Respiratory Failure

1
Respiratory Failure
2
PiO2 150mmHg
Externel respiration
Ventilation
PAO2 100 PACO2 40
Gas exchange
PvO2 40mmHg PvCO2 46mmHg
PaO2 100mmHg PaCO2 40mmHg
3
Concept
External respiratory dysfunction ?
PaO2 lt60mmHg(at sea level)
Hypoxemic Type I ----- No
hypercapnia Hypercapnic Type II -- PaCO2
gt50mmHg Differential diagnosis
4
Etiology and Pathogenesis
1. Ventilatory disorder -----hypoventilation
Restrictive restricted inspiration

• 1) Paralysis of respiratory muscle
• 2) Low compliance of chest wall
• 3) Low compliance of lung
• 4) Hydrothorax or pneumothorax

5
Obstructive----airway obstruction due to
congestion, edema of mucous membrane
bronchial spasm airway space obstruction
Dyspnea ----inspiratory or expiratory
Forced expiration?closure of airway

6
Expiration
Inspiration
Expiration
Inspiration
Dyspnea due to intrathoracic and extrathoracic
airway obstruction
7
0
0
5
10
10
20
20
20
30
20
20
20
35
25
20
20
20
20
Normal
emphysema
Equal pressure point shifted up ? airway closure
during forced expiration PA Ppl PER
8
PaO2
100 13.3
PaCO2 PaO2 (kPa) SaO2
SaO2
7.6
Arterial blood pH
75 10.7
pH
7.4
50 8.00
7.2
PaCO2
25 5.33
N
Alveolar ventilation (L/min)
9
Blood gas alterations
Alveolar hypoventilation
? d PaCO2 ? d PaO2
R


PACO2
PAO2 PiO2
R
PaCO2 the best index of alveolar
ventilation
0.863VCO2 VA
PACO2

10
?. Diffusion disorder
1, Surface area of diffusion membrane? 2,
Thickness of diffusion membrane ?
Increased blood flow
Blood gas variations PaO2
? PaCO2 N or ?
11
2. Diffusion disorder
? Surface area of diffusion membrane ?
Thickness of diffusion membrane
increased blood flow
Blood gas variations ? PaO2
N or ? PaCO2
12
PCO2( kPa )
PO2
13.33
PaO2
PvCO2
10.67
6.13
8.00
PvO2
5.33
PaCO2
2.67
0
0.75 s
0.25
0.50
Variation of blood gas in alveolar
capillary -----------by patient with diffusion
disorder
13
3. Ventilation-perfusion imbalance
4L
VA
Normal
0.8


Q
5L
lt? 10cmH2O

50
-20
-10
0
-30
gt - 2.5cm H2O
14
Normal ventilation and blood flow distribution in
lung
15
PaO2 ?? ??
?
CaO2 ?? ?
?
16
Local hypoperfusion ? dead space like
ventilation

17
2?Local hypoperfusion ? dead space like

ventilation
18
4. Anatomic shunt
Bronchial vein
Pulmonary vein
Pulmonary artery
19
Acute respiratory distress syndrome(ARDS)
Acute lung injury
inflammation
bronchospasm
pulm.edema
vasoconstrction thrombosis
atelectasis
dead space like ventilation
diffusion disorder
functional shunt
hypoxemia
20
Metabolic and functional alterations

• PaO2 lt 60mmHg compensation
• lt 30mmHg disturbances
• PaCO2 gt 50mmHg compensation
• gt 80mmHg disturbances

See chapter Hypoxia and Respiratory
acidosis
21
Principles of Treatment

• Treating causes
• Increasing PaO2
• Decreasing PaCO2
• Correcting metabolic and functional disturbances
• The difference of oxygen therapy between
• type I and type II respiratory failure ?

22

• 48?,?,????????????
• ??????????,????????,??????,???????????
  ?,????????????????????????????,???????20?,????,?
  6???40??
• ?? ??????????????????,???,??110,??
  170/110mmHg,??18,????????,??????????,?????,?????
• ???PaO2 50?PaCO2 65?pH 7.33,Hct 49
  ,WBC??????, X?????,???,??2.6mg/dl(1-2),BUN
  65mg/dl(9-20)?

23

• ??,????,???????ICU??????????????,
  ???????????????????,??????????????70mmHg?
• ?ICU??????,BUN????????????????????4????
  ?,??????????????????????????,????30?,???38s(15s),S
  aO2???58????????????,????????????????????????????
  ???????????,?????????????, ??????,????????????????
  ????????,???????,????45/20mmHg?

24

• ??1????????????????
• ????
• 2???????????
• 3?????????????
• 4???????????
• 5?????????????
• 6????BUN?????
• 7??????????
• 8??????????,????????
• 9?????,????