title: Respiratory muscle decline in Duchenne muscular dystrophy.
abstract: OBJECTIVE
  Duchenne muscular dystrophy (DMD) causes progressive respiratory muscle weakness. The aim of the study was to analyze the trend of a large number of respiratory parameters to gain further information on the course of the disease.
  
  
  METHODS
  Retrospective study.
  
  
  METHODS
  48 boys with DMD, age range between 6 and 19 year old, who were followed in our multidisciplinary neuromuscular clinic between 2001 and 2011.
  
  
  METHODS
  Lung function, blood gases, respiratory mechanics, and muscle strength were measured during routine follow-up over a 10-year period. Only data from patients with at least two measurements were retained.
  
  
  RESULTS
  The data of 28 patients were considered for analysis. Four parameters showed an important decline with age. Gastric pressure during cough (Pgas cough) was below normal in all patients with a mean decline of 5.7 ± 3.8 cmH2 O/year. Sniff nasal inspiratory pressure (SNIP) tended to increase first followed by a rapid decline (mean decrease 4.8 ± 4.9 cmH2 O; 5.2 ± 4.4% predicted/year). Absolute forced vital capacity (FVC) values peaked around the age of 13-14 years and remained mainly over 1 L but predicted values showed a mean 4.1 ± 4.4% decline/year. Diaphragmatic tension-time index (TTdi) increased above normal values after the age of 14 years with a mean increase of 0.04 ± 0.04 point/year.
  
  
  CONCLUSIONS
  This study confirms the previous findings that FVC and SNIP are among the most important parameters to monitor the evolution of DMD. Expiratory muscle strength, assessed by Pgas cough, and the endurance index, TTdi, which are reported for the first time in a large cohort, appeared to be informative too, even though measured through an invasive method.
authors.affiliation: S2A Santé, Ivry-sur-Seine, France; Pediatric Pulmonary Department, AP-HP, Hôpital Armand Trousseau, Paris, France.
authors.forename: Sonia
authors.initials: S
authors.lastname: Khirani
authors.forename: Adriana
authors.initials: A
authors.lastname: Ramirez
authors.forename: Guillaume
authors.initials: G
authors.lastname: Aubertin
authors.forename: Michèle
authors.initials: M
authors.lastname: Boulé
authors.forename: Chrystelle
authors.initials: C
authors.lastname: Chemouny
authors.forename: Véronique
authors.initials: V
authors.lastname: Forin
authors.forename: Brigitte
authors.initials: B
authors.lastname: Fauroux
mesh_terms: D000293:Adolescent; D000367:Age Factors; D002648:Child; D015331:Cohort Studies; D003371:Cough; D003964:Diaphragm / Q000503:physiopathology*; D018450:Disease Progression; D006801:Humans; D008137:Longitudinal Studies; D008168:Lung / Q000503:physiopathology*; D008297:Male; D053580:Muscle Strength; D018908:Muscle Weakness / Q000209:etiology / Q000503:physiopathology*; D020388:Muscular Dystrophy, Duchenne / Q000150:complications / Q000503:physiopathology*; D011312:Pressure; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics; D012132:Respiratory Muscles / Q000503:physiopathology*; D012133:Respiratory Paralysis / Q000209:etiology / Q000503:physiopathology*; D012189:Retrospective Studies; D013270:Stomach; D014797:Vital Capacity; D055815:Young Adult
keywords: Duchenne muscular dystrophy; longitudinal study; muscles strength; pulmonary function