呼吸力学

•Tidal volume remains constant
•As I:E ratio is changed, autoPEEP is seen only with tracheal pressures •PIP increases and Compliance decreases
Evaluation of pressure/volume loops based on intratracheal pressure measurements during dynamic conditions;S.Karason et al, Acta Anesthesiol Scand 2000;44:571-577
♥
气道阻力(RAW)
♣ RAW = PRAW/(flow rate) : 2~3 (cmH2OL/s) ♣ 包括呼吸道与气管导管的阻力
Airway Pressure (VCV)
Airway Pressure (VCV)
压 力
Why Spontaneous Breath Should Be Needed
意义:
病人的呼吸力量参数. 病人吸气肌力量的标志物. 作为脱机以及评价神经肌肉疾病进展情 况的标准. 在脊柱后侧突，老年，COPD 以及神 经肌肉疾病的病人会其绝对值会降低。
P100 测量---定义
呼吸驱动 (P100), 探测到病人吸气努力开始计 算，第一个100 ms 内所形成的最大吸气负压。
Christian Putensen
August, 2006
Current Opinion in Critical Care 2002, 8:51–57
Fabry Chest 1995:107:1387
Asynchrony is still a problem
Patient-ventilator asynchrony during assisted mechanical ventilation
呼吸机波形与参数
♥ 压力－pressure
♣ 近端压力 ♣ 远端压力 ♣ 气管内压力 ♣ 食管压力，内源性PEEP
♥ 容量－volume，压力-容量环 ♥ 流量－flow，流速-容量环 ♥ 呼吸做功，等
基本图形
Pressure
Volume
Flow
P-V loop
F-V loop
各压力参数
♥ 吸气峰压（PIP）
机械通气的呼吸力学
Respiratory mechanics of mechanical ventilation WWW
Xiangyu Zhang, MD, FCCP
张翔宇 SICU Shanghai Tenth People’s Hospital Shanghai Tongji University Shanghai, China
Baydur Method, to confirm balloon placement
Calculations based on differential pressures
Tracheal Pressure Measurements
•Intended typically for intermittent use
Airway Pressure
Flow
Static PEEPi End-Expiratory Hold
Flow
Exp Hold Exp Hold
Airway Pressure
Static PEEPi
Static PEEPi
Set PEEP = 0 cmH2O
Problems with auto PEEP expiratory hold measurements
1. Patient trigger work before PEEP applied
2. Note PEEP application
3. Patient trigger work after PEEP applied
F-V loop
F-V loop and leaking
漏气
Leak,漏气
SIMV+PSV，通气管路存在漏气
Rise time 1%
P circuit P eso P plural
Rise time 100%
P circuit P eso P plural
Esens 1%
P circuit P eso P plural
Esophageal Balloon
Approximates pleural pressure Polyethylene 10 cm long balloon 100 cm long tubing Positioned in the lower 1/3 of the esophagus Filled with 0.5-1.0cc air
♣ PIP = PRAW + Pplateau
♥ 平台压（ Pplateau）
♣ Pplateau = VT/CRS
♥ 呼气末压（EEP）
♥ 气道阻压（PRAW）
♣ PRAW = RAW ×（flow rate）
呼吸力学监测
♥ 顺应性（Compliance）
♣ 静态顺应性（Cst ） Cst = VT/（Pplateau — PEEP） ♣ 动态顺应性(Cdyn) Cdyn = VT/（PIP — PEEP）


Advance Tracn ET plus adapters Withdraw 1-2cm if patient continues to cough

Evaluation of pressure/volume loops based on intratracheal pressure measurements during dynamic conditions;S.Karason et al, Acta Anesthesiol Scand 2000;44:571-577
Resp Lab @ MGH
Asia Vent Forum @ Shanghai TCI
亚洲通气论坛
Our study settings
Pressure Support
P circuit P eso P plural
Rise time 1%
P circuit P eso P plural
Auto PEEP
MIP 测量---定义
MIP (Maximum Inspiratory Pressure，最 大吸气压) / P100 ，测量病人在自主呼吸 状态下，压力曲线上的负向最大值。
MIP 测量---意义
正常值: 成人 < -70 to -100 cm H2O 儿童 < -20 to -100 cm H2O 脱机标准 < -20 cm H2O
♥ 在压力控制通气时，由于气管内插管造成的气流 阻力升高，导致肺内压力达不到理想水平 ♥ AVEA可以测量气管内压力，并作为一条曲线显示。 ♥ 吸气压力可以根据气管内压进行调节
Ptr (tracheal pressure) 作为压力控制呼吸的向导
♥ Paw = 28 ♥ Ptr = 25
用气管压和食道压计算力学负担
TC,气道阻力与流速的关系
25 20
7.5mm导管两端压力差
15
Delta P
10 5 0
0 10 20 30 40 50 60 70 80
Flow Rate
TC/ATC
ATC
Haberthur ICM 1999;25:514
Does the tube-compensation function of two modern mechanical ventilators provide effective work of breathing relief?

Proper placement of the balloon is imperative for accurate measurements. An approximate level of placement can be made by measuring the distance from the tip of the nose to the bottom of the earlobe and then from the earlobe to the distal tip of the xiphoid process.
为何测量呼吸功?
用气管压和食道压计算力学负担
♥ WOBpt 测定病人实际的呼吸功水平
♣ 正常 .3-.6 Joules/Liter ♣ <.3 病人做功太低，废用性萎缩 ♣ >.75 病人可能出现疲劳
♥ 长期机械通气病人脱机成功的关键是能否为他们 提供一个正常的呼吸功
♣ MacIntyre; Crit Care Med 1999; 27:1040
♥ ♥ ♥ ♥ Better cardiac output Better ventilation/perfusion Better end expiratory lung volume (EELV) Better clinical outcome
Current Opinion in Critical Care 2005, 11:63–68
ArnaudW. Thille Pablo Rodriguez Belen Cabello Franç ois Lellouche Laurent Brochard
Intensive Care Med (2006) 32:1515–1522
Ti in PSV
Inspiration termination Criteria (Esens)
Vent=75% of work