影响肺顺应性和气道阻力的因素(薛张纲)

Lung Elastic Recoil
“Balloon-like”

“deflates”
Model of lung compliance
来自百度文库
Model of lung compliance under artificial ventilation
Pressure – volume diagram
肺的压力-容量曲线的特点
Volum e Tidal Com pliance Static PPlateau PEEP
Com pliance Dynamic Volum e Tidal PPeak PEEP
50~70 ml/cmH2O
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
1 CTotal 1 C Lung 1 CThoracicCage
CLung CTC CLung CTC
Compliance Total
Mucosal swelling (asthma, bronchitis, pulmonary edema)
Emphysema (dynamic airway compression)
Bronchospasm Foreign body Tumor stenosis Iatrogenic causes
Normal values of compliance
Normal values of lung & thoracic compliance
– Lung Compliance – Thoracic Compliance – Total Compliance – Newborn 0.2 L/cmH2O 0.2 L/cmH2O 0.1 L/cmH2O 0.003 ~ 0.005 L/cmH2O
Dynamic Airway Compression
图示
– 用力呼气时
– 胸腔内 压 增加 至+30 cmH2O
– 当胸腔 内 压大 于气道内压时， 气道变得狭窄， 甚至出 现 支气 管关闭
Cause of increased airway resistance
Excessive secretions-retention of secretions
Mechanics - movement of gas into the lung
Lung Mechanics
Chest Wall
Mechanics
Respiratory
System Mechanics
Recall... Lung Mechanics
Transpulmonary Press

Ptp = Palv - Ppl
– Infants
– Small Children
0.01 ~ 0.02 L/cmH2O
0.02 ~ 0.04 L/cmH2O
Causes of reduced compliance
Parenchymal alterations
– – – –
– – – –
ARDS Pneumonia Pulmonary edema Fibrosis
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
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
C dV dP
– 静态顺应性（Static）和动态顺应性（Dynamic）
Lung & Thoracic Cage Compliance Relationships
Adults 2 ~ 4 cmH2O· L-1· sec-1
Adults（Intubated）4 ~ 6 cmH2O· L-1· sec-1
Effective resistance
Pmax Pplateau Flow( L / sec)
Resistance is affected by……
8l R 4 r
Effects of increased airway resistance
Increase the time needed to complete
exhalation
Cause dyspnea, particularly during
exhalation
Decrease rate of breathing
ARDS Alveolar pulmonary edema Atelectasis Aspiration
Surfactant-Functional Disorder
Volume Reduction（FRC reduction）
– Pneumothorax – Elevated diaphragm……
Factors Affecting Pulmonary Compliance & Airway Resistance
Xue Zhanggang, M.D. Shanghai Medical University
C
dV dP
Tissue Elasticity & Compliance
Elasticity（弹性）是指组织在外力作用下发生变
思考题
Explain
– Lung compliance – Dynamic compliance – Static compliance – Specific compliance
Answers to the Questions
Compliance Compliance Specific FRC
– 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，
Effects of Decreased Compliance
Increased work of breathing. Compensatory mechanisms
– Increased respiratory rate – Decrease tidal volume
Alveolar ventilation is not uniform
Radius of the airway（r） Nature of the gas flow（laminar flow or turbulent flow or density of the gas）
Bronchial lumen variation with phase of respiration
在一定驱动压力下经
过管道的气体容积
计算公式
dP R V
单位：cmH2O· L-1· sec-1
Normal Values of Airway Resistance
Newborn
Infants
30 ~ 50 cmH2O· L-1· sec-1
20 ~ 30 cmH2O· L-1· sec-1
Small Children 20 cmH2O· L-1· sec-1