Info
🌱 來自: Huppert’s Notes
Hypercarbic Respiratory Failure🚧 施工中
Hypercarbic Respiratory Failure
• Definition: Respiratory failure due to alveolar hypoventilation → ineffective carbon dioxide elimination
• Pathophysiology: 1) Impaired respiratory drive (i.e., CNS cause) 2) Impaired neuromuscular strength 3) Increased load on respiratory system
• Differential diagnosis by mechanism:
- Impaired respiratory drive
• Brainstem injuries
• Drug overdose (e.g., opiates, sedatives)
• Severe hypothyroidism
- Impaired neuromuscular strength
• Neuromuscular diseases (e.g., myasthenia gravis, amyotrophic lateral sclerosis, Guillain-Barré syndrome, multiple sclerosis)
• Weakness of respiratory muscles (e.g., myopathy, fatigue from increased work of breathing, severe electrolyte derangement)
- Increased load
• Increased resistive load: Bronchospasm (e.g., COPD, asthma)
• Decreased compliance:
- Lung: Restrictive disease, auto-PEEP
- Chest wall: Chest wall skeletal disorder, obesity, pleural effusion, ascites/distension
• Increased required minute ventilation: DKA, sepsis, pulmonary embolism
• Physiologic response:
- Hyperventilate to increase alveolar ventilation and blow off more CO2
- Vicious cycle: ↑PaCO2 → decline in mental status → reduction in ventilator drive → further ↑PaCO2
• Physical exam: See physical exam under dyspnea above
• Work-up:
- ABG or VBG, CBC, CMP, consider troponin, BNP
- CXR, ECG, cardiac and pulmonary point of care ultrasound (POCUS), consider Chest CT or CT-PE
- Consider PFTs, testing maximum inspiratory pressure (MIP) and maximum expiratory pressure (MEP), other testing based on clinical suspicion
• Treatment:
- Identify and treat underlying cause
- Consider NIPPV if not contraindicated; best evidence for use in COPD exacerbations