Question 23

A 65-year-old male is in ICU following an out of hospital cardiac arrest secondary to a large anterior ST elevation myocardial infarction. His ICU stay has been complicated by aspiration pneumonia. He is now day 14 from admission, with a tracheostomy in situ, and has started weaning from the ventilator.

You have been asked to review him as he is communicating that he 'can't get enough air' despite on-going mechanical ventilatory support.

Outline your approach to this problem.

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College answer

Urgent attention to A, B, C – Give 100% oxygen and exclude/treat immediate threats to life. 
Focused history and examination considering differential diagnoses: 
Patient factors 
Airway / trache – blocked, displaced or too small diameter 
Respiratory e.g. pneumonia, PE, PTX 
Cardiac – ongoing ischaemia, cardiac failure, fluid overload 
Neuromuscular – weakness, fatigue 
Central – increased respiratory drive, pain, agitation 
Ventilator factors 
Unsuitable mode 
Triggering threshold too high 
Inspiratory flow rate too low 
Prolonged inspiratory time 
Inappropriate cycling 
Inadequate pressure support 
Inadequately set tidal volume 
Ventilator malfunction 
100% O2, suction trache, exclude obstruction/malposition, end tidal CO2 etc. 
Assess ventilation 
Mode, respiratory rate and pattern 
Spontaneous and delivered TV / MV / airway pressures 
Expiratory flow-time curve, PEEPi (if possible) 
Titrated pain relief  
May need to carefully sedate to gain control of the situation if he is very distressed and agitated. Rarely need to paralyse after sedation 
Basic Investigations – e.g. ABG, ECG, CXR, cultures 
Further investigations as indicated – e.g. Echo, CTPA, BNP, Troponin etc.  
Management of underlying cause: 
Change trache if indicated 
Consider change ventilator settings or mode  
Increase pressure support etc 
ACV Vs SIMV Vs BiLevel 
An acceptable answer included the following elements: 
Address causes of dyssynchrony 
     Patient factors 
     Ventilator factors 
Approach to management 

Additional Examiners‟ Comments: 
Most candidates put together a reasonable answer. Some treated it only as a blocked airway question. Many were not well organised for such a common and important clinical question that has been asked previously. Few candidates thought broadly. 



Apart from slightly different wording, this question closely resembles Question 4 from the second paper of 2012. The discussion section from that question is therefore reporduced below, with minimal modification.

This question lends itself well to a systematic approach.

  • Immediate management:
    • Increase the FiO2 to 100%
    • consider disconnecting the patient from the ventilator, and manually bag-ventilating them
    • Simultaneously assess and manage threates to life in a systematic manner:
  • Airway
    • machine factors:
      • check for condensation in the ventilator tubing
      • change HME and ventilator filter
    • patient factors:
      • check tracheostomy diameter (too narrow?)
      • check inner cannula (encrusted with inspissated secretions?)
      • check tracheostomy patency (blocked with secretions?)
      • Check tracheostomy position (dislodged during last turn?)
      • suction the patient, loking for fresh blood and clots (unrecognised pulmonary haemorrhage?)
  • Breathing
    • machine factors
      • Check for ventilator malfunction
      • Look for patient-ventilator dyssynchrony and adjust the settings accordingly;
        • is the trigger insufficiently sensitive, or over-sensitive?
        • is the tidal volume and inspiratory flow sufficient to satisfy patient demand?
        • Is the mode inappropriately mandatory?
    • patient factors
      • Assess lung compliance by observing ventilator peak pressures, or qualitatively by manually bag-ventilating the patient
      • Examine the patient and organise an ABG and chest Xray, looking for evidence of...
        • bronchospasm
        • pneumothorax
        • pulmonary oedema
        • impaired gas exchange
          • consider a CTPA if an unexplained A-a gradient has been discovered
        • metabolic acidosis, driving respiratory effort
        • cardiac dysfunction, eg. MI or new arrhythmia
  • Circulation
    • Organise an ECG and bedside TTE, looking for evidence of
      • MI
      • Pulmonary oedema
      • arrhythmia
      • new onset of heart failure
      • evidence of right heart strain
  • Neurology
    • look for muscle weakness or new neurological deficit
    • Look for evidence of poorly controlled pain driving the respiratory effort
    • Assess for delirium and agitation as the primary driver of increased respiratory effort


Jairo I. Santanilla "The Crashing Ventilated Patient"; Chapter 3 in Emergency Department Resuscitation of the Critically Ill, American College of Emergency Physicians, 2011.