3. Multiple organ failure syndrome with shock is the most common cause
of death in patients with ARDS ( attributable mortality: 45%)
4. Have we made any difference to survival ?
Have we understood the disease or shall we
call it the final common effect of various
diseases?
Lets revisit the basic science
9. Instigation
Endothelial injury: increased permeability of
alveolar - capillary barrier
Epithelial injury : alveolar flood, loss of
surfactant, barrier vs. infection
Pro-inflammatory mechanisms
10. Direct insult
Common
• Aspiration pneumonia
• Pneumonia
Less common
• Inhalation injury
• Pulmonary contusions
• Fat emboli
• Near drowning
• Reperfusion injury
Indirect insult
Common
• Sepsis
• Severe trauma
• Shock
Less common
• Acute pancreatitis
• Cardiopulmonary bypass
• Transfusion-related TRALI
• Disseminated intravascular
coagulation
• Burns
• Head injury
• Drug overdose
11.
12.
13.
14.
15. Leucocytes and soluble
mediators
Coagulation and platelets
Surfactant
Ventilator induced lung injury
Late phase : dysregulated and
maladaptive repair.
16. Primary lung insult is
associated with cascade of
events.
The corner stone of such
cascade is inflammatory
cells mainly neutrophils.
Recruitment of neutrophils
and activation of
macrophages leads to
release of both pro-
inflammatory and anti-
inflammatory cytokines
22. Leucocytes and soluble mediators
Coagulation and platelets
Surfactant
Ventilator induced lung injury
Late phase : dysregulated and maladaptive
repair.
23. Histological Land mark of ALI and ARDS.
• Intra-alveolar Hyaline Membrane
• Microvascular Thrombi
• Deposition of Fibrin in the lung due to
imbalance in the production and degradation.
• In uninjured lung fibrinolytic state is
maintained through action of urokinase
plasminogen activator which converts
plasminogen to plasmin which is fibrinolytic.
24. Leucocytes and soluble mediators
Coagulation and platelets
Surfactant
Ventilator induced lung injury
Late phase : dysregulated and maladaptive
repair.
25. Produced by type II alveolar epithelial cells
Composed of lipoprotein complex
Function :
Biophysical - decrease surface tension at air/liquid
interface
Immunologic – innate host defense
26. Surfactant production and composition
altered in ARDS: low lecithin-
sphingomyelin ratio
Components of edema fluid may
inactivate surfactant
27.
28. Leucocytes and soluble mediators
Coagulation and platelets
Surfactant
Ventilator induced lung injury
Late phase : dysregulated and maladaptive
repair.
36. Lung inflammation “biotrauma”
• Lung overinflation or overstretching produces regional and
systemic inflammatory response
• Factors converting the shear stress applied to an injured lung into
regional and systemic inflammation are still incompletely
elucidated but could include:
- Repetitive opening and collapse of lung units
- Surfactant alterations
- Loss of alveolo-capillary barrier function
- Bacterial translocation
- Over inflation of lung regions
Rouby JJ, et al. Anesthesiology. 2004.
Dreyfuss D, et al. Am J Respir Crit Care Med. 2003.
37.
38. Positive pressure ventilation may injure the lung
via several different mechanisms
VILI
Alveolar distension
“VOLUTRAUMA”
Repeated closing and opening
of collapsed alveolar units
“ATELECTRAUMA”
Oxygen toxicity
Lung inflammation
“BIOTRAUMA”
39. VILI can predispose to ALI/ARDS, while
ALI/ARDS patients are more prone to
effects of VILI
40. Leucocytes and soluble mediators
Coagulation and platelets
Surfactant
Ventilator induced lung injury
Late phase : dysregulated and maladaptive
repair.
41. The pathological features of ARDS are
typically described as passing through three
overlapping phases:
• exudative,
• proliferative
• fibrotic phase