The "ruler sign"--a semiquantitative physical sign of chronic obstructive pulmonary disease.

This report describes a simple and reproducible physical sign of chronic obstructive pulmonary disease--the "ruler sign." With the patient standing erect, a ruler is placed on the trapezius muscle and the clavicle at the midclavicular line. The ruler forms an angle with the horizontal line. At the end of a normal expiration this angle was 36 degrees +/- 4 SD in healthy control subjects as compared with 15 degrees +/- 4 SD in patients with severe chronic obstructive pulmonary disease. A simple device is described that enables convenient measurement of this angle at the bedside.