Idiopathic pulmonary fibrosis

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Background

  • Normal lung parenchyma is interspersed with areas of decrease compliance
    • Unlike ARDS, in which lung injury more uniform
    • Mechanical ventilation strategies learned from ARDS not completely transferrable
  • Median survival time 3 yrs after diagnosis
  • Prevalence about 10-20 cases per 100,000 people
  • AE-IPF = Acute Exacerbation of IPF
  • Acute exacerbations carry mortality up to 80%
  • 60% die from idiopathic pulmonary fibrosis, others die from:
    • VTE
    • Cardiovascular (ACS, CHF)
    • Infection

Clinical Features

Acute exacerbation of IPF

  • Diagnosis of IPF
  • Unexplained worsening of dyspnea within 30 days
  • Hypoxemia deviated from baseline ABG
  • No evidence of pulmonary infection
  • Exclusion of alternative causes (i.e. VTE)
  • CT with bilateral ground-glass abnormalities/consolidation on a background reticular/honeycomb pattern consistent with interstitial pneumonia[1]
    • 100% have bilateral ground-glass opacities
    • ~70% have consolidation

Differential Diagnosis

Pulmonary Fibrosis

  • Interstitial pneumonias (acute, lymphocytic)
  • Lung malignancy
  • Aspiration pneumonitis
  • Aspiration pneumonia
  • Bacterial pneumonia
  • Viral pneumonia
  • Fungal pneumonia
  • Cryptogenic organizing pneumonia
  • Interstial lung disease associated with collagen-vascular disease
  • Drug-induced pulmonary toxicity (amiodarone, bleomycin, amphotericin B, carbamazepine, etc.)
  • Eosinophilic granuloma (Histiocytosis X)
  • Radiation pneumonitis
  • Sarcoidosis
  • Pneumoconiosis (Workplace exposure)
    • Asbestosis
    • Berylliosis
    • Chemical worker's lung
    • Coal worker's pneumoconiosis
    • Silicosis

Evaluation

  • CBC, leukocytosis
  • CRP elevated
  • LDH elevated
  • ABG with hypoxemia, hypercapnea
  • ECG
  • CXR with likely need for CT
  • Echo to assess for pulmonary hypertension, rule out CHF
  • BAL in ICU to rule out infection

Management

  • All treatments controversial and of questionable efficacy
  • Methylprednisolone 500-1000mg QD for 3 days[2][3]
  • Heparin drip
    • Alveolar injury predisposes to prothrombotic state
    • Prevents further vascular injury
  • Cyclosporine A 1-2mg/kg/day with steroids[4]

Mechanical Ventilation Strategies

  • Current strategies controversial, with some contending mechanical ventilation adds insult to AE-IPF
  • Non-invasive may be use as a temporizing measure
  • Low TVs at 6 cc/kg
  • Permissive hypercapnea may be necessary
  • Maintaining minute ventilations
    • High respiratory rates may be necessary
    • Heavy sedation with possible paralysis with cisatricurium
  • Deviations from ARDS treatment strategies
    • Must restrict PEEP given to AE-IPF
    • No place for recruitment maneuver or prone postioning
    • Questionable benefit of APRV (BiVent) and high-frequency oscillation ventilation

Disposition

  • ICU
  • ECMO has been used as a bridge to lung transplant
  • Transfer to transplant center if candidate
    • Lung transplant is the only proven therapy to increase long term survival

See Also

References

  1. Akira M, Kozuka T, Yamamoto S, Sakatani M. Computed tomography findings in acute exacerbation of idiopathic pulmonary fibrosis. Am J Respir Crit Care Med 2008;178:372-8.
  2. Rice AJ, Wells AU, Bouros D, Du Bois RM, Hansell DM, Polychronopoulos V, et al. Terminal diffuse alveolar damage in relation to interstitial pneumonias. An autopsy study. Am J Clin Pathol 2003;119:709-14.
  3. Saydain G, Islam A, Afessa B, Ryu JH, Scott JP, Peters SG. Outcome of patients with idiopathic pulmonary fibrosis admitted to the intensive care unit. Am J Respir Crit Care Med 2002;166:839-42.
  4. Meduri GU, Golden E, Freire AX, Taylor E, Zaman M, Carson SJ, et al. Methylprednisolone infusion in early severe ARDS: Results of a randomized controlled trial. Chest 2007;131:954-63.