This document discusses acute respiratory distress syndrome (ARDS) and respiratory failure. It provides definitions and criteria for diagnosing ARDS and respiratory failure. ARDS is characterized by severe dyspnea, hypoxemia, diffuse pulmonary infiltrates, and respiratory failure. It outlines the exudative, proliferative and fibrotic phases of ARDS. Treatment involves mechanical ventilation, fluid management, glucocorticoids and other supportive therapies. Complications of mechanical ventilation are also discussed. Respiratory failure is defined as the lungs' inability to maintain adequate gas exchange and can be type 1 (hypoxemia without hypercapnia) or type 2 (hypoxemia with hypercapnia). Causes, clinical features, diagnosis and

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ARDS, Respiratory Failure
Dr. Manu Mohan K
Dept. of Pulmonary Medicine

2. ARDS
• Severe dyspnea of rapid onset
• Hypoxemia
• Diffuse pulmonary infiltrates
• Respiratory failure
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3. Etiology
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Harrison’s Principles of Internal
Medicine 17th
ed.

4. Clinical features
• Diagnostic criteria for ALI and ARDS
• Oxygenation
ALI – PaO2/FiO2 < 300mm of Hg
ARDS - PaO2/FiO2 < 200mm of Hg
• Onset
Acute
• Chest radiograph
Bilateral alveolar or interstitial infiltrates
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Harrison’s Principles of Internal
Medicine 17th
ed.

5. • Absence of left atrial hypertension
PCWP < 18 mm of Hg or no clinical
evidence of increased left atrial
pressure
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Medicine 17th
ed. 5

6. www.images.google.co.in 6

7. http://radiology.rsna.org/content/2
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8. Clinical course and
pathophysiology
• Exudative
• Proliferative
• Fibrotic
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Medicine 17th
ed. 8

9. Exudative phase
• First 7 days
• Alveolar and interstitial edema
• Hyaline membrane whorls
• Atelectasis
• Decreased lung compliance
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Medicine 17th
ed. 9

10. Proliferative Phase
• 7 to 21 days
• Early pulmonary fibrosis
• Proliferation of Type 2 pneumocytes
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Medicine 17th
ed. 10

11. Fibrotic stage
• 3 to 4 weeks
• Extensive alveolar duct and interstitial
fibrosis
• Emphysema and bullae
• Pulmonary hypertension
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Medicine 17th
ed. 11

12. Treatment
• General
• Mechanical ventilation
Ventilator induced lung injury
Prevention of alveolar collapse
PEEP
Inverse ratio ventilation
Prone position ventilation
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Medicine 17th
ed. 12

13. • Other strategies of mechanical ventilation
High frequency ventilation
Extracorporeal membrane oxygenation
Partial liquid ventilation
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14. General support during
ventilation
• Fluid management
Maintaining low left atrial filling pressure
• Glucocorticoids
• Other therapies
Surfactant replacement
Nitric oxide inhalation
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15. Complications of Mechanical
ventilation
• Pulmonary complications
• Barotrauma
• Nosocomial pneumonia
• Oxygen toxicity
• Tracheal stenosis
• Deconditioning of respiratory muscles
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Medicine 17th
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16. • Hypotension
• GI - Stress ulcer and mild cholestasis
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17. Prognosis
• Mortality 41-65%
• >80 % deaths due to nonpulmonary
complications
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18. • Functional recovery
Recover maximum lung function in 6
months
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19. Respiratory failure
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Respiratory failure
• When lungs cannot fulfill their primary
function of maintaining adequate gas
exchange at rest, or during exercise
• This results in an inability to maintain
normal blood gases, so that the Po2 (less
than 60) is low with or without Hypercarbia
(more than 50).

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• Two types of respiratory failure
• Type I and Type II
• Type I - Hypoxemia without Hypercarbia
• Type II- Hypoxemia with Hypercarbia
• It can be acute or chronic

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• Type I respiratory failure causes
• Chronic bronchitis and emphysema
• Pneumonia
• Pulmonary edema
• Pulmonary fibrosis
• Asthma
• Pneumothorax
• Pulmonary embolism
• Bronchiectasis

23. • Obesity
• ARDS
• Cyanotic heart disease
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24. Type II Hypercarbic
Respiratory failure causes
• COPD
• Asthma
• Drug overdose
• Poisoning
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25. • Myasthenia Gravis
• Polyneuropathy
• Poliomyelitis
• Sleep apnea syndrome
• Pulmonary edema
• ARDS
• Tetanus
• Foreign body
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26. Mechanism
• Oxygenation failure and ventilatory failure
• Type I respiratory failure
Ventilation perfusion mismatch is marked
Control of ventilation is intact
So excess CO2 is exerted by normal
areas of lung
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• Type II
Ventilatory failure marked
PaCO2 rises due to alveolar
hypoventilation, PaO2 falls.

28. Clinical features
• Clinical evidence of hypoxemia
• Central cyanosis best assessed by
examining the oral mucous membrane.
• Not useful in anemia
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• CNS effects- irritability impaired
intellectual function and clouding of
consciousness
• Progress to convulsion, coma and death
• Persistent hypoxemia can lead to
secondary polycythemia

30. Clinical evidence of
hypercapnia
• CNS effects- irritability, confusion,
somnolence and coma, tremor, myoclonic
jerks, asterixis, even seizures, headache,
papilledema.
• Warm flushed skin with bounding pulse.
• Tachycardia and sweating
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• Gastric dilatation, paralytic ileus
• Head ache on waking up common in
chronic hypercapnia due to progressive
increase in CO2retention during sleep.

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DIAGNOSIS
• ABG
• It is important to measure arterial pH and
assess degree on compensation.
• In acute respiratory failure 10mm of Hg
increase in CO2 increases HCO3 by
1meq/L pH increase by 0.08 units. In
Chronic 10mm Hg increase in CO2
increase pH by 0.03 and HCO3 by
3.5meq/L

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Management
• Type I
• Treatment of primary cause
• Correction of arterial hypoxemia highest
priority
• The goal should be to increase saturation
of oxygen to at least 85-90% without risk
of oxygen toxicity.

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• High Fi02 for short period can be used.
The use of PEEP, change in position,
sedation and paralysis may help in
lowering Fi02
• Fever, agitation, overfeeding, vigorous
respiratory activity and sepsis increases
the oxygen demand.

35. General indication of ventilation
• Inadequate oxygenation despite an
increasing Fi02
• Increased PaCO2 associated with
decreased mental status or increasing
fatigue.
• Failure to control secretions
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36. Methods
• Non invasive mechanical ventilation
• Mechanical ventilation
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37. Mechanical ventilation
• Indications
• PaO2 less than 60 mm Hg despite FiO2 >
0.6 with hypercapnia
• Rapid increase in CO2 causing
uncompensated
• Respiratory acidosis
• Tachypnea > 35 breaths per minute
• Clinical judgment on impending
exhaustion of the patient
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38. Complications
• Barotrauma
• GIT bleeding
• Nosocomial Pneumonia
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39. • LTOT - long term oxygen therapy
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