This comes up a lot, being a part of the the bread and butter routine of ICU management. SAQs which have required the analysis of ventilator waveforms include the following:
In short, its a popular topic. Usually the curves are those of a patient with high airway resistance, auto-PEEP and gas trapping; the college expect you to be able to identify this and make some comment as to how you would change the ventilator settings to improve the situation. Alternatively, the college might ask you to draw and label a diagram of a pressure-time curve for a patient with normal airways and a patient with bronchospasm. Either way, it seems bronchospasm is the major focus of these questions.
This is a brief summary, and will not go into great depth. Local long-form discussions of these matters include the following chapters:
This waveform graphic is seen in Question 21.1 from the first paper of 2014. Obviously, its not the college's own graphic (though they did use some of their own artwork in Question 26.1 from the second paper of 2008).
The candidate should be able to both identify the major features which are characteristic of bronchospasm, and to reproduce them on paper.
Specific features of increased airway resistance seen here are:
After asking questions about waveform interpretation, the college typically goes on to ask further about what precisely one would do to manage such a problem. The answer typically revolves around increasing the I:E ratio, decreasing the respiratory rate, dropping the PEEP to zero, and so forth. This topic is explored in greater detail by the chapter on Intrinsic PEEP and dynamic hyperinflation.
Even though one's instincts might be strongly trending towards bronchospasm as the cause of such a picture, one must systematically consider all possible causes:
Correger, E., et al. "Interpretation of ventilator curves in patients with acute respiratory failure." Medicina Intensiva (English Edition) 36.4 (2012): 294-306.