This condition had appeared in Question 13 from the first paper of 2017, in the form of a 56 year old woman dying of hypoxic respiratory failure. Optimise her lung function, the college beckoned to the candidates. And discuss the barriers to weaning.
A brief introduction to this disease is offered by Collard et al (2007), as a review article on acute exacerbations. The authors described acute exacerbations as "clinically significant deteriorations of unidentifiable cause". Generally speaking, this disease is hideous. Median survival from the time of diagnosis is approximately 3 years. Earlier this century the actual ICU and hospital mortality rates for acute exacerbations were 45% and 61%, respectively (Saydain et al, 2002).
For answering management questions, there is probably nothing better than the American Thoracic Society Guidelines (Raghu et al, 2011). Together with the UpToDate page on this topic, these guidelines were summarised into the brief SAQ answer below.
There is not much out there on ICU-specific management of these patients. Juarez et al (2015) had a good article on pharmacotherapy, but it seems to be better suited to an audience who run respiratory outpatient clinics. Whenever one searches for an article to guide the approach to ventilation, one finds a hald dozen articles describing the futility of such ventilation. The only useful contribution was from Fernandez et al (2008), who retrospectively analysed a cohort of 94 mechanically ventilated IPF patients to see what worked and what didn't.
Management of idiopathic pulmonary fibrosis in the ICU
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 hyperapnia; 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)
- 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)
- Consider the possibility that lung transplantation will be required - explore options for referral to a centre where such a thing could be offered.
- Consider that the patient will probably die. In one study, Rangappa and Moran (2009) found that the median survival after an ICU admission is 16 days, and mortality for mechanically ventilated patients was 96%.
- Refer the patient to palliative care. This is not an end-of-life step: palliative measures to control dyspnoea symptoms are greatly appreciated by patients at all stages of the disease spectrum. According to a recent article by Zhang et al (2017), many end up dying in the ICU before their third respiratory clinic visit, so an early palliative care referral is crucial.
Barriers to weaning in an IPF patient
This is specifically to answer Question 13 from the first paper of 2017.
Barriers 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
Barriers 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
- Residual effect of high-dose sedative medication