acute respiratory distress syndrome by dr tahir javed assistant professor of pediatrics, king edward...
TRANSCRIPT
ACUTE RESPIRATORY DISTRESS SYNDROME
By
Dr Tahir JavedAssistant Professor of Pediatrics,King Edward Medical University
LAHORE
HISTORY• Ashbaugh: 1967, “adult respiratory distress
syndrome” • American-European Consensus Conference
(AECC) : 1994 “ Acute substituted for ADULT”• B/L Lung infiltrates & severe hypoxemia
without cardiogenic pulmonary edema• The Berlin Definition: 2012-The PaO2/FiO2
• mild ARDS: 201 - 300 mmHg (≤ 39.9 kPa)• moderate ARDS: 101 - 200 mmHg (≤ 26.6 kPa)• severe ARDS: ≤ 100 mmHg (≤ 13.3 kPa)
The Respiratory System: Gross Anatomy
• The Airway– Extra thoracic
» Supraglottic» Glottic Conduction of Air» Infraglottic
– Intrathoracic• The Lungs– Lobes Conduction of Air + gas Exchange
– Segments• The Pleura• Blood Supply
The extrathoracic airway is1-Pleura2-Supraglottic3-Lobe of the lung4-Chest wall muscle
The Trachea
• Extent• The length• The AP diameter• The layers: Mucosa, Submucosa, Cartilage/ Muscle, Adventitia• The Bronchi• The blood supply
• Inferior Thyroid• Intercostal• Bronchial
Question
Length of trachea at birth isa-7cmb-3cmc-10cmd-14cm
Answer
• B
The Trachea: Histology
The Bronchial Epithelium
The Lungs
The Lungs
Functional unit of the lung is called1-Lobe2-Segment3-Alveoli4-Bronchus
The Pleura
The Pulmonary Vasculature
The Respiratory Zone
Mechanics of Breathing
• Inspiration• Expiration• Compliance• Resistance
The Gas Exchange
Lung Volumes
The Protective Mechanisms
• The Nose
• The Cough
• The Mucociliary Escalator
• The Alveolar Macrophages
A C U T E R E S P I R A T O R Y
D I S T R E S S S Y N D R O M E
ARDS
• Disease of Alveoli: ↓ Gas Exchange– Diffuse Alveolar damage– Lung capillary endothelial Injury
• Early Phase: Exudative• Late Phase: Fibro-proliferative
Pathophysiology
• ↑capillary permeability: fluid accumulation• Type 1 cell damage: ↓clearance from alveolar spaces• Type 2 cell damage: ↓Surfactant→ ↓Compliance ALVEOLAR COLLAPSE• Role of Neutrophils: Reactive rather than causative• Role of cytokines
Question
Type-II cell damage is caused by1-Surfactant deficiency2-Oxygen inhalation3-Sepsis4-Barotrauma
Answer
• 1
Pathophysiology
• Barotrauma: Pneumothorax & Interstitial leaks• Volutrauma: Further damage• Intra pulmonary shunting• High FiO2: DAD (diffuse alveolar damage) Hyaline membrane formation and fibrosis • Pulmonary Hypertension• Pulmonary fibrosis: ↑PCP-III: High mortality
Causes
• No risk factors in 20% cases• Advanced age, female gender, alcoholism and
smoking increase the risk of ARDS• Sepsis is the most common cause• Other causes include Pneumonia, fractures,
trauma, burns, drug overdose, Aspiration, near drowning, post perfusion injury, pancreatitis and fat embolism
Epidemiology
• Incidence: 75/100,000 population in USA• Incidence increases with age– 15-19 Yrs-16 cases /100,000 person Yrs– 75-84 Yrs-306 cases/100,000 person Yrs
• Gender: Incidence slightly more in females when cause is Trauma
• 190,600 new cases every year with 74,500 deaths
Prognosis• MORTALITY• 40-70% mortality in 1990• 30-40 % recently• Better understanding of Sepsis• Use of mechanical ventilation• MORBIDITY• long hospital Stays• High risk of Nosocomial infections• Muscle wasting• Functional impairment
History
• Dyspnea 1st at exertion and soon at rest• Anxiety & agitation• Increasing need for higher O2 concentrations• Onset: 12-48 Hrs but may take several days• Patients are critically ill, may be already
admitted with multi-organ failure & may not furnish Hx
Examination
• Tachypnea• Dyspnea• Cyanosis• Hypotension: ↑CRT, cold extremities, weak
thready pulses• Rales in the chest• Absent breath sounds if pneumothorax• Agitation, Somnolence
Investigations
• Hematologic: TLC, Platelet count esp. with DIC B:N• Renal: deranged function tests when ATN• Hepatic: Disturbed functions• ABGs: Respiratory alkalosis later metabolic acidosis
as CO2 rises• PaO2/FiO2<200• High IL-1, IL-6, IL-8• Normal Echocardiogram. May help diagnose
Pulmonary Hypertension
What is pneumothorax?
Question
Pneumothorax is suggested by1-Absent breath sound2-Stony dull percussion3-Bronchial breathing4-Vesicular breathing
Radiology
Radiology
Radiology
CT Chest
• More sensitive to detect – Pulmonary interstitial Emphysema– Pneumothorax– pneumomediastinum– Pleural effusion– Cavitation– Mediastinal lymphadenopathy
SEQ
• A 6 hours old neonate born at 28 weeks of gestation, to Para5 mother via emergency C-section, weighing 0.9 kg. He has developed respiratory distress at 2 hours of birth. There is nasal flaring and intercostal and subcostal recessions. Baby is cyanosed & grunting. Chest X-ray shows ground glass appearance with air bronchogram throughout the lungs. His condition is worsening.
• 1-What is diagnosis?• 2-What further investigations you will do?• 3-What is treatment option?
Answer
• Hyaline membrane disease• ABGs• Mechanical ventilation
Complications• Barotrauma: high PEEP, CPAP & mean AWP leading to leak pathologies• Accidental extubation & right mainstem intubation• Prolonged ventilation requiring tracheostomy will eventually lead to sub-glottic stenosis• Nosocomial infections: VAP, Line sepsis, UTI, Sinusitis,
Clostridium difficile colitis, MRSA,VRE.• Renal failure esp. When cause of ARDS is sepsis, • Stress gastritis, Anemia• PCM and difficult rehabilitation