Procedure
Anthropometric data included age, gender, height, weight and BMI.
Further, thorax circumference (measured horizontally at the xiphoid
process) was also calculated at maximum inspiration and expiration in
standing position with 90º of arms abduction17.
For ultrasound imaging, participants were in prone with their arms in
abduction of 90º and elbows flexed. The assessment point was selected
following the procedure as described by Folli et al.12which has been found to be highly reliable. Firstly, the spinous process
and the inferior angle of the scapula was identified by manual
palpation, and the half distance between these points was calculated.
Second, a horizontal projection was traced medially to the spinous
process of the thoracic spine. The transducer was therefore placed in
the middle-distance between these points (Fig. 1 ).
The following distances skin to pleura, skin to the lowest limit of
major rhomboid, and lowest limit of major rhomboid to pleura were
calculated by using an ultrasound equipment Alpinion Ecube 8
(Gyeonggi-do, Korea) with a linear transducer E8-PB-L3-12T 3-12 MHz
(Fig. 2 ). The mean of three repeated trials performed by the
same clinician with more than 10 years of experience using ultrasound
imaging was calculated for the main analysis at two moments, maximum
inspiration and maximum expiration.