1. ACUTE RESPIRATORY DISTRESS SYNDROME
Dr Tasaduk Khan. MD. FRCP(UK). FCCP(USA) Consultant Internist & Pulmonologist.
Security Forces Hospital
Riyadh.

2. History In 1960s military clinicians in Vietnam called it shock lung.
Civilian clinicians called it Adult respiratory distress.
Subsequent finding in all age groups labeled it as Acute respiratory distress syndrome (ARDS).

3. ACUTE RESPIRATORY DISTRESS SYNDROME
Synonyms:
Non-Cardiogenic pulmonary edema
Adult hyaline membrane disease
Capillary leak syndrome
Stiff lung syndrome
Shock lung

4. ARDS: Definitions
First described in 1967 as Adult Respiratory Distress Syndrome
American-European Consensus Conference Committee (1994) criteria
Acute onset
Bilateral infiltrates in chest radiography
Pulmonary-artery wedge pressure<18 mmHg
Acute lung injury PaO2/FiO2<300
Acute respiratory distress syndrome PaO2/FiO2<200

5. Diagnostic criteria Berlin definition of ARDS.
Respiratory symptoms must have begun within 1 week of clinical insult or new or worsening symptoms during past week.
Bilateral edema consistent with pulmonary edema on CXR/ CT.
Pts resp failure must not e fully explained by CCF or volume overload.
A moderate to severe impairment of oxygenation must be present as defined by PaO2/ FIO2 ratio. Severity of hypoxia defines severity of ARDS.
Mild ARDS: PaO2/FIO2> 200 but <300 on vent settings with PEEP>5cm H2O.
Mod: PaO2/ FIO2 >100 but< 200 with PEEP >5 cm H2O
Severe: PaO2/ FIO2 < 100 on PEEP >5cm H2O.

6. DEFINITION ACUTE LUNG INJURY (ALI): ARDS: Severe form of ALI.
A syndrome of inflammation and increased permeability that is associated with a constellation of clinical, radiologic, and physiologic abnormalities that cannot be explained by, but may co-exist with, left atrial or pulmonary hypertension.
ARDS:
Severe form of ALI.

7. ARDS:Epidemiology Incidence: 80 per 100,000 Outcomes:
Traditionally 40-60% mortality
Majority of deaths due to MSOF
Low tidal volume ventilation decreases mortality
Other critical care improvements may be involved
Predictive factors for death: CLD, non pulmonary organ dysfunction, sepsis and advance age
Survivors: Most of them will have normal pulmonary function within a year

8. CRITERIA FOR ALI & ARDS
PARAMETER
ALI
ARDS
ONSET
ACUTE
HYPOXEMIA
Pao2/ Fio2 < 300 mm Hg
Pao2/ Fio2 < 200 mm Hg
CHEST XRAY
B/L DIFFUSE INFILTRATES
NONCARDIAC CAUSE
PULMONARY ARTERY WEDGE PRESSURE < 18 mm of Hg.
No clinical evidence of left atrial hypertension

9. ARDS causes Direct Lung Injury: Aspiration of gastric contents
Diffuse pulmonary infections
(bacterial, viral, fungal)
Pulmonary contusion
Near drowning
Inhalation injury
Reperfusion pulmonary edema after lung transplant
Radiation

10. ARDS causes Indirect lung injury: Sepsis
Severe trauma w/ shock hypoperfusion
Acute pancreatitis
Severe burns
TRALI (Transfusion related acute lung injury)
Cardiopulmonary bypass
Anaphylaxis
Lymph reticular malignancy

11. ARDS - PATHOGENESIS
Insult (direct or indirect) Activation of inflammatory cells & mediators Damage to alveolar capillary membrane Increased permeability of alveolar capillary membrane Influx of protein rich edema fluid and inflammatory cells into air spaces Dysfunction of surfactant

13. PATHOLOGICAL STAGES OF ARDS
Exudative (acute) phase (0- 4 days) Proliferative phase (4- 8 days) Fibrotic phase ( >8 days) Recovery

15. ARDS: Exudative Phase
CT Scan During Acute Phase

16. ARDS: Fibroproliferative phase
CT Scan during fibroproliferative phase.
Diffuse interstitial opacities and bullae

17. PHYSIOLOGICAL ABNORMALITIES
Decreased ventilation Impaired diffusion Reduced perfusion

18. CLINICAL FEATURES – symptoms
Precipitating insult is usually evident
Early (24 – 48hrs)
- cough, breathlessness, fatigue
Late (after 48hrs)
- due to worsening hypoxemia
- agitation, anxiety, confusion

19. CLINICAL FEATURES – signs
Dyspnoea
Tachypnoea
Tachycardia
Restlessness
Cyanosis even with supplemental oxygen ( refractory hypoxemia)

20. Differential diagnosis
Cardiogenic pulmonary edema
Diffuse alveolar hemorrhage
Acute pulmonary embolism
Acute eosinophilic pneumonia
Hypersensitivity pneumonitis
Pulmonary alveolar protienosis
Sarcoidosis
Leukemic infiltration
Drug induced pulmonary edema
Acute exacerbation of IPF/ chronic ILD.
Cryptogenic Organizing Pneumonia( COP).

21. Investigations Chest x-ray & CT thorax:
Bilateral diffuse alveolar infiltrates more on the peripheral lung fields.
R/O Cardiogenic edema if there is
* cardiomegaly
* pulmonary artery dilatation
* bat’s wing perihilar distribution
* responding to diuretics

22. Ards

23. Cardiogenic pulmonary edema

24. NEONATAL RESPIRATORY DISTRESS SYNDROME

26. INVESTIGATIONS Arterial blood gas analysis:
PaO2 range 55 – 60 mm of Hg
Initially respiratory alkalosis later mixed acidosis
Routine CBC, urea, creatinine, Na, K
Echocardiogram to R/O Cardiogenic cause.
PAWP < 18mm of Hg  ALI / ARDS
Bronchoscopy ( DAH, AEP, PAP)

27. ASSESSMENT OF SEVERITY
Murray lung injury score:
- Chest x-ray
- Hypoxemia
- PEEP
- Compliance
Score 0  no lung injury
0.1 –  mild to moderate lung injury
>  severe lung injury

28. Complications (ACUTE)
Acute respiratory failure.
Delirium.
Ventilator associated pneumonia(VAP)
Ventilator associated lung injury.
Barotrauma ( pneumothorax).
DVT and Pulmonary embolism.
Gastrointestinal bleeding.
Catheter related infections.

29. Complications (CHRONIC)
Reduced exercise capacity due to abnormal lung functions.
Post trauma stress disorder (PTSD)
(depression, anxiety, decreased memory & concentration)
Bed sores.
Critical illness polymyoneuropathy.
Pulmonary fibrosis.
Rarely acquired cystic lung disease.

30. Treatment of ALI/ARDS 1 TREATMENT OF CAUSE
e.g. antibiotics for pneumonia 2
Supportive therapy (5P’s)
Perfusion, position, protective lung ventilation, protocol weaning, preventing complications 3
Pharmacological treatment
Steroids, vasodilators, surfactant, anti inflammatory , DVT Px, Reflux Px & sedation.

31. Long term management. Quit smoking. Quit alcohol. Vaccinations.
Pulmonary rehabilitation.
Join a support group.
Seek professional help/ treat depression.

32. POOR PROGNOSIS FACTORS
Advanced age
Male sex
Extra pulmonary organ dysfunction
Sepsis
HIV
Alcoholism
Active malignancy
Organ transplantation

33. Thank you