Question 8

College answer

Introductory statement

• Recruitment maneuvers are ventilator manipulations to improve oxygenation in moderate to severe ARDS. Often used as part of an open lung strategy.

 Rationale

• In ARDS, collapsed/consolidated alveoli are unable to take part in gas exchange. In addition, the recurrent opening and closing of units can contribute to atelectrauma.
• Recruitment maneuver is a temporary increase in pulmonary pressures to open collapsed alveoli. Subsequent PEEP titration aims to prevent cyclical opening/closing of these units. 

 Advantages

• May lead to improved oxygenation, compliance and markers of inflammation (decreased). Cheap, Simple, quick c.f. ECMO, iNO

 Disadvantages

• Need for sedation/paralysis
• Transient oxygenation response
• Risk barotrauma
• VILI
• Worsening of shunt
• Cardiovascular instability
• No consensus on how they should be performed.

 Evidence

• Studies in mod – severe ARDS, including a Meta-analysis have failed to demonstrate patient-centred outcome benefit. Trials generally of poor quality, high risk of bias.
• Latest trial ART: showed increased 6/12 mortality, barotrauma and length of mechanical ventilation in group undergoing RMs cf no RMs (and there were 3 cardiac arrests during RMs). Considered a large well designed trial, potential weaknesses include inability to blind and the use of stepwise PEEP recruitment.
• PHARLAP – another large trial examining this issue has now ceased recruitment in the light of the ART results.

Own practice

Anything reasonable here including “I do not perform recruitment maneuvers”

If a candidate was unaware of the ART trial and described a routine use of Recruitment Maneuvers they were should be marked down at the examiners discretion.

 Examiners Comments:

 This question was overall answered well by many candidates. A logical explanation of the rationale for recruitment and its benefits as well as possible harm along with a mention of recent literature was required to score marks. Good candidates understood that although oxygenation may improve with recruitment maneuvers mortality benefit was not demonstrated in any trials. The risk of possible harm from the ART study as well PHARLAP ceasing recruitment due to this was noted by some candidates.

Discussion

Introduction/definition

• A recruitment manoeuvre is any technique that transiently increases alveolar pressure above normal tidal ventilation, and sustains that pressure beyond the normal inspiratory time (Hodgson et al, 2016)

Rationale for the use of recruitment manoeuvres

• ARDS is characterised by heterogeneity of lung disease (Gattinoni & Pesenti, 2006)
• Some areas of lungs may be collapsed/atelectatic and not be participating in gas exchange
• These regions may be reinflated by the application of enough positive transpulmonary pressure
• If these regions can subsequently be kept inflated by an open-lung (high PEEP) strategy, an improvement in gas exchange should result
• An improvement in gas exchange should decrease hypoxia, produce a decrease in the required FiO₂, and therefore decrease oxygen toxicity and organ dysfunction due to hypoxia and hypercapnea.  

Advantages of recruitment manoeuvres

• They are easy to perform (all you need is a ventilator)
• Compared to other techniques of improving oxygenation, this is the cheapest (followed by prone position). Other techniques either require expensive consumables (inhaled nitric oxide, prostacycline) or equipment (high frequency oscillation, ECMO).
• There is a range of different manoeuvres in the literature, which means one is not restricted to one technique. It is possible to tailor the therapy to the patient and vary the technique depending on the degree of atelectasis, haemodynamic performance and expected friability of the lungs.
• Oxygenation may improve. This is the one thing which is consistently demonstrated by all the studies, including those which did not find any beneficial effect on mortality.
• The patient with ARDS will usually already be paralysed and sedated, i.e. it is not inconvenient to sedate and paralyse them just for this procedure
• In the prone position, recruitment manoeuvres are more effective.

Disadvantages of recruitment manoeuvres

• Nobody can agree on how much pressure to use, or for how long (i.e. the fact that there is a range of techniques is a mixed blessing)
• They may not be appropriate in all conditions, eg. the classically fragile lung in PJP pneumonia
• If the patient has already had a pneumothorax, obviously it will get worse 

Possible complications

• Barotrauma and ventilator-induced lung injury
  • Pneumothorax
  • Subcutaneous emphysema
  • Pneumomediastinum
  • ​​​​​​Cyclic atelectasis (i.e. with repeated recruitment manoeuvres, after each the reinflated lung may just collapse again)
  • The pressure will first be selectively distributed to well-aerated lung, potentially damaging those alveoli which were previously performing well as gas exchange units. After such an assault, these lung units may have impaired gas exchange. 
• Poor or unexpectedly opposite effect on oxygenation:
  • The recruitment manoeuvre may be ineffective because the pressure used may be insufficient, and a sufficient pressure may be comically excessive. 
  • The effect on oxygenation is only transient: 
  • The effect of increasing pressure may produce worsening shunt (i.e. instead of recruiting the collapsed lung regions, you push more blood flow into them, increasing the shunt fraction and therefore degrading oxygenation).
• Haemodynamic effects
  • Because of increased intrathoracic pressure, RV afterload increases and RV preload decreases. The consequence of this is a decrease in cardiac output. In the critically ill patient, this will manifest as a marked fall in blood pressure
  • A cytokine/endotoxin shower may be produced by the shunt. The blood shunted through diseased lung will incrrease the systemic delivery of bacterial toxin and cytokines, contributing to haemodynamic instability which may be sustained even after the manoeuvre is completed.

Evidence for and against recruitment manoeuvres

• Experimental animal models have demonstrated improved lung mechanics and gas exchange (summarised by Moran et al, 2003), which encouraged human studies
• Small-scale trials have demonstrated benefits in specific patient categories and scenarios, but this evidence has been inconsistent and patchy. For example, post-suctioning recruitment manoeuvres work really well in pigs (Kasim et al, 2009) but not in human children (Morrow et al, 2007)
• The 2016 Cochrane review by Hodgson et al found that only low-quality evidence supported the use of recruitment manoeuvres, in terms of improved ICU mortality (but not hospital mortality). In total, data from 1658 trial participants were compiled.
• The ART trial (Cavalcanti et al, 2017) enrolled 1010 patients and found an increased 28-day all-cause mortality associated with recruitment manoeuvres to 50-60 cmH₂O. ​​​​​​​
• The PHARLAP trial (Hodson et al, 2019) was stopped early because the steering committee lost equipoise following the publication of ART. What data they managed to collect did not suggest any improvement in patient-centred outcomes.