3D visualization of the chest and abdomen surface in static condition is a simple and
inexpensive solution to measure regional volume changes between two static respiratory volume
positions. Five seconds of apnea is necessary for visualizing the thoraco-abdominal surface.
If the two positions visualized correspond to the functional residual capacity (FRC) and the
total lung capacity (TLC) the volume difference is inspiratory capacity (IC) which depends to
the inspiratory muscles activation. This IC can be split in different thoraco-abdominal
compartments and in supine position the abdominal contribution of this IC volume appreciates
non-invasively diaphragmatic function. In addition asymmetry between right and left sides can
appreciate unilateral diaphragmatic.
The aim of this study is first to validate an IC measurement using analysis of two 3D
acquisitions, and to appreciate the inter-observer variability of this IC measurement between
a trained technician of respiratory function analysis and a trained pulmonologist.
Accordingly, patients addressed for suspicion of diaphragmatic dysfunction, and able to
maintain 5 sec of apnea in supine position will be proposed, by using the informed consent
process, to participate to this study which consisted to beneficiate to a 3D trunk
visualization at FRC and TLC during a spirometric IC measurement in supine position.
Thoraco-abdominal volume difference between the two positions (FRC and TLC) will be
calculated to obtain a 3D-IC volume. Then a Bland-Altman comparison will be done between the
3D-IC volumes measured and calculated by the two different observers (technician and
pulmonologist), and the spirometric-IC volume considered as the reference. The Bland-Altman
average discrepancies (the bias) and to the wide of the limits of agreement obtained will
allow to select the best observer between the technician and the pulmonologist.
After the validation of the 3D-IC measurement against spirometry (difference > 10%), and
after having confirmed that this analysis can be performed in routine by a pulmonary function
technician, the next step will be to validate that the decrease of abdominal contribution of
3D-IC is an non-invasive index of diaphragmatic dysfunction. Accordingly, a linear regression
analysis will be used in this study between the abdominal contribution to 3D-IC and the other
parameters issued from exams prescribed by the clinician to confirm and evaluate
diaphragmatic dysfunction. These other parameters are usually the fall of CV in supine
position and/or a decrease of transdiaphragmatic pressure (Pdi) measurement by estimating the
difference between oesophageal pressure (Peso) (intrathoracic pressure) and gastric pressure
(Pga) (intra-abdominal pressure), [Pdi=Pga-Peso]. Pdi can be obtained during maximal
voluntary efforts (the most frequent being the sniff test (Sniff Pdi)) or by using
non-volitional test such as magnetic stimulation of the phrenic nerves (Twitch Pdi).
