Lung and chest wall volume during vital capacity manoeuvre in Osteogenesis Imperfecta

Background: Although Osteogenesis Imperfecta (OI) affects the connective tissue, pulmonary function might be compromised because of thoracic deformities. OI is known to be a restrictive lung disease, but spirometry provides global measurement without localizing the site of the restriction. Opto-electronic plethysmography (OEP), is a non-invasive method able to underline altered respiratory function as well as ventilatory thoraco-abdominal paradoxes during spontaneous breathing. We aimed to reconstruct the thoraco-abdominal surface, to perform local analyses of trunk motion and to make quantitative comparison of trunk shape and respiratory kinematics according to OI severity, particularly during maximal inspiratory and expiratory expansions. This is a cross-sectional study where we have studied the thoraco-abdominal compartmental analysis in 26 adult OI patients (14 Type III) at rest and during vital capacity manoeuvre using OEP. We have also applied a new method that created realistic and accurate 3D models to perform local analyses of trunk motion and to make quantitative comparison of trunk shape and respiratory kinematics. Results: Type III patients were characterized by lower spirometric lung volume, by lower sleep quality, by a more compressed thoracic configuration aggravated by severe scoliosis, by reduced global expansion at rest and during maximal maneuvers because of the reduced expansion of the pulmonary ribcage at rest (12% vs. 65% in healthy subjects), during maximal inspiration (37% vs. 69%) and expiration (16% vs. 68%) with local paradoxical movement occurring on the side of the ribcage region. Conclusion: The kinematics of the trunk changed to compensate for the severe structural deformities by shifting the expansion in the abdomen both at rest and during maximal manoeuvre because of a restricted thorax. For the first time, we have quantified and localized the site of the restriction in OI patients in the lateral part of the thorax. The 3D analysis proposed seemed a promising graphical immediate new method for pathophysiology study of chest wall restriction.