1. Respiratory Failure

3. Respiration
external respiration（pulmonary ventilation and gas exchange in lung）
transport of gas
internal respiration

4. respiratory insufficiency
Respiratory failure
concept and classification
respiratory insufficiency
The condition in which the lungs can not take in sufficient oxygen or expel sufficient carbon dioxide to meet the needs of the cells of the body. Also called pulmonary insufficiency.

5. 2. respiratory failure normal reference values ：
Respiratory failure is a syndrome in which the respiratory
system fails in one or both of its gas exchange functions:
oxygenation and carbon dioxide elimination.
In practice, respiratory failure is defined as a PaO2 value
of less than 60 mm Hg while breathing air or a PaCO2 of more than 50 mm Hg.
normal reference values ：
PaO2 < 60mmHg（8kPa）
with or without PaCO2 > 50mmHg（6.67kPa）
RFI = PaO2/FiO2 ≤ 300

6. 3．classification （1）according to PaCO2
■ hypoxemic (Group Ⅰ) respiratory failure
a PaO2 of less than 60 mm Hg with a normal or low PaCO2.
Cause of: Edema, Vascular disease, Chest Wall.
■ hypercapnic (Group Ⅱ ) respiratory failure
a PaO2 low 60 mm Hg and PaCO2 of more than 50 mm Hg.
Cause of: Airway obstruction, Neuromuscular disease.

7. （2）according to pathogenic mechanism
■ ventilatory disorders
■ gas exchange disorders
（3）according to primary site
■ central respiratory failure
■ peripheral respiratory failure
（4）according to duration
■ acute respiratory failure
■ chronic respiratory failure

8. ventilatory disorders gas exchange disorders ventilation-perfusion
etiology and pathogenesis
【classification of respiration failure mechanism】
ventilatory disorders
gas exchange disorders
respiratory failure
obstructive ventilatory
disorders
restrictive ventilatory
diffusion disorders
ventilation-perfusion
mismatching

9. Ⅰ. ventilatory disorders
1. restrictive ventilatory disorders
Restrictive hypoventilation is caused by the diseases that affect the distensibility of the alveolar.

10. Respiratory movement
forced breathing

11. Respiratory movement ↓ alveolar distensibility
▲ Disorders of the respiratory muscles
Respiratory movement ↓
Depression of CNS
damage of CNS
drug overdose
Respiratory
movement
disorder
neuro-muscular disorders
decreased strength, myasthenia gravis
hypoxia, acidosis
alveolar distensibility
Restrictive
ventilatory
disorders
respiratory failure

12. deformity of thorax , fracture of several ribs, tension
▲ decreased lung compliance
● decrease of pulmonary surfactants and increase of
surface tension force
● diffuse interstitial fibrosis
▲ decreased thoracic compliance of lung
deformity of thorax , fracture of several ribs, tension
pneumothorax, thickened constrictive pleural layer.

13. 2. obstructive ventilatory disorders
原因和机制
2. obstructive ventilatory disorders
■ obstructive ventilatory disorders are caused by the diseases which share the common characterestic of causing enough narrowing within the tracheobronchial tree to increase resistance to the flow of air.
■ etiology
asthma, emphysema, chronic bronchitis, and bronchiectasis.

14. three depression sign 1） central airway obstruction
defined as airway obstruction between the glottis and the carina
three depression sign
■Obstruction is located in the
airway outside the thorax：
inspiratory dysnea +
■Obstruction is located in the
airway inside the thorax：
expiratory dysnea
expire inspire

15. equal pressure point (EPP)
2） peripheral airway obstruction
smaller airways less than 2 mm in diameter.
Determinants of airway closure are the intrinsic caliber of peripheral airways.
Smooth muscle tone, thickness of the wall,
mechanical properties of the surface film,
and secretions in the lumen ,bingding
effect of attachments of the surrounding
lung parenchyma.
equal pressure point (EPP)
In forced expiration, the point where intrapleural pressure and alveolar pressure are equal.

16. Peripheral airway obstruction may be caused by: specific chemical mediators (such as histamine, leukotrienes, prostaglandins ), other substances released during inflammatory and allergic responses.
forced expiration
EPP moves distally as expiration progresses because as air leaves the alveolar unit, the pressure in the alveolar decreases hence the pressure in the airway decreases as well.

17. 3. The alteration of blood gas
1）Low PaO2 ： PaO2 < 60mmHg
2）PaCO2 change：
A. hypoventilation：high PaCO2.
R=40/50 mmHg=0.8；
B. part hypoventilation: Low PaO2 and normal or low PaCO2.

18. Ⅱ. gas-exchanging dysfunction
1. diffusion disorders
The diffusion impairment is characterized by a disruption in the exchange of O2 or CO2 or both across the alveolar-capillary membrane.
Causes:
reduction and/or thicken of alveolar-capillary membrane or reduction of the diffuse time.

19. 1） etiology of diffusion disorders
■ reduction of diffusion membrane area
Abnormalities of diffusion may not cause arterial hypoxia in
persons at rest unless they are extremely severe.
(total: 80 mm2; at rest: 30~40 mm2)
Causes: emphysema, pneumonia, lobectomy
■ increase of diffusion membrane thickness
edema, fibrosis, capillary vessel dilatation
■ decreased time of blood contacts with alveolar

20. 2. ventilation/perfusion imbalance
The dysfunction of gas exchange can arise secondary to ventilation /perfusion mismatching.
VA Q VA/ Q
Top L/min L/min
Middle L/min L/min
Bottom L/min L/min

21. · · · 1) type and cause of ventilation-perfusion-mismatching
(1) decreased ratio of VA/Q
underventilated in relation to their perfusion
asthma, chronic bronchitis, obstructive emphysema, fibrosis, edema
VA/ Q↓ part alveolar ventilatory ↓
functional shunt↑>30% respiratory failure

22. · · poor perfusion in relation to their ventilation with air
(2) increased ratio of VA/Q
poor perfusion in relation to their ventilation with air
pulmonary artery embolization, DIC in lung, vessels contract, pulmonary arteritis,
dead space like ventilation VA/Q↑ poor perfusion↓
respiratory failure

23. Pulmonary A-V shunt open↑
3）increased of anatomical shunt
Right-to-left shunts or anatomic shunt
▲ increased of anatomical shunt
bronchiectasis
anatomic shunt↑
Pulmonary A-V shunt open↑
true shunt↑
Respiratory
failure
pulmonary consolidation,Atelectasis
anatomical-like shunt
▲ increased of 结

24. Ⅲ. Acute respiratory distress syndrome（ARDS）
[concept]
ARDS is a clinical description of severe lung injury characterized by increased permeability of alveolar-capillary membranes, development of protein-rich pulmonary edema, marked hypoxemia refractory to increase in inspired oxygen concentration, and the absence of left ventricular failure.

25. [etiology] shock from any cause, multisystem trauma,
infection including bacterial and nonbacterial pneumonia,
inhaled toxic substances,
overdose of some drug,
acute pancreatitis.

26. [ pathogenesis of ARDS]
1．direct injury of damage factor
2．indirect injury of inflammation medium

27. [Mechanisms of respiratory failure]
ARDS
[Mechanisms of respiratory failure]
1. diffusion disorders
damage of alveolar-capillary membrane increased permeability
diffusion disorders
2. ventilatory disorders
▲edema, type Ⅱalveolar epithelial cells damage decreased lung volume
airway obstruction obstructive ventilatory restrictive ventilatory
disorders disorders
▲inflammation medium bronchia spasm respiratory failure
3．VA/Q mismatching
• •

28. Effects of respiratory failure
Acid-base disturbances & disorders of electrolyte balance
Alteration of the respiratory system
peripheral chemoreceptor
■ PaO2↓＜60mmHg respiratory center(+) respiratory movement↑
＜30mmHg respiratory center (-) respiratory movement ↓
■ PaCO2↑ central chemoreceptor (+) respiratory movement↑
＞80mmHg respiratory center (-) respiratory movement ↓

29. 3. Alteration of the respiratory system
■ compensatory reaction
PaO2<60 mmHg，PaCO2 increase cardiovascular center(+)
increase in cardiac output : increase in stroke volume and heart rate
redistribution of blood flow
■ injurious changes
PaO2< 40 mmHg，PaCO2> 80 mmHg cardiovascular center(-)
rate slow, decreased blood pressure
cardiac output decrease
pulmonary hypertension

30. blood resistance↑ co pulmonale ■ co pulmonale
■PaO2↓
blood resistance↑
pulmonary vasoconstriction
RBC↑ blood viscosity ↑
Stenosis
Pulmonary vascular wall
thickening and hardening
co pulmonale
afterload to right ventricle↑
chronic pulmonary hypertension
■pulmonary arterial embolism, capillary damage
■ Hypoxia, acidosis myocardial systolic
and diastolic function(-)
■difficulty breathing Restricted diastolic

31. 4. Alteration of the nervous system
功能和代谢
4. Alteration of the nervous system
(1) Hypoxia: the nervous system is very sensible to oxygen lack.
< 40~50 mmHg, serious but reversible deterioration in cerebral function
( orientation, arithmetic tasks, memory) occurs, and restlessness and
confusion are common.
< 30 mmHg, loss of consciousness results.
< 20 mmHg, irreversible damage of neural cells.
(2) Hypercapnia: CO2 nacosis.
a condition of confusion, tremors, convulsions, and possible coma that
may occur if blood levels of carbon dioxide increase to 80 mm Hg or higher.

32. pulmonary encephalopathy
■ cerebrovascular injury
PaCO2↑, acidosis Cerebral vasodilation Cerebral blood flow↑
hypoxia vascular endothelial damage extracellular brain edema
edema on brain cell Vascular compression
Increased cerebral anoxia
Intracranial pressure↑
■ Brain cell injury
CSF pH↓＜ EEG slow or stop
GABA↑
pulmonary encephalopathy
lysosomal membrane stability↓ lysosomal enzyme release nerve cell necrosis

33. 4. Alteration of the renal function
5. Alteration of the digestive system

34. Thanks for attention