Understanding basic pathophysiological principles underpins the practice of many healthcare workers, particularly in a critical care setting. Undergraduate curricula have the potential to separate physiology teaching from clinical contexts, making understanding difficult. We therefore assessed the use of analogous imagery as an aid to understanding. Two groups of first year physiotherapy students were randomly assigned to receive either a control lecture (oxygen delivery and hypoxaemia) or a study lecture (control lecture plus images of a train set delivering rocks: an analogy to oxygen delivery.) Qualitative assessment of the lectures showed a significant (p < 0.001) improvement in understanding by the study group, and increased the proportion of students that found the lecture 'interesting and stimulating' (p = 0.01). Quantitative assessment demonstrated a significant increase in the multiple choice questionnaire marks of the study group (p = 0.03). In conclusion, analogous imagery can significantly increase the understanding of this physiological concept.