Question 13

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.