ILD

Interstitial Lung Disease – Gaby Schroeder

Background

  • MANY CAUSES, one mnemonic to use:
    • Sarcoidosis
    • Hypersensitivity Pneumonitis
    • Idiopathic Interstitial Pneumonias (IIPs- UIP/IPF, NSIP, OP, RB-ILD, DIP, LIP, AIP)
    • Tuberculosis
    • Fungal
    • Aspiration/ Asbestosis (and other Pneumoconiosis)
    • Connective Tissue Disease + Cancer
    • Eosinophilic Pneumonia
    • Drugs

 

Evaluation

  • History: Ask about 1) Duration, timing, severity of primary respiratory symptoms 2) Exposures: Pets, Occupation, Residence, Mold, Feathers, Smoking, Illicits, Travel, Hobbies, Medications (especially amiodarone, nitrofurantoin and chemotherapies) 3) Symptoms of systemic autoimmune disease 4) Family history 
  • Chest Imaging: HRCT is best for characterization, but often not achievable or desirable in inpatient setting when patients are critically ill.
  • Labs:
    • Rule out fungal infection: Histo Antigen, Blasto Antigen, Aspergillus Galactomannan, 1,3-β-D-Glucan, sputum GMS (orderable as 'Cytology/Pneumocystis Stain')
    • Rheumatologic Work Up: ANA w/ Reflex, CK, Aldolase, consider full myositis panel
        • RA: RF, Anti-CCP
        • Scleroderma: Anticentromere, Anti-SCL-70
        • Mixed Connective Tissue Disease: Anti-ribonuclear protein
        • DM/PM: Anti-Jo
        • SLE: Anti-ds DNA, Anti-sm, APL
        • Sjogren: Anti-SS-A (Ro), Anti-SS-B (La)
    • If risk factors present: Sputum AFB, Hypersensitivity Panel
  • PFTs, 6-minute walk test
  • Bronchoscopy: BAL (Cell counts, cultures, cytology) + Tissue Biopsy (Transbronchial vs. Cryobiopsy vs. surgical/VATS)
     

Management

  • Treat underlying condition
  • In the inpatient setting, often determine if a patient would benefit from immunosuppression therapy (i.e. steroids) initially, but will need to rule out to infection first
  • Consider lung transplantation for rapidly progressive or refractory cases in appropriate candidate

 

Primary Respiratory Acidosis:

  • Assess patient’s history: Is this acute or chronic?
    • Acute respiratory acidosis and hypercarbia will often present with somnolence or AMS
    • Similarly, if a PCO2 is 80, and the patient is talking to you, it is most likely chronic
  • Common Acute Causes: Decreased respiratory drive (opiates, intoxication) or respiratory muscle weakness (i.e. myasthenia gravis exacerbation)
  • Common Chronic Causes: COPD, sleep apnea
  • Appropriate metabolic compensation?
  • If acute, every 10 mmHg increase in pCO2 above normal (40) should raise HCO3 by 1
    • Expected HCO3 = 24 + ((pCO2 -40)/10))
  • If chronic, every 10 mm Hg in pCO2 above normal (40) should raise HCO3 by 3.5
    • Expected HCO3 = 24 + 3.5 ((pCO2-40/10)).
  • If HCO3 higher than expected à additional metabolic alkalosis