A 56-year-old female with idiopathic pulmonary fibrosis (IPF) is transferred to your ICU from a regional hospital having presented with an acute exacerbation and hypoxic respiratory failure. She has been intubated and ventilated, with SP02 88% on a Fi02 1.0.

Outline how you would optimise lung function in this patient.         (50% marks)

Outline the barriers to weaning from mechanical ventilation in this patient.          (50% marks)

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College answer

a) Optimise lung function

  • Look for and treat reversible features e.g. fluid overload, infection, bronchospasm, heart failure
    • Diuretics / fluid limitation
    • Appropriate antimicrobial treatment
    • Bronchodilators
  • Disease modifiers – steroids, immunosuppressants, novel agents e.g. tyrosine kinase inhibitors
  • Pulmonary vasodilators
  • Lung protective strategies and be cautious about high PEEP as the more compliant part of the lungs may be over inflated
  • Involvement of respiratory physicians
    • They may know the patient
    • Advice regarding prognostication
  • V-V ECMO as bridge to transplantation, now being pursued in some centres

b) Outline the barriers to weaning in this patient with IPF?

  • Oxygenation can be significantly impaired – set realistic goals of PaO2 / SpO2
  • Compliance can be severely impaired affecting ventilator synchrony – leading to difficulties in sedation
  • Spontaneous respiratory rate can be high, leading to staff wanting to increase analgesia / sedation
  • Muscle strength can be poor
    • Progressive disease
    • Chronic malnutrition
    • Weakness exacerbated by steroids
    • CIPM
  • Immunosuppression can lead to recurrent infections
  • Pulmonary hypertension can lead to significant CVS dysfunction
  • Patient cognition and emotional status
  • Negative attitudes to a bad prognostic disease

Discussion

As far as "optimise lung function" goes, there are three main domains: try to control the disease process, get some gas exchange happening and control the pulmonary hypertension.

Specific management of the disease process

  • High dose corticosteroids
  • Nintendanib, a a receptor blocker for multiple tyrosine kinases
  • Pirfenidone, a collagen synthesis inhibitor

Manipulation of gas exchange

  • Inhaled pulmonary vasodilators may improve shunt (eg. inhaled prostacycline, inhaled nitric oxide)
  • Mechanical ventilation strategies are largely extrapolated from ARDS management protocols, with some notable differences.
    • Use smaller tidal volumes (like ARDS), 6ml/kg
    • Minimise PEEP (unlike ARDS management): Fernandez et al (2008) found that high PEEP settings failed to improve oxygenation and were associated with worse outcome.
    • Avoid recruitment manoeuvres. IPF patients have minimal recruitable lung, and are vulnerable to overdistension injury.
    • Tolerate hypercapnia; use high respiratory rate
    • Use heavy sedation and neuromuscular junction blockers to improve tolerance of this sort of ventilation strategy
    • There is no evidence to promote the use of prone ventilation
    • Unless the patient is being prepared for a lung transplant, VV ECMO would be a bridge to nowhere and therefore should not be offered. 

Management aimed to control pulmonary hypertension

  • There is a concern that any systemically administered pulmonary vasodilators may worsen shunt. 
  • Sildenafil may improve pulmonary haemodynamics, and does not seem to worsen the shunt (Ghofrani et al, 2002)
  • Endothilin receptor antagonists, eg. bosantan (which might also have some sort of antifibrotic properties) have some role to play in long term management (Minai et al, 2008)

Supportive management

  • Anti-acid therapy for chronic microaspiration
    • The microaspiration of gastric content is viewed as one of the potential triggers of these acute exacerbations. Thus, PPI is indicated.
  • Antimicrobial therapy for any pulmonary infective complications (i.e. there may be a treatable component in all this)

Barriers to weaning:

Due to the disease process

  • Impaired lung mechanics due to restrictive lung disease
  • Increased work of breathing due to hypoxia and respiratory acidosis
  • Concomitant right heart failure due to severe pulonary hypertension

Due to side effects of therapy

  • Corticosteroid-induced myopathy
  • Weakness due to prolonged use of neuromuscular junction blockers

Sequelae of prolonged ICU stay

  • ICU-acquired weakness
  • Malnutrition
  • Residual effect of high-dose sedative medication 

Hilariously, the college has included "negative attitudes to a bad prognostic disease" as one of the barriers to weaning, implying that an intensivists' natural apathetic nihilism will sabotage the process of respiratory recovery. Presumably, a vigorous and positive attitude towards IPF influences survival by virtue of generating fewer palliative care referrals.

References

References

Saydain, Ghulam, et al. "Outcome of patients with idiopathic pulmonary fibrosis admitted to the intensive care unit." American journal of respiratory and critical care medicine 166.6 (2002): 839-842.

Collard, Harold R., et al. "Acute exacerbations of idiopathic pulmonary fibrosis." American journal of respiratory and critical care medicine 176.7 (2007): 636-643.

Liang, Zhan, et al. "Referral to Palliative Care Infrequent in Patients with Idiopathic Pulmonary Fibrosis Admitted to an Intensive Care Unit.Journal of palliative medicine 20.2 (2017): 134-140.

Moran, J. L., and P. Rangappa. "Outcomes of patients admitted to the intensive care unit with idiopathic pulmonary fibrosis." Critical Care and Resuscitation 11.2 (2009): 102.

Raghu, Ganesh, et al. "An official ATS/ERS/JRS/ALAT statement: idiopathic pulmonary fibrosis: evidence-based guidelines for diagnosis and management." American journal of respiratory and critical care medicine 183.6 (2011): 788-824.

Ghofrani, Hossein Ardeschir, et al. "Sildenafil for treatment of lung fibrosis and pulmonary hypertension: a randomised controlled trial." The Lancet 360.9337 (2002): 895-900.

Minai, Omar A., et al. "Vaso-active therapy can improve 6-min walk distance in patients with pulmonary hypertension and fibrotic interstitial lung disease." Respiratory medicine 102.7 (2008): 1015-1020.

Fernández-Pérez, Evans R., et al. "Ventilator settings and outcome of respiratory failure in chronic interstitial lung disease." CHEST Journal 133.5 (2008): 1113-1119.

Juarez, Maya M., et al. "Acute exacerbation of idiopathic pulmonary fibrosis—a review of current and novel pharmacotherapies.Journal of thoracic disease 7.3 (2015): 499-519.