These are the notes Dr David Popple (ITU Consultant), took during the Updates in Respiratory Critical Care Meeting at the RCOA back in November. I merely took them, expanded them and added links etc. Thanks to him for providing these. Update in renal replacement coming too. So…onward, what’s new then?
Identifying and managing ventilator asynchrony
- Approx 1/3 of ICU pts affected.
- If the patient is asynchronous, adjust the vent rather than sedation.
- If >10% breaths are asynchronous, this increases duration of ventilation, mortality and number of tracheostomies.
Types of asynchrony:
- Too much ASB causing periodic breathing
- Too little ASB causing over-work
- Trigger asynchrony – most commonly due to iPEEP (pt can’t exceed this to trigger), trigger may be set too high…compounded by neuromuscular weakness.
- Treat by reducing trigger, reduce ASB (reduces insp. time and increases exp. time, hence reducing iPEEP), reduce sedation, increase PEEP to meet iPEEP.
- Double triggering with a large inspiratory effort is a sign of pt still inspiring when vent has moved to exp phase.
- Auto triggering
- When trigger on vent is too sensitive
- Flow asynchrony – flow mismatch. i.e. inadequate PS which increases WOB.
- Treat by increasing PS.
- Cycling asynchrony
- Inspiration cycles ‘off’ when flow reduced to 25% of max during expiration.
- Can adjust this to when flow = 10% exp. flow etc.
- Early flow change on the graph is often a marker of premature exp. triggering
Weaning from mechanical ventilation
- Around 10% of patients will experience difficulty in weaning and will spend on average >28 days on vent.
- 25% of them will need home NIV!
Approach to patient looking for cause
- Is it CNS (trigger)?
- Do neuro exam +/- imaging
- Is it neuromuscular (transmission)
- do neuro exam +/- imaging and Nerve Conduction Studies (hyper-reflexia and muscle wasting is most often MND)
- Is it Respiratory
- Is it cardiac (pump)
- Muscle weakness occurs early and fast.
- Diaphragm wastes 2x as frequently as periph muscles.
- Both muscle and diaphragm wasting predict poor outcome.
- Wasting is worse in MOF than single organ failure.
- Pts with poor premorbid condition (i.e. LVF/COPD), take much longer to rehabilitate
- Sometimes, especially in elderly with chronic disease, need to stop wean and rehabilitate, then weaning tends to happen on its own.
- Physio’s are the key!
- We should focus more on number of sitting to standing / distance walked per day, rather than arbitrary weaning 1cmH2O/day!
The ICS 2007 Weaning Guidelines
See this weaning review here.
Hypercapnoeic respiratory failure
- High CO2 in ARDS is associated with higher mortality, higher CVS failure, higher renal failure rate.
- No RCTs have examined this.
- Noted from observational studies with attempts to control for confounding variables
Approach to hypercapnoea on PCV:
- Do insp hold to determine plateau pressure and adjust vent pressure to achieve VT around this pressure, (as per Dixiegraph below)
- Do Exp hold to determine iPEEP (total PEEP) with vent set to zero end exp. pressure
- Try adding vent PEEP and reassess iPEEP to see if it remains the same or improves.
- Keep vent PEEP at it’s highest level possible so as not to increase total PEEP. (Improves V/Q matching and CO2 removal).
- Adjust RR so there is zero flow at end of expiration.
- Avoid increasing frequency to the point where it encroaches on higher flow section of flow time loop!
- Adjust Ti to achieve sub max VT.
Is it ARDS?
See our section here on big papers in ARDS.
- Pts often labelled as ARDS, when the likelihood is that it’s severe pneumonia.
- Be suspicious when there is single organ failure, a prodromal illness and haemoptysis
Interstitial Lung Disease
- Difficult with this in the background, as minimal infection on top will give a picture of ALI.
- Diffuse alveolar haemorrhage often do better on ECMO
- Look at eosinophils – normally low in critically ill.
- Acute eosinophilic pneumonia often present with normal eosinophils and all symptoms and signs of CAP.
- Can be precipitated by smoking.
- Later eosinophils go up and need pulsed methyl-pred / other immunosuppression.
- Early liaison with Rheumatology/resp.
NIV post NCEPOD
- New guidance published 2017
- Found very poor care for NIV pts nationally.
- Most pts on NIV in UK very frail (Rockwood frailty index)
- Should be started when pH 7.3-7.35
- Should not be used in all pts
- 54% pts deemed inappropriate.
- Associated mortality 35%
FOB in the critically ill
- Little new except increasing use of DNAse for clearing thick airway secretions (no evidence in adult ICU, but there may be in paeds post cardiac surgery).
- Need to have endobronchial blockers on standby, in case of pulm. haemorrhage from bronchoscopy in high risk bleed cases.
- Little new
- If B lines/lung sliding seen – no pneumo
- To diagnose a pneumo, need absence of sliding and to see lung point (point below which you see lung sliding and above none).
- Don’t view as diagnostic tool, but clinical aid like stethoscope.
See our Section here
Submassive PE – Thrombolysis is the treatment of choice?
- Mostly same as new guidelines
- General move to use ½ dose thrombolysis for anything less than very near death PE.
- Suggested use PESI to risk stratify – if high risk mod PE, should come to ICU.
- Then can observe whilst anticoagulating and thrombolyse early if deteriorates.
- Suggested use of UFH in this group, as able to stop this to thrombolyse, but not very logical as time to reverse anticoag effect 4-6 hours and T1/2 of Alteplase is 4-5 mins, so not reversed by time thrombolysis finished.
- Also, often pts subtherapeutically anticoag with UFH, so not getting benefit and probably more likely to deteriorate and need tPA!
- Therefore reserve UFH for AKI/liver dysfunction.
- Not much support for thrombolysis in submassive PEs, as numbers needed to harm (major or intracranial bleed) worse than NNT.
- Use of catheter guided thrombolysis not proven yet.
- Reserved for centres with experience and adequate interventional radiology cover to support it and saved for cases with high bleeding risk. Not for Us at NGH!
- Newer options for I.R. include ultrasonic clot disruption and hydrodistruction. Not yet studied properly.
- New study starting to look at ½ dose rtPA for PEs to look more at this.
What we said about it all
Notes by: Dr David Popple (ITU Consultant)
Edited by: Dr Jonny Wilkinson
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