Idiopathic pulmonary fibrosis

Background

• Normal lung parenchyma is interspersed with areas of decrease compliance
  • Unlike ARDS in which lung injury more uniform
  • MV 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

• Diagnosis of exclusion
• Presentations with rapid deterioration without obvious cause commen
• May co-exist with pulmonary HTN and heart failure
• Diagnostic criteria for acute exacerbation of IPF:
  • Dx 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 b/l ground-glass abnormalities/consolidation on a background reticular/honeycomb pattern c/w interstitial pneumonia
    • 100% have b/l ground-glass opacities
    • ~70% have consolidation

Diagnostics

• CBC, leukocytosis
• CRP elevated
• LDH elevated
• ABG with hypoxemia, hypercapnea
• EKG
• CXR with likely need for CT
• Echo to assess for pulm HTN, r/o CHF
• BAL in ICU to r/o infection

DDx

Pulmonary Fibrosis

• Interstitial pneumonias (acute, lymphocytic)
• Lung malignancy
• Aspiration pneumonia or pneumonitis
• Bacterial, viral, or fungal pneumonia
• Cryptogenic organizing pneumonia
• Interstitial 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

Management

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

Mechanical Ventilation Strategies

• Current strategies controversial, with some contending MV adds insult to AE-IPF
• NIV 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 tx 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

• Pulmonary hypertension

Sources

• Bhatti H et al. Approach to acute exacerbation of idiopathic pulmonary fibrosis. Ann Thorac Med. 2013. Vol 8, Issue 2. Pg 71-77.
• Collard HR et al. Acute Exacerbations of Idiopathic Pulmonary Fibrosis. Am J Respir Crit Care Med. 2007 Oct 1; 176(7): 636–643.
• Ryerson CJ et al. Acute exacerbation of idiopathic pulmonary fibrosis: shifting the paradigm. Eur Respir J. 2015 Aug;46(2):512-20.
• Juarez MM et al. Acute exacerbation of idiopathic pulmonary fibrosis—a review of current and novel pharmacotherapies. J Thorac Dis. 2015 Mar; 7(3): 499–519.