Acute Respiratory Distress Syndrome (ARDS) Flashcards
Causes
Alveolar capillary interface becomes damaged and more permeable to intravascular fluid
Alveoli fill with fluid
• Sepsis* • Pneumonia • Aspiration • Trauma* • Massive transfusions • Pancreatitis • Shock states Inflammation
ARDS
Failure of Oxygenation how it happens?
Ratio?
- Acute onset
- Bilateral infiltrates
• Severe, refractory hypoxemia – PaO2/FiO2 ratio • 200 – 300 – mild ARDS • 100-200 – moderate ARDS • <100 – severe ARDS
*in the absence of isolated cardiogenic pulmonary edema
Severe V/Q mismatch and shunting of
pulmonary capillary blood result in ?
…refractory hypoxemia
- Unresponsive to increasing O2 concentrations
- Lungs become less compliant
- Increased airway pressures must be generated
Exudative Phase Changes
•Inflammatory mediators • Disruption of alveolar capillary membrane • Fluid in the alveoli • V/Q mismatch • Loss of surfactant=alveolar collapse
Exudative Phase Manifestations
• Tachypnea and
tachycardia
• Mild hypoxemia and
respiratory alkalosis
caused by
hyperventilation
• Dyspnea, tachypnea,
cough, restlessness
• Chest auscultation may
be normal or may reveal
fine, scattered crackles
Proliferative Phase Changes:
• Inflammatory mediators cross ACM = damaged alveolar and capillary epithelium = diffusion defects
• V/Q worsens
• Pulmonary HTN due to
hypoxemic
vasoconstriction=R HF
• Fibrotic changes
Proliferative Phase Manifestations:
• Decreased lung
compliance=increased
work of
breathing=tachypnea
• Hypercarbia and
worsening refractory
hypoxemia
• Diaphoresis, decreased
LOC, cyanosis, and pallor
• Increased peak
inspiratory pressures
Fibrotic Phase Changes:
• Diffuse scarring • Worsening pulmonary HTN • Worsening V/Q mismatch, diffusion defects and shunting
Fibrotic Phase Manifestations :
• R sided HF • Decreased BP, CO • Refractory hypoxemia • Tissue hypoxia/lactic acidosis (increased lactate)
Diagnosis
• CXR – bilateral infiltrates
– Ground glass appearance
• Laboratory testing – ABGs – CBC with differential – Cultures – CMP
Treatment
• Treat the Cause! • Mechanical Ventilation with PEEP • Diuresis • Antibiotics • Steroids - improve oxygenation, not survival – use is controversial • Hydration – maintain circulatory volume, decrease viscosity of secretions • Nutrition
Respiratory Therapy
• Mechanical ventilation – Low Tidal Volumes to reduce barotrauma – High PEEP to aid in recruitment – No mode proven to improve outcomes – Requires advanced airway*
Positive End Expiratory Pressure
PEEP
• Increase FRC and open up collapsed alveoli
• Higher levels of PEEP are often needed to maintain
PaO2 at 60 mm Hg or greater
• High levels of PEEP can compromise venous return
• ↓ Preload, CO, and BP
Nursing Interventions
• Optimize O2 delivery
– Frequent assessment – hemodynamic and ventilatory
– Keep the airways clear
• Minimize O2 demand - Decrease O2 consumption – Comfort – Sedation – Pain relief – Neuromuscular blockade
• Positioning
– Prone positioning
– Elevate HOB
– Frequent changes