Question 7

Created on Fri, 05/29/2015 - 01:13
Last updated on Thu, 10/01/2015 - 03:13
Pass rate: 66%
Highest mark: ?

Other SAQs in this paper

Other SAQs on this topic

Examine this flow time curve generated from a mechanically ventilated patient.

What pathological process is revealed by this flow time trace?

b)  List 4 other features (both clinical and adjunctive tests) may support the diagnosis of this pathological process?

c)  List 2 therapeutic measures you will undertake on observing this phenomenon.

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College Answer

What pathological process is revealed by this flow time trace?

- The trace reveals the commencement of inspiration before expiratory flow returns to zero, thus setting the scene for dynamic hyperinflation/ small airway obstruction. (Importantly, the trace does not reveal Auto-PEEP as that is a pressure measurement performed after an expiratory pause)

b)  List 4 other features (both clinical and adjunctive tests) may support the diagnosis of this pathological process?

  • Clinical: On auscultation, commencement of inspiration before end of expiration
  • Evidence of obstructive lung disease, the typical scenario in which this happens
  • Increased Auto PEEP
  • Increased Plateau pressure
  • Ventilator settings such as short exp time f) VEI > 20 ml /Kg

c)  List 2 therapeutic measures you will undertake on observing this phenomenon.

  •  Bronchodilators
  •  Increase exp time

Discussion

This is another in the long line of questions which ask the candiate to interrogate the flow/time waveform and make the diagnosis of airflow limitation.

Yes, yet again the flow curve fails to return to zero, demonstrating incomplete emptying and possibly gas trapping.

Again, 4 features of this are asked for. One could produce many more.

  • wheeze
  • prolonged expiratory phase
  • increased chest distension
  • decreased chest expansion
  • bilaterally decreased air entry
  • increased autoPEEP in the expiratory hold manoeuvre
  • increased peak airway pressures
  • increased plateau pressures
  • short expiratory time setting on the ventilator

Again, suggestions for management are asked for.

Apart from adjusting the ventilation (decreasing the I:E ratio and respiratory rate) one may consider using bronchodilators and steroids.