A 65-year-old man had 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 ventilation.
You have been asked to review him as he is communicating that he ‘can’t get enough air’ despite ongoing mechanical ventilatory support.
How would you manage this patient who reports being breathless on a ventilator?

 

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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 eg pneumonia, PE, PTX 
Cardiac – ongoing ischaemia, cardiac failure, fluid overload

Neuromuscular – weakness, fatigue 
Sepsis

Metabolic 
Central – increased respiratory drive, pain, agitation

Ventilator factors 
Unsuitable mode

Triggering threshold too high 
Inadequate flow

Prolonged inspiratory time 
Inappropriate cycling

Inadequate pressure support 
Ventilator malfunction

Treatment:

100% O2, suction trachy, 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

Investigations

Basic Investigations – eg ABG, ECG, CXR, cultures 
Further investigations as indicated – eg Echo, CTPA, BNP, Troponin etc

Discussion

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