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.
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?
c) List 2 therapeutic measures you will undertake on observing this phenomenon.
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.
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.
Milic-Emili, J. "Dynamic pulmonary hyperinflation and intrinsic PEEP: consequences and management in patients with chronic obstructive pulmonary disease." Recenti progressi in medicina 81.11 (1990): 733-737.