diagram 肺的压力-容量曲线的特点 呈S形，可以分成三段 下部平坦段 中部陡峭段 上部平坦段 Recall... Chest Wall Mechanics 弹性回缩取决于肺容量 当肺容量75%肺活量时，胸壁呈向外的牵张 当肺容量75%肺活量时，胸壁呈排气状态 在低肺容量时，胸壁的顺应性下降 Recall... Respiratory System Mechanics 呼吸系统的弹性回缩是肺和胸壁的总和 在大肺容量时，肺的弹性占主导作用 在低肺容量时，胸壁的弹性发挥主导作用 Total Compliance Normal values of compliance Normal values of lung thoracic compliance Lung Compliance 0.2 L/cmH2O Thoracic Compliance 0.2 L/cmH2O Total Compliance 0.1 L/cmH2O Newborn 0.003 ~ 0.005 L/cmH2O Infants 0.01 ~ 0.02 L/cmH2O Small Children 0.02 ~ 0.04 L/cmH2O Causes of reduced compliance Parenchymal alterations ARDS Pneumonia Pulmonary edema Fibrosis Surfactant-Functional Disorder ARDS Alveolar pulmonary edema Atelectasis Aspiration Volume Reduction（FRC reduction） Pneumothorax Elevated diaphragm…… Effects of Decreased Compliance Increased work of breathing. Compensatory mechanisms Increased respiratory rate Decrease tidal volume Alveolar ventilation is not uniform Can results in regional ventilation-perfusion variability Airway Resistance – a Measure of Flow Resistance Airway resistance = airflow resistance，定义为单位时间内，在一定驱动压力下经过管道的气体容积 计算公式 单位：cmH2O·L-1·sec-1 Normal Values of Airway Resistance Newborn 30 ~ 50 cmH2O·L-1·sec-1 Infants 20 ~ 30 cmH2O·L-1·sec-1 Small Children 20 cmH2O·L-1·sec-1 Adults