15 May 2012

The spitting image

The two images on the left are from one of my textbooks. They are theoretical readouts from a spirometer, a simple yet important machine that measures how quickly air flows in and out of the lungs while the patient takes the deepest breath they can. At top left is a hypothetical normal patient; at bottom left is a hypothetical patient with obstructive lung disease (a common outcome of cigarette smoking). The diseased lungs are especially bad at exhalation.

Now for the part that fascinated me. Look at the readout on the right, from a patient in clinic today. Then look at the image at bottom left. Compare the outlines of both, as well as where the outlines reside on the x- and y-axes (you can ignore the noisy lines inside). Even without knowing a thing about pulmonology, you can see that they're virtually identical.

Even though each person is complex and unique, diseases can be consistent and predictable in the way they present. Today's case was one of these "textbook" examples.