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LIU Chuan Yong 刘传勇 Department of Physiology Medical School of SDU Tel 88381175 (lab) 88382098 (office) Email: [email protected] Website: www.physiology.sdu.edu.cn. Chapter 3. Elastic Properties of the Respiratory System. Reference - Textbook. P 29 – 40. P 210 - 218.

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slide1

LIU Chuan Yong

刘传勇

Department of Physiology

Medical School of SDU

Tel 88381175 (lab)

88382098 (office)

Email: [email protected]

Website: www.physiology.sdu.edu.cn

chapter 3

Chapter 3

Elastic Properties of the Respiratory System

reference textbook
Reference - Textbook

P 29 – 40

P 210 - 218

P 471 – 475

slide6

Key Steps in Respiration

  • Ventilation: Movement of air into and out of lungs
  • Gas exchange between air in lungs and blood
  • Transport of oxygen and carbon dioxide in the blood
  • Internal respiration: Gas exchange between the blood and tissues
newborn rds signs and syndrome
Newborn RDS : Signs and Syndrome
  • Baby Aldridge
    • Premature infant (28 weeks gestation)
    • Breathing very fast
    • Dyspnea
      • Chest was indrawing with each breath
      • Making a grunting sound
    • Question
      • The mechanism?
      • Treatment and prevention
outline
Outline
  • Part I Intrapleural Pressure and Mechanism of the Ventilation
  • Part IILung Compliance
  • Part III The Effect of Disease
slide10

Ventilation

  • Occurs because the thoracic cavity changes volume
  • Insipiration uses external intercostals and diaphragm
  • Expiration
    • passive at rest
    • uses internal intercostals and abdominals during severe respiratory load
  • Breathing rate is 10-20 breaths / minute at rest, 40 - 45 at maximum exercise in adults
slide11

Rib Cage

Contract

IntercostalsContractto Lift

Spine

Rib

Diaphragm

Volume

Volume

Ribs

Mechanisms of Breathing: How do we change the volume of the rib cage ?

  • To Inhale is an ACTIVE process
    • Diaphragm
  • External Intercostal Muscles

Both actions occur simultaneously – otherwise not effective

slide14

Pleural fluid produced by pleural membranes

    • Acts as lubricant
    • Helps hold parietal and visceral pleural membranes together
slide20

Alveolar Pressure Changes

During Respiration

slide21

Conducting

Airways

Lungs

Gas Exchange

Pleural Cavity

Very small space

Maintained at negative pressure

Transmits pressure changes

Allows lung and ribs to slide

Chest Wall

(muscle, ribs)

Diaphragm

(muscle)

Pleural CavityImaginary Space between

Lungs and chest wall

Principles of Breathing

Functional Unit: Chest Wall and Lung

Follows Boyle’s Law:Pressure (P) x Volume (V) = Constant

slide22

CW

Principle of Breathing

Follows Boyle’s Law: PV= C

At Rest with mouth open Pb = Pi = 0

Pb

Airway Open

A

Pi

PS

D

1

slide23

Principle of Breathing

Follows Boyle’s Law: PV= C

  • At Rest with mouth open Pb = Pi = 0
  • Inhalation:
  • Increase Volume of Rib cage
  • Decrease the pleural cavity pressure- Decrease in Pressure inside (Pi) lungs

Pb

Airway Open

A

Pi

PS

CW

D

2

slide24

Principle of Breathing

Follows Boyle’s Law: PV= C

  • At Rest with mouth open Pb = Pi = 0
  • Inhalation:
  • Pb outside is now greater than Pi- Air flows down pressure gradient
  • Until Pi = Pb

Pb

Airway Open

A

Pi

CW

PS

D

3

slide25

Principle of Breathing

Follows Boyle’s Law: PV= C

Pb

  • At Rest with mouth open Pb = Pi = 0
  • Exhalation: Opposite Process
  • Decrease Rib Cage Volume

Airway Open

A

Pi

CW

PS

D

4

slide26

Principle of Breathing

Follows Boyle’s Law: PV= C

  • At Rest with mouth open Pb = Pi = 0
  • Exhalation: Opposite Process
  • Decrease Rib Cage Volume
  • Increase in pleural cavity pressure - Increase Pi

Pb

Airway Open

A

Pi

CW

PS

D

5

slide27

Principle of Breathing

Follows Boyle’s Law: PV= C

  • At Rest with mouth open Pb = Pi = 0
  • Exhalation: Opposite Process
  • Decrease Rib Cage Volume
  • Increase Pi
  • Pi is greater than Pb
  • Air flows down pressure gradient
  • Until Pi = Pb again

Pb

Airway Open

A

Pi

CW

PS

D

6

resistance of the ventilation
Resistance of the Ventilation
  • Elastic Resistance
    • Determined by the Compliance
    • Lung and Thoracic Cage Compliance
  • Inelastic Resistance
    • Airway Resistance
slide31

What is lung compliance?

  • Change in lung volume for each unit change in transpulmonary pressure = stretchiness of lungs
    • DV/DP
  • Transpulmonary pressure is the difference in pressure between alveolar pressure and pleural pressure.
slide32

Compliance diagram of lungs

  • There are 2 different curves according to different phases of respiration.
  • The curves are called :
      • Inspiratory compliance curve
      • Expiratory compliance curve
  • Shows the capacity of lungs to “adapt” to small changes of transpulmonary pressure.
  • Hysteresis (滞后现象)
slide33

How do lungs adapt and why?

  • Compliance of lungs occurs due to elastic forces.
    • Elastic forces of the lung tissue itself
  • Elastic forces of the fluid that lines the inside walls of alveoli and other lung air passages

B

A

Elastin + Collagen fibres

  • Surface Tension
slide34

Why is B the most important mechanism?

Conclusion of this experiment:

Tissue elastic forces (A) = represent 1/3 of total lung elasticity

Fluid air surface tension (B) = 2/3 of total lung elasticity.

Experiment:

  • By adding saline solution there is no interface between air and alveolar fluid. (B forces were removed)
  • surface tension is not present, only elastic forces of tissue (A)
  • Transpleural pressures required to expand normal lung = 3x pressure to expand saline filled lung.
slide35

Surface tension

  • water molecules are attracted to one another.
  • The force of surface tension acts in the plane of the air-liquid boundary to shrink or minimize the liquid-air interface
  • In lungs = water tends to attract forcing air out of alveoli to bronchi = alveoli tend to collapse (!!!)

surface tension elastic force

Elastic contractile force of the entire lungs (forces B)

slide36

Why are we talking about surfactant?

  • Surface active agent in water = reduces surface tension of water on the alveolar walls
slide37

Pulmonary surfactant

  • Phospholipid produced by alveolar type II cells.
    • Develop at 24 weeks’ gestation
    • Produces surfactant at 34 weeks
  • Lowers surface tension.
    • Reduces attractive forces of hydrogen bonding
    • by becoming interspersed between H20 molecules.
slide38

Laplaces law

  • “The pressure inside a balloon is calculated by twice the surface tension, divided by the radius.”
  • Pressure to collapse generated by alveoli is inversely affected by radius of alveoli
    • the smaller a bubble, the higher the pressure acting on the bubble
    • Smaller alveoli have greater tendency to collapse
slide39

AirFlow

Expand

Collapse

Effect of Surface Tension on Alveoli size

physiology importance of surfactant
Physiology Importance of Surfactant
  • Reduces surface tension and elastic recoil,
    • making breathing easier
  • Reduces the tendency to pulmonary edema
  • Equalize pressure in large and small alveoli
  • Produces hysteresis, which “props” alveoli open
slide42

Compliance of thorax and lung together

  • The compliance of lungs + thorax = 1/2 of lungs alone.
part iii the effect of disease
Part III The Effect of Disease
  • Lung fibrosis (肺纤维化)
  • Emphysema (肺气肿)
  • Respiratory Distress Syndrome (RDS) of the Newborn (新生儿呼吸窘迫综合症)
lung fibrosis
Lung fibrosis
  • The lungs are stiffened
    • By the laying down of collagen and fibrin bundles
  • Compliance is reduced
emphysema
Emphysema
  • Destroy of the parenchyma
    • Less elastic recoil
  • Compliance increase
newborn rds signs and syndrome1
Newborn RDS : Signs and Syndrome
  • Baby Aldridge
    • Premature infant (28 weeks gestation)
    • Breathing very fast
    • Dyspnea
      • Chest was indrawing with each breath
      • Making a grunting sound
    • Question
      • The mechanism?
      • Treatment and prevention
newborn rds
Newborn RDS
  • Most common respiratory illness in NICU
  • Occur in premature neonate
  • Surfactant deficiency
  • Risk factors
    • Asphyxia (窒息)
    • Male
    • Acidosis
    • DM mother
slide49

早产

窒息

低体温

剖宫产

糖尿病母亲婴儿(IDM)

肺泡 PS

肺泡不张

V/Q  PaO2 

PaCO2  通气 

呼吸性酸中毒

代谢性酸中毒

严重酸中毒

肺毛细血管通透性

透明膜形成

气体弥散障碍

chest x ray
Chest X-ray

Ground glass appearance

Reticulogranular

air bronchograms

slide54

Treatment: Surfactant Replacement

Before PStreatmentAfter PStreatment

home work case study
Home Work:Case Study
  • Mechanics of Breathing.pdf
  • Pulmonary Structure and Lung Capacities.pdf
  • Pneumothorax.pdf
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