Weaning from mechanical ventilation has appeared in Question 1c from the second paper of 2000, Question 1d from the first paper of 2001 and Question 1d from the first paper of 2000. Though this is a frequently examined topic in the vivas and hot cases, which makes it more surprising that it has not come up more often in the written exam. A more recent Question 24 from the second paper of 2014 also touches upon the topic of the various indices of extubation readiness, and discussed elective extubation on to NIV.
The rapid shallow breathing index, the spontaneous breathing trial and the various bedside tests to assess readiness for extubation are explored in greater detail in the chapter on the assessment of extubation readiness. This chapter is more about the techniques one may use to bring the patient closer to this assessment, and to ensure they satisfy those criteria.
Some of the best resources for this broad topic include the following:
- Less limited and biased by human decision-making than physician-directed weaning
- Developed based on best evidence; less influenced by personal or local opinion
- Efficacy and safety supported by numerous clinical investigations
- Can make up for limitations in local resources or staff availability
- Free physicians to perform other duties in the ICU
- Facilitate quality monitoring and improvement
- Can be the basis of a systematic approach to learning
- Enhance transparency and communication
- Flexible and adaptive to the needs of individual patients
- Can lead to innovative changes in practice
- Equivalent to weaning protocols in some studies, especially in ICUs with high staffing levels
- Promotes education and leads to highly skilled practitioners
- Does not require the additional resources needed to design, implement, and sustain weaning protocol use
- Avoids institution-wide acceptance of a treatment strategy before best evidence is available
Again, the LITFL entry on this topic does it justice. "Weaning failure" is defined as failure to pass a spontaneous breathing trial, or the need for reintubation within 48 hours.
There are some definitions for the degree of weaning difficulty:
Simple wean: extubated on the first SBT
Difficult wean: Up to 3 SBTs, or up to 7 days
Prolonged wean: longer than 7 days
These classifications were defined by the International Concensus Conference in 2005 (Boles et al, 2007) on the basis of outcomes data. "Simple wean" patients represent 69% of the ventilated population, and have low mortality (ICU mortality 5%, hospital mortality 12%). The rest have 25% mortality.
Causes of difficult weaning weaning failure can be summarised as a table. The one below is based extensively on the article by Boles et al (2007). A super-keen exam candidate may attempt to come up with another hundred or so causes, but the list offered here may already be on the long side, and certainly beyond the needs of a ten minute CICM SAQ answer.
Increased work of breathing
Table 2 from the McConville paper lists the risk factors for unsuccessful extubation:
One may view these strategies as answers to the questions posed by the causes of difficult weaning. The same table again can be turned to this purpose:
Reduce the work of breathing
|Musculoskeletal and mechanical causes||
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