Respiration Support

  
  Oxygen Method Selection by Condition + PT Red Flags
  
        Oxygen Method
        Conditions
        ABG Profile
        Main Goal
        PT Red Flags
      
        Low-Flow O₂
        Mild pneumonia, post-op atelectasis, mild COPD
        ↓PaO₂, normal PaCO₂
        Increase FiO₂ modestly
        
          • SpO₂ < 88% at rest

          • New desaturation ≥4% with minimal activity

          • MAP < 65 mmHg or SBP < 90 mmHg
        
        High-Flow O₂ / HFNC High FiO₂
        Severe pneumonia, ARDS, COVID-19 hypoxemia
        ↓PaO₂, PaCO₂ normal/↓
        Deliver high FiO₂ to overcome V/Q mismatch
        
          • SpO₂ < 90% despite FiO₂ ≥ 0.6

          • High work of breathing, RR ≥ 30

          • Hemodynamic instability during exertion
        
        HFNC High Flow, Low FiO₂
        COPD hypercapnia, OHS, neuromuscular weakness
        ↑PaCO₂, PaO₂ near normal
        Washout CO₂, avoid hyperoxia
        
          • SpO₂ < 88% or > 96% (risk of CO₂ retention)

          • pH < 7.35 (respiratory acidosis)

          • Lethargy or altered mental status
        
        CPAP/BiPAP
        COPD with acidosis, pulmonary edema, high WOB
        ↓PaO₂ + ↑PaCO₂
        Positive pressure, CO₂ clearance
        
          • Inability to tolerate mask

          • New arrhythmia with instability

          • SpO₂ < 85% despite support
        
        Mechanical Ventilation
        ARDS, refractory hypoxemia, impending arrest
        Severe ↓PaO₂ ± ↑PaCO₂
        Full ventilatory + airway support
        
          • Sedated, intubated (No mobilization unless cleared)

          • FiO₂ > 0.6 or PEEP > 10 cmH₂O

          • Hemodynamic instability (MAP < 65 or pressors ↑)