The following ventilator waveforms shown below (Figure 2) are from a patient who is sedated, paralysed and ventilated in a pressure regulated volume control mode (pressure control mode with a target tidal volume). The patient has a history of bronchiectasis.

PRVC - bronchiectasis with secretions

Give the most likely cause for the abnormal oscillations in the waveforms .           (10% marks)

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College answer

Secretions in ETT or fluid in circuit.

Discussion

The college image was somewhat unlike the one I have presented here; their oscillations were much more impressive. Some of the settings on the ventilator were also different, and flow/pressure/volume loops were available (showing the exact same oscillations)  However, none of that really does much to change the interpretation of this SAQ. Like a very similar SAQ from long ago (Question 5.1 from the first paper of 2012) this one tends to have only two main interpretations: either it is pus bubbling in the patient's lungs, or this is water "rain-out" collecting in the circuit.

References

References

Correger, E., et al. "Interpretation of ventilator curves in patients with acute respiratory failure." Medicina Intensiva (English Edition) 36.4 (2012): 294-306.