Measuring chest expansion; A study comparing two different instructions

Abstract The aim of this study was to examine and compare the effect of two alternative instructions when measuring chest expansion. In 100 healthy subjects, chest expansion was measured using a circumference tape. In 30 healthy subjects, chest expansion was measured by a Respiratory Movement Measuring Instrument (RMMI). Both measurements were made at the level of the fourth rib and the xiphoid process. The two instructions evaluated were the traditional one: “breathe in maximally” and “breathe out maximally”, which were compared with a new one “breathe in maximally and make yourself as big as possible” and “breathe out maximally and make yourself as small as possible”. The addition of “make yourself as big/small as possible” in the new instruction resulted in a significantly increased thoracic excusion, 1.4 cm in upper and 0.9 cm in lower level of thorax, measured by tape, compared with the traditional instruction (p < 0.001). Measurements obtained using the RMMI also showed a significant difference, 2.3 mm in upper and 4.1 mm in lower level of thorax, between the two instructions in favour of the new instruction (p < 0.05). The verbal instruction during measurement of chest expansion is of importance when measured by tape and RMMI. To assess the maximal range of motion in the chest, the patient should be instructed not only to “breathe in/out maximally”, but also instructed to “make yourself as big/small as possible”.