title: Rib cage deformities alter respiratory muscle action and chest wall function in patients with severe osteogenesis imperfecta.
abstract: BACKGROUND
  Osteogenesis imperfecta (OI) is an inherited connective tissue disorder characterized by bone fragility, multiple fractures and significant chest wall deformities. Cardiopulmonary insufficiency is the leading cause of death in these patients.
  
  
  METHODS
  Seven patients with severe OI type III, 15 with moderate OI type IV and 26 healthy subjects were studied. In addition to standard spirometry, rib cage geometry, breathing pattern and regional chest wall volume changes at rest in seated and supine position were assessed by opto-electronic plethysmography to investigate if structural modifications of the rib cage in OI have consequences on ventilatory pattern. One-way or two-way analysis of variance was performed to compare the results between the three groups and the two postures.
  
  
  RESULTS
  Both OI type III and IV patients showed reduced FVC and FEV(1) compared to predicted values, on condition that updated reference equations are considered. In both positions, ventilation was lower in OI patients than control because of lower tidal volume (p<0.01). In contrast to OI type IV patients, whose chest wall geometry and function was normal, OI type III patients were characterized by reduced (p<0.01) angle at the sternum (pectus carinatum), paradoxical inspiratory inward motion of the pulmonary rib cage, significant thoraco-abdominal asynchronies and rib cage distortions in supine position (p<0.001).
  
  
  CONCLUSIONS
  In conclusion, the restrictive respiratory pattern of Osteogenesis Imperfecta is closely related to the severity of the disease and to the sternal deformities. Pectus carinatum characterizes OI type III patients and alters respiratory muscles coordination, leading to chest wall and rib cage distortions and an inefficient ventilator pattern. OI type IV is characterized by lower alterations in the respiratory function. These findings suggest that functional assessment and treatment of OI should be differentiated in these two forms of the disease.
authors.affiliation: TBMLab, Dipartimento di Bioingegneria, Politecnico di Milano, Milano, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: LoMauro
authors.forename: Simona
authors.initials: S
authors.lastname: Pochintesta
authors.forename: Marianna
authors.initials: M
authors.lastname: Romei
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: D'Angelo
authors.forename: Antonio
authors.initials: A
authors.lastname: Pedotti
authors.forename: Anna Carla
authors.initials: AC
authors.lastname: Turconi
authors.forename: Andrea
authors.initials: A
authors.lastname: Aliverti
mesh_terms: D000293:Adolescent; D000328:Adult; D000886:Anthropometry; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008297:Male; D009929:Organ Size; D010013:Osteogenesis Imperfecta / Q000473:pathology / Q000503:physiopathology*; D015656:Respiratory Mechanics / Q000502:physiology*; D012132:Respiratory Muscles / Q000098:blood supply / Q000473:pathology / Q000503:physiopathology*; D012272:Ribs / Q000002:abnormalities* / Q000473:pathology / Q000503:physiopathology*; D016683:Supine Position / Q000502:physiology; D035441:Thoracic Wall / Q000473:pathology / Q000503:physiopathology*; D013990:Tidal Volume / Q000502:physiology; D055815:Young Adult