title: Inspiratory work capacity is more severely depressed than inspiratory muscle strength in patients with heart failure: Novel applications for inspiratory muscle training.
abstract: BACKGROUND
  We hypothesized that the ability to sustain maximal inspiratory pressure (SPImax) over time as a measure of work capacity may be more severely affected than inspiratory muscle strength (PImax) in patients with heart failure (HF).
  
  
  METHODS
  We retrospectively investigated eighty patients with HF, NYHA II/III/ ambulatoryIV and a (mean±SD) LVEF 27±8%, and compared them to 25 healthy subjects (HS). During a maximal inspiratory manoeuvre from residual volume (RV) to total lung capacity, PImax was measured as the maximum mouth pressure at RV, inspiratory contraction time (ICT) as the time from RV to end of inspiration and SPImax as the area under a pressure-time curve using an electronic pressure manometer with designed-purpose software (Trainair(®), Project Electronics Ltd., London, UK). Exercise capacity was assessed with cardiopulmonary exercise testing and the 6-minute walk test (6MWT).
  
  
  RESULTS
  Patients achieved a (mean±SD) peak VO2=15.7±3.4ml/kg/min and 6MWT=338±88m. PImax, ICT and SPImax were reduced in HF pts at 75%***, 61%*** and 52%*** of HS, and correlated with NYHA (r=-0.485***), (r=-0.507**), (r=-0.500***), peakVO2 (r=0.501***), (r=0.655***), (r=0.508***) and 6MWT (r=0.477***), (r=0.345**), (r=0.530***), respectively (*p<0.05, **p<0.01, ***p<0.001).
  
  
  CONCLUSIONS
  PImax, ICT and SPImax were impaired in HF patients compared to HS and may be important determinants of exercise capacity. SPImax was severely depressed even in patients with relatively preserved PImax and should be considered as an additional target index for inspiratory muscle training. Equations are provided to predict SPImax in relation to age and exercise capacity in HF.
authors.affiliation: Onassis Cardiac Surgery Center, Athens, Greece. Electronic address: ylaoutaris@yahoo.gr.
authors.forename: Ioannis D
authors.initials: ID
authors.lastname: Laoutaris
authors.affiliation: Onassis Cardiac Surgery Center, Athens, Greece.
authors.forename: Stamatis
authors.initials: S
authors.lastname: Adamopoulos
authors.affiliation: Onassis Cardiac Surgery Center, Athens, Greece; Mediterraneo Hospital, Athens, Greece.
authors.forename: Athanassios
authors.initials: A
authors.lastname: Manginas
authors.affiliation: Department of Nutrition - Dietetics, School of Health Science and Education Harokopio University, Athens, Greece.
authors.forename: Demosthenes B
authors.initials: DB
authors.lastname: Panagiotakos
authors.affiliation: Onassis Cardiac Surgery Center, Athens, Greece; Biomedical Research Foundation, Academy of Athens, Greece.
authors.forename: Dennis V
authors.initials: DV
authors.lastname: Cokkinos
authors.affiliation: Onassis Cardiac Surgery Center, Athens, Greece.
authors.forename: Athanasios
authors.initials: A
authors.lastname: Dritsas
mesh_terms: D000367:Age Factors; D000368:Aged; D001945:Breathing Exercises / Q000379:methods*; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test / Q000379:methods; D017079:Exercise Tolerance / Q000502:physiology; D005260:Female; D006333:Heart Failure / Q000175:diagnosis / Q000503:physiopathology / Q000534:rehabilitation; D006801:Humans; D007320:Inspiratory Capacity / Q000502:physiology*; D008297:Male; D000072277:Maximal Respiratory Pressures / Q000379:methods; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology*; D012132:Respiratory Muscles / Q000503:physiopathology*; D000070857:Walk Test / Q000379:methods
keywords: Exercise capacity; Heart failure; Inspiratory muscles; Rehabilitation; Strength; Training